AU2004200567B2 - Blood-Related Dialysis and Treatment - Google Patents

Description

AUSTRALIA

Patents Act 1990 Gradipore Limited COMPLETE SPECIFICATION Invention Title: Blood-Related Dialysis and Treatment The invention is described in the following statement:

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2 Technical Field The present invention relates to methods suitable for treating or processing blood or plasma to remove or reduce the concentration of unwanted components, and particularly dialysis methods applicable to renal dialysis.

Background Art In healthy individuals, the kidney functions to remove excess water, salts and small proteins from the blood circulation. Nitrogenous wastes removed by the kidney include urea, the final metabolic destiny of excess dietary nitrogen, creatinine which is produced during muscle activity, and uric acid, an endpoint product of nucleotide metabolism. Current renal dialysis technology relies on equilibrium/diffusion principles and transmembrane pressure to remove nitrogenous wastes, salts and excess water from the bloodstream of patients experiencing chronic or acute renal failure. This requires two to three hours of dialysis treatment on three or four occasions each week. There are significant deficiencies in existing dialysis technologies, including sub-optimal biocompatibility of the dialysis membranes used, the inadequacy of existing technology in the removal of some solutes such as phosphates, and poor removal of low molecular weight proteins such as beta-2 microglobulin.

Internationally, 800,000 people suffer from chronic renal failure which implies that their kidneys can never perform the way they should. In medicine, dialysis is a therapy which eliminates the toxic wastes from the body due to kidney failure. There are two types of dialysis a) haemodialysis and b) peritoneal dialysis.

Haemodialysis is usually performed in dialysis centres, where the treatment entails dialysis for 4 hours three times a week. This sharply interferes with the quality of life of patients and also their productivity to the community at large. The present technology entails the re-routing of blood from the body to a filter made of plastic capillaries. The blood is purified when the waste products diffuse from the blood across the membrane of these tiny capillaries. The blood is then return to the body via the arm. The main advantage to this system is that patient training is not required.

The main disadvantages are that dialysis graft failure is common and there is lack of freedom on the part of the patient because of the requirement to report to a centre for treatment.

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In peritoneal dialysis, the body's own membrane is used as a filter, and the fluid drained in and out of the abdomen replaces the kidneys in getting rid of toxins. There are some great advantages to this system which include the fact that this can be done at home. The domestic use of this, however, requires careful technique and has the added disadvantage of peritonitis and membrane failure.

The present inventors have developed membrane-based electrophoresis technology that can be used to perform blood dialysis for purposes of renal replacement therapy, such that these deficiencies in conventional dialysis could be addressed. These deficiencies can be addressed by including the application of an electrical potential through a blood dialysis chamber to accelerate the removal of charged solutes such as phosphate ions and proteins, as well as charged nitrogenous wastes and other salt ions such as sodium, potassium, chloride and so on. The demonstrated protein separation capacity of membrane-based electrophoresis Gradiflow T M technology can be applied to the removal of specific proteins from the blood or plasma circulations, with the intention of treating disease symptoms mediated by those proteins. Examples of such disease states include rheumatoid arthritis and a host of other autoantibody mediated autoimmune diseases, which could be treated by the selective removal of autoantibody or other disease related proteins from the patients blood circulation.

The present inventors have developed a device based on membrane-based electrophoresis (Gradiflow T M technology (AU 601040)) which can be used to selectively remove solutes, metabolites and proteins from either blood or plasma.

Such a device can be used as either an add-on module to existing dialysis machines, or as a stand-alone device used to filter the blood of dialysis patients as a specific therapeutic measure to remove metabolites and proteins after conventional dialysis therapy has already been applied.

One of the key advantages of the GradiflowTM is its capacity to desalt. In the present system, this is achieved by the retention of the desired macromolecule in a chamber sandwiched between two electrophoresis membranes. The present inventors have re-configured the GradiflowTM so that dialysis of a mixture of components is possible.

Disclosure of Invention In a first general aspect, the present invention consists in use of membranebased electrophoresis in the processing of blood or plasma from a subject in order to remove or reduce the concentration of unwanted solutes metabolic contaminants, and macromolecules from the blood or plasma.

In a preferred embodiment, membrane-based electrophoresis is used in renal dialysis, either as a replacement of current dialysis methods or as a supplement to current renal dialysis.

Preferably, the membrane-based electrophoresis is based on the GradiflowTM technology developed by the present applicant.

In a second aspect, the present invention consists in a method of treating blood or plasma of a subject to remove or reduce the concentration of metabolic contaminants comprising: placing blood or plasma from the subject in a first solvent stream of an electrophoresis apparatus, the first solvent stream being separated from a second solvent stream by an electrophoretic membrane; applying an electric potential between the two solvent streams causing movement of metabolic contaminants from the blood or plasma through the membrane into the second solvent stream while cellular and biomolecular components of the blood or plasma are substantially retained in the first sample stream, or if entering the membrane, being substantially prevented from entering the second solvent stream; optionally, periodically stopping and reversing the electric potential to cause movement of any cellular and biomolecular components of the blood or plasma having entered the membrane to move back into the first solvent stream, wherein substantially not causing any metabolic contaminants that have entered the second solvent stream to re-enter the first solvent stream; maintaining step and optionally step if used, until the desired amount of removal of the metabolic contaminants from the blood or plasma in the first solvent stream is achieved; and returning the treated blood or plasma in the first solvent stream to the subject.

In a preferred embodiment, the subject is a renal dialysis patient.

The blood or plasma is preferably recirculated between the subject and the first solvent stream.

In a further preferred embodiment of the second aspect of the present invention, the electrophoretic. membrane has a molecular mass cut-off close to the apparent molecular mass of metabolic contaminants. It will be appreciated, however, that the membrane may have any required molecular mass cut-off depending on the application.

Preferably, the metabolic contaminants are solutes including phosphates, nitrogenous wastes like urea and uric acid, or macromolecules including beta-2 microglobulin and other unwanted proteins including autoantibodies.

Preferably, the electrophoretic membrane has a molecular mass cut-off of between about 3 and 1000 kDa. It will be appreciated, however, that other size membranes may be applicable, depending on the treatment process required. A number of different membranes may also be used in a desired or useful configuration.

The electric potential applied during the method should preferably not substantially adversely effect the cells or proteins present in blood or plasma. An electric potential of up to about 100 volts has been found to be suitable. It will be appreciated, however, that other voltages may be used.

In a third aspect, the present invention consists in a method of renal dialysis, the method comprising carrying out haemodialysis on blood or plasma of a patient followed by subjecting the blood or plasma of the patient to the method according to the second aspect of the present invention.

As conventional haemodialysis often fails to remove certain metabolic contaminants from the blood of renal patients which can result in the build-up of these contaminants, a second treatment process using the method according to the second aspect of the present invention has the potential to selectively remove these contaminants.

Preferably, the method comprises: carrying out haemodialysis on blood or plasma of the patient; placing blood or plasma from the haemodialysed patient in a first solvent stream of a membrane-based electrophoresis apparatus, the first solvent stream being separated from a second solvent stream by an electrophoretic membrane; applying an electric potential between the two solvent streams causing movement of metabolic contaminants from the blood or plasma through the membrane into the second solvent stream while cellular and biomolecular components of the blood or plasma are substantially retained in the first sample stream, or if entering the membrane, being substantially prevented from entering the second solvent stream; optionally, periodically stopping and reversing the electric potential to cause movement of any cellular and biomolecular components of the blood or plasma having entered the membrane to move back into the first solvent stream, wherein substantially not causing any metabolic contaminants that have entered the second solvent stream to re-enter the first solvent stream; maintaining step and optionally step if used, until the desired amount of removal or reduction of the metabolic contaminants from the blood or plasma in the first solvent stream is achieved; and returning the treated blood or plasma in the first solvent stream to the patient.

The contaminants can be phosphates or proteins such as beta-2 microglobulin or autoantibodies. It will be appreciated, however, that other unwanted metabolic contaminants can also be removed in this process.

As used herein, first stream can be used interchangeably with Upstream (US) and second stream can be used interchangeably with Downstream (DS).

GradiflowTM is a trade mark owned by Gradipore Limited, Australia.

Throughout this specification, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed in Australia before the priority date of each claim of this application.

In order that the present invention may be more clearly understood preferred forms will be described with reference to the accompanying drawings.

Brief Description of Drawings Figure 1. Removal of Urea in PBS from upstream to downstream of a membrane-based electrophoresis apparatus.

Figure 2. Removal of endogenous and exogenous Urea from plasma by passive diffusion.

Figure 3. The rate of Urea removal is dependent on the membrane molecular weight cutoff.

Figure 4. Increasing temperature increases the rate of Urea removal in the membrane-based electrophoresis apparatus.

Figure 5. The rate of Urea removal, expressed in mg Urea removed per minute, is proportional to the Urea concentration on the sample stream.

Figure 6. Creatinine was rapidly removed from the upstream of the membranebased electrophoresis apparatus at 25V. Creatinine entered the downstream of the apparatus, but was not retained by the 3 kDa restriction membrane, so the downstream concentration was also rapidly depleted.

Figure 7. Creatinine removal is dependent on pH, with lower pH conditions resulting in more rapid removal of creatinine from aqueous solutions.

Figure 8. The application of increasing voltage in the membrane-based electrophoresis apparatus accelerated the removal of creatinine from the sample stream.

Figure 9. Increasing the size of the membrane molecular mass cutoff value allowed creatinine removal to proceed at a progressively faster rate.

Figure 10. Creatinine was removed from plasma using 10 and 20V potentials.

Figure 11. Uric acid was rapidly removed from the upstream, passing through the downstream to reach the buffer stream.

Figure 12. Increasing voltages resulted in more rapid removal of Uric acid from Hepes/Imidazole buffer.

Figure 13. Increasing the molecular mass cutoff of the electrophoresis membranes resulted in more rapid removal of Uric acid from the sample stream.

Figure 14. The addition of NaCI caused a dose-dependent decrease in the rate of uric acid removal.

Figure 15. Increasing buffer temperature resulted in morerapid removal of Uric acid.

Figure 16. Uric acid was readily removed from human plasma in a voltage dependent manner.

Figure 17. Phosphate ions were found to migrate from the upstream, through the downstream, into the buffer stream in a voltage dependent manner.

Figure 18. Phosphate was rapidly removed from plasma using a 50V electric potential.

Figure 19. Native PAGE analysis of proteins removed from whole blood using the membrane-based electrophoresis apparatus. Lanes 1 and 10 are molecular weight markers, with size in kDa shown at the right side. Lane 2 is diluted plasma.

Lane 3 is red cell lysate, predominantly haemoglobin. Lane 4 shows albumin and other smaller proteins removed from blood that had been passed through the apparatus 10 times with an applied voltage of 50V at 4C. Lanes 5 and 6 show proteins removed from blood using 100V at 4C after 5 and 10 passes respectively.

Lanes 7,8 and 9 show proteins removed from whole blood after 10 passes at room temperature, using 0, 50 and 100V respectively.

Figure 20. The accumulation of protein removed from plasma. The triangles indicate the A280 (total protein absorbance) in the downstream. The squares indicate the relative amount of beta-2 microglobulin in the downstream.

Modes for Carrying Out the Invention Before describing the preferred embodiments in detail, the principal of operation of a membrane-based electrophoresis apparatus will first be described. An electric field or potential applied to ions in solution will cause the ions to move toward one of the electrodes. If the ion has a positive charge, it will move toward the negative electrode (cathode). Conversely, a negatively-charged ion will move toward the positive electrode (anode).

In the apparatus used for present invention, ion-permeable barriers that substantially prevent convective mixing between the adjacent chambers of the apparatus or unit are placed in an electric field and metabolic contaminants in blood or plasma is selectively transported through an ion-permeable barrier. The particular ionpermeable barriers used will vary for different applications and generally have characteristic average pore sizes and pore size distributions and/or isoelectric points allowing or substantially preventing passage of different components.

APPARATUS

A number of membrane-based electrophoresis apparatus have been developed by, or in association with, Gradipore Limited, Australia. The apparatus are marketedand used under the name GradiflowTM. In summary, the apparatus typically includes a cartridge which houses a number of membranes forming at least two chambers, cathode and anode in respective electrode chambers connected to a suitable power supply, reservoirs for samples, buffers and electrolytes, pumps for passing samples, buffers and electrolytes, and cooling means to maintain samples, buffers and electrolytes at a required temperature during electrophoresis. The cartridge contains at least three substantially planar membranes disposed and spaced relative to each other to form two chambers through which sample or solvent can be passed. A separation membrane is disposed between two outer membranes (termed restriction membranes as their molecular mass cut-offs are usually smaller than the cut-off of the separation membrane). When the cartridge was installed in the apparatus, the restriction membranes are located adjacent to an electrode. The cartridge is described in AU 738361. Description of membrane-based electrophoresis can be found in US 5039386 and US 5650055 in the name of Gradipore Limited, incorporated herein by reference. An apparatus particularly suitable for use in isoelectric separation applications can be found in WO 02/24314 in the name of The Texas A&M University System and Gradipore Limited, incorporated herein by reference.

One electrophoresis apparatus. suitable for use in the present invention comprises: a first electrolyte chamber; a second electrolyte chamber, a first chamber or stream disposed between the first electrolyte chamber and the second electrolyte chamber; a second chamber or stream disposed adjacent to the first chamber disposed and between the first electrolyte chamber and the second electrolyte chamber; a first ion-permeable barrier disposed between the first chamber and the second chamber, the first ion-permeable barrier prevents substantial convective mixing of contents of the first and second chambers; a second ion-permeable barrier disposed between the first electrolyte chamber and the first chamber, the second ion-permeable barrier prevents substantial convective mixing of contents of the first electrolyte chamber and the first chamber; a third ion-permeable barrier disposed between the second chamber and the second electrolyte chamber, the third ion-permeable barrier prevents substantial convective mixing of contents of the second electrolyte chamber and the second chamber; and electrodes disposed in the first and second electrolyte chambers.

The electrophoresis apparatus may further comprise one or more of: an electrolyte reservoir; a first reservoir and a second reservoir;.

means for supplying electrolyte from the electrolyte reservoir to the first and second electrolyte chambers; and means for supplying sample or liquid from at least the first reservoir to the first chamber, or from the second reservoir to the second chamber.

The apparatus may comprise: a first electrolyte reservoir and a second electrolyte reservoir; and means for supplying electrolyte from the first electrolyte reservoir to the first electrolyte chamber and electrolyte from second electrolyte reservoir to the second electrolyte chamber.

The apparatus may further comprise one or more of: means for circulating electrolyte from the electrolyte reservoir(s) through the electrolyte chambers forming electrolyte streams in the electrolyte chambers; and means for circulating contents from each of the first and second reservoirs through the respective first and second chambers forming first and second streams in the respective chambers; means for removing and replacing sample in the first or second reservoirs; and means to maintain temperature of electrolyte and sample solutions.

In one form, the first ion-permeable barrier is a membrane having a characteristic average pore size and pore size distribution. In one preferred form, all the ion-permeable barriers are membranes having a characteristic average pore size and pore size distribution. This configuration of the apparatus is suitable for separating compounds on the basis of charge and or size.

In another form, the second and third ion-permeable barriers are membranes having a characteristic average pore size and pore-size distribution.

In order to control substantial bulk movement of liquid under the influence of an electric field an inducible electro-endo-osmotic membrane can be used in at least one of the second or third ion-permeable barriers. The inducible electro-endo-osmotic membrane is preferably a cellulose tri-acetate (CTA) membrane. It will be appreciated that the inducible electro-endo-osmotic membrane can be formed from any other suitable membrane material such as poly(vinyl alcohol) cross-linked with glutaraldehyde (PVAl+glut).

The present inventors have found that a polyaccrylamide membrane having a molecular mass cut off of less than about 60 kDa is particularly suitable for use in the apparatus. It will be appreciated that other molecular mass cut-offs would also be suitable for the apparatus.

The electrophoresis apparatus may contain a separation unit housing the chambers and ion-permeable barriers which is provided as a cartridge or cassette fluidly connected to the electrolyte reservoir(s) and, if present, the reservoirs.

In use, a blood or plasma to be treated is placed in the first or second chamber.

Electrolyte is placed in the first and second electrolyte chambers. Electrolyte or other liquid can be placed in the first and/or second chamber. An electric potential is applied to the electrodes wherein metabolic contaminants in the first and/or second chamber are caused to move through a diffusion barrier to the second and/or first chamber.

The GradiflowTM is a unique preparative electrophoresis technology for macromolecule separation which utilises tangential flow across a polyacrylamide membrane when a charge is applied across the membrane. The general design of the Gradiflow

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M system facilitates the purification of proteins and other macromolecules under near native conditions. This results in higher yields and excellent recovery. The present inventors have surprisingly found that membranebased electrophoresis can be adapted to medical application such as renal dialysis.

This is unexpected and surprising as systems developed for laboratory or commercial macromolecular separations or applications are not necessarily considered adaptable for medical uses.

Current dialysis therapies remove toxins from blood by diffusion, attempting to mimic the role of the kidney. Dialysis therapies are unable to purify the contents of blood cells, but are able to remove the toxins surrounding bloods in the extra-cellular fluid, plasma. To demonstrate the capability of Gradiflow TM in renal replacement therapies, experiments were designed to show that toxins could be removed from plasma (the location of the toxins) rather than whole blood. Plasma was also chosen over whole blood so that assays were not contaminated by blood cell by-products allowing the results to provide a better representation of the removal of toxins by GradiflowTM. It will be appreciated by persons skilled in the art that the plasma or blood could be readily returned to a patent after treatment by membrane-based electrophoresis according to the present invention. This is supported by the fact that treated blood and plasma removal and return is routinely carried out by standard haemodialysis methods.

RESULTS

Urea Removal by passive diffusion Demonstration of the removal of Urea from aqueous solutions Method One mg/mL Urea was dissolved in phosphate buffered saline (PBS) and placed in the upstream of a GradiflowTM device. PBS buffer, chilled to 4 0 C with ice, was recirculated in the buffer stream. The up and down streams were pumped through the GradiflowTM device at 20 mL/min and samples taken from both streams at 10 minute intervals. No voltage or current was applied during this procedure. The timed samples were then assayed for urea content.

Results The data in Figure 1 show the concentration of Urea in the upstream (solid squares) and in the downstream (hatched squares). The concentration of Urea in the upstream decreased over time, while the concentration of urea in the downstream increased. This result indicates that urea can be removed from aqueous solution by passive diffusion.

Removal of Urea from plasma Method Unmodified human plasma, or human plasma to which 1 mg/mL Urea had been added, was placed in the upstream of a GradiflowTM device. PBS buffer, chilled to 4 0 C with ice, was recirculated in the buffer stream. The up and down streams were pumped through the Gradiflow T M device at 20 mL/min and samples taken from both streams at 10 minute intervals. No voltage or current was applied during this procedure. The timed samples were then assayed for urea content.

Results The data in Figure 2 show the concentration of endogenous Urea in the upstream (solid diamonds) and in the downstream (hatched diamonds) when unmodified plasma was used in this experiment. The concentration of Urea in the upstream and downstream when exogenous Urea was added to the sample is shown in red squares and pink triangles respectively. As shown above for aqueous solution, the concentration of Urea in the upstream decreased over time, while the concentration of urea in the downstream increased. This result indicates that urea may be removed from plasma by passive diffusion as occurs in current dialysis therapies.

Factors affecting the removal of Urea from aqueous solutions Method Urea was dissolved in an appropriate buffer and placed in the sample stream of a GradiflowTM device, with the GradiflowTM cartridge constructed in dialysis configuration. The circulating buffer stream was selected to match the solution in which Urea had been dissolved. The starting Urea concentration, buffer pH, salt concentration, temperature of the system and applied voltage/current were varied systematically to determine the effect each variable had on the rate of Urea removal.

The Urea solution was pumped through the Gradiflow T M device at 20 mLlmin, with samples generally being taken at 10 minute intervals. The timed samples were then assayed for urea content.

The effect of applied current on Urea removal One mg/mL Urea was dissolved in Tris Borate buffer, pH 9.0 and processed through the GradiflowTM as described above. Electrical currents from 0 to 1.5 Amps were applied to the system, however, no change in Urea removal rate was observed, indicating that the rate of Urea removal was insensitive to the applied current.

Voltage dependence of Urea movement One mg/mL Urea was dissolved in Tris/Borate buffer at pH 9.0 and circulated in the sample stream of a GradiflowTM cartridge constructed in the dialysis configuration.

Various electrical potentials from 0 to 100V were applied to the GradiflowTM system.

Varying the applied voltage resulted in no significant alteration to the rate of Urea removal from the sample stream.

pH dependence of Urea removal One mg/mL Urea was dissolved in GABA/acetic acid buffer pH 3, Hepes Imidazole buffer pH 6.0 and Tris/Borate buffer pH 9.0, and processed through the Gradiflow T M with an applied electrical potential of 50V. No significant difference in the rate of Urea removal was observed as a function of changes in buffer pH.

The effect of NaCI concentration on Urea removal One mg/mL Urea was dissolved in 20 mM phosphate buffer containing 0 to 150 mM NaCI and processed through the Gradiflow T M in dialysis configuration using kDa cutoff membranes. No electrical potential was applied in these experiments. The presence of increasing concentrations of NaCI had no effect on the diffusion of Urea in the GradiflowTM instrument.

The effect of membrane pore size on the removal of Urea from aqueous solutions One mg/mL Urea was dissolved in PBS and processed in the GradiflowTM using membranes with molecular weigh cutoff values between 3 and 75 kDa. Ten minute time samples were taken during these runs and the slope of these curves determined as the rate of Urea removal. Figure 3 shows the relationship between membrane molecular weight cutoff and the rate of Urea removal from aqueous solutions.

The effect of temperature on the removal of Urea One mg/mL Urea was dissolved in PBS and processed in the GradiflowTM as described previously. The buffer temperature was maintained at temperatures between 4 and 37 0 C and the removal of Urea determined. Figure 4 shows that increasing buffer temperature increased the rate of Urea removal, consistent with a passive diffusion phenomenon.

The effect of Urea concentration on the rate of Urea removal Urea at concentrations between 1 and 50 mg/mL was dissolved in PBS and processed through the GradiflowTM as above. The rate of Urea removal was determined from time course experiments and calculated in units of urea removed per minute. Figure 5 shows that the rate of Urea removal increases with Urea concentration, again consistent with a passive diffusion phenomenon.

Electrically driven Creatinine removal Demonstration of the migration of Creatinine One hundred Tg/mL creatinine was dissolved in GABA/acetate buffer, pH 3, and placed in the upstream of a GradiflowTM device, using 3 kDa restriction membranes and a 50 kDa separation membrane. GABA/acetate buffer, chilled to 4 0 C, was recirculated in the buffer stream. An electrical potential of 25V was applied to the system, using 'reverse polarity'. Samples were collected from the up and down streams at 5 minute intervals and the creatinine concentrations in these samples determined. The results obtained show that creatinine was rapidly removed from the upstream. The transient rise in the downstream creatinine concentration indicates that creatinine moved through the downstream, but was not retained by the 3 kDa membrane. Creatinine therefore passed through the restriction membrane into the buffer stream.

Figure 6 shows that Creatinine was rapidly removed from the upstream of the GradiflowTM instrument at 25V. Creatinine entered the downstream of the GradiflowTM, but was not retained by the 3 kDa restriction membrane, so the downstream concentration was also rapidly depleted.

Factors affecting creatinine removal in the GradiflowTM apparatus Method Creatinine was dissolved in an appropriate buffer and placed in the sample stream of a GradiflowTM device, with the Gradiflow T M cartridge constructed in dialysis configuration. The circulating buffer stream was selected to match the solution in which creatinine had been dissolved. The buffer pH, salt concentration, temperature of the system and applied voltage/current were varied systematically to determine the effect each variable had on the rate of creatinine removal. The creatinine solution was pumped through the Gradiflow T M device at 20 mL/min, with samples generally being taken at 5 minute intervals. The timed samples were then assayed for creatinine content.

The effect of pH on Creatinine removal One hundred Mg/mL Creatinine was dissolved in buffers with pH varying from 3 to 9 and processed through the Gradiflow T M using an electrical potential of Creatinine has a pK of 10.4, indicating that creatinine is uncharged at pH 10.4, and positively charged at pH conditions lower than this pK value. Creatinine removal was most rapid at pH 3, and was observed to be progressively slower as the buffer pH was raised to 9.

Figure 7 shows Creatinine removal is dependent on pH, with lower pH conditions resulting in more rapid removal of creatinine from aqueous solutions.

The effect of voltage on Creatinine removal One hundred Mg/mL creatinine was dissolved in GABA/acetate buffer, pH 3, and processed in the GradiflowTM as above. Electrical potentials between 0 and 100 V were applied to the system. The increase in applied voltage accelerated the removal of creatinine from the sample stream.

Figure 8 shows the application of increasing voltage in the Gradiflow T M system accelerated the removal of creatinine from the sample stream.

The effect of NaCI on the removal of Creatinine One hundred Mg/mL creatinine was dissolved in GABA/acetate buffer, pH 3, with the buffer containing NaCI at concentrations between 0 and 150 mM. The addition of NaCI caused a slight decrease in the rate of creatinine removal, suggesting that the presence of other charge carrying molecules in the solution reduced the level of electrical force available for driving the removal of creatinine.

The effect of membrane molecular weight cutoff on Creatinine removal One hundred Mg/mL creatinine was dissolved in GABA/acetate buffer, pH 3, and processed in the GradiflowTM as previously, using membranes with varying molecular weight cutoff values between 3 and 75 kDa. The results generated indicated that the movement of creatinine was influenced by membrane molecular mass cutoff, with the rate of removal of creatinine becoming progressively faster as the membrane pore size was increased.

Figure 9 shows increasing the size of the membrane molecular mass cutoff value allowed creatinine removal to proceed at a progressively faster rate.

The effect of temperature on the rate of Creatinine removal One hundred Mg/mL creatinine was dissolved in GABA/acetate buffer and processed in the GradiflowTM as above. The circulating GABA/acetate buffer was maintained at temperatures between 4 and 37 0 C to examine the effect of temperature on the rate of creatinine removal. It was observed that the rate of creatinine removal increased with increasing buffer temperature.

Removal of creatinine from plasma Normal human plasma was made 100 Mg/mL in creatinine and the plasma processed in the Gradiflow T M using 10 and 20V potentials. Figure 10 shows that creatinine was successfully removed from human plasma under these conditions.

Electrically driven Uric Acid removal Demonstration of the removal or Uric acid Three hundred mg/mL Uric acid was dissolved in Hepes Imidazole buffer, pH 7.26 and placed in the upstream of the Gradiflow T M instrument. Hepes Imidazole buffer, chilled to 4C, was recirculated in the buffer stream of the Gradiflow T M device.

The membrane cartridge used included 3 kDa restriction membranes and a 50 kDa separation membrane. When the GradiflowTM instrument was run using an electrical potential of 15V, Uric acid was found to be removed from the upstream. The Uric acid was found to accumulate transiently in the downstream, from which it was subsequently removed to the buffer stream.

Figure 11 shows that Uric acid was rapidly removed from the upstream, passing through the downstream to reach the buffer stream.

Factors affecting the removal of Uric Acid Method Uric acid was dissolved in an appropriate buffer and placed in the sample stream of a GradiflowTM device, with the GradiflowTM cartridge constructed in dialysis configuration. The circulating buffer stream was selected to match the solution in which uric acid had been dissolved. The membrane pore size, salt concentration, temperature of the system and applied voltage/current were varied systematically to determine the effect each variable had on the rate of uric acid removal. The uric acid solution was pumped through the GradiflowTM device at 20 mL/min, with samples generally being taken at 5 minute intervals. The timed samples were then assayed for uric acid content.

The effect of Voltage on Uric acid removal Three hundred Tg/mL Uric acid in Hepes/Imidazole buffer was processed in the Gradiflow T M at using electrical potentials from 0 to 100 V. It was observed the Uric acid removal was faster with increasing voltage.

Figure 12 shows increasing voltages resulted in more rapid removal of Uric acid from Hepes/Imidazole buffer.

The effect of membrane pore size on Uric acid removal Three hundred Tg/mL Uric acid in Hepes/Imidazole buffer was processed in the GradiflowTM as above, using an electrical potential of 10V. The molecular weight cutoff of the membranes used in the GradiflowTM cartridge was varied between 3 and 75 kDa. It was observed that as the molecular mass cutoff value of the membranes was increased, Uric acid was more rapidly cleared from the GradiflowTM sample stream.

Figure 13 shows increasing the molecular mass cutoff of the GradiflowTM membranes resulted in more rapid removal of Uric acid from the sample stream.

The effect of NaCI on Uric acid removal Three hundred Tg/mL Uric acid in Hepes/Imidazole was processed in the Gradiflow T M using 25 kDa cutoff membranes and an electrical potential of 10V. NaCI was included in the sample and buffer streams at concentrations from 0 to 150 mM.

The addition of increasing concentrations of NaCI to the buffer system resulted in a progressive decrease in the rate of uric acid clearance.

Figure 14 shows that the addition of NaCI caused a dose-dependent decrease in the rate of uric acid removal.

The effect of temperature on the rate of Uric acid removal Three hundred Tg/mL Uric acid in Hepes/Imidazole buffer was processed in the GradiflowTM as above, using 25 kDa membranes and a 10V potential. The recirculating buffer was maintained at temperatures between 4 and 37 0 C. The rate of Uric acid removal was found to increase with increasing temperature.

Figure 15 shows that increasing buffer temperature resulted in more rapid removal of Uric acid.

The removal of Uric acid from plasma Normal human plasma was made 300Tg/mL in Uric acid. This modified plasma was processed in the GradiflowTM as previously, using 25 kDa membranes, PBS buffer and using voltages from 10 to 30V. Figure 16 shows that Uric acid was readily removed from human plasma in a voltage dependent manner.

Electrically driven removal of Phosphate ions Phosphate removal is one of the key deficiencies in existing renal replacement dialysis technology. The capacity of the GradiflowTM to rapidly desalt/dialyse aqueous solutions suggested the applicability of the Gradiflow TM technology in the area of rapid phosphate removal from blood. The GradiflowTM system was found to rapidly remove phosphate ions from both aqueous solutions and plasma.

Demonstration of phosphate removal from aqueous solution One hundred Tg/mL sodium phosphate was dissolved in Hepes/Imidazole buffer and placed in the upstream of the GradiflowTM device. Hepes/Imidazole buffer, pH 7.2 was placed in the downstream and buffer stream of the GradiflowTM instrument. The membrane cartridge used included 3 kDa restriction membranes and a 10 kDa separation membrane. Electrical potentials from 0 to 50V were applied and the changes in phosphate concentration monitored as a function of time. When a voltage was applied, phosphate ions were found to leave the upstream and enter the downstream. The quantity of phosphate in the downstream was also rapidly depleted, indicating that the phosphate ions continued to migrate towards the positive electrode, leaving the downstream and entering the recirculating buffer stream. The rate of phosphate removal was also observed to be dependent on the applied voltage.

Figure 17 shows phosphate ions were found to migrate from the upstream, through the downstream, into the buffer stream in a voltage dependent manner.

Removal of phosphate from plasma Unmodified human plasma, or plasma containing an additional 0.1 mg/mL phosphate, was processed in the GradiflowTM. The membrane cartridge was constructed in dialysis configuration using 10 kDa restriction and separation membranes, Hepes/Imidazole buffer, pH 7.2, and an electrical potential of Samples of the plasma Were taken every 5 minutes and assayed for phosphate content. The results shown in Figure 18 demonstrate the rapid removal of phosphate from human plasma.

Removal of proteins from plasma and whole blood General protein removal (using human serum albumin (HSA) as an example) The ability to eliminate disease related proteins from the circulation of patients relies on the capacity of the GradiflowTM system to remove proteins from whole blood.

Albumin was chosen as a target blood protein to demonstrate the process according to the present invention. In practice, however, proteins like autoantibodies (typically IgG or IgM classes) will be targeted for removal from blood or plasma. To demonstrate this phenomenon, whole blood was circulated in the upstream of a Gradiflow T M device, with PBS buffer placed in the downstream and in the recirculating buffer tank, which was maintained at either 4 0 C or room temperature. Either 50 or 100V potential was applied in the GradiflowTM system. Samples of the downstream were collected and analysed by native PAGE on a 4-20% polyacrylamide gel. Figure 19 shows that albumin (the most abundant protein in blood) is readily removed after passing a volume of blood through the GradiflowTM, and that the quantity of protein removed appears to be dependent on the temperature and voltage applied in the GradiflowTM system.

Removal of beta-2 microglobulin Beta-2 microglobulin is a normal component of MHC Class I molecules, which are found on the surface of all nucleated cells. This protein is frequently released in to the blood circulation during episodes of immunological activity, such as infections.

Normal plasma contains very low concentrations of beta-2 microglobulin, in the order of 3 Tg/mL. This concentration is raised in renal dialysis patients, firstly due to the increased frequency of infections experienced when on dialysis, and secondly due to the poor capacity of conventional renal dialysis technology to remove this protein. As a result of the inability of conventional renal replacement therapy to remove beta-2 microglobulin, the concentration of this protein increases in the blood circulation of renal dialysis patients. The primary consequence of this accumulation of beta-2 microglobulin is the development of beta-2 microglobulin amyloid fibrils in the bones and other tissues of renal dialysis patients, which affects bone structure and bone marrow function.

The present inventors have tested the ability of the GradiflowTM to remove beta-2 microglobulin from normal human plasma. Forty mL of plasma was diluted 1:1 in Tris/borate buffer pH 9 and processed in the GradiflowTM using 3 kDa restriction membranes and 25 kDa separation membranes. A maximum potential of 250V was applied to the system, with the circulation buffer maintained at 4C. The absorbance at 280nm of the downstream was measured at 30 minute intervals, and the beta-2 microglobulin content of the downstream was determined by and ELISA method in samples taken every hour. The ELISA method employed a rabbit polyclonal antiserum specific to detect beta-2 microglobulin specifically. Figure 20 shows that low molecular weight proteins were rapidly removed from plasma, and that beta-2 microglobulin was detectable in the downstream. The gradual reduction in total protein in the downstream (A280 points) may relate to the gradual electrophoresis of very small proteins and peptides through the 3 kDa restriction membranes or the adhesion of proteins to the bottom restriction membranes.

SUMMARY

Urea removal has been shown to be independent of voltage, current, pH and salt concentration. Urea removal has been shown to be dependent on temperature, membrane molecular weight cutoff and the starting concentration of urea. Urea removal from plasma has been demonstrated. Urea, being an uncharged molecule, does not move in response to electrical field variations, rather its movement is due entirely to passive diffusion phenomena as observed in current dialysis therapies. The ability of the membrane-based electrophoresis system to remove Urea is of significance to its renal dialysis application, as urea is the major nitrogenous waste that must be removed. This is also the first demonstration of passive diffusion phenomena in membrane-based electrophoresis system, indicating the membranebased electrophoresis system can be used for the removal and/or purification of uncharged solutes while simultaneously removing charged molecules by electrophoretic means.

Creatinine is a charged nitrogenous waste material which has been shown to be removed from plasma, and whose rate of removal has been shown to be dependent on voltage, pH, salt concentration, temperature and membrane pore size.

The capacity of the membrane-based electrophoresis system to rapidly remove charged nitrogenous wastes is significant to the system capacity in renal dialysis.

Uric acid was removed from aqueous solutions and from plasma. Removal of Uric acid was shown to be dependent on voltage, membrane pore size, temperature and salt concentration. Uric acid removal is another example of electrically driven dialysis which allows rapid removal of nitrogenous wastes from plasma.

The removal of phosphate ions from blood and plasma is a critical application of membrane-based electrophoresis technology to the field of renal dialysis. The inability of current dialysis technologies to remove phosphate ions is an area that could be readily addressed by a variation of the membrane-based electrophoresis technology using electrically driven dialysis to remove charged solutes. The general principle of removing charged ions which is demonstrated here can also be considered to apply to other salt ions such as sodium, potassium, chloride and so on.

The removal of excess concentrations of these ions would also be made more rapid using electrically driven dialysis systems.

The demonstration of the ability of membrane-based electrophoresis technology to remove proteins, specifically albumin and beta-2 microglobulin, from whole blood and plasma implies that, using the correct conditions of membrane molecular weight cutoff, voltage and buffer solution, individual disease related proteins may be removed from blood or plasma for therapeutic purposes. This potential should not be restricted to the two proteins for which the principle has been demonstrated. In theory, any protein for which a specific combination of electrical field and membrane selectivity can be specified, could be removed from blood or plasma for therapeutic purposes.

Combining all the experimental data for the removal of general uremic toxins (urea, creatinine, uric acid, phosphate and proteins) a series of key membrane-based electrophoresis conditions can be identified for use in renal replacement therapies.

The first key requirement was for membrane-based electrophoresis system was to use membranes which were between 25-50 kDa. Although experiments demonstrated that albumin could be moved, these results were to demonstrate the capability of membrane-based electrophoresis to move plasma protein (albumin). In a dialysis application a membrane with a cut-off less than albumin (66.5 kDa) would be chosen. The second important factor was a voltage between 25-50 V. A voltage between 25-50 V proved successful in removing the charged nitrogenous and ionic toxins, and it would be anticipated that increasing the voltage would increase the rate of toxin removal. Third, a physiological pH (pH 7) was found to be suitable for the removal of the toxins, therefore not allowing the pH of plasma to be maintained during the separation. Being able to conduct the separation at physiological pH allows the blood/plasma to be maintained at a normal healthy pH range.

It is anticipated the outcome and the conditions used for the plasma experiments would be easily mimicked using whole blood. In addition, if whole blood from a particular patient proved to be problematic, then the whole blood could be separated into plasma and blood cells using plasmapheresis or plasma separation filter. The plasma could then be purified using membrane-based electrophoresis technology and re-combined with the blood cells after the toxins had been removed from the plasma.

CONCLUSIONS

It is apparent from the data presented that a membrane-based electrophoresis system is useful for the removal of nitrogenous wastes, phosphate ions, and proteins such as albumin and beta-2 microglobulin, from aqueous solutions, plasma and blood.

The ability to remove waste or unwanted materials from blood or plasma by the simultaneous use of diffusive and electrophoretic principles in a single cartridge system is an advantage. For example, urea can be removed on the basis of latent diffusion while other waste materials can be removed on the basis of charge during the same process. The capacity of the~basic GradiflowTM system to perform these functions indicates the potential applications of the GradiflowTM system in the field of renal dialysis and other blood purification applications which require the selective removal of proteins and other charged or uncharged species from circulating blood or plasma. Modified versions of the GradiflowTM device can be constructed which could be used either as a complete renal dialysis device, addressing all renal replacement

I

therapy needs including removal of salts, phosphate, nitrogenous wastes, excess water balancing blood pH and removing beta-2 microglobulin. Alternatively, a simpler device may be constructed to function as an addition to existing renal dialysis systems, whose function is to address the deficiencies of the existing systems, ie the removal of phosphate and beta-2 microglobulin from either blood or plasma. The present inventors have demonstrated that a membrane-based electrophoresis system is capable of removing all these solutes and proteins. The correct combination of membrane chemistry, dialysis solution, voltage and current conditions, cartridge and tubing materials, pump design etc as taught herein are all integral to the functioning of the system.

Furthermore, given that individual proteins may be removed from blood and/or plasma, it'will be feasible to construct a version of the membrane-based electrophoresis system which is designed to selectively remove proteins such as autoantibodies, which may be related to autoimmune diseases such as rheumatoid arthritis, lupus and so on, as well as other proteins which may be causative factors in other diseases. Examples of other proteins or blood contaminants may include the removal of bacterial endotoxins or specific lipoproteins from blood or plasma as a therapeutic measures for treating septic shock or lipid metabolism disorders respectively.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made 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 (42)

1. A method for selectively removing metabolic contaminants from at least one blood component, comprising: selecting a first selective membrane composed of a polyacrylamide hydrogel; directing a first solvent stream having a selected pH and including at least a metabolic contaminant capable of obtaining a charge and at least one blood component, so as to flow along the first selective membrane, wherein such pH produces a net charge on the metabolic contaminant; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, the pressure in both streams being substantially equal, wherein the application of such voltage potential causes movement of at least a portion of the charged metabolic contaminants through the first selective membrane into the second solvent stream while at least a portion of the at least one blood component is prevented from entering the second solvent stream wherein substantially all transmembrane migration of the charged metabolic contaminant is initiated by the voltage potential; and maintaining step until the first solvent stream contains the desired purity of the at least one blood component.

The method according to claim 1 further wherein at least a portion of uncharged metabolic contaminants contained in the first solvent stream migrate through the selective membrane into the second solvent stream.

3. The method according to claim 2 further comprising placing the at least one blood component from a subject into the first solvent stream.

4. The method according to claim 2 wherein the metabolic contaminants are selected from the group consisting of urea, creatinine, uric acid, phosphate ions, beta-2- microglobulin, autoantibodies, other proteins, and combinations thereof.

The method according to claim 2 wherein the separation membrane has a molecular mass cut-off of at least about 3 kDa.

6. The method according to claim 1 further comprising directing a third solvent stream separated from a selected one of the first and second solvent streams by a second selective membrane and applying concurrently the voltage potential across the third solvent stream so as to cause the migration of at a portion of a the charged metabolic contaminants through the second selective membrane and into the third solvent stream.

7. The method according to claim 6 further comprising directing a fourth solvent stream separated from the other of the first and second solvent streams by a third selective membrane and applying concurrently the voltage potential across the fourth solvent stream so as to cause the migration of at least a portion of the charged metabolic contaminants through the third selective membrane and into the fourth solvent stream.

8. A method for selectively removing metabolic contaminants from at least one blood component, comprising: directing a first solvent stream having a selected pH and including at least a metabolic contaminant capable of obtaining a charge and at least one blood component, so as to flow along a first selective membrane comprising a polyacrylamide hydrogel, wherein such pH produces a net charge on the metabolic contaminant; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, whereby the application of such voltage potential moves at least a portion of the charged metabolic contaminants through the first selective membrane into the second solvent stream while at least a portion of the at least one blood component is prevented from entering the second solvent stream, whereby substantially all transmembrane migration of the charged metabolic contaminant is initiated by the voltage potential; periodically stopping and reversing the voltage potential to cause movement of at least any of the at least one blood component having entered the first selective membrane-to move back into the first solvent stream and wherein substantially not causing any of the metabolic contaminants that have entered the second solvent stream to re-enter the first solvent stream; and maintaining steps or until the first solvent stream contains the desired purity of the at least one blood component.

9. A method for selectively removing metabolic contaminants from at least one blood component, comprising: placing at least one blood component from a subject into a first solvent stream; directing a first solvent stream having a selected pH and including at least a metabolic contaminant capable of obtaining a charge and at least one blood component, so as to flow along a first selective membrane, wherein such pH produces a net charge on the metabolic contaminant; directing a second solvent stream along the first selective membrane so as be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, whereby the application of such voltage potential moves at least a portion of the charged metabolic contaminants through the first selective membrane into the second solvent stream while at least a portion of the at least one blood component is prevented from entering the second solvent stream, whereby substantially all transmembrane migration of the charged metabolic contaminant is initiated by the voltage potential; maintaining step until the first solvent stream contains the desired purity of the at least one blood component; and returning at least one blood component in the first solvent stream to the subject.

The method according to claim 9 wherein .the at least one blood component is recirculated between the subject and the first solvent stream.

11. A method for selectively removing metabolic contaminants from at least one blood component, comprising: directing a first solvent stream having a selected pH and including at least a metabolic contaminant capable of obtaining a charge and at least one blood component, so as to flow along a first selective membrane, wherein such pH produces a net charge on the metabolic contaminant, and at least one blood component has undergone treatment consisting of diffusive hemodialysis, convective hemodialysis, hemofiltration, hemodialfiltration, and combinations thereof prior to, subsequent to, or concurrently therewith step directing a second solvent stream along the first selective membrane so as be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, whereby the application of such voltage potential moves at least a portion of the charged metabolic contaminants through the first selective membrane into the second solvent stream while at least a portion of the at least one blood component is prevented from entering the second solvent stream, whereby substantially all transmembrane migration of the charged metabolic contaminant is initiated by the voltage potential; and maintaining step until the first solvent stream contains the desired purity of the at least one blood component.

12. A method for selectively removing metabolic contaminants from at least one blood component, comprising: selecting a first selective membrane composed of a polyacrylamide hydrogel; directing a first solvent stream having a selected pH and including at least a metabolic contaminant capable of obtaining a charge, an uncharged metabolic contaminant, and at least one blood component, so as to flow along the first selective membrane, wherein such pH produces a net charge on the metabolic contaminant capable of obtaining a charge; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, the pressure in both streams being substantially equal, wherein the application of such voltage potential causes movement of at least a portion of the charged metabolic contaminants through the first selective membrane into the second solvent stream while at least a portion of the at least one blood component is prevented from entering the second solvent stream wherein substantially all transmembrane migration of the charged metabolic contaminants is initiated by the voltage potential, wherein at least a portion of the uncharged metabolic contaminants contained in the first solvent stream migrates through the selective membrane into the second solvent stream; and maintaining step until the first solvent stream contains the desired purity of the at least one blood component.

13. The method according to claim 12 further comprising directing a third solvent stream separated from a selected one of the first and second solvent streams by a second selective membrane and applying concurrently the voltage potential across the third solvent stream so as to cause the migration of at least a portion of a the charged metabolic contaminants through the second selective membrane and into the third solvent stream.

14. The method according to claim 13 further comprising directing a fourth solvent stream separated from the other of the first and second solvent streams by a third selective membrane and applying concurrently the voltage potential across the fourth solvent stream so as to cause the migration of at least a portion of the charged metabolic contaminants through the third selective membrane and into the fourth solvent stream.

The method according to claim 12 further comprising placing at least one blood component from a subject into the first solvent stream.

16. The method according to claim 12 wherein the metabolic contaminants are selected from the group consisting of urea, creatinine, uric acid, phosphate ions, beta-2- microglobulins, autoantibodies, other proteins, and combinations thereof.

17. The method according to claim 12 wherein the selective membrane has a molecular mass cut-off of at least about 3 kDa.

18. A method for selectively removing metabolic contaminants from at least one blood component, comprising: directing a first solvent stream having a selected pH and including at least a metabolic contaminant capable of obtaining a charge, an uncharged metabolic contaminant, and at least one blood component, so as to flow along a first selective membrane comprising a polyacrylamide hydrogel, wherein such pH produces a net charge on the metabolic contaminant capable of obtaining a charge; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, wherein the application of such voltage potential causes movement of at least a portion of the charged metabolic contaminants through the first selective membrane into the second solvent stream while at least a portion of the at least one blood component is prevented from entering the second solvent stream wherein substantially all transmembrane migration of the charged metabolic contaminants is initiated by the voltage potential, wherein at least a portion of the uncharged metabolic contaminants contained in the first solvent stream migrates through the selective membrane into the second solvent stream; and periodically stopping and reversing the voltage potential to cause movement of at least any of the at least one blood component having entered the first selective membrane to move back into the first solvent stream and wherein substantially not causing any of the metabolic contaminants that have entered the second solvent stream to re-enter the first solvent stream; and maintaining steps or until the first solvent stream contains the desired purity of O O the at least one blood component.

19. A method for selectively removing metabolic contaminants from at least one blood component, comprising: placing at least one blood component from a subject into a first solvent stream; directing the first solvent stream having a selected pH and including at least a rmetabolic contaminant capable of obtaining a charge, an uncharged metabolic Ocontaminant, and at least one blood component, so as to flow along a first selective membrane, wherein such pH produces a net charge on the metabolic contaminant capable of obtaining a charge; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, wherein the application of such voltage potential causes movement of at least a portion of the charged metabolic contaminants through the first selective membrane into the second solvent stream while at least a portion of the at least one blood component is prevented from entering the second solvent stream wherein substantially all transmembrane migration of the charged metabolic contaminants is initiated by the voltage potential, wherein at least a portion of the uncharged metabolic contaminants contained in the first solvent stream migrates through the selective membrane into the second solvent stream; maintaining step until the first solvent stream contains the desired purity of the at least one blood component; and returning at least one blood component in the first solvent stream to the subject.

The method according to claim 19 wherein the at least one blood component is recirculated between the subject and the first solvent stream.

21. A method for selectively removing metabolic contaminants from at least one blood component, comprising: placing at least one blood component from a subject into a first solvent stream, wherein at least one blood component has undergone treatment consisting of diffusive hemodialysis, convective hemodialysis, hemofiltration, hemodialfiltration, and combinations thereof prior to, subsequent to, or concurrently therewith step directing the first solvent stream having a selected pH and including at least a metabolic contaminant capable of obtaining a charge, an uncharged metabolic contaminant, and at least one blood component, so as to flow along a first selective membrane, wherein such pH produces a net charge on the metabolic contaminant capable of obtaining a charge; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, wherein the application of such voltage potential causes movement of at least a portion of the charged metabolic contaminants through the first selective membrane into the second solvent stream while at least a portion of the at least one blood component is prevented from entering the second solvent stream wherein substantially all transmembrane migration of the charged metabolic contaminants is initiated by the voltage potential, wherein at least a portion of the uncharged metabolic contaminants contained in the first solvent stream migrates through the selective membrane into the second solvent stream; and maintaining step until the first solvent stream contains the desired purity of the at least one blood component.

22. A method for selectively removing metabolic contaminants from at least one blood component, comprising: selecting a first selective membrane composed of a polyacrylamide hydrogel; directing a first solvent stream having a selected pH and including at least a metabolic contaminant and at least one blood component so as to flow along the first selective membrane; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, the pressure in both streams being substantially equal, wherein the application of such voltage potential causes movement of at least a portion of the at least one blood component through the first selective membrane into the second solvent stream while at least a portion of the metabolic contaminants is prevented from entering the second solvent stream wherein substantially all transmembrane migration of the at least one blood component is initiated by the voltage potential; and maintaining step until the second solvent stream contains the desired purity of the at least one blood component.

23. The method according to claim 22 further comprising directing a third solvent stream separated from a selected one of the first and second solvent streams by a second selective membrane and applying concurrently the voltage potential across the third solvent stream so as to cause the migration of at least a portion of at least one of the at least one blood component and any metabolic contaminants through the second selective membrane and into the third solvent stream.

24. The method according to claim 23 further comprising directing a fourth solvent stream separated from the other of the first and second solvent streams by a third selective membrane and applying concurrently the voltage potential across the fourth solvent stream so as to cause the migration of at least a portion of at least one of the at least one blood component and metabolic contaminants through the third selective membrane and into the fourth solvent stream.

The method according to claim 22 further comprising placing the at least one blood component from a subject into the first solvent stream.

26. The method according to claim 22 wherein the metabolic contaminants are selected from the group consisting of urea, creatinine, uric acid, phosphate ions, beta-2- microglobulins, autoantibodies, and other proteins, and combinations thereof.

27. The method according to claim 22 wherein the selective membrane has a molecular mass cut-off at least about 3 kDa.

28. A method for selectively removing metabolic contaminants from at least one blood component, comprising: directing a first solvent stream having a selected pH and including at least a metabolic contaminant and at least one blood component so as to flow along a first selective membrane comprising a polyacrylamide hydrogel; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, wherein the application of such voltage potential causes movement of at least a portion of the at least one blood component through the first selective membrane into the second solvent stream while at least a portion of the metabolic contaminants is prevented from entering the second solvent stream wherein substantially all transmembrane migration of the least one blood component is initiated by the voltage potential; periodically stopping and reversing the voltage potential to cause movement of at least any of the metabolic contaminants having entered the first selective membrane to move back into the first solvent stream and wherein substantially not causing any of the at least one blood component that has entered the second solvent stream to re-enter the first solvent stream; and maintaining steps or until the second solvent stream contains the desired purity of the at least one blood component.

29. A method for selectively removing metabolic contaminants from at least one blood component, comprising: placing at least one blood component form a subject into a first solvent stream; directing the first solvent stream having a selected pH and including at least a metabolic contaminant and at least one blood component so as to flow along a first selective membrane; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, wherein the application of such voltage potential causes movement of at least a portion of the at least one blood component through the first selective membrane into the second solvent stream while at least a portion of the metabolic contaminants is prevented from entering the second solvent stream wherein substantially all transmembrane migration of the at least one blood component is initiated by the voltage potential; maintaining step until the second solvent stream contains the desired purity of the at least one blood component; and returning at least one blood component in the second solvent stream to the subject.

The method according to claim 29 wherein the at least one blood component is recirculated between the subject and the first solvent stream.

31. A method for selectively removing metabolic contaminants from at least one blood component, comprising: directing a first solvent stream having a selected pH and including at least a metabolic contaminant and at least one blood component so as to flow along a first selective membrane, wherein at least one blood component has undergone treatment consisting of diffusive hemodialysis, convective hemodialysis, hemofiltration, hemodialfiltration, and combinations thereof prior to, subsequent to, or concurrently therewith step directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second, solvent streams, wherein the application of such voltage potential causes movement of at least a portion of the at least one blood component through the first selective membrane into the second solvent stream while at least a portion of the metabolic contaminants is prevented from entering the second solvent stream wherein substantially all transmembrane migration of the least one blood component is initiated by the voltage potential; and maintaining step until the second solvent stream contains the desired purity of at least one blood component.

32. A method for selectively removing selected compounds from at least one blood component, comprising: selecting a first selective membrane composed of a polyacrylamide hydrogel; directing a first solvent stream having a selected pH and including at least a selected compound capable of obtaining a charge and at least one blood component, so as to flow along the first selective membrane, wherein such pH produces a net charge on the metabolic contaminant; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, the pressure in both streams being substantially equal, wherein the application of such voltage potential causes movement of at least a portion of the selected charged compounds through the first selective membrane into the second solvent stream while at least a portion of the at least one blood component is prevented from entering the second solvent stream wherein substantially all transmembrane migration of the charged compound is initiated by the voltage potential; and maintaining step until the first solvent stream contains the desired purity of the at least one blood component.

33. The method according to claim 32 further wherein at least a portion of selected uncharged compounds contained in the first solvent stream migrate through the selective membrane into the second solvent stream.

34. A method for selectively removing selected compounds from at least one blood component, comprising: placing at least one blood component from a subject into a first solvent stream; directing the first solvent stream having a selected pH and including at least a selected compound capable of obtaining a charge and at lease one blood component, so as to flow along a first selective membrane, wherein such pH produces a net charge on the metabolic contaminant; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, wherein the application of such voltage potential causes movement of at least a portion of the selected charged compounds through the first selective membrane into the second solvent stream while at least a portion of the at least one blood component is prevented from entering the second solvent stream wherein substantially all transmembrane migration of the charged compound is initiated by the voltage potential; maintaining step until the first solvent stream contains the desired purity of the at least one blood component; and returning at least one blood component in the first solvent stream to the subject.

A method for selectively removing selected compounds from at least one blood component, comprising: selecting a first selective membrane composed of a polyacrylamide hydrogel; directing a first solvent stream having a selected pH and including at least a selected compound capable of obtaining a charge, a selected uncharged compounds, and at least one blood component, so as to flow along the first selective membrane, wherein such pH produces a net charge on the selected compound capable of obtaining a charge; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, the pressure in both streams being substantially equal, wherein the application of such voltage potential causes movement of at least a portion of the selected charged compounds through the first selective membrane into the second solvent steam while at least a portion of the at least one blood component is prevented from entering the second solvent stream wherein substantially all transmembrane migration of the selected charged compounds is initiated by the voltage potential, wherein at least a portion of the selected uncharged compounds contained in the first solvent stream migrates through the selective membrane into the second solvent stream; and maintaining step until the first solvent stream contains the desired purity of the at least one blood component.

36. A method for selectively removing selected compounds from at least one blood component, comprising: placing at least one blood component from a subject into a first solvent stream; directing the first solvent stream having a selected pH and including at least a selected compound capable of obtaining a charge, a selected uncharged compounds, and at least one blood component, so as to flow along a first selective membrane, wherein such pH produces a net charge on the selected compound capable of obtaining a charge; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, wherein the application of such voltage potential causes movement of at least a portion of the selected charged compounds through the first selective membrane into the second solvent stream while at least a portion of the at least one blood component is prevented from entering the second solvent stream wherein substantially all transmembrane migration of the selected charged compounds is initiated by the voltage potential, wherein at least a portion of the selected uncharged compounds contained in the first solvent stream migrates through the selective membrane into the second solvent stream; maintaining step until the first solvent stream contains the desired purity of the at least one blood component; and returning at least one blood component in the second solvent stream to the subject.

37. A method for selectively removing selected compounds from at least one blood component, comprising: selecting a first selective membrane composed of a polyacrylamide hydrogel; directing a first solvent stream having a selected pH and including at least a selected compound and at least one blood component so as to flow along the first selective membrane; directing a second solvent stream along the first selective membrane so as tobe isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, the pressure in both streams being substantially equal, wherein the application of such voltage potential causes movement of at least a portion of the at least one blood component through the first selective membrane into the second solvent stream while at least a portion of the selected compounds is prevented from entering the second solvent stream wherein substantially all transmembrane migration of the at least one blood component is initiated by voltage potential; and maintaining step until the second solvent stream contains the desired purity of the at least one blood component.

38. A method for selectively removing selected compounds from at least one blood component, comprising: placing at least one blood component from a subject into a first solvent stream; directing the first solvent stream having a selected pH and including at least a selected compound and at least one blood component so as to flow along a first selective membrane; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; applying at least one voltage potential across each of the first and second solvent streams, wherein the application of such voltage potential causes movement of at least a portion of the at least one blood component through the first selective membrane into the second solvent stream while at least a portion of the selected compounds is prevented from entering the second solvent stream wherein substantially all transmembrane migration of the at least one blood component is initiated by the voltage potential; and maintaining step until the second solvent stream contains the desired purity of the at least one blood component; and returning at least one blood component in the second solvent stream to the subject.

39. A method for selectively removing selected compounds from at least one blood component, comprising: selecting a first selective membrane composed of'a polyacrylamide hydrogel; directing a first solvent stream having a selected pH and including at least a selected compound and at least one blood component so as to flow along the first selective membrane; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby, the pressure in both streams being substantially equal; causing migration of at least a portion of the selected charged compounds through the first selective membrane into the second solvent stream while at least a portion of the at least one blood component is prevented from entering the second solvent stream wherein the transmembrane migration of the selected charged compounds is assisted by at least one of an application of a voltage potential across the first and second solvent streams, selected pH of first solvent stream, salt concentration in at least one of first and second solvent streams, concentration of the at least one blood component in the first solvent stream, concentration of the selected compounds in at least one of the first and second solvent streams, temperature of at least one of the first and second solvent streams, and preselected pore size of the selective membrane; and maintaining step until the first solvent stream contains the desired purity of the at least one blood component.

A method for selectively removing selected compounds from at least one blood component, comprising: placing at least one blood component from a subject into a first solvent stream; directing the first solvent stream having a selected pH and including at least a selected compound and at least one blood component so as to flow along a first selective membrane; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; causing migration of at least a portion of the selected charged compounds through the first selective membrane into the second solvent stream while at least a portion of the at least one blood component is prevented from entering the second solvent stream wherein the transmembrane migration of the selected charged compounds is assisted by at least one of an application of a voltage potential across the first and second solvent streams, selected pH of first solvent stream, salt concentration in at least one of first and second solvent streams, concentration of the at least one blood component in the first solvent stream, concentration of the selected compounds in at least one of the first and second solvent streams, temperature of at least one of the first and second solvent streams, and preselected pore size of the selective membrane; maintaining step until the first solvent stream contains the desired purity of the at least one blood component; and returning at least one blood component in the first solvent stream to the subject.

41. A method for selectively removing selected compounds from at least one blood component, comprising: selecting a first selective membrane composed of a polyacrylamide hydrogel; directing a first solvent stream having a selected pH and including at least a selected compound and at least one blood component so as to flow along a first selective membrane; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby, the pressure in both streams being substantially equal; causing migration of at least a portion of the at least one blood component through the first selective membrane into the second solvent stream while at least a portion of the selected compound is prevented from entering the second solvent stream wherein the transmembrane migration of the selected charged compounds is assisted by at least one of an application of a voltage potential across the first and second solvent streams, selected pH of first solvent stream, salt concentration in at least one of first and second solvent streams, concentration of the at least one blood component in the first solvent stream, concentration of the selected compounds in at least one of the first and second solvent streams, temperature of at least one of the first and second solvent streams, and preselected pore size of the selective membrane; and maintaining step until the first solvent stream contains the desired purity of the at least one blood component.

42. A method for selectively removing selected compounds from at least one blood component, comprising: placing at least one blood component from a subject into a first solvent stream; directing the first solvent stream having a selected pH and including at least a selected compound and at least one blood component so as to flow along a first selective membrane; directing a second solvent stream along the first selective membrane so as to be isolated from the first solvent stream thereby; causing migration of at least a portion of the at least one blood component through the first selective membrane into the second solvent stream while at least a portion of the selected compound is prevented from entering the second solvent stream wherein the transmembrane migration of the selected charged compounds is assisted by at least one of an application of a voltage potential across the first and second solvent streams, I selected pH of first solvent stream, salt concentration in at least one of first and second solvent streams, concentration of the at least one blood component in the first solvent stream, concentration of the selected compounds in at least one of the first and second solvent streams, temperature of at least one of the first and second solvent streams, and preselected pore size of the selective membrane; maintaining step until the first solvent stream contains the desired purity of the at least one blood component; and returning at least one blood component in the second solvent stream to the subject. Dated this 3rd day of August 2005 Gradipore Limited Patent Attorneys for the Applicant: ALLENS ARTHUR ROBINSON Patent Trade Marks Attorneys