AU2005289374B2 - Gels - Google Patents

Abstract

The present invention relates to silicon-containing biostable gels and processes for their preparation. The gels possess properties which make them useful in the manufacture and repair of biomaterials and medical devices, articles or implants, in particular the manufacture of soft tissue implants such as breast implants and the repair of orthopaedic joints such as spinal discs.

Description

WO 2006/034547 PCT/AU2005/001491 GELS The present invention relates to silicon-containing biostable gels and processes for their preparation. The 5 gels possess properties which make them useful in the manufacture and repair of biomaterials and medical devices, articles or implants, in particular the manufacture of soft tissue implants such as breast implants and the repair of orthopaedic joints such as 10 spinal discs. BACKGROUND Polymer gels are semi-solid systems that respond in a liquid like fashion under certain circumstances but their 15 molecules do not have motion that is independent of each other, hence they behave like solids in other circumstances. Gels can be synthesised as physical gels where a cross-linked network is swelled by a non reactive liquid. 20 Without the presence of this swelling medium the cross linked network would be a solid. Silicone gels currently used in breast implants are physical gels where a cross linked polydimethylsiloxane (PDMS) system is swollen by a non reactive, low molecular weight PDMS. These gels are 25 inherently prone to leakage of the low molecular weight liquid PDMS and contain heavy metal catalysts such as platinum and tin which can leach out of the implant in an in-vivo situation. Hydrogels are other examples of physical gels, where 30 hydrophilic groups in the cross-linked network can attract water molecules and are swollen by them. In a physical gel the parts by weight of the swelling medium can be as high as 90%. This swelling medium can be extracted out of the gel by most solvents and biological fluids. 35 There is a need for a gel that mimics the behaviour of a PDMS-based physical gel, but is chemically formulated so as to avoid the complications of a physical gel.

-2 SUMMARY According to the present invention there is provided a chemical gel comprising at least one silicon-containing biostable polymer having monomers with an average 5 functionality in the range of from 2.05 to 3.5, preferably from 2.1 to 3.25 in which the biostable polymer is a polyurethane or polyurethane urea which is a reaction product of: (a) at least one silicon-containing polyol or 10 polyamine having 2 or more functional groups in which the silicon-containing polyol or polyamine (a) is a compound of formula (I), (I , (III) or (IV) 15 R3 R

R

1 0 SO S OR 2 R4 R6 R8 20 R10 O O O 25

(R

9

)

2 I Si(R9) 2 0 (Rg) 2 Si O Si(R9)2 / . Si(R9)2 n ( 9)2S' n 30

R

1 0 OR 1

OR

1 (II) 2599248_1 (GHMatters) P54387.AU.1 - 2a in which R 1 and R 2 are independently selected from C 1 -6 alkylene optionally substituted with OH or NR'R'' in which R' and R'' are independently selected from H, CO 2 H and C 1 -6 5 alkyl;

R

3 to R 8 are independently selected from C 1

.

6 alkyl and

C

1 - alkylene which may be optionally interrupted by 0 and optionally substituted with OH or NR'R'' in which R' and R'' are as defined above; 10 R 9 is C 1

..

4 alkyl;

R

10 is optionally substituted C 1

-

4 alkyl or Si(Rg) 2 Si(Rg) 2 0 n 15 in which Ri and R 9 are as defined above; x is 5 to 30; y is 1 to 10; and n is 1 to 10; 20 RI, R 12 I I

A-R

5 -Si--0-Si--R16-A' I I R13 R 14 25 (III) in which A and A' are OH or NHR wherein R is H or an optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon radical; 30 R 1 1, R 1 2 , R 13 and R 1 4 are the same or dif ferent and selected from hydrogen or an optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon radical; Ris and R 16 are the same or different and selected from 35 an optionally substituted straight chain, branched or cyclic alkylene, alkenylene, alkynylene or heterocyclic divalent radical; and 25992481 (GHMatters) P54387.AU.1 - 2b p is an integer of 1 or greater; R11 R12 O R1 R12- O R1 I F }111 11

A-R

15 -S- R 17 -Si -R 16 -O--C-- -R 5 -Si- -R 7 -Si- 16-0-C -O-R15-i R13 R 14 m R 13 R14 R 13 5 - _ m _ x R12 R R 1 2 R17-Si -R16- -R 1 -C-0-R 1 >-C-R1 5 -O-Si- R -R16-A' I~~ |7S R14 m- -yz R13 - R14 IV) in which 10 R11, R12, R13, R14 and Ris are as defined in formula (III) above; Ri6 is an optionally substituted straight chain, branched or cyclic alkylene, alkenylene, alkynylene or heterocyclic divalent radical; 15 R17 is a divalent linking group; Ri8 and Ris are same or different and selected from hydrogen or an optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon divalent radical; 20 A and A' are as defined in formula (III) above; m, y and z are integers of 0 or more; and x is an integer of 0 or more; and (b) a polyisocyanate. In one embodiment the polyurethane or polyurethane 25 urea defined above may also be the reaction product of: (c) at least one non-silicon containing compound having 1 or more functional groups 2599248_1 (GHMatters) P54387.AU.1 - 2c The present invention also provides a process for preparing the polyurethane polyurethane urea defined above which comprises the step of: 5 (i) mixing components (a), (b) and (c) (when present) as defined above. In an alternative embodiment, the process for preparing the polyurethane or polyurethane urea defined above comprises the steps of: 10 (i) reacting components (a) and (b) as defined above to form a prepolymer having terminally reactive polyisocyanate groups ; and (ii) mixing the prepolymer of step (i) with component (c) (when present) as defined above. 15 In a further embodiment, the process for preparing the polyurethane or polyurethane urea defined above comprises the steps of: 2599248_1 (GHMatters) P54387.AU.1 - 3 (i) mixing components (a) and (b) and (c) (when present) as defined above with a photoinitiater; and (ii) subjecting the mixture to UV radiation. Some of the silicon-containing polyols (a) defined above are novel and form part of the invention. There is also provided a silicon-containing polyol or polyamine of formula (I) or (II): R3 - R5- - R7

R

1 0 SiOR 2 1 H R4 R6 Re (1) O O

R

1 0 oR 1 ROR 0 O S(R<9)2 ' iR ) n 9)2Si n R10 OR1, R 0 (II) in which R, and R 2 are independently selected from C 1

.

6 alkylene optionally substituted with OH or NR'R'' in which R' 5 and R'' are independently selected from H, CO 2 H and C 1

.

6 alkyl; 2707274_1 (GHMatters) P54387.AU.1 - 4 R 3 to R 8 are independently selected from C 1 .- alkyl and C1.3 alkylene which may be optionally interrupted by 0 and optionally substituted with OH or NR'R'' in which R' and R'' 5 are as defined above;

R

9 is C 1

.

4 alkyl;

R

10 is optionally substituted C 1

-

4 alkyl or Si(R 9

)

2 Si(Rg) 2 OR, -0 Z0O in which R 1 and R 9 are as defined above; x is 5 to 30; 5 y is 1 to 10; and n is 1 to 10. There is further provided a process for the preparation of the silicon-containing polyol of formula (I) or (II) defined above which comprises the steps of: D (i) reacting a compound of formula (A) or (B)

R

3 -R5 R7 . R 1 0 H I O"" O H O 111 O SI Si Si1 5 R - I IR X R 8 - ' HSi(R 9

)

2 HSi(Rg)2 HSi(Rg) 2 (A) (B) in which R 3 to R 10 and x are as defined above and y' is 0 to 10. 0 with a compound of formula (C)

(CH

3

)

2 Si 0 O Si(CH 3

)

2 I ; and

(CH

3

)

2 Si / 0-Si

(CH

3

)

2 (C) 2707274_1 (GHMatters) P54387.AU.1 WO 2006/034547 PCT/AU2005/001491 -5 (ii) subjecting the product of step (i) to hydrosilation. The gels of the present invention possess visco elastic properties and have a natural tissue feel to suit, 5 for example, soft tissue implant gel applications such as breast implants. These gels also have a low level of extractables preferably less than 35%, more preferably less than 30%, most preferably less than 21% based on the total weight of the gel. 10 Thus, the present invention also provides a biomaterial, device, article or implant which is wholly or partly composed of the gels defined above. The present invention further provides a filler material for a medical implant which comprises the gel 15 defined above. DETAILED DESCRIPTION The gel of the present invention which comprises at least one silicon containing biostable polymer is a 20 chemical gel. When a cross-linked network is formulated such that the reactive groups are in a perfect balance then, during the course of the reaction, the network begins to vitrify and ends up being a hard solid. If the reaction is not allowed to go to completion by creating an 25 imbalance in the reactive groups, then an off stoichiometric system occurs which is capable of gelation. Thus, one reactive -group is in excess and remains incompletely reacted. This excess amount acts similar to the non-reactive swelling medium in physical gels. 30 However, usually lower amounts of unreacted material, in comparison to the swelling agents, can be formulated to achieve a similar effect to a physical gel and that, in turn, implies lower extractable species. The level of extractables in the gel of the present invention is 35 preferably less than 35%, more preferably less than 30%, most preferably less than 21% based on the total weight of the gel.

-6 The term "extractables" refers to the unreacted portion of the gel which is generally fluid and free to migrate out of the gel at body temperature of 38 0 C and more specifically, refers to the unreacted fluid portion 5 of a gel which is extracted by organic solvents at temperatures in the range from 200C to 400C. The term "biostable" refers to the stability of the polymer when in contact with cells and/or bodily fluids of living animals or humans. 10 The term "average functionality" of a polymerisation system refers to the average number of functional groups per monomer for all types of monomer molecules and is defined by the following formula: nf fovg = in which 15 ni is number of molecules of monomer i with functionality groups fi. Preferably, the average functionality of the monomers in the gel is in the range of from 2.05 to 3.5, more preferably from 2.1 to 3.25. 20 The polyurethane or polyurethane urea may be formed from a silicon-containing polyol or polyamine having 2 or more functional groups (a), a polyisocyanate (b) and optionally a non-silicon containing compound having 2 or more functional groups (c). 25 The functional groups of components (a) and (c) may be any types of groups which can react with isocyanate and are preferably selected from OH, NR'R'' in which R' and R' Iare the same or different and selected from H, CO 2 H and

C

1 6 alkyl, preferably H and C1- 4 alkyl or are groups 30 capable of activation by free radical initiation such as double or triple bonds. The silicon-containing polyol or polyamine (a) can have 1 or more functional groups provided that the average 2599248_1 (GHMatter) P54387.AU.1 - 7 functionality of the biostable polymer is in the range from 1 to 5. Suitable silicon-containing polyols or polyamines (a) include compounds of the formula (I), (II), (III) or (IV) 5 defined above. Representative examples of compounds of the formula (I) are as follows: CH, CH3 C 10 HO O (Ia) CH' CH2 - CH CH3-, 0-6 1 C _,O,, C 15 (Ib) CH6 C-b CHs n (Ic) CNa CHK CH3 20 HO 0 0 OH OH CH, CH3 - 3 nOH OH O

CH

3

CH

3 (Id) HOg 1 Os Si OS SiiOO CH3 - CH, CH 2599248_1 (GHMatters) PS4387.AU 1 WO 2006/034547 PCT/AU2005/001491 - 8 CH 3 0 0 5 CH, CH 3 HO O i 0 i SI O OH I I |

OH

3 - CH CH 3 X Y 10 The molecular weight of the compounds of formula (I) is preferably from 400 to 5000. It will be understood that the molecular weight values referred to herein are "number average molecular weights". Representative examples of compounds of the formula 15 (II) are as follows: MeSi ( 20 SiMAe \SI~ e2( I a ) 25 OH OH OH Me 2 Me 2 H SiOOSiO 0 OH n 00 30 1 SiMe 30Me 2 Si Me Si~O 0hb SiMe 2 ) n Me 2 S1 n 3HOf 00 0 OH

H

WO 2006/034547 PCT/AU2005/001491 -9 The molecular weight of the compounds of formula (II) is preferably from 1000 to 5000. The polysiloxane may be hydroxy or amine terminated. Suitable polysiloxane macrodiols or macrodiamines may be 5 represented by the formula (III):

R

1 1 R A-R5~-SIi--O-SIi-- R 16 -- A'

R

13

R

14 P 10 (III) in which A and A' are OH or NHR wherein R is H or an optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon radical, preferably 15 C 1 _- alkyl, more preferably C 1

.

4 alkyl;

R

11 , R 12 , R 1 3 and R 1 4 are the same or different and selected from hydrogen or an optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon radical; 20 Ris and Ri 6 are the same or different and selected from an optionally substituted straight chain, branched or cyclic alkylene, alkenylene, alkynylene or heterocyclic divalent radical; and p is an integer of 1 or greater. 25 Preferred polysiloxanes are polysiloxane macrodiols which are polymers of the formula (III) wherein A and A' are hydroxy. A preferred polysiloxane is PDMS which is a compound of formula (III) in which A and A' are hydroxyl, Ra 1 to R 1 4 30 are methyl and R 15 and R 16 are as defined above. Preferably

R

1 and R 16 are the same or different and selected from propylene, butylene, pentylene, hexylene, ethoxypropyl

(-CH

2

CH

2

OCH

2

CH

2

CH

2 -), propoxypropyl and butoxypropyl. Other silicon-containing diols of the formula (III) 35 are 1, 3-bis (4-hydroxybutyl) tetramethyl disiloxane (BHTD) (compound of formula (III) in which A and A' are OH, R 11 ,

R

12 , R 13 and R 14 are methyl, R 15 and Ri 6 are butyl and R 17 is - 10 0), 1,4-bis (3-hydroxypropyl) tetramethyl disilylethylene (compound of formula (III) in which A and A' are OH, R 1 ,

R

12 , R 1 3 and R 1 4 are methyl, R 15 and R 16 are propyl and R 17 is ethylene) and 1-4-bis(3-hydroxypropyl)tetramethyl 5 disiloxane, more preferably BHTD. The polysiloxanes may be obtained as commercially available products such as X-22-160AS from Shin Etsu in Japan or prepared according to known procedures. The preferred molecular weight range of the polysiloxane 10 macrodiol is 200 to 6000, more preferably from 200 to 5000. Other preferred polysiloxanes are polysiloxane macrodiamines which are polymers of the formula (III) wherein A is NH 2 , such as, for example, amino-terminated 15 PDMS. Suitable silicon-containing polycarbonates include those described in International Patent Publication No. WO 98/54242, the entire content of which is incorporated herein by reference. 20 The silicon-containing polycarbonate has the formula (IV): R11 R12 OR1 ~ 12 1 A-R15-Si- R17-Si -R16-0-C- ( -R5-Si- -R7-Si- 16-0-C -O-Rj13- I I I | | R13 R 14 m R13 R14

R

13 - -1 -11m_ 2 R12 O0 R1 - R12 I Ii 1 | | R1

-O-R

1 s-OSi R 1 7 -Si 25 - R14 m -9-yf z R3 - R14 (IV) ' in which

R

11 , R 1 2 , R 1 3 , R 1 4 and R 1 s are as defined in formula (III) above; 30 R 16 is an optionally substituted straight chain, 2599248_1 (GHMallers) P54387.AUA WO 2006/034547 PCT/AU2005/001491 - 11 branched or cyclic alkylene, alkenylene, alkynylene or heterocyclic divalent radical;

R

17 is a divalent linking group, preferably 0, S or NRi 8 ; 5 R 18 and R 19 are same or different and selected from hydrogen or an optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon divalent radical; A and A' are as defined in formula (III) above; 10 m, y and z are integers of 0 or more; and x is an integer of 0 or more. Preferably z is an integer of 0 to 50 and x is an integer of 1 to 50. Suitable values for m include 0 to 20, more preferably 0 to 10. Preferred values for y are 0 15 to 10, more preferably 0 to 2. A preferred silicon-containing polycarbonate is a compound of the formula (IV) in which A and A' are hydroxyl. Particularly preferred silicon-containing 20 polycarbonate macrodiols are compounds of the formula (IV) in which A and A' are hydroxyl, R 11 , R 12 , R 13 and R 14 are methyl, R 18 is ethyl, R 19 is hexyl, Ris and R 16 are propyl or

R

14 butyl and R 1 is 0 or -CH 2

-CH

2 -,more preferably R 5 and

R

16 are propyl when R 1 7 is 0 and R 15 and RIG are butyl when 25 R 1 7 is -CH 2

-CH

2 -. The preferred molecular weight range of the silicon-based polycarbonate macrodiol is from 400 to 5000, more preferably from 400 to 2000. The term "polyisocyanate" refers to di or higher isocyanates such as polymeric 4,4'-diphenylmethane 30 diisocyanate (MDI). The polyisocyanate is preferably a diisocyanate which may be aliphatic or aromatic diisocyanates such as, for example MDI, methylene - biscyclohexyl diisocyanate (H 12 MDI), p-phenylene diisocyanate (p-PDI), trans-cyclohexane-1,4-diisocyanate 35 (CHDI), 1,6-diisocyanatohexane (DICH), 1,5-diisocyanatonaphthalene (NDI), para-tetramethylxylenediisocyanate (p-TMXDI), - 12 meta-tetramethylxylene diisocyanate (m-TMXDI), 2,4-toluene diisocyanate (2,4-TDI) isomers or mixtures thereof or isophorone diisocyanate (IPDI). MDI is particularly preferred. 5 The non-silicon containing compound having 1 or more functional groups (c) may be a polyether, polycarbonate, polyalkylene or C1_ alkane. The polyethers and polycarbonates may contain hydroxy or amine functional groups. 10 Suitable polyether macrodiols and macrodiamines include those represented by the formula (V)

A-[(CH

2 ), -O,, -A' (V) 15 in which A and A' are as defined in formula (III) above OH or NHR wherein R is H or an optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon radical, preferably C1_ alkyl, more preferably 20 C 1 4 alkyl; m is an integer of 4 or more, preferably 5 to 18; and n is an integer of 2 to 50. Polyether macrodiols of formula (V) wherein m is 5 or higher such as polyhexamethylene oxide (PHMO), 25 polyheptamethylene oxide, polyoctamethylene oxide (POMO) and polydecamethylene oxide (PDMO) are preferred over the conventional polytetramethylene oxide (PTMO). The more preferred macrodiols and their preparation are described in Gunatillake et a1 3 and US 5403912. Polyethers such as 30 PHMO described in these references are particularly useful as they are more hydrophobic than PTMO and more compatible with polysiloxane macrodiols. Examples of tri- and tetra- functional polyethers include Voranol which is a polyether triol resulting from 35 a base catlysed reaction of glycerol and propylene oxide, and N,N,N'-tri(2-hydroxypropyl)-N'-hydroxyethyl ethylene diamine (Poly Q), respectively. 2599248_1 (GHMalters) P54387 AU.I WO 2006/034547 PCT/AU2005/001491 - 13 The preferred molecular weight range of the polyether is from 200 to 5000, more preferably from 200 to 2000. Suitable polycarbonate macrodiols include poly(alkylene carbonates) such as poly(hexamethylene 5 carbonate) and poly(decamethylene carbonate); polycarbonates prepared by reacting alkylene carbonate with alkanediols for example 1,4-butanediol, 1,10 decanediol (DD), 1,6-hexanediol (HD) and/or 2,2-diethyl 1,3-propanediol (DEPD); and silicon based polycarbonates 10 prepared by reacting alkylene carbonate with 1,3-bis(4 hydroxybutyl)-1,1,3,3-tetramethyldisiloxane (BHTD) and/or alkanediols. It will be appreciated when both the polyether and polycarbonate macrodiols are present, they may be in the 15 form of a mixture or a copolymer. An example of a suitable copolymer is a copoly(ether carbonate) macrodiol represented by the formula (VI) r 0 20 HO-R-0- O-R1-0-- O-R 2 01 -p (VI) wherein 25 R, and R 2 are the same or different and selected from an optionally substituted straight chain, branched or cyclic alkylene, alkenylene, alkynylene or heterocyclic divalent radical; and p and q are integers of 1 to 20. 30 Although the compound of formula (VI) above indicates blocks of carbonate and ether groups, it will be understood that they also could be distributed randomly in the main structure. Examples of C 1 -6 alkanes having 1 or more 35 functional groups include methane diol, butane diol or hexane diol.

WO 2006/034547 PCT/AU2005/001491 - 14 In one embodiment, components (a) and (c) may be a combination of silicon-containing polyols and non-silicon containing polyols having different amounts of functional groups. For example, component (c) may contain a 5 combination of a tri-functional polyether and a tetra functional polyether. The components (a), (b) and (c) are preferably mixed so that the NCO/OH or NH 2 ratio is less than 1, more preferably from 0.4 to 0.7 so as to provide the 10 appropriate rheological response. In a particularly preferred embodiment suitable for breast implant applications, the gel is a polyurethane urea which is the reaction product of: (a) silicon-containing polyols having 2 to 4 15 functional groups, namely PDMS (MW 1000) and one or more compounds of the formulae (Id) (MW 1210), (IIa) (MW 1150), (Ic) (MW 430) and (IIb) (MW 1520) ; and (b) a disocyanate, namely MDI. 20 The term "alkylene" is a divalent radical equivalent of the term "alkyl". The two bonds connecting the alkylene to the adjacent groups may come from the same carbon atom or difference carbon atoms in the divalent radical. 25 The "hydrocarbon radical" may include alkyl, alkenyl, alkynyl, aryl or heterocyclyl radicals. The term "alkyl" denotes straight chain, branched or mono- or poly-cyclic alkyl, preferably C 1 2 alkyl or cycloalkyl, more preferably C1- alkyl, most preferably C 1 4 30 alkyl. Examples of straight chain and branched alkyl include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, amyl, isoamyl, sec-amyl, 1,2-dimethylpropyl, 1,1-dimethylpropyl, pentyl, neopentyl, hexyl, 4-methylpentyl, 1-methylpentyl, 2-methylpentyl, 35 3-methylpentyl, 1,1-dimethylbutyl, 2,2-dimethylbutyl, 3,3-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 1,2,2-trimethylpropyl, 1,1,2-trimethylpropyl, heptyl, WO 2006/034547 PCT/AU2005/001491 - 15 5-methylhexyl, 1-methylhexyl, 2,2-dimethylpentyl, 3,3-dimethylpentyl, 4,4-dimethylpentyl, 1,2-dimethylpentyl, 1,3-dimethylpentyl, 1,4-dimethylpentyl, 1,2,3-trimethylbutyl, 5 1,1,2-trimethylbutyl, 1,1,3-trimethylbutyl, octyl, 6-methylheptyl, 1-methylheptyl, 1,1,3,3-tetramethylbutyl, nonyl, 1-, 2-, 3-, 4-, 5-, 6- or 7-methyloctyl, 1-, 2-, 3-, 4- or 5-ethylheptyl, 1-, 2- or 3-propylhexyl, decyl, 1-, 2-, 3-, 4-, 5-, 6-, 7- and 8-methylnonyl, 1-, 2-, 3-, 10 4-, 5- or 6-ethyloctyl, 1-, 2-, 3- or 4-propylheptyl, undecyl, 1-, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-methyldecyl, 1-, 2-, 3-, 4-, 5-, 6- or 7-ethylnonyl, 1-, 2-, 3-, 4- or 5-propyloctyl, 1-, 2- or 3-butylheptyl, 1-pentylhexyl, dodecyl, 1-, 2-, 3-, 4-, 5-, 6-, 7-, 8-, 9- or 15 10-methylundecyl, 1-, 2-, 3-, 4-, 5-, 6-, 7- or 8-ethyldecyl, 1-, 2-, 3-, 4-, 5- or 6-propylnonyl, 1-, 2-, 3- or 4-butyloctyl, 1,2-pentylheptyl and the like. Examples of cyclic alkyl include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, 20 cyclononyl, cyclodecyl and the like. The term "alkenyl" denotes groups formed from straight chain, branched or mono- or poly-cyclic hydrocarbon groups having at least one double bond, preferably C 2

-

12 alkenyl, more preferably C 2 - alkenyl. The 25 alkenyl group may have E or Z stereochemistry where applicable. -Examples of alkenyl include vinyl, allyl, 1-methylvinyl, butenyl, iso-butenyl, 3-methyl-2-butenyl, 1-pentenyl, cyclopentenyl, 1-methyl-cyclopentenyl, 1-hexenyl, 3-hexenyl, cyclohexenyl, 1-heptenyl, 3 30 heptenyl, 1-octenyl, cyclooctenyl, 1-nonenyl, 2-nonenyl, 3-nonenyl, 1-decenyl, 3-decenyl, 1,3-butadienyl, 1,4-pentadienyl, 1,3- cyclopentadienyl, 1,3-hexadienyl, 1,4-hexadienyl, 1,3-cyclohexadienyl, 1,4-cyclohexadienyl, 1,3-cycloheptadienyl, 1,3,5-cycloheptatrienyl, 35 1,3,5,7-(cycloocta-tetraenyl) and the like. The term "alkynyl" denotes groups formed from straight chain, branched, or mono- or poly-cyclic WO 2006/034547 PCT/AU2005/001491 - 16 hydrocarbon groups having at least one triple bond. Examples of alkynyl include ethynyl, 1-propynyl, 1- and 2-butynyl, 2-methyl-2-propynyl, 2-pentynyl, 3-pentynyl, 4-pentynyl, 2-hexynyl, 3-hexynyl, 4-hexynyl, 5-hexynyl, 5 10-undecynyl, 4-ethyl-l-octyn-3-yl, 7-dodecynyl, 9-dodecynyl, 10-dodecynyl, 3-methyl-l-dodecyn-3-yl, 2-tridecynyl, 11-tridecynyl, 3-tetradecynyl, 7-hexadecynyl, 3-octadecynyl and the like. The term "aryl" denotes single, polynuclear, 10 conjugated and fused residues of aromatic hydrocarbons. Examples of aryl include phenyl, biphenyl, terphenyl, quaterphenyl, phenoxyphenyl, naphthyl, tetrahydronaphthyl, anthracenyl, dihydroanthracenyl, benzanthracenyl, dibenzanthracenyl, phenanthrenyl and the like. 15 The term "heterocyclyl" denotes mono- or poly-cyclic heterocyclyl groups containing at least one heteroatom selected from nitrogen, sulphur and oxygen. Suitable heterocyclyl groups include N-containing heterocyclic groups, such as, unsaturated 3 to 6 membered 20 heteromonocyclic groups containing 1 to 4 nitrogen atoms, for example, pyrrolyl, pyrrolinyl, imidazolyl, pyrazolyl, pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazolyl or tetrazolyl; saturated 3 to 6 membered heteromonocyclic groups containing 1 to 4 nitrogen atoms, such as 25 pyrrolidinyl, imidazolidinyl, piperidino or piperazinyl; unsaturated condensed heterocyclic groups containing 1 to 5 nitrogen atoms, such as, indolyl, isoindolyl, indolizinyl, benzimidazolyl, quinolyl, isoquinolyl, indazolyl, benzotriazolyl or tetrazolopyridazinyl; 30 unsaturated 3 to 6-membered heteromonocyclic group containing an oxygen atom, such as, pyranyl or furyl; unsaturated 3 to 6-membered heteromonocyclic group containing 1 to 2 sulphur atoms, such as, thienyl; unsaturated 3 to 6-membered heteromonocyclic group 35 containing 1 to 2 oxygen atoms and 1 to 3 nitrogen atoms, such as, oxazolyl, isoazolyl or oxadiazolyl; saturated 3 to 6-membered heteromonocyclic group containing 1 to 2 WO 2006/034547 PCT/AU2005/001491 - 17 oxygen atoms and 1 to 3 nitrogen atoms, such as, morpholinyl; unsaturated condensed heterocyclic group containing 1 to 2 oxygen atoms and 1 to 3 nitrogen atoms, such as, benzoxazolyl or benzoxadiazolyl; unsaturated 3 to 5 6-membered heteromonocyclic group containing 1 to 2 sulphur atoms and 1 to 3 nitrogen atoms, such as thiazolyl or thiadiazolyl; saturated 3 to 6-membered heteromonocyclic group containing 1 to 2 sulphur atoms and 1 to 3 nitrogen atoms, such as, thiadiazolyl; and 10 unsaturated condensed heterocyclic group containing 1 to 2 sulphur atoms and 1 to 3 nitrogen atoms, such as benzothiazolyl or benzothiadiazolyl. In this specification, "optionally substituted" means that a group may or may not be further substituted with 15 one or more groups selected from oxygen, nitrogen, sulphur, alkyl, alkenyl, alkynyl, aryl, halo, haloalkyl, haloalkenyl, haloalkynyl, haloaryl, hydroxy, alkoxy, alkenyloxy, alkynyloxy, aryloxy, carboxy, benzyloxy, haloalkoxy, haloalkenyloxy, haloalkynyloxy, haloaryloxy, 20 nitro, nitroalkyl, nitroalkenyl, nitroalkynyl, nitroaryl, nitroheterocyclyl, azido, amino, alkylamino, alkenylamino, alkynylamino, arylamino, benzylamino, acyl, alkenylacyl, alkynylacyl, arylacyl, acylamino, acyloxy, aldehydo, alkylsulphonyl, arylsulphonyl, alkylsulphonylamino, 25 arylsulphonylamino, alkylsulphonyloxy, arylsulphonyloxy, heterocyclyl, heterocycloxy, heterocyclylamino, haloheterocyclyl, alkylsulphenyl, arylsulphenyl, carboalkoxy, carboaryloxy, mercapto, alkylthio, arylthio, acylthio and the like 30 The polyurethanes of the present invention may be prepared by any technique familiar to those skilled in the manufacture of polyurethanes. These include one or two-step procedures. The polymerisation can be carried out in conventional apparatus or within the confines of a 35 reactive injection moulding or mixing machines. In a one-step procedure the appropriate amount of components (a), (b) and (c) if present are mixed. The WO 2006/034547 PCT/AU2005/001491 - 18 mixture is then cured by heating in an oven to about 70 0 C. In an alternative one-step procedure, components (a) and (c) (when present) are added to component (b) slowly. It has also been found that the order of addition of 5 components (a) and (c) may effect the properties of the gel. The polyurethanes can also be prepared by a two-step procedure where a prepolymer having terminally reactive polyisocyanate groups is prepared by reacting components 10 (a) and (b). The prepolymer is then reacted with the component(c) if present. The polyurethanes may be further prepared by UV curing which involves the addition of a photoinitiator to components (a), (b) and (c) followed by the application of 15 UV radiation. If desired, conventional polyurethane processing additives such as catalysts for example dibutyl tin dilaurate (DBTD), stannous oxide (SO), 1,8 diazabicyclo[5,4,0] undec-7-ene (DABU), 1,3-diacetoxy 20 1,1,3,3-tetrabutyldistannoxane (DTDS), 1,4-diaza-(2,2,2) bicyclooctane (DABCO), N,N,N',N'-tetramethylbutanediamine (TMBD) and dimethyltin dilaurate (DMTD); antioxidants for example Irganox (Registered Trade Mark); radical inhibitors for example trisnonylphenyl phosphite (TNPP); 25 stabilisers; lubricants for example Irgawax (Registered Trade Mark); dyes; pigments; inorganic and/or organic fillers; and reinforcing materials; and initiators such as photoinitiators, for example, Iragacure 819 can be incorporated into the biostable polymer during 30 preparation. Such additives are preferably added in step (i) of the processes of the present invention up to 10% based on the total weight of gel, preferably up to 5%, more preferably 2% or less. The polyurethanes of the present invention are 35 particularly useful in preparing biomaterials and medical devices, articles or implants. The term "biomaterial" refers to a material which is WO 2006/034547 PCT/AU2005/001491 - 19 used in situations where it comes into contact with the cells and/or bodily fluids of living animals or humans. The medical devices, articles or implants may include soft tissue implants designed to replace and augment 5 tissues including breast tissue, testicular tissue, cartilage, muscle and any connective tissue apart from teeth and bone; orthopaedic joints or parts thereof including spinal discs and small joints; bone suture anchors; reconstructive facial surgery; controlled drug 10 release devices; components in key hole surgery; biosensors; tools and accessories for insertion of medical devices, infusion and flow control devices; and urethral, neurological or vascular bulking agents. In the description of the invention, except where the 15 context requires otherwise due to express language or necessary implication, the words "comprise" or variations such as "comprises" or "comprising" areused in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or 20 addition of further features in various embodiments of the invention. EXAMPLES The invention will now be described with reference to 25 the following non-limiting examples. PHYSICAL PROPERTY TESTS Biological Stability: The biological stability of the 30 gels is achieved by the incorporation of large amount of silicon. Rheology: Both the natural feel and the form stability can be related to rheological factors. A good creep 35 recovery performance describes the feel or the elasticity. The parameters of storage modulus (G') and loss modulus (G") as measured in frequency sweep measurement on a WO 2006/034547 PCT/AU2005/001491 - 20 rheometer describe the form stability. G'>G" at low frequencies (O.01s-1 to 1s1) implies form stability. Procedure for Creep Recovery & Frequency Sweep Analysis 5 The Creep Recovery is tested using Haake RheoStress 1 Rheometer. After the initialisation process under compressed air atmosphere, the parallel plates are subjected to zero point measurement. The sample is loaded and the gap position set. The excess sample is trimmed and 10 is ready for the experiment. The creep recovery analysis is carried out at 37 0 C. The sample is thermostated for 300s before the actual experiment starts to ensure temperature equilibrium. The experiment is carried at a force of 10 Pa for a duration 15 of 60s and from the plot of J (1/Pa, compliance) Vs t(s), the creep recovery results can be obtained. For frequency sweep measurement, after trimming the sample, the experiment was conducted at 370C, with similar temperature equilibrating conditions. It is carried out in 20 the frequency range of 0.01 Hz to 10 Hz. The frequency sweep provides about the structural conditions of the sample. It is possible to distinguish between a particle solution, an entangled solution (paste) and a three dimensional network (gel) simply by the shape of G', G'' 25 (Pa) and q* (Pa s) Vs f (Hz) curves. Extractables: The extractables in hexane as measured in the Soxhlet extraction technique over 24 hours shows an average value of around 50% for the silicone gels. 30 Extraction procedure The extraction procedure involved five pieces of apparatus: condenser, soxhlet extractor tube, extraction thimble, 250 mL round-bottom flask and a heating mantle. 35 The procedure was carried out as follow: e Accurately weighed the 250mL round bottom (R.B.) flask.

WO 2006/034547 PCT/AU2005/001491 - 21 " Poured approximately 160mL of Hexane into the R.B. flask " Placed a known amount of gel sample into the thimble and the thimble was placed in the soxhlet extractor 5 tube. e The R.B. flask was adapted to the lower end of the soxhlet extractor tube and the condenser was adapted the top end of the tube. " The gel sample was allowed to reflux in Hexane for 22 10 hours. * At the end of the extraction period, the extractables in Hexane were collected in the R.B. flask. " Hexane was removed using rotary evaporator. e The R.B. flask containing the extractable residue was 15 accurately weighed * The amount of extractable residue was calculated from the weight of the gel used for extraction. e The results were report as % weight loss. 20 Basic Strategy The approaches used in the formulation of gels involve initiation of cross-linking by the use of various functionalities of the reactants including unsaturated or double bonds in the PDMS molecule and then making the 25 double bond reactive by using a ultraviolet light source or other techniques. Reactants used for Gel Synthesis The reactants used for synthesising the gels include 30 a di-isocyanate in the form of MDI and different hydroxyl terminated polyols of functionalities varying from 1 to 4. The reactants are set out in Table 1 below: 35 WO 2006/034547 PCT/AU2005/001491 - 22 TABLE 1 Isocyanate Methylene diphenylene isocyanate (MDI) Silicon containing bi- bis(6-hydroxyethoxypropyl) functional macro-diol polydimethylsiloxane (PDMS) of number average molecular weight (Mn) between 900 2100 Tri-functional Polyols e A mixture of silicon containing polyols of different functionalities with an effective functionality of 3 * A silicon containing polyol having an actual functionality of 3 * Tri-functional polyether polyol - Voranol 2070 (Dow Chemicals) of Mn 700 Tetra functional e A mixture of silicon containing polyols of different functionalites with an effective functionality of 4 e A silicon containing polyol having' an actual functionality of 4 e N,N,N'-tri(2-hydroxy propyl)-N'-hydroxy ethyl ethylene diamine, Poly Q 40 800, from Arch Chemicals Inc. of Mn 237 5 Some of the above reactants are available commercially, however, the silicon-containing WO 2006/034547 PCT/AU2005/001491 - 23 multifunctional polyols are not available commercially have been synthesised in Examples A to E below. EXAMPLE A 5 This example illustrates the preparation of a statistical (1:2:1) mixture of a,o-bis(hydroxyethoxypropyl) polydimethylsiloxane (Ia), a-(hydroxyethoxypropyl)-o-(6,7 dihydroxyethoxypropyl) polydimethylsiloxane (Ib), and a,o-bis(6,7- dihydroxyethoxypropyl) polydimethylsiloxane 10 (Ic). 276.00g of octamethylcyclotetrasiloxane (D 4 ) and 125.00g of 1, 1, 3, 3-tetramethyldisiloxane (TMDS) were mixed in a glass bottle containing a magnetic stirrer bar. 0.71g of trifluoromethanesulfonic acid was added to the 15 mixture and the bottle sealed with an air tight cap. The mixture was stirred vigorously for 6 hours at room temperature after which 20g of sodium carbonate was added. The bottle was resealed and stirred over night, after which the sodium carbonate was filtered off to give 20 388.58g of hydride terminated PDMS intermediate. In a three-neck 1L round bottomed flask equipped with a water cooled condensed equipped with a silica gel drying tube, a 250-mL pressure compensating dropping funnel, and a thermometer were placed 310g of the hydride terminated 25 PDMS intermediate given above and 300mL of dry toluene. The mixture was heated, whilst stirring, to 60 0 C. 2mL of a toluene solution of Karstedt's catalyst (containing 36.8 x 106 moles Pt/mL) was added to the mixture. A mixture of 76.64g of 2-allyloxyethanol and 95.29g of 3-allyloxy-1,2 30 propanediol was added drop wise to the mixture from the dropping funnel. The addition was made over a 30 minute period during which time the temperature of the mixture rose to 116 0 C after which the reaction mixture was maintained at 80"C for 18 hours. Silanic hydrogen content 35 was checked by infrared spectroscopy. When no trace was detectable the reaction was considered to be complete. The reaction mixture was allowed to cool to room temperature WO 2006/034547 PCT/AU2005/001491 - 24 and treated with 15g of activated carbon for 18 hours whilst stirring. The reaction mixture was filtered through celite to remove the carbon. The toluene was removed by rotary evaporator at 80 0 C under a reduced pressure of 20 5 torr. The mixture was transferred to a kugelrohr distillation apparatus and stripped of low molecular weight species at 130 0 C under a reduced of 1 x 10- torr to give 338.73g of the statistical (1:2:1) mixture of a,w bis(hydroxyethoxypropyl) polydimethylsiloxane (Ia), a 10 (hydroxyethoxypropyl)-o-(6,7- dihydroxyethoxypropyl) polydimethylsiloxane (Ib), and a,o-bis(6,7 dihydroxyethoxypropyl) polydimethylsiloxane (Ic) as a colourless oil (n=4.893, MW 767). 15 EXAMPLE B This example illustrates the preparation of hydroxyethoxypropyl terminated 9.09%- (hydroxyethoxypropyl methyl siloxane) (dimethyl siloxane) copolymer (Id). 296.64g of D 4 , 30.67g of 1,3,5,7 20 tetramethylcyclotetrasiloxane, and 67.17g of TMDS were mixed in a glass bottle containing a magnetic stirrer bar. 0.61g of trifluoromethanesulfonic acid was added to the mixture and the bottle sealed with 'an air tight cap. The mixture was stirred vigorously for 18 hours at room 25 temperature after which log of sodium carbonate was added. The bottle was resealed and stirred for 6 hours, after which the sodium carbonate was filtered off to give 384.50g of hydride terminated (methylhydrosiloxane) (dimethylsiloxane) copolymer intermediate. 30 In a three-neck 1L round bottomed flask equipped with a water cooled condensed equipped with a silica gel drying tube, a 250-mL pressure compensating dropping funnel, and a thermometer were placed 384.50g of the hydride terminated poly(methylhydrosiloxane) (dimethylsiloxane) 35 copolymer given above and 200mL of dry toluene. The mixture was heated, whilst stirring, to 60*C. 0.6mL of a toluene solution of Karstedt's catalyst (containing 36.8 x WO 2006/034547 PCT/AU2005/001491 - 25 106 moles Pt/mL) was added to the mixture. 203.75g of 2 allyloxyethanol was added drop wise to the mixture from the dropping funnel. The addition was made over a 30 minute period during which time the temperature of the 5 mixture rose to 114 0 C after which the reaction mixture was maintained at 70 0 C for 1 hour. Silanic hydrogen content was checked by infrared spectroscopy. When no trace was detectable the reaction was considered to be complete. The reaction mixture was allowed to cool to room temperature 10 and treated with 20g of activated carbon for 18 hours whilst stirring. The reaction mixture was filtered through celite to remove the carbon. The toluene was removed by rotary evaporator at 80 0 C under a reduced pressure of 20 torr. The mixture was transferred to a kugelrohr 15 distillation apparatus and stripped of low molecular weight species at 100*C under a reduced of 1 x 101 torr to give 484.50g of hydroxyethoxypropyl terminated 9.091 (hydroxyethoxypropyl methyl siloxane) (dimethyl siloxane) copolymer (Id) as a colourless oil (x=9.53, y=1.29,MW 20 1189). EXAMPLE C This example illustrates the preparation of aa',a" (methylsilylidyne)tris-[o[(hydroxyethoxypropyldimethyl 25 silyl)oxy]poly(dimethylsilyene)]] (9Cl) (IIa). 282.38g of D 4 and 170.48g of methyltris (dimethylsiloxy) silane were mixed in a glass bottle containing a magnetic stirrer bar. 0.59g of trifluoromethanesulfonic acid was added to the mixture and 30 the bottle sealed with an air tight cap. The mixture was stirred vigorously for 7 hours at room temperature after which 10g of sodium carbonate was added. The bottle was resealed and stirred overnight, after which the sodium carbonate was filtered off to give 431.10g of hydride 35 terminated a,a',a"-(methylsilylidyne)tris [o[(dimethylhydrosilyl) oxy]poly(dimethylsilyene)]](9Cl) intermediate.

WO 2006/034547 PCT/AU2005/001491 - 26 In a three-neck 1L round bottomed flask equipped with a water cooled condensed equipped with a silica gel drying tube, a 250-mL pressure compensating dropping funnel, and a thermometer were placed 431.10g of the aa',a" 5 (methylsilylidyne) tris- [co [ (dimethylhydrosilyl) oxylpoly(dimethylsilyene)]] (9Cl) intermediate given above and 250mL of dry toluene. The mixture was heated, whilst stirring, to 70 0 C. 0.5mL of a toluene solution of Karstedt's catalyst (containing 0.1mmoles Pt/mL) was added 10 to the mixture. 210.37g of 2-allyloxyethanol was added drop wise to the mixture from the dropping funnel. The addition was made over a 45 minute period during which time the temperature of the mixture rose to 95 0 C after which the reaction mixture was maintained at 70 0 C for 1 15 hour. Silanic hydrogen content was checked by infrared spectroscopy. When no trace was detectable the reaction was considered to be complete. The reaction mixture was allowed to cool to room temperature and treated with 20g of activated carbon for 18 hours whilst stirring. The 20 reaction mixture was filtered through celite to remove the carbon. The toluene was removed by rotary evaporator at 80 0 C under a reduced pressure of 20 torr. The pale yellow product was treated with log of activated carbon for 3 days to remove the residual colour. The oil was filtered 25 through celite to remove the carbon and then transferred to a kugelrohr distillation apparatus and stripped of low molecular weight species at 140 0 C under a reduced of 1 x 101 torr to give 526.25g a,a',a"-(methylsilylidyne)tris [o[(hydroxyethoxypropyldimethylsilyl)oxy]poly 30 (dimethylsilyene)]] (9Cl) (IIa) as a colourless oil (n=1.97,MW 1021). EXAMPLE D This example illustrates the preparation of aa',a", 35 a,''- tetrakis-[o[(hydroxyethoxypropyldimethylsilyl) oxy]poly(dimethylsilyene)]]silane(9Cl) (IIb).

WO 2006/034547 PCT/AU2005/001491 - 27 33.80g of D 4 and 75.00g of tetrakis(dimethylsiloxy) silane were mixed in a glass bottle containing a magnetic stirrer bar. 0.128g of trifluoromethanesulfonic acid was added to the mixture and the bottle sealed with an air 5 tight cap. The mixture was stirred vigorously for 4 days at room temperature after which log of sodium carbonate was added. The bottle was resealed and stirred for 6 hours, after which the sodium carbonate was filtered off to give 91.92g of hydride terminated tetrakis 10 (polydimethylsiloxane) silane intermediate. In a three-neck 1L round bottomed flask equipped with a water cooled condensed equipped with a silica gel drying tube, a 250-mL pressure compensating dropping funnel, and a thermometer were placed 91.92g of the hydride terminated 15 methyltris(polydimethylsiloxane)silane intermediate given above and 100mL of dry toluene. The mixture was heated, whilst stirring, to 60 0 C. 0.5mL of a toluene solution of Karstedt's catalyst (containing 0.1mmoles Pt/mL) was added to the mixture. 98.42g of 2-allyloxyethanol was added drop 20 wise to the mixture from the dropping funnel. The addition was made over a 30 minute period during which time the temperature of the mixture rose to 104 0 C after which the reaction mixture was maintained at 80 0 C for 1 hour. Silanic hydrogen content was checked by infrared 25 spectroscopy. When no trace was detectable the reaction was considered to be complete. The reaction mixture was allowed to cool to room temperature and treated with log of activated carbon for 18 hours whilst stirring. The reaction mixture was filtered through celite to remove the 30 carbon. The toluene was removed by rotary evaporator at 80 0 C under a reduced pressure of 20 torr and then transferred to a kugelrohr distillation apparatus and stripped of low molecular weight species at 120 0 C under a reduced of 1 x 101 torr to give 133.27g of aa',a", a''' 35 tetrakis-[w[(hydroxyethoxypropyldimethylsilyl) oxy]poly(dimethylsilyene)]]silane(9Cl) (IIb) as a colourless oil (n=1.75, MW 986).

WO 2006/034547 PCT/AU2005/001491 - 28 EXAMPLE E This example illustrates the preparation of hydroxyethoxypropyl terminated 3.55 %-( methylmethacryloxypropyl methyl siloxane) (dimethyl 5 siloxane) copolymer (Ie). 25.22g of 1, 3, 5, 7-tetramethylcyclotetrasiloxane, and 400.00g of of a,o-bis(hydroxyethoxypropyl) polydimethylsiloxane (MW 954) were mixed in a glass bottle containing a magnetic stirrer bar. 1.96g of 10 trifluoromethanesulfonic acid was added to the mixture and the bottle sealed with an air tight cap. The mixture was stirred vigorously for 3.5 hours at room temperature after which 20g of sodium carbonate was added. The bottle was resealed and stirred for over night, after which the 15 sodium carbonate was filtered off to give 417.78g of hydroxyethoxypropyl terminated (methylhydrosiloxane) (dimethyl siloxane) copolymer intermediate. In a three-neck 3L round bottomed flask equipped with a water cooled condensed equipped with a silica gel drying 20 tube, a 250-mL pressure compensating dropping funnel, and a thermometer were placed 417.78g of hydroxyethoxypropyl terminated (methylhydrosiloxane) (dimethyl siloxane) copolymer intermediate given above and 300mL of dry toluene. The mixture was heated, whilst stirring, to 60 0 C. 25 0.GmL of a toluene solution of Karstedt's catalyst (containing 66.04 x 106 moles Pt/mL) was added to the mixture. 70.48g of allylmethacrylate was added drop wise to the mixture from the dropping funnel. The addition was made over a 20 minute period during which time the 30 temperature of the mixture rose to 72 0 C after which the reaction mixture was maintained at 70 0 C for 18 hour. Silanic hydrogen content was checked by infrared spectroscopy. When no trace was detectable the reaction was considered to be complete. The reaction mixture was 35 allowed to cool to room temperature and treated with 20g of activated carbon for 18 hours whilst stirring. The reaction mixture was filtered through celite to remove the WO 2006/034547 PCT/AU2005/001491 - 29 carbon followed by filtration through a 0.2pm Teflon filter. 0.094g of MEHQ was added to the toluene solution and then the toluene was removed by rotary evaporator at 60*C under a reduced pressure of 20 torr. The mixture was 5 transferred to a kugelrohr distillation apparatus and stripped of low molecular weight species at 50 0 C under a reduced of 1 x 10- torr for 20 minutes, this process was repeated 3 times to give 403.70g of hydroxyethoxypropyl terminated 3.55%- (methylmethacryloxypropyl methyl 10 siloxane) (dimethyl siloxane) copolymer (Ie) as a pale yellow oil (x=9.56,y=0.352, MW 1039). The synthetic routes for Examples A to E are shown in Scheme 1 below.

WO 2006/034547 PCT/AU2005/001491 - 30 CH3 CH, H , O H hydride terminated PDMS intermediate HOHO OH CH3 C Ha CH O OO O [ OH HO H (1a) OH CUN CH3 CHI O OH OH, CH, HO o S, I ~-~0 (b OH H3OH, ]OH OH OH OH L~Cra CH3 C H nO I -{ {KNIH (mtyhdrslxn)(dimthylioxn) intermediat OH 0 CH, iCH3 OHl, CH, (Id) Sy WO 2006/034547 PCT/AU2005/001491 -31 Me Ie I be u,c&,c"-(methylsilylidyne)tris Me20l esi 0[ci4(dimethylhydrosilyl)oxy]poly(dimethylsilyene I )Ii1(9G1) intermediate. 5nMe2n HM (e 2 S 'i M S Me Me I Siwe M2S' Me2 O), SiSe 2 K (Iha) 0 0 0 HO fo% OH OH Me Me 2 SI iMe cL,Q' ,"-(methylsilylidyne)tris Me2S! e2Si o(04(dimethyllhydrosilyl)oxy]poly(dimethylsilyene f..i~e)( )]](9CI) intermediate. H n"H2i Me o 0 0 HO0f OH O WO 2006/034547 PCT/AU2005/001491 - 32 H I CH H hydroxyethoxypropyl terminated Ho H (methylhydrosiloxane)(dimethyl IH - H CH siloxane) copolymer intermediate

OH

3 0 0 CH[ CH, ,I SI 0 CH, . CH CH CH CH CL H

((H

3

)

2 (H3C)28i O O- i H 3 OH1 3

(OH

3

)

2 CH, CHI H I H hydride terminated PDMS intermediate

CH.

3 CHa n

OH

3

CH

3

CH

3 si slOH (Ia) HO O L OH CV13 CHa - CH3 n

CH

3

CH

3

CH

3 SI O", -, O , HOH O L H (Ib) OH CN3 CHa - CH,

CH

3

CH

3

CH

3 HO O O OH (Ie) OH OH 3 CHa - CH OH Scheme 1 WO 2006/034547 PCT/AU2005/001491 - 33 Gel Synthesis The gels were synthesised using different processes: One Shot Process - All reactants of the gel were added and mixed together. 5 Two Stage Process - The gel synthesis in this process occurred with the formation of a di-functional isocyanate terminated pre-polymer in the first stage followed by the addition of the hydroxyl terminated multifunctional polyols. 10 Slow Addition Process - All the reactants of the gel were mixed in together but the polyols are added to the diisocycanate in a drop wise fashion. Sequenced Slow Addition - This is similar to the slow addition process except that certain polyol 15 functionalities are added before the others. UV Curing - For the process of curing with ultra-violet light, a formulation containing an unsaturation in the polyol segment was prepared. A photoinitiator was added to the mixture and this in the presence of an externally 20 supplied, long wavelength, ultraviolet radiation resulted in the formation of a cross linked gel. EXAMPLE 1: ONE SHOT PROCESS 4, 4'-Diphenylmethane diisocyanate (MDI) was 25 accurately weighed in a paper cup. In a Schott bottle, a mixture of polyol adduct viz. polyethylene monoalcohol, polydimethylsiloxane (Mw 1000 & 2000), voranol-2070 and N, N, N' -tri (2 -hydroxypropyl) -N' -hydroxyethylethylenediamine (Poly Q 40-800) was added to the MDI in bulk and stirred 30 for 4 minutes and placed in the oven at 70 0 C overnight to cure. The formulations, with the parts by weight (PBW) of all the reactants, stoichiometry, average functionality and the results of the extractables are set out in Table 2 35 below.

WO 2006/034547 PCT/AU2005/001491 - 34 Table 2 NCO/OH MDI Diol Triol Tetra- Ext Fave 01 (%) 0.01 10 0.6 20.79 PDMS-2000 87 3 14.2 2.77 - 10 0.7 24.25 PDMS-2000 87 3 15.6 2.74 - 10 0.5 16.76 PDMS-2000 82 3 31.2 2.8 - 15 0.6 20.11 PDMS-2000 82 3 30.5 2.76 - 15 0.4 21.55 PTMO 87 3 15.1 2.75 421.8 273 10 0.4 21.39 PDMS-1000 85 3 7.82 2.74 407 122 12 0.4 22.23 PTMO 85 3 21.17 2.71 565.2 113 20 0.4 20.57 PDMS-1000 80 2.75 13.4 2.72 881.3 192 16 1 32.32 PDMS-1000 10 2 4.66 2.19 - 1_ 1 90 1 1 1 5 EXAMPLE 2: TWO STAGE PROCESS The gels were prepared in two steps; preparation of prepolymer with difunctional polyols to get desired NCO index (NCO/OH) followed by reaction of pre-polymer with 10 multifunctional polyols to get desired stoichiometric imbalance "r". The ratio of the reactants "r" can be compared to the stoichiometry NCO to OH group: r = Z f. n/Af/ g. n]3 15 WO 2006/034547 PCT/AU2005/001491 - 35 in which f and nf are the functionality and number mole of NCO, g and nB, are the functionality and the total number mole of the OH group materials such as polydimethylsiloxane (Mw 2000), 1,4-butanediol, voranol-2070 and N,N,N'-tri(2 5 hydroxypropyl)-N'-hydroxyethylethylenediamine (Poly Q 40 800). Preparation of Prepolymer The PDMS (MW 2000) was degassed at 70 0 C under vacuum 10 prior to synthesis. Molten MDI was placed in a three necked round bottom flask which was fitted with a mechanical stirrer and nitrogen inlet. The flask was placed in an oil bath set at 70 0 C. The degassed PDMS was added to MDI and was stirred by mechanical stirrer under a 15 nitrogen atmosphere for 2 hours. After completion the addition of PDMS, the temperature of the oil bath was increased to 80 0 C. The prepolymer stirred at 100 rpm under nitrogen atmosphere for 2 h. The prepolymer was degassed for 1 hour under 20 vacuum. Prepolymers with 2% and 4% free NCO contents were made. The free NCO% is based on the ratio of excess NCO functional group by the amount of prepolymer in weight percentage. The excess NCO functional group is determined by the amount of excess MDI which contains 33.6% by weight 25 NCO group. The excess MDI is the amount which remains after reaction with hydroxyl terminated PDMS. Reaction with multifunctional polyol A mixture of polyol adducts viz. 1, 4-butanediol 30 (BDO)/bis-hydroxy butyl tetramethyldisiloxane (BHTD), voranol-2070 and N, N, N'-tri (2-hydroxypropyl)-N' hydroxyethylethylenediamine (Poly Q 40-800) stirring at 70*C. The adduct was then added to the prepolymer and allowed to mix using a high shear mechanical stirrer for 4 35 minutes at 5000rpm. The polymer was transferred into the oven and allowed to cure in a nitrogen blanketed oven overnight at 70*C.

WO 2006/034547 PCT/AU2005/001491 - 36 The parts by weight (PBW) of the reactants in the formulations, stiochiometries, average functionality and extractables (%) are given in Table 3, 4 and 5 below. The amount of multifunctional polyols is based on 1Og of 5 prepolymer. Table 3 Pre-polymer MDI Diol Triol Tetra-ol r * NCO/OH Voranol Poly-Q Fave 0.01 10 2.9 37.80 50.43 0 0.5 2.64 - 2.9 37.80 35.42 0 0.75 2.52 - 2.9 37.80 29.5 0 0.9 2.45 - 37.80 BDO BHTD 2.9 37.80 10 111.5 0 0.35 2.47 - 2.9 37.80 10 111.5 0 0.35 2.56 - 2.9 37.80 112 5 0.35 2.67 - 2.9 37.80 95 10 0.35 2.75 - 2.9 37.80 115 4 0.35 2.71 - 2.9 37.80 5 117 10 0.35 2.62 Table 4 Pre-polymer MDI Triol Tetra-ol r Extractables Fave. 7* NCO/OH Voranol Poly-Q (% ) 0.01 0.01 2.2 28.23 49.5 0 0.6 27.1 2.45 - 2.2 28.23 67.3 1.5 0.45 12.24 2.58 - 2.2 28.23 58.1 1.5 0.5 13.94 2.55 - 2.2 28.23 52.42 1 0.55 21.54 2.52 - 2.2 28.23 50.75 1.5 0.55 28.01 2.52 - 2.2 28.23 50.82 0.5 0.575 19.28 2.48 - 2.2 28.23 49.17 1 0.575 14.86 2.49 - 2.2 28.23 54.11 0.75 0.55 16.15 2.5 - 10 WO 2006/034547 PCT/AU2005/001491 - 37 Table 5 Pre-polymer MDI Triol Tetra-ol r Extractables F,,,, * NCO/OH Voranol Poly-Q (%) 0.01 0.01 2.2 28.23 66.7 1.5 0.45 21.96 2.58 - 2.2 28.23 60 0.75 0.5 29.09 2.53 - 2.2 28.23 52.7 0.75 0.55 19.5 2.5 - 2.2 28.23 51.87 1 0.55 16.17 2.51 - 2.2 28.23 50.2 1.5 0.55 23.74 2.52 - 2.2 28.23 47.3 0.5 0.6 13.83 2.46 - 2.2 28.23 42.97 1 0.625 15.16 2.46 - 2.2 28.23 49.93 0.75 0.575 17.71 2.49 - 2.2 28.23 47.73 1.5 0.575 18.8 2.51 - 2.2 28.23 46.9 0.75 0.6 9.82 2.47 - 2.2 28.23 64.1 1 0.6 12.33 2.48 - 2.2 28.23 44.48 1.5 0.6 20.1 2.49 - EXAMPLE 3: SLOW ADDITION PROCESS 4, 4'-Diphenylmethane diisocyanate (MDI) was 5 accurately weighed in a Schott bottle equipped with a magnetic stirrer and placed in an oil bath at 800C.- In another Schott bottle, a mixture of polyol adduct viz. polydimethylsiloxane (Mw 1000-1300), hydroxyethoxypropyl terminated 9.09%- (hydroxyethoxypropyl methyl siloxane) 10 (dimethyl siloxane) copolymer (Mw 1210) /aoa',ca" (methylsilylidyne) tris- [[ (hydroxyethoxypropyldimethylsilyl) oxylpoly (dimethylsilyene)l] (Mw 1000-5000) and a,co-bis(6,7 dihydroxyethoxypropyl) polydimethylsiloxane (Mw 400-500)/ 15 a,a',a", x'''- tetrakis [w[(hydroxyethoxypropyldimethylsilyl) oxy]poly (dimethylsilyene)]]silane (Mw 1400-1600) placed in an oil bath at 80 0 C. The adduct was added to MDI at the rate of WO 2006/034547 PCT/AU2005/001491 - 38 iml/min with constant stirring under a nitrogen atmosphere till the viscosity built up. With an increase in viscosity, the addition of adduct was increased to 2ml/min until the viscosity increased again. The highly viscous 5 solution was then transferred to a paper cup and placed in the oven at 70 0 C overnight to cure. The parts by weight (PBW) of the reactants in the formulations, stoichiometries, average functionalities and extractables (%) are given in Table 6 below: 10 Table 6 NCO/O MDI Diol Triol Tetra-ol Extraction Fave 11* H PDMS- Voranol PoIyQ (%) 1000 0.01 0.01 0.75 21.66 90 10 0 29.34 2.1 3596 331 0.8 32.11 90 10 0 17.79 2.1 - 0.7 20.27 95 6 0.5 30 2.10 2052 182 0.7 20.52 95 7.5 0.25 30.96 2.10 1304 292 Si Triol Si-tet MW MW 1151 430 0.7 19.62 75 25 0.2 19.58 2.18 1705 113 0.7 19.73 72.5 27.5 0.2 22.46 2.19 - PDMS- Si Triol 1000 MW 1151 0.7 19.78 75 25 0.4 18.56 2.18 - 0.7 20.53 80 25 0.2 18.27 2.17 1189 136 0.7 19.39 80 20 0.2 2.15 - Si-tet MW 1140 WO 2006/034547 PCT/AU2005/001491 - 39 Table 6 cont. 0.7 19.51 75 25 0.2 22.22 2.17 2900 243 Si-tet MW 1519 0.7 19.50 75 25 0.2 16.8 2.17 839 261 Si-tet MW 1519 0.7 20.42 80 25 0.2 20.75 2.16 716 173 Si-tet MW 1140 0.7 20.43 80 25 0.2 21.14 2.16 2067 213 Si-Triol Si-tet MW121 MW 0 1519 T shape 0.7 20.14 80 25 0.2 25.97 2.16 3244 159 Si-tet MW 430 0.7 20.26 80 25 0.2 28.57 2.16 1835 212 0.7 19.17 80 20 0.2 23.96 2.14 1313 228 Si-tet MW 1519 0.7 19.06 80 20 0.2 12.18 2.13 605.6 196 Si-tet MW 430 0.7 19.71 80 22.5 0.2 24.46 2.15 356.2 290 Si-tet MW 1519 0.7 19.60 80 22.5 0.2 19.78 2.14 878.7 120 Si-tet MW 430 0.7 18.63 80 17.5 0.2 2.13 1435 160 WO 2006/034547 PCT/AU2005/001491 - 40 EXAMPLE 4: SEQUENCED SLOW ADDITION PROCESS 4, 4'-Diphenylmethane diisocyanate (MDI) was accurately weighed in a Schott bottle equipped with a 5 magnetic stirrer and placed in an oil bath at 700C. In another Schott bottle, a mixture of polyols viz. polydimethylsiloxane (Mw 1000/2000) and voranol-2070 placed in an oil bath at 700C. The mixture of polyols was added to MDI with constant stirring by magnetic stirrer in 10 5 minutes intervals (1ml/5min). N, N, N'-tri (2 hydroxypropyl) -N' -hydroxyethylethylenediamine (Poly Q 40 800) was added finally and continued stirring until the viscosity increases. The highly viscous solution was then transferred to a paper cup and placed in the oven at 70 0 C 15 overnight to cure. The results are shown in Table 7 below. Tabl-e 7 NCO/OH MDI PDMS Triol Tetra- Ext (%) F.. 1* 01 0.01 0.01 0.3 5.76 24.7 75 0.3 30.9 2.72 - 0.3 12.93 24.9 75 0.1 24.1 2.71 - 0.7 22.05 80 20 0 21.24 2.2 2438 124 20 4, 4'-Diphenylmethane diisocyanate (MDI) was accurately weighed in a Schott bottle equipped with a magnetic stirrer and placed in an oil bath at 700C. The addition of polyols mixture was added in the following manner: i) polydimethylsiloxane (Mw 1000) was added first; 25 ii) a mixture of polyethylene monoalcohol and voranol-2070 was added last. The polyols were added to MDI while stirring by magnetic stirrer in five minute interval (1ml/5min). The resulting reaction mixture was allowed to stir until the viscosity increases. The highly viscous WO 2006/034547 PCT/AU2005/001491 - 41 solution was then transferred to a paper cup and placed in the oven at 700C overnight to cure. The results are shown in Table 8 below: 5 Table 8 NCO/OH MDI PDMS Triol Mono- Fave. 1000 ol 1.7 15.41 34.59 11.95 11.95 2.16 4, 4'-Diphenylmethane diisocyanate (MDI) was accurately weighed in a Schott bottle equipped with a magnetic stirrer and placed in an oil bath at 70 0 C. The 10 addition of polyols mixture was added in the following manner: i) polydimethylsiloxane (Mw 1000) was added first; ii) voranol-2070 was added and iii) polyethylene monoalcohol was added finally. The polyols were added to MDI while stirring by magnet stirrer in 5 minute interval 15 (1ml/5min). The resulting reaction mixture was allowed to stir until the viscosity increases. The highly viscous solution was then transferred to a paper cup and placed in the oven at 70 0 C overnight to cure. The results are shown in Table 9 below: 20 Table 9 NCO/OH MDI PDMS Triol Mono- Fave. 11* 1000 01 0.01 0.01 1.7 15.41 34.59 11.95 11.95 2.16 - 4, 4'-Diphenylmethane diisocyanate (MDI) was accurately weighed in a Schott bottle equipped with a 25 magnet stirrer and placed in an oil bath at 70 0 C. The addition of polyols mixture was added in the following WO 2006/034547 PCT/AU2005/001491 - 42 manner: i) 50%wt of polydimethylsiloxane (Mw 1000) was added first; ii) a mixture of 50%wt of polydimethylsiloxane (Mw 1000), and 50%wt of voranol-2070 was added second iii) a mixture of 50%wt of voranol-2070 5 and 100%wt of polyethylene monoalcohol was added finally. The polyols were added to MDI while stirring by magnet stirrer in 5 minute intervals (1ml/5min). The resulting reaction mixture was allowed to stir until the viscosity increases. The highly viscous solution was then 10 transferred to a paper cup and placed in the oven at 700C overnight to cure. The results are shown in Table 10 below. Table 10 NCO/OH MDI PDMS Triol Mono- Fave. r 1000 ol 0.01 0.01 1.3 12.70 37.30 8.00 4.00 2.14 - 15 EXAMPLE 5: UV CURING UV-curing systems rely upon externally-supplied, long wavelength, ultraviolet radiation to produce free radicals within the material. UV light does not usually have 20 sufficient energy levels to interact with the reactive groups of the molecules and generate free radicals. When a photoinitiator is added to the formulation, which when exposed to UV of a specific wavelength, absorbs the UV light and produces free radicals which start the cross 25 linking process and results in virtually instant polymerisation. In the free radical formulation the reaction will only continue as long as the formulation is subjected to the UV light. The appropriate amount of synthesised 30 hydroxyethoxypropyl terminated 3.55 % (methylmethacryloxypropyl methyl siloxane) (dimethyl siloxane) copolymer of Mw 1039 was accurately weighed in a WO 2006/034547 PCT/AU2005/001491 - 43 Petri dish and mixed thoroughly using a spatula with required weight percentage (w/w) of photoinitiator (Irgacure 819) (varying percentage from 0.25 % - 2 % w/w) in -1ml of toluene and placed in the UV chamber (UV lamp 5 5mW, 366 nm) for 48h to cure. In another example using UV curing, the molten MDI was placed in a three necked round bottom flask which was fitted with a mechanical stirrer and nitrogen inlet. The flask was placed in an oil bath set at 60WC. The 10 synthesised hydroxyethoxypropyl terminated 3.55 % (methylmethacryloxypropyl methyl siloxane) (dimethyl siloxane) copolymer of Mw 1039 was added to MDI and stirred by mechanical stirrer under a nitrogen atmosphere for 2 h and was degassed for 1 h under vacuum. The chain 15 extended polymer accurately weighed in a petri dish and mixed thoroughly using a spatula with required weight percentage (w/w) of photoinitiator (Irgacure 819) (varying percentage from 0.25 % - 2 % w/w) in -1ml of toluene and placed in the UV chamber (home built) (UV lamp 5mW, 366 20 nm) for 48h to cure. The results are shown in Table 11 below. Table 11 NCO/OH MDI Vinyl double Fave. Y* (Moles) bonded diol (Moles) 0.01 0.01 1.73 0.1144 0.066 2.89 - 25 In another example using UV curing, the molten MDI was placed in a three necked round bottom flask which was fitted with a mechanical stirrer and nitrogen inlet. The flask was placed in an oil bath set at 600C. The synthesised hydroxyethoxypropyl terminated 3.55 % 30 (methylmethacryloxypropyl methyl siloxane) (dimethyl siloxane) copolymer of Mw 1039 was added to MDI and stirred by mechanical stirrer under a nitrogen atmosphere WO 2006/034547 PCT/AU2005/001491 44 for 2 h and was degassed for 1 h under vacuum. PDMS 1000/2000 was then added to prepolymer and allowed to mix using a shear mechanical stirrer for 4 min at 5000 rpm. The polymer then accurately weighed for different 5 formulation in a petri dish and mixed with required weight percentage (w/w) of photoinitiator (Irgacure 819) (varying percentage from 0.25 % - 2 % w/w) in -lml of toluene thoroughly using a spatula and placed in the UV chamber (home built) (UV lamp 5mW, 366 nm) for 48h to cure. 10 Results are shown in Table 12 below. Table 12 NCO/OH MDI Vinyl double PDMS Fave. 11* (Moles) bonded diol 1000 (Moles) (Moles) 0.01 0.01 0.67 0.132 0.066 0.132 2.273 - EXAMPLE 6: CYTOTOXICITY STUDY USING THE ISO-ELUTION METHOD 15 Purpose To evaluate the biocompatibility of a test article extract using an in vitro mammalian cell culture test. This study is based on the requirements of the 20 International Organization for Standardization 10993; Biological Evaluation of Medical Devices, Part 5: Tests for Cytotoxicity: in vitro Methods. Ratio of Test Material to Extraction Vehicle: 25 Material thickness less than 0.5 mm - ratio of 60 cm 2 :10 ml (based on the USP ratio 120 cm 2 :20 ml) Extraction Vehicles: Single strength Minimum Essential Medium supplemented 30 with 5% serum and 2% antibiotics (1X MEM) WO 2006/034547 PCT/AU2005/001491 - 45 Extraction Conditions: The extraction conditions shall attempt to exaggerate the clinical use conditions so as to define the potential toxicological hazard; however, they should not in any -5 instance cause physical changes such as fusion or melting, which results in a decrease in the available surface area. A slight adherence of the pieces can be tolerated. Control Articles: 10 Negative Control: high density polyethylene, will be prepared based on a ratio of 60 cm 2 :20 ml extraction vehicle. A single preparation of the material will be made, and will be extracted using the same conditions as described for the test article. 15 Reagent Control: A single aliquot of the extraction vehicle without test material will be prepared using the same conditions as described for the test article. Positive Control: Current positive control material*, tin stabilized at polyvinylchoride, will be prepared based 20 on a ratio of 60 cm 2 :20 ml extraction vehicle. A single preparation of the material will be made and extracted at 37 0 C for.24 hours. Serial dilutions will be prepared for an end-point titration procedure. 25 *NOTE: The current positive control material has been qualified as an acceptable replacement for the USP recommended control material. Test System and Justification: 30 Mammalian cell culture monolayer, L-929, mouse fibroblast cells, (ATCC CCL 1, NCTC Clone 929, of strain L, or equivalent source), will be used. In vitro mammalian cell culture studies have been used historically to evaluate cytotoxicity of biomaterials and medical devices 35 (Wilsnack, et al., 1973).

WO 2006/034547 PCT/AU2005/001491 - 46 Test System Management: L-929, mouse fibroblast cells, (ATCC CCL 1, NCTC Clone 929, of strain L, or equivalent source) will be propagated and maintained in open wells containing single 5 strength Minimum Essential Medium supplemented with 5% serum and 2% antibiotics (lx MEM) in a gaseous environment of 5% carbon dioxide (C0 2 ). For this study, 10 cm 2 wells will be seeded, labeled with passage number and date, and incubated at 37 0 C in 5% CO to obtain confluent monolayers 10 of cells prior to use. Aseptic procedures will be used in the handling of the cell cultures following approved Standard Operating Procedures. Methods and Route of Administration: 15 Each culture well will be selected which contains a confluent cell monolayer. The growth medium in triplicate cultures will be replaced with 2 ml of the test extract. Similarly, triplicate cultures will be replaced with 2 ml of the reagent control, negative control extract and the 20 undiluted and each titer of the positive control. Each well will be incubated at 37 0 C in 5% CO 2 for 48 hours. Following incubation, the cultures will be examined microscopically (100X) to evaluate cellular characteristics and percent lysis. 25 Evaluation Criteria and Statistics: The confluency of the monolayer will be recorded as (+) if present and (-) if absent. In addition, the color of the test medium will be observed and compared to the 30 negative control medium. Each culture well will be evaluated for percent lysis and cellular characteristics using the following criteria: 35 WO 2006/034547 PCT/AU2005/001491 - 47 Grade Reactivity Observations 0 None Discrete intracytoplasmic granules No lysis I Slight Not more than 20% of the cells are round, Not more than 20% lysis loosely attached, and without intracytoplasmic granules 2 Mild Not more than 50% of the cells are round Not more than 50% lysis. and devoid of intracytoplasmic granules 3 Moderate Not more than 70% of the cell monolayer Not more than 70% lysis contains rounded cells 4 Severe Nearly complete destruction of the cell Greater than 70% lysis monolayer For the test to be valid, the reagent control and the negative control must have a reactivity of none (grade 0) 5 and the positive control must be a grade 3 or 4. The test sample meets the requirements of the test if the biological response is less than or equal to grade 2 (mild). The test will be repeated if the controls do not perform as anticipated and/or if all three test wells do 10 not yield the same conclusion. References for Example 6: 21 CFR 58 (GLP Regulations). 15 International Organization for Standardization 10993: Biological Evaluation of Medical Devices, Part 5: Tests for Cytotoxicity: in vitro Methods. 20 United States Pharmacopeia (USP), current edition. Wilsnack, R. E., "Quantitative Cell Culture Biocompatibility Testing of Medical Devices and Correlation to Animal Tests" Rio materials, Medical 25 Devices and Art/Icfal Organs 4 (1976): 235-261.

WO 2006/034547 PCT/AU2005/001491 - 48 Wilsnack R. B., P.S. Meyer and 3.0. Smith, 'Human Cell Culture Toxicity Testing of Medical Devices and Correlation to Animal Tests,' Biomaterials, Medical Devices and Artificial Organs 1(1973): 543-562. 5 EXAMPLE 7: SENSITIZATION STUDY IN THE GUINEA PIG (Maximization Method) Purpose of the Study: 10 The objective of the maximization test in the guinea pig is to identify the potential for dermal sensitization. The Magnusson and Kligman method has been effective in identifying a variety of allergies. This study will be based on the requirements of the International 15 Organization for Stanardization 10993: biological Evaluation of Medical Devides, Part 10: Tests for Irritation and Sensization. Test Article: 20 The sample will be prepared as follows: 1. Ratio of test article extraction vehicle: Material thickness less than 0.5mm - ratio of 120cm 2 20 ml 25 2. Extraction vehicle: 0.9% sodium chloride USP solution (SC) cottonseed oil, NF (CSO) 30 3. Extraction condition: 37 0 C, 72 hours (±2 hours) Control Article: The vehicle used to prepare the extract will be 35 prepared in the same manner as the extract (but without test article) serve as the control measure. Untreated skin WO 2006/034547 PCT/AU2005/001491 - 49 will serve as an additional control reference for scoring dermal reactions during the challenge phase. Test System: 5 Species: Guinea pig (Cavia porcellus) Strain: Crl:(HA) BR Source: Charles River Laboratories Sex: No particular gender is 10 prescribed for this test. If females are used) they will be nulliparous and not pregnant. Body Weight Range: 300-500 grams at identification Age: Young adults 15 Acclimation Period: Minimum 5 days Number of Animals: 15 (per extract) Identification Method: Ear punch Justification of Test System: 20 The Hartley albino guinea pig has been used historically for sensitization studies (Magnusson and Kilgman, 1970). The guinea pig is believed to be the most sensitive animal model for this type of study. The susceptibility of the Hartley strain to a known 25 sensitizing agent, 1-chloro-2,4-dinitrobenzene (DNCB) has been substantiated with this method. Test and Control Article Preparation: Fresh extracts will be prepared at each phase of the 30 study as previously indicated (see Test Article). If the test material is suitable for patching, a topical application of the test sample (2 cm x 2 cm patch) will be used at the challenge. The vehicle used to prepare the extract will be prepared in the same manner as the extract 35 (but without test article) to serve as the control measure.

WO 2006/034547 PCT/AU2005/001491 - 50 Methods and Route of Administration: The day prior to treatment, 15 guinea pigs per extract (10 test, 5 control) will be weighed and identified. The fur from the dorsoscapular area of the 5 animals will be removed with an electric clipper. Induction I: Three pair of intradermal injections will be administered to the animals within an approximate 2 cm x 4 10 cm area the dorsoscapular region as follows: Control Animals: a. 0.1 ml of 50:50 (v/v) mixture of Freund's Complete Adjuvant (FCA) and the chosen vehicle 15 b. 0.1 ml of vehicle c. 0.1 ml of a 1:1 mixture of the 50:50 (v/v) FCA and the vehicle Test Animals: 20 a. 0.1 ml of 50:50 (v/v) mixture of FCA and the chosen vehicle b. 0.1 ml of test extract c. 0.1 ml of a 1:1 mixture of the 50:50 (v/v) FCA and the test extract 25 To minimize tissue sloughing the 'a" and "c' injections will be slightly deeper than "b'. Site 'c" will be injected slightly more caudal than site 'b". 30 Induction II: Six days later, the injection sites will be clipped free of fur again and treated with 0.5 to 1 g of a 10% (w/w) sodium lauryl sulfate (SLS) suspension prepared by mixing the powdered SLS with petrolatum. The day following 35 the SLS treatment, any remaining SLS residue will be gently wiped from the area with gauze.

WO 2006/034547 PCT/AU2005/001491 - 51 A 2 cm x 4 cm filter paper patch (3MM, Whatman), saturated with 0.3 ml of the extract preparation or vehicle, will be applied over the same injection area and secured with a nonreactive tape. The trunk of each animal 5 will then be wrapped snugly with an elastic band for 48 hours (+2 hours). Challenge: At 13 days after unwrapping induction II wraps, the 10 fur will be clipped from the sides and flanks of all guinea pigs. On the following day, a nonwoven cotton disk backed by a flexible chamber (e.g. Hill Top Chamber) and semiocclusive hypoallergenic tape, will be saturated with 0.3 ml of freshly prepared test material extract and 15 applied to the right flank or dorsum of each animal. In addition, the vehicle control will be patched to the left flank or dorsum of each animal. An approximate 2 cm x 2 cm section of test material itself (if appropriate) will be applied to the right flank. 20 The trunk of each animal will be wrapped for 24 hours (±2 hours). At patch removal the sites will be wiped with gauze. At 24 hours (± 2 hours) after patch removal, the challenged sites and surrounding area will be shaved. The sites will be examined for signs of ahy irritation or 25 sensitization reaction, as indicated by erythema and edema at a minimum of 2 hours and a maximum of 4 hours following the shave and at 48 (±2 hours) and 72 (±2 hours) hours after removal of the dressings. Prior to scoring, each site will be wiped gently with a 35% isopropyl alcohol 30 gauze sponge. Should the original challenge results prove to be equivocal, the animals may be rechallenged with a fresh test extract and vehicle control approximately 7 days after the first challenge patch application. The 35 rechallenge will be conducted in the same manner as the challenge but at virgin sites on the opposite flank. After WO 2006/034547 PCT/AU2005/001491 - 52 the test is completed, all animals will be handled in accordance with approved procedures. Evaluations and Statistics: 5 Daily challenge scores for reactions will be recorded at 24, 48 and 72 hours after patch removal in accordance with the following Table: ERYTHEMA (ER) EDEMA (ED) Reaction Numerical Grading Reaction Numerical Grading No erythema 0 No edema 0 Slight erythema 1 Slight edema I Well-definded erythema 2 Well-defined edema 2 Moderate erythema 3 Moderate edema 3 Severe erythema to 4 Severe edema 4 slight eschar formulation 10 Any other observation relating to the site will be footnoted. The responses will be compared within the test animal group and between test and control conditions. Control conditions are (1) the vehicle control solution on the 15 test animals and (2) the test extract, control solution and biomaterial (if applied) on the control animals. In the final analysis of data, consideration will be given to the overall pattern, intensity, duration, and character of reactions of the test as compared to the 20 control conditions. Statistical manipulation of data is not applicable to this study. An effect interpreted as "irritation" is generally observed at 24 hours, but diminishes thereafter, and is also concurrently present as a transient response in the control animals. Closed 25 patches typically show maximal sensitization readings 48 to 72 hours after patch removal in the test condition but not in the control condition. Grades of 1 or greater in the test group generally indicate sensitization, provided WO 2006/034547 PCT/AU2005/001491 - 53 that grades of less than 1 are observed on the control animals. If grades of 1 or greater are noted on control animal then the reactions of test animals which exceed the most severe control reaction are considered to be due to 5 sensitization. Background or artifactual reactions (e.g., from fur clipping, patch chamber edge, nonspecific FCA effects) will not be considered as evidence of a sensitization response. The treatment with FCA and occlusive dressings 10 may lower the threshold level for skin irritation. If the test group has a greater number of animals showing responses that are not greater than the control animals, a rechallenge may be conducted. The rechallenge will be conducted approximately 7 days after the first 15 challenge at virgin sites on the opposite flank of the animals. Absence of dermal response at rechallenge may nullify earlier findings. Recurring observations in at least one of the same animals verify earlier findings. 20 References for Example 7: 21 CFR 58 (GLP Regulations). Guide for the Care and Use of Laboratory Animals, 25 Institute for Laboratory Animal Research, National Academy of Sciences (Washington: National Academy Press, 1996). International Organization for Standardization 10993: Biological Evaluation of Medical Devices, Part 10: Tests 30 for Irritation and Sensitization. Magnusson, B. and A. Kligman, Allergic Contact Dermatitis in the Guinea Pig (Springfield: C.H. Thomas, 192Q) 35 OLAW, Public Health Service Policy on Humane Care and Use of Laboratory Animals (NIH Publication) WO 2006/034547 PCT/AU2005/001491 - 54 United States Code of Federal Regulation (CFR) 9: The Animal Welfare Act. EXAMPLE 8: ACUTE INTRACUTANEOUS REACTIVITY STUDY IN THE 5 RABBIT Purpose: The objective of this study is to evaluate the local dermal irritant effects of leachables extracted from the 10 test article following intracutaneous injection in rabbits. This study will be based on the requirements of the International Organization for Standardisation 10993: Biological Evaluation of Medical Devices, Part 30: Tests for Irritation and Sensitization. 15 This study will be conducted in accordance with the Detailed information of the FDA Good Laboratory Practice (GLP) Regulations, 21CFR 58. Test Article: 20 The sample will be prepared as follows: 1. Ratio of test article to extraction vehicle: Material thickness less than 0.5 mm - ratio of 120 cm 2 ;20 ml. 25 3. Extraction vehicle: 0.9% sodium chloride USP solution (SC). 4. Extraction conditions: 37*C, 72 hours ( 2 hours) Control Article: 30 Reagent controls (extraction vehicle without test material) will be prepared in the same way and at the same time as the test extracts. Test System: 35 Species: Rabbit (Oryctolagus cuniculus) Strain: New Zealand White WO 2006/034547 PCT/AU2005/001491 - 55 Source: Single USDA licensed supplier Sex: No particular gender is prescribed in this test Body Weight Range: 2.0 kg or greater at selection 5 Age: Young adults Acclimation Period: Minimum 5 days Number of Animals: Three per pair of extracts Identification Method: Ear tag 10 Justification of Test System: The intracutaneous injection test in rabbits is specified in the current ISO testing standards and has been used historically to evaluate biomaterial extracts. 15 Methods and Route of Administration: The day prior to treatment, each rabbit will be weighed and clipped free of fur from the back and both sides of the spinal column to yield a sufficient injection area. The clipped area of the back will be wiped with a 20 70% alcohol soaked gauze pad just before injection and allowed to dry. Due to concern with the crowding and subsequent obscuring of injection sites, the test and control sites will not be cranial and caudal on the same side of the back as defined in the ISO standards. Each 25 test extract will be administered in five intracutaneous injections of 0.2 ml each on the right side of each rabbit's back. Five reagent control injections will be injected similarly on the left side of the back. No more than two test extracts and the corresponding reagent 30 controls will be injected into each animal. Injections will be about 2 cm apart. The appearance of the injection sites will be noted immediately after injection. Observations for erythema and edema will be noted for each injection site at 24 (± 2 hours), 48 (± 2 hours) and 35 72 (± 2 hours) hours after injection. Reactions will be scored on a 0 to 4 basis. Other adverse changes at the injection sites will also be noted. After the test is WO 2006/034547 PCT/AU2005/001491 - 56 completed, all animals will be handled in accordance with approved procedures. The reactions will be evaluated according to the subjective rating scale as shown below: ERYTHEMA (ER) EDEMA (ED) 0 No erythema 0 No edema I Very-slight erythema (barely 1 Very-slight edema (barely perceptible) perceptible) 2 Well-defined erythema 2 Well-defined edema (edges of area well defined by definite raising) 3 Moderate erythema 3 Moderate edema (raised approximately 1 mm) 4 Severe erythema (beet redness) to 4 Severe edema (raised approximately I mm, eschar formation preventing grading and extending beyond exposure area) of erythema) 5 Evaluations and Statistics: No statistical analysis of the data will be performed. For each animal, the erythema and edema scores obtained at each time interval will be added together and 10 divided by the total number of observations. This calculation will be conducted separately for each test extract and reagent control. The score for the reagent control will be subtracted from the score for the test extract to obtain the Primary Irritation Score. The 15 Primary Irritation Score of each animal will be added together and divided by the total number of animals. The value obtained is the Primary Irritation Index (PII). The Primary Irritation Index is characterized by number and description as follows: 0-0.4 (negligible), 0.5-1.9 20 (slight), 2.0-4.9 (moderate), 5.0-8.0 (severe). If the response in the initial test is equivocal, additional testing may be necessary. Any adverse reaction noted in the test extract will be compared to the corresponding reagent control. 25 Report: WO 2006/034547 PCT/AU2005/001491 - 57 The final report will include a description of the methods employed, individual dermal scores for each test and control injection site, and the assessment of the results (Primary Irritation Scores and the Primary 5 Irritation Index). Records: Test article and reagent control preparation data, dates of relevant activities (such as the study initiation 10 and completion), the appearance of each injection site immediately after injection, individual dermal scores at 24, 48 and 72 hours, the Primary Irritation Score, and the Primary Irritation Index will be recorded. 15 References for Example 8: 21 CFR 58 (GLP Regulations). Guide for the Care and Use of Laboratory Animals, 20 Institute for Laboratory Animal Research, National Academy or Sciences (Washington: National Academy Press, 1996). International Organization for Standardization 10993: Biological Evaluation of Medical Devices, Part 10: Tests 25 for Irritation and Sensitization. OLAW, Public Health Service Policy on Humane Care and Use of Laboratory Animals. 30 United States Code of Federal Regulation (CFR) 9: The Animal Welfare Act. United States Pharmacopeia (USP), current edition. 35 EXAMPLE 9: USP AND ISO SYSTEMIC TOXICITY STUDY

EXTRACT

WO 2006/034547 PCT/AU2005/001491 - 58 Purpose: The objective of this study is to evaluate acute systemic toxicity of leachables extracted from the test article following a single intravenous or intraperitoneal 5 injection in mice. This study will be conducted in accordance with the methods recommended by the International Organization for Standardization 10993: Biological Evaluation of Medical Devices, Part II: Tests for Systemic Toxicity. 10 Test Article: The sample will be prepared as follows: 1. Ratio of test article to extraction vehicle: 15 - Material thickness less than 0.5 mm - ratio of 120 cm 2 :20 ml - Material thickness greater -than or equal to 0.5 mm ratio of 60 cm 2 :20 ml - Irregularly shaped objects and/or sponsor option 20 ratio of 4 g:20 ml 2. Extraction vehicles: - 0.9% sodium chloride USP solution (SC) - alcohol in saline 1:20 solution (AS) 25 - polyethylene glycol 400 (PEG)* - vegetable oil Note: Due to the known pH of these vehicles, the pH of the test article extracts will not be determined. *If PEG is used, the PEG test extract and reagent control 30 will be diluted with saline to obtain 200mg of PEG/mI. 3. Extraction conditions: - 1210C, 1 hour - 700C, 24 hours 35 - 50 0 C, 72 hours - 37 0 C, 72 hours WO 2006/034547 PCT/AU2005/001491 - 59 Control Article: Blank controls (extraction vehicle without test material) will be prepared in the same way and at the same time as the test extracts. 5 Test System: Species: Mouse (Mus musculus) Strain: Outbred albino 10 Source: approved supplier Sex: No particular gender is prescribed for this test Body Weight Range: 17-23 grams at injection Age: No particular age is prescribed 15 for this test Acclimation Period: Minimum 1 day Number of Animals: Five per extract and control Identification Method: Ear punch 20 Justification of Test System: Mice have historically been used to evaluate biomaterial extracts. The use of albino mice injected with a single intravenous (iV) or intraperitoneal (IP) dose of test article extract or control blank have been suggested 25 by the current USP and ISO for evaluation of medical plastics. Methods and Route of Administration: Prior to dosing, the mice will be identified and 30 weighed. Five animals will each be injected with the appropriate test extract at a dose of 50 ml/kg (SC, AS, vegetable oil) or 10 g/kg (PEG). Five mice will be similarly injected with the corresponding extraction vehicles. The SC and AS will be injected intravenously via 35 the lateral tail vein while the PEG and vegetable oil will be injected intraperitoneally.

WO 2006/034547 PCT/AU2005/001491 - 60 Mice will be observed for adverse reactions immediately after dosing, and at 4, 24, 48 and 72 hours after injection. Following the 72 hour observation, the animals will be weighed. Any animal found dead will be 5 subjected to a gross necropsy of the viscera. After the test is completed, all animals will be handled in accordance with approved procedures. Evaluations and Statistics: 10 No statistical analysis of the data will be performed. If during the observation period none of the mice treated with the test extract show a significantly greater reaction than the corresponding control mice, then the test sample meets the test requirements. If two or 15 more mice die, or if abnormal behavior such as convulsions or prostration occurs in two or more mice, or if body weight loss greater than 2 grams occurs in three or more mice, the test sample does not meet the test requirements. If any mice treated with the test extract show only 20 slight signs of toxicity and not more than one mouse shows gross signs of toxicity or dies, a ten mouse retest may be required. If all ten mice treated with the test extract on the repeat test show no significant reaction greater than the control mice, then the test sample meets the current 25 test requirements. Report: The final report will include a description of the methods employed, individual body weights, and any 30 observations. Records: Test article preparation, dates of relevant activities (such as the study initiation and completion), 35 initial and final body weights, and observations will be recorded.

WO 2006/034547 PCT/AU2005/001491 - 61 References for Example 9: 21 CFR 58 (GLP Regulations). 5 Guide for the Care and Use of Laboratory Animals, Institute for Laboratory Animal Research, National Academy of Sciences (Washington: National Academy Press, 1996). International Organization for Standardization 10993: 10 Biological Evaluation of Medical Devices, Part 11: Tests for Systemic Toxicity. OLAW, Public Health Service Policy on Humane Care and Use of Laboratory Animals (NIH Publication). 15 United States Pharmacopeia (USP), current edition. EXAMPLE 10: RAT SUBCHRONIC INTRAVENOUS TOXICITY STUDY 20 Purpose: The objective of this study is to evaluate the subchronic systemic toxicity of leachables extracted from the test article following repeated intravenous injections in rats for a period of 14 consecutive days. 25 Test Article: 1. Ratio of test article to extraction vehicle: - Material thickness less than 0.5 mm - ratio of 120 cm 2:20 ml 30 - Material thickness greater than or equal to 0.5mm ratio of 60 cm 2 :20 ml - Irregularly shaped objects and/or sponsor option ratio of 4 g:20 ml 35 2. Extraction conditions: - 1210C, 1 hour - 70 0 C, 24 hours WO 2006/034547 PCT/AU2005/001491 - 62 - 500C, 72 hours The extracts will be used within 24 hours of completion of the extraction process or as directed by the 5 sponsor. Control Article: A vehicle control (SC without test article) will be prepared in the same way and at the same time as the test 10 extract. A single group of common control animals may be dosed when multiple test articles are evaluated at the same time. Test System: 15 Species: Rat (Rat us norvigicus) Strain: Hlao:(SD)CVF* Source: Hilltop Lab Animals, Inc. Sex: Ten male, ten female Body Weight Range: No particular weight range 20 is prescribed for this study, however, individual pretreatment body weights will be within 20% of the group mean for each sex 25 Age: Approximately 6 to 8 weeks old at first treatment Acclimation Period: Minimum 5 days Number of Animals: Twenty Identification Method: Ear punch or tag 30 Methods and Route of Administration: No more than one day prior to the first dose, rats will be weighed and randomly assigned to each treatment group. Ten rats (five male, five female) will receive an 35 injection of the test article extract once each day for 14 consecutive days. The test extract will be injected via the lateral tail vein at a dose of 10.0 ml/kg. The WO 2006/034547 PCT/AU2005/001491 - 63 individual daily dose will be based on the weight of each animal on the first dose day of each week. The appropriate dose volume will be calculated to the nearest 0.1 ml. An appropriate gauge needle attached to a disposable syringe 5 will be used to deliver the injection. The injection rate will be approximately 1.0 ml/10 seconds. Animals will be dosed at approximately the same time each day. Ten rats (five male, five female) will be similarly injected with the control blank. The first day of dosing will be 10 designated as day 1. Laboratory Observations: 1. Animals will be observed daily for general health. Rats 15 will also be observed for any adverse reactions immediately after injection. 2. Detailed examinations for clinical signs of disease or abnormality will be conducted at randomization and on 20 days 8 and 15. 3. Body weights will be recorded to the nearest whole gram prior to the first dose, on day 8, 14 (pre-fasted weight) and 15 (fasted weight). 25 4. In the event of mortality, the following contingencies will apply: a. Should any animal die during the study, a 30 macroscopic examination of the viscera will be conducted. Because of rapid postmortem tissue changes in small rodents, no final body weight or blood collection will be attempted. The organs and tissues designated in the Terminal Procedures 35 portion of this protocol will be collected and fixed for histopathologic evaluation. The number of WO 2006/034547 PCT/AU2005/001491 - 64 days the animal was on test will be considered in the final evaluation. b. Should any animal exhibit adverse clinical signs 5 or suffer from cage injury that for humane reasons necessitates euthanasia, it will be subject to the Terminal Procedures. The number of days the animal was on test will be considered in the final evaluation. 10 Terminal Procedures: At the end of the workday on day 14, the animals will be weighed and food will be withheld for a maximum of 20 hours. On day 15, the animals will be weighed and then 15 anesthetized by intraperitoneal injection of ketamine hydrochloride and xylazine (88 mg/kg + 12 mg/kg) dosed at 3.0 ml/kg. The abdomen will be opened and a blood specimen will be collected from the posterior vena cava. The blood specimens will be forwarded to a contract laboratory for 20 complete blood cell count with differential and clinical chemistry analyses. Rats will be euthanized by exsanguination while anesthetized. Following exsanguination, a macroscopic observation of the viscera will be conducted. The following organs 25 will be removed: heart, lungs, liver, spleen, thymus, kidneys (2), adrenal glands (2), mesenteric lymph nodes, submandibular lymph nodes, gonads (2) and any tissue with visible gross lesions. The liver, spleen, thyrnus, kidneys, adrenal glands and gonads will be weighed. Paired 30 organs will be weighed together. The tissues will be preserved in 10% neutral buffered forrnalin (NBF) until further processing. The carcasses will be discarded. After fixation, the tissues will be histologically processed (embedded, sectioned and stained in hematoxylin 35 and eosin) for microscopic evaluation by a qualified pathologist.

WO 2006/034547 PCT/AU2005/001491 - 65 Evaluation and Statistics: Body weight data, organ weight data, organ/body weight ratios, hematology and clinical chemistry data will be evaluated statistically. Pre-fasted body weights will 5 be used to determine weight gain and the fasted body weights will be used to determine anesthetic dosages at termination and organ/body weight ratios. Descriptive statistics and group comparisons of data will be accomplished using a validated statistical software 10 package. After screening the data for normality and equal variance, the appropriate parametric or nonparametric tests will be performed. Normally distributed data with equal variance will be considered parametric and evaluated using an 'unpaired t-test" for comparison of two groups. 15 Jf data is nonparametric, the "Mann-Whitney Rank Sum Test" is used for two group comparisons. The data to be analyzed will include: body weight, organ weight and hematological parameters. The treatment groups will be used as variables. Calculations resulting in probability (p) 20 values less than 0,05 will be considered statistically significant. If directed by the evaluating pathologist, statistical evaluation of pathologic findings may be conducted. Clinical signs of systemic illness or death will not 25 be analyzed statistically unless a rationale (such as frequently observed clinical signs or emergence of a pattern) for such analysis is apparent from these data. If the incidence of occurrence of any one or more observations is sufficient to warrant analysis, a 30 chisquare test will be employed. Data from male and female rats for body weights will be analyzed separately until and unless a rationale exists for combining the sexes. Body weight data will be expressed as absolute values. Data from male and female 35 rats for hematology parameters will be analyzed separately unless a rationale exists for combining the sexes. In the event of statistical significance for any hematologic WO 2006/034547 PCT/AU2005/001491 - 66 parameter, the results will be compared to a reference range to aid in determining biological significance. Report: 5 The final report will include a description of the methods employed, clinical observations, body weight data, hematology and clinical chemistry data, organ weight data, organ/body weight ratios, necropsy findings, the microscopic evaluation in the histopathology report, the 10 statistical analyses and conclusions. References for Example 10: 21 CFR 58 (GLP Regulations). 15 Guide for the Care and Use of Laboratory Animals, Institute for Laboratory Animal Research, National Academy of Sciences (Washington: National Academy Press, 1996). 20 ISO 10993-11. Biological Evaluation of Medical Devices, Part 11: Tests for Systemic Toxicity. OECD Guideline for Testing of Chemicals, Repeated Dose Oral Toxicity - Rodent: 28-day or 14-day Study, Document 25 Number 407. OLAW, Public Health Service Policy on Humane Care and use of Laboratory Animals (NIH Publication). 30 EXAMPLE 11: GENOTOXICITY: BACTERIAL REVERSE MUTATION STUDY Purpose of the Study: The purpose of the study is to evaluate whether an extract of the test material or a solubilized material 35 will cause mutagenic changes in a tryptophan-dependent strain of Escherichia coli or in one or more strains of histidine-dependent Salmonella typhimurium in the presence WO 2006/034547 PCT/AU2005/001491 - 67 or absence of 59 metabolic activation. The Bacterial Reverse Mutation Study will be used as a rapid screening procedure for the determination of inutagenic and potential carcinogenic hazards and should be used in 5 conjunction with other tests that characterize potential genotoxicity properties. This study will be based on OECD guidelines and the requirements of the International Organization for Standardization: Biological Evaluation of Medical Devices - Part 3: Tests for Genotoxicity, 10 Carcinogenicity and Reproductive Toxicity. Test Article: The sample will be prepared as follows: 15 Test article form: - Soluble material (solid or liquid) - complete "Preparation of Soluble Material" 20 - Insoluble material - complete "Preparation of Extract" Preparation of Extract (for insoluble materials): 25 1. Ratio of test material to vehicle: - Material thickness less than 0.5 mm, use ratio of 120 cm2 :20 ml - Material thickness greater than or equal to 0.5 nun, use ratio of 60 cm 2 :20 ml 30 - Irregularly shaped objects and/or sponsor option, use ratio of 4 g:20 ml 2. Vehicle: - 0.9% Sodium Chloride for Injection , USP 35 - Dimethyl sulfoxide (DMSO)* - 95% ethanol (EtOH)** WO 2006/034547 PCT/AU2005/001491 - 68 *Dimethyl sulfoxide can be extracted at 370 C for 72 hours, 700 C for 24 hours or 500 C for 72 hours. **95% ethanol can only be extracted at room temperature (various times can be used). 5 3. Conditions (use highest temperature that will not degrade material); - 1210C, 1 hour 10 - 70 0 C,24 hours - 500C, 72 hours - 370C,24 hours - room temperature, 72 hours 15 Preparation of Soluble Material: 1. - Solid: One gram of the sample will be transferred to a 10 ml volumetric flask. Various sized flasks may be used to 20 accommodate nature of test material utilizing 100 mg/ml or 10% w/v. Appropriate vehicle (specified below) will be added (q.s.) to the 10 ml (or appropriate) demarcation to achieve 100 mg/ml or a 10% (w/v) solution of the material. 25 2. - Liquid: One milliliter of the sample will be transferred to a 10 ml volumetric flask. Various sized flasks may be used to accommodate nature of test material utilizing 30 100 mg/ml or 10% v/v. Appropriate vehicle (specified below) will be added (q.s.) to the 10 ml (or appropriate) demarcation to achieve 100 mg/ml or a 10% (v/v) solution of the material. 35 NOTE: GLP regulations 21 CFR 58.113 requires concentration analysis and stability determination for mixtures with carriers.

WO 2006/034547 PCT/AU2005/001491 - 69 Vehicles: - 0.9% Sodium Chloride for Injection, USP 5 - Dimethyl sulfoxide (DMSO) - 95% ethanol (EtOH) All preparations of soluble materials will be performed the day of test. In the event the material does 10 not completely dissolve at these concentrations, serial dilutions will be prepared. The highest possible concentration that achieves complete dissolution of the material will be used for testing purposes. 15 Test System: Each S. typhimurium tester strain contains a specific mutation in the histidine operon and other mutations that increase their ability to detect mutagens. The E. coli strain contains a mutation in the tryptophan operon and a 20 deletion in the uvrA gene. These genetically altered S. typhimurium strains (TA9S, TA100, TA1535, and TA1537) and E. coli strain (WP2uvrA) cannot grow in the absence of histidine or tryptophan, respectively. When placed in a histidine-free (for S. typhimurium) or tryptophan-free 25 (for E coli) medium, only those cells which mutate spontaneously back to their wild type state (histidine independent by manufacturing their own histidine, or tryptophan independent by manufacturing their own iryptophan) are able to form colonies. The spontaneous 30 mutation rate (or reversion rate) for any one strain is relatively constant, but if a mutagen is added to the test system, the mutation rate is significantly increased. Tester Strain Mutations/Genotypic Relevance 35 S. typhimurium TA98 hisD3052, rfa, uvrB, frameshift, pKM101 WO 2006/034547 PCT/AU2005/001491 - 70 S. typhimurium TA 100 hisG46, rfa, uvrB, missense, pKMl01 S. typhimurium TA 1535 hisG46, rfa, uvrB, missense S. typhimurium TA 1537 hisC3076, rfa, uvrB, frameshift 5 E. coli WP2uvrA trpEG5, uvrA, missense rfa = causes partial loss of the lipopolysaccharide wall which increases permeability of the cell to large 10 molecules (i.e., crystal violet inhibition) uvrB or uvrA = deficient DNA excision - repair system (i.e., ultraviolet sensitivity) frameshift = base-pair addition/deletion 15 missense = base-pair substitution pKM101 = plasmid confers ampicillin resistance (R factor) and enhances sensitivity to mutagens 20 Metabolic Activation: Aroclor 1254 - induced rat liver (s9 homogenate) will be used as metabolic activation. The material is prepared from male, Sprague Dawley rats. The rats are induced with one intraperitoneal injection of Aroclor 1254 (500 mg/ml) 25 5 days prior to sacrifice. The S9 homogenate is purchased from Organon Teknika Corporation, Box 15969, Durham, NC 27704-0969. Just prior to use, the S9 homogenate will be mixed with a buffer containing 0.4 M MgCl 2 /65 M KC1, 1.0 M Glucose-6-phosphate, 0.1 M NADP, 0.2 M sodium phosphate 30 buffer and sterile water. Preparation of Tester Strains: Cultures of Salmonella typhimurium, TA98, TA100, TA1535 and TA1537, and Escherichia coli, WP2uvrA, will be 35 inoculated to individual Erlenmeyer flasks containing oxoid broth. The inoculated broth cultures will be WO 2006/034547 PCT/AU2005/001491 - 71 incubated at 37 20C in an incubator shaker operating at 115-125 rpm for 10-12 hours. Preparation of Negative Control: 5 Negative control (vehicle without test material) will be utilized for each tester strain with and without S9 activation. Preparation of Positive Controls: 10 A known mutagen, Dexon (paradimethylaminobenzene diazosulfonic acid sodium salt), will be used as a positive control to demonstrate that tester strains TA98, TA100, and TA1537 are sensitive to mutation to the wild type state. For tester strain TA 1535, sodium azide will 15 be used as a positive control. For tester strain TAIO, 2 aminofluorene will be used as a positive control. For tester strain WP2uvrA, 2-aminoanthracene and methylmethane-sulfonate will be used as positive controls. Although metabolic activation is only required with 2 20 aminofluorene and 2-aminoanthracene to induce mutagenic results, all positive controls will be tested with and without S9 homogenate. Strain Characteristics and Strain Standard Plate Counts: 25 Strain characteristics will be verified and viable counts will be determined. Spot Plate Inhibition Screen: The extract(s) or solubilized material(s) and 30 negative control(s) will be evaluated by a spot plate technique modeled after the antimicrobial zone of inhibition test. This screen is used to evaluate extract or solution concentrations for toxicity which are noninhibitory to the Salmonella strains and the E. coli 35 strain. Separate tubes containing 2 ml of molten top agar supplemented with histidine-biotin (for S. typhimurium) or WO 2006/034547 PCT/AU2005/001491 - 72 with tryptophan (for E. coli) will be inoculated with 0.1 ml of culture for each of the five tester strains. After mixing, the agar will be poured across the surface of separate Minimal E plates labeled with lab number, 5 appropriate tester strain, and dose level (when necessary). Once the agar solidifies, sterile filter discs will be placed in the center of the plates. A 0.1 ml aliquot of the extract or solubilized material will be added to the filter discs on each of the labeled plates. 10 Parallel testing will be conducted with a negative control. To demonstrate a positive zone of inhibition, lOX stock Dexon will be used. The plates will be incubated at 37 + 2 0 C for 2-3 days. Following the incubation period, the zone of growth 15 inhibition will be recorded. If significant inhibition of the background lawn occurs, the extract or solubilized material concentration will be adjusted by preparing one or more dilutions and repeating the inhibition screen to find a nontoxic level. 20 Standard Plate Incorporation Assay: Separate tubes containing 2 ml of molten top agar supplemented with histidine-biotin solution (for S. typhimurium) or tryptophan (for E. coil) will be 25 inoculated with 0.1 ml of culture for each of the five tester strains, and 0.1 ml of the test material. A 0.5 ml aliquot of SWI or S9 homogenate, simulating metabolic activation, will be added when necessary. The mixture will be poured across triplicate Minimal B plates labeled with 30 lab number, appropriate tester strain, and 59 metabolic activation (when applicable). Parallel testing will be conducted on a negative control and five positive controls. Histidine-free media plates (for S. typhimurium) and 35 tryptophan-free media plates (for E. coli) will be prepared in triplicate as follows: WO 2006/034547 PCT/AU2005/001491 - 73 1. Extract or solubilized material with and without 59 activation 2. Negative control with and without S9 activation 3. 1X Dexon (known mutagen) with and without S9 5 activation with strains TA9S, TA100, and TA1 537 4. 1X 2-aminofluorene (known mutagen) with and without S9 activation with strain TA 100 5. 1X Sodium azide (known mutagen) with and without S9 activation with strain TA1535 10 6. 1X 2-aminoanthracene (known mutagen) with and without S9 activation with strain WP2uvrA 7. IX Methylmethane-sulfonate (known mutagen) with and without S9 activation with strain WP2uvrA 15 The plates will be incubated at 37 + 2 0 C for 2-3 days. After the incubation period, the revertant colonies on each plate (test, negative and positive) will be counted and recorded. The mean number of revertants will be calculated. 20 Evaluation of Test Results: The mean number of revertants of the triplicate test plates will be compared to the mean number of revertants of the triplicate negative control plates for each of the 25 five tester strains employed. The means obtained for the positive controls are used as points of reference. For a test material to be identified as a test failure or "potential mutagen" there must be a 2-fold or greater increase in the number of mean revertants over the means 30 obtained from the negative control, for any/all five tester strains. If no 2-fold increase is present, the test material is considered nonmutagenic. Any apparent "positive response" will be confirmed by demonstrating a dose-response relationship using three 35 nontoxic dose levels of the test material. There should be a range of concentrations that produce a linear dose response. In the event linearity cannot be established, WO 2006/034547 PCT/AU2005/001491 - 74 the assay will be repeated with an appropriate change in dose levels. A test material will be judged mutagenic if it causes a dose-related increase in the number of revertants over a minimum of two increasing dose 5 concentrations. Test Validity: For any assay to be considered valid, it must meet the following criteria: 10 1. Strain characteristics: All S typhimurium tester strains (TA98, TA100, TA1535, and TA1537) must exhibit sensitivity to crystal violet (rfa mutation), and ultraviolet light (uvrB), and must 15 exhibit no growth on biotin plates, and growth on histidine-biotin plates. Tester strains TA98 and TA 100 must exhibit resistance to ampicillin (R factor); tester strains TA1535 and TA1537 must exhibit sensitivity to ampicillin. Tester strain 20 WP2uvrA must exhibit sensitivity to ultraviolet light, no growth on tryptophan deficient plates, growth on tryptophan supplemented media and sensitivity to ampicillin. 25 2. Strain Standard Plate Counts: A viable count on the working culture suspensions for each tester strain (TA98, TA100, TA1535, TA1537 and WP2uvrA) should not be less than 1 x 10 CFU/ml. 30 3. Spot Plate Inhibition Screen: Each prepared extract or solubilized material will be evaluated for inhibition or toxicity to the cells. A test sample that is noninhibitory to moderately noninhibitory to the tester strains will be tested by the standard 35 plate incorporation method. In the event a test material is inhibitory, dilutions will be required to find a nontoxic level.

WO 2006/034547 PCT/AU2005/001491 - 75 4. Standard Plate Incorporation Assay: Each positive control mean must exhibit at least a 3-fold increase over the respective negative control mean of the 5 Salmonella tester strain employed, and at least a 2 fold increase over the respective negative control mean of the E. coli tester strain. Exceptions include conditions not intended to provoke a mutagenic response (e.g. 2-aminoanthracene and 2 10 aminofluorene without metabolic activation). The negative control results of each tester strain will exhibit a characteristic number of spontaneous revertants. Spontaneous reversion rates may vary, but should be consistent with the ranges specified 15 (see Table below). The Table is meant as a guideline only. Negative control results for tester strains may fall outside of the range listed. In such an instance, the results should be evaluated with caution. 20 Species Tester Strain Number of Spontaneous Revertants S.typhimurium TA98 15-50 TA100 120-240 TA1537 3-28 TA1535 10-35 E. coli W'P2uvrA 20-125 References for Example 11: Ames, B.N., McCann, 3., and Yamasaki, E., "Methods for 25 Detecting Carcinogens and Mutagens with the Salmonella/Mammalian-Microsome Mutagenicity Test" Mutation Research 31, (1975): 347-364. Brusick, D.J., V.F. Simmon, H.S. Rosenlcranz, V.A. Ray, 30 and KS. Stafford, "An Evaluation of the Escherichia coli WP2 and WP2uvrA Reverse Mutation Assay," Mutation Research 76, (1980): 169-190.

WO 2006/034547 PCT/AU2005/001491 - 76 Maron, Dorothy M., Ames, Bruce N., "Revised Methods for the Salmonella Mutagenicity Test," Mutation Research, 113 (1983): 175-215. 5 ISO 10993-3. Biological Evaluation of Medical Devices, Part 3: Tests for Genotoxicity, Carcinogenicity and Reproductive Toxicity. 10 OECD Guideline for the Testing of Chemicals, Proposal for Replacement of Guidelines 471 Bacterial Reverse Mutation Test, Document Number 471. Ortiz, A.J., M.T. Pollastrini, M. Barea, and D. Ord6hez, 15 "Bacterial Mutagenic Evaluation of Luxabendazole, a New Broad Spectrum Antihelminic, with the Salmonella typhimurium Histidine and the Escherichia coli Tryptophan Reversions Tests," Mutagenesis 11(1996): 27-31. 20 Test validation, Bacterial Mutagenicity Test: NAMSA lab number 98T-00785-00. It will-be appreciated by persons skilled in the art that numerous variations and/or modifications may be made 25 to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims (31)

1. A chemical gel comprising at least one silicon containing biostable polymer having monomers with an average functionality in the range of from 2.05 to 5, in 5 which the biostable polymer is a polyurethane or polyurethane urea which is a reaction product of: (a) at least one silicon-containing polyol or polyamine having 2 or more functional groups in which the silicon-containing polyol or polyamine 10 (a) is a compound of formula (I), (II), (III) or (IV) R3 R5- R7 15 R 1 0 Sj O S OR 2 R 4 R6 R 8 (I) 20 0 0 (R9)2 1 Si(Rg) 2 25 0 Si(R9)2SiR ) n ( )2si n n 30 R 1 0 OR, OR 1 in which Ri and R 2 are independently selected from C 1 .. 6 alkylene optionally substituted with OH or NR'R'' in which 2599248_1 (GHMatters) P54387.AU.1 - 78 R' and R' ' are independently selected from H, CO 2 H and C 1 .. alkyl; R 3 to R 8 are independently selected from Ci-6 alkyl and C 1 . 6 alkylene which may be optionally interrupted by 0 and 5 optionally substituted with OH or NR'R'' in which R' and R'' are as defined above; R 9 is C 1 - 4 alkyl; R 10 is optionally substituted C1.. 4 alkyl or 10 Si(R 9 ) 2 Si(R 9 ) 2 OR, 0 O n in which R, and R 9 are as defined above; x is 5 to 30; 15 y is 1 to 10; and n is 1 to 10; R11 R12 20I I A--Rig-Si--O--Si--R16-A' | | 20 R13 R14 _P (III) in which A and A' are OH or NHR wherein R is H or an 25 optionally substituted straight chain, branched or cyclic, saturated or unsaturated hydrocarbon radical; R 11 , R 1 2 , R 13 and R 1 4 are the same or different and selected from hydrogen or an optionally substituted straight chain, branched or cyclic, saturated or 30 unsaturated hydrocarbon radical; R 15 and R 16 are the same or different and selected from an optionally substituted straight chain, branched or cyclic alkylene, alkenylene, alkynylene or heterocyclic divalent radical; and 35 p is an integer of 1 or greater; 2599248_1 (GHMatters) P54387.AU.1 - 79 R11 R 12 0R R12- O R11 I 1 J1 1]0 A-R 15 -Si- R 17 -Si -R 16 -0-C- C-R 5 -Si- -R 7 -Si-11 6 -0-C -0-R15-Si- I I I I 13 R14 m R 1 3 R14 R13 - -, -11m_ 2 R12 O0 Ri - R12 1 1 1 R17--Si -R16- -R1811 - 0o-C-0-R 1 O-C-R1 5 -0-Si- R 17 -Si -R1-A' R14 m-z R13 - R141 5 (IV) in which R 11 , R 1 2 , R 13 , R 1 4 and R 15 are as defined in formula (III) above; R 16 is an optionally substituted straight chain, branched 10 or cyclic alkylene, alkenylene, alkynylene or heterocyclic divalent radical; R 1 7 is a divalent linking group; R 18 and R 19 are same or different and selected from hydrogen or an optionally substituted straight chain, 15 branched or cyclic, saturated or unsaturated hydrocarbon divalent radical; A and A' are as defined in formula (III) above; m, y and z are integers of 0 or more; and x is an integer of 0 or more; and 20 (b) a polyisocyanate.

2. A gel according to claim 1 in which the average functionality is from 2.1 to 3.25. 25

3. A gel according to claim 1 or 2 in which the polyurethane or polyurethane urea is also the reaction product of: 2599248_1 (GHMatters) P54387.AU.1 - 80 (c) at least one non-silicon containing compound having 1 or more functional groups.

4. A gel according to claim 3 in which the functional 5 groups of components (a) and (c) are group(s) which react with isocyanate or group(s) capable of activation by free radical initiation.

5. A gel according to claim 4 in which the functional 10 group is selected from OH, NR'R'' in which R' and R'' are the same or different and selected from H, CO 2 H and C 1 . 6 alkyl.

6. A gel according to any one of claims 1 to 5 in which 15 the compound of formula (I) is as follows: CH 3 CHa CH, HO OO Si O OH (Ia) Cp3 CH, - CHa n 20 C-b CF CF I o o H (Ib) 25 CH C-6 CH- CFLJ n 25 CH 3 CH, CH 3 HO O O { OSi OH (Ic) OH CH, OH 3 - CH3 n OH 25992481 (GHMatters) P54387AU.1 - 81 OH 0 5 (Id) CH, CH CH 3 10 0 0 CH3 CH CIH, - CH, CH3 x Y in which n, x and y are as defined in claim 1. 20

7. A gel according to claim 6 in which the molecular weight of the compound of formula (I) is from 400 to 5000.

8. A gel according to any one of claims 1 to 7 in which 25 the compound of formula (II) is as follows: !~e iMe 2 SiMe 2 Me 2 SI SiMe S e SiMe 2 n SiMe2(a) 0 0 00 OH OOOOH S1H 2599248_1 (GHMattems) P54387.AU I - 82 O Me Me 2 OH 5n Me 2 Si SiMe Me 2 Si O Si M2 SiMe2 / 10n (IIb) 0 15 HO O OH in which n is as defined in claim 1.

9. A gel according to claim 8 in which the molecular 20 weight of the compound of formula (II) is from 1000 to

5000.

10. A gel according to any one of claims 1 to 9 which further comprises a polysiloxane macrodiol or 25 macrodiamine.

11. A gel according to any one of claims 1 to 10 in which the polysiloxane is polylmethylsiloxane (PDMS) which is a compound of formula (III) in which A and A' 30 are hydroxyl, R 1 to R 14 are methyl and R 15 and R 16 are as defined in claim 15.

12. A gel according to any one of claims 1 to 10 in which the compound of formula (III) is 1,3-bis(4 35 hydroxybutyl)tetramethyl disiloxane (BHTD) in which A and A' are OH, R1, R 2 , R 3 and R 4 are methyl, R 15 and R 16 are butyl and R 17 is 0. 9AA4A i (rMattern PUA4 7 AJ I - 83

13. A gel according to any one of claims 1 to 12 in which the polyisocyanate (b) is polymeric 4,4'-diphenylmethane diisocyanate (MDI), methylene biscyclohexyl diisocyanate (H 1 2 MDI), p-phenylene 5 diisocyanate (p-PDI), trans-cyclohexane-1,4-diisocyanate (CHDI), 1,6-diisocyanatohexane (DICH), 1,5-diisocyanatonaphthalene (NDI), para-tetramethylxylenediisocyanate (p-TMXDI), meta-tetramethylxylene diisocyanate (m-TMXDI), 10 2,4-toluene diisocyanate (2,4-TDI) isomers or mixtures thereof or isophorone diisocyanate (IPDI).

14. A gel according to claim 3 in which the non-silicon containing compound having 1 or more functional groups 15 (c) is a polyether, polycarbonate or CI_ alkane.

15. A gel according to claim 14 in which the polyether is of the formula (V) A-[(CH 2 ), -01 -A' 20 (V) in which A and A' are as defined in claim 1; m is 4 or more; and 25 n is 2 to 50.

16. A gel according to claim 14 in which the polyether is Voranol which is a polyether triol resulting from a base catalysed reaction of glycerol and propylene oxide, 30 and N,N,N'-tri(2-hydroxypropyl)-N'-hydroxyethyl ethylene diamine (Poly Q).

17. A gel according to claim 15 or claim 16 in which the molecular weight range of the polyether is from 200 35 to 5000. 2599248 1 fGHMat1ers)P54387.AU.1 - 84

18. A gel according to claim 14 in which the polycarbonate is a poly(alkylene carbonate); a polycarbonate prepared by reacting alkylene carbonate 5 with alkanediol or a silicon based polycarbonate prepared by reacting alkylene carbonate with 1,3-bis(4 hydroxybutyl)-1,1,3,3-tetramethyldisiloxane (BHTD) and/or alkanediol. 10

19. A gel according to claim 14 in which the C1s alkane having 1 or more functional groups is methane diol, butane diol or hexane diol.

20. A gel according to any one of claims 1 to 19 having 15 an NCO/OH or NH 2 ratio less than 1.

21. A gel according to claim 20 in which the NCO/OH or NH 2 ratio is from 0.4 to 0.7. 20

22. A gel according to any one of claims 1 to 21 having less than 35% extractables.

23. A process for preparing the gel according to any one of claims 1 to 22 which comprises the step of: 25 (i) mixing components (a), (b) and (c) (when present).

24. A process for preparing the gel according to any one of claims 1 to 22 which comprises the steps of: 30 (i) reacting components (a) and (b) to form a prepolymer having terminally reactive polyisocyanate groups ; and (ii) mixing the prepolymer of step (i) with 35 component (c) (when present). 2599248 1 (GHMatters) P54387.AU.I - 85

25. A process according to claim 23 or 24 in which one or more additives are added in step (i) selected from catalysts, antioxidants, radical inhibitors, stabilisers, lubricants, dyes, pigments, inorganic and/or organic fillers, reinforcing agents and initiators.

26. A process for preparing the gel according to any one of claims 1 to 22 which comprises the steps of: (i) mixing components (a) and (b) and (c) (when present) with a photoinitiator; and (ii) subjecting the mixture of step (i) to UV radiation.

27. A biomaterial, device, article or implant which is wholly or partly composed of the gel according to any one of claims 1 to 22.

28. A biomaterial, device, article or implant according to claim 27 selected from soft tissue implants; orthopaedic joints or parts thereof; bone suture anchors; reconstructive facial surgery; controlled drug release devices; components in key hole surgery; biosensors; tools and accessories for insertion of medical devices, infusion and flow control devices; and urethral, neurological or vascular bulking agents.

29. A breast implant which is wholly or partly composed of the gel according to any one of claims 1 to 22.

30. A filler material for a medical implant which comprises the gel according to any one of claims 1 to 22. 2715284 1 (GHMatters) P54387.AU.1 - 86

31. Chemical gels; processes for their preparation; or biomaterials, devices, articles or implants wholly or partly composed of them, substantially as herein described with reference to the accompanying examples. 5 2707274_1 (GHMatters) P54387.AU.1