JP3349786B2 - Hydrophobic polymer film for taste sensor and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amphipathic ion concentration sensor. It is intended for use as a sensor for human senses, especially for taste.

[0002]

2. Description of the Related Art An applicant who is partially identical to the present application has previously filed a patent application for the invention of "taste sensor and its manufacturing method" (Japanese Patent Application No. 1-190819; hereinafter, referred to as prior application invention A). According to the description and drawings, a group of so-called lipid molecules housed in a surface matrix of a certain high molecular polymer with a specific molecular arrangement, saltiness, sourness called basic taste,
It was shown that the sensor showed sensitivity to bitterness and sweetness. Moreover, it has been shown that this type of sensor can measure taste instead of taste, which is one of the human five senses.

[0003] This will be described in a little more detail. In the prior invention A, for example, polyvinyl chloride (PVC) is used as a polymer, and dioctyl phthalate (D
A mixture of a plasticizer such as OP) and a lipid in a weight ratio of about 2: 3: 1 is melted in tetrahydrofuran (THF), transferred to a flat-bottomed container, and placed on a uniformly heated plate for about 30 minutes. The mixture was kept at 2 ° C. for 2 hours to evaporate THF to obtain a lipid membrane, that is, a lipid molecular membrane contained in a surface matrix of PVC. Experiments have confirmed that this lipid membrane serves as a taste sensor. At this time, when the lipid membrane is immersed in an aqueous solution of potassium chloride (KCl), it appears that the hydrophilic groups of the lipid molecules are arranged in a face-up manner on the surface of the lipid membrane, and the sensor (membrane potential) It was shown that the sensitivity and stability of the compound were improved.

However, using a lipid membrane formed in this way as a sensor, although a measurement result can be obtained to a certain extent, the production method of placing lipid molecules in the surface matrix of a high molecular polymer requires a molecular level. Structure is not constant,
In other words, it is not always possible to obtain a constant surface matrix itself, and it is difficult to guarantee that a lipid membrane containing lipid molecules is always of constant quality. The orientation of the reactive molecules is also poor, and therefore, the measurement of the membrane potential and the electrical resistance is likely to cause variations in the data and the sensitivity is inadequate.

[0005] In addition, the types of lipid molecules that can be relatively easily accommodated in the surface matrix of a high molecular polymer have been limited. For example, phosphatidylcholine (P
Lipids constituting a biological membrane, such as C), have poor compatibility with a polymer material such as polyvinyl chloride (PVC), so that it has been difficult to form a lipid membrane used for a taste sensor. As a means for solving the above-mentioned problem, the same applicant has previously filed a patent application for the invention of "taste sensor and its manufacturing method" (Japanese Patent Application No. 3-20450; hereinafter, referred to as prior application invention B). , Its specification and drawings show a new method of forming a single layer of amphipathic molecules and bitter substances, this single layer improves the sensitivity, Stability is obtained, and there is little variation in measured values for each sensor.
Moreover, it was shown that a sensor having logarithmic linearity could be obtained.

This will be described in a little more detail. According to the invention of the prior application B, for example, a substrate covered with a substance having a property of being familiar with a hydrophobic part of an amphipathic molecule group or a bitter substance molecule group is provided. Forming a monolayer (monolayer) with the hydrophilic groups of the amphipathic molecules or the bitter substance molecules exposed on the surface using the LB method or the modification method. did. As described above, it has been experimentally shown that the sensor surface can be made closer to human taste characteristics by forming a uniform monolayer.

[0007]

However, the membrane of the prior invention A and the membrane of the prior invention B have a problem in measuring bitterness. That is, when the solution to be measured contains a bitter substance, the bitter substance is adsorbed to the membrane, and thus the reproducibility of the measurement for the bitter taste is poor. As a countermeasure, there is a method in which a bitter substance is adsorbed on the film surface in advance, but the sensitivity is deteriorated even if the reproducibility is improved.

There is also a problem in durability. The membrane of the invention A of the prior application has a structure in which lipid molecules are contained in a surface matrix of a polymer, and the bonding between the polymer and the lipid molecules is due to van der Waals force and mechanical entanglement. Further, the membrane of the invention B of the prior application is characterized in that the suction force between the hydrophobic group of the amphiphilic substance or the bitter substance and the portion of the base film which is close to the hydrophobic group, and the hydrophobic group of the amphiphilic substance or the bitter substance and the water This is because it is fixed to the base film only by the repulsive force. In any of the films, the film material (lipid, amphiphilic substance, bitter substance) is easily dissolved in the solution to be measured. This leads to deterioration of the film itself, and also causes the melted film material to be adsorbed to the film of another channel and change the characteristics of the other film.

SUMMARY OF THE INVENTION It is an object of the present invention to realize a durable taste sensor film which has not been realized by a conventional taste sensor film, has good bitterness reproducibility, has high bitter taste sensitivity, and is durable.

[0010]

Means for Solving the Problems In order to solve the above-mentioned problems, a hydrophobic polymer film for a taste sensor according to the first invention (hereinafter, referred to as a "taste sensor") is disclosed.
The film is called a film having hydrophobicity as the name implies, and a film containing charged groups (charged groups) to such an extent that the hydrophobicity of the film is not impaired. That is, the film was composed of a mixture of a polymer and a plasticizer, and part or all of the polymer had a charged group in a part of its molecular structure. In the method for producing a hydrophobic polymer film for a taste sensor according to the second invention, the polymer is obtained by copolymerization of an alkene having no charged group (main agent) and an alkene having a charged group (secondary agent). After mixing the obtained copolymer and the plasticizer using a common solvent, the common solvent was evaporated to form a film.

[0011]

The membrane does not respond to hydrophilic ions (acidity, saltiness) but reacts to amphipathic ions (bitterness) because the membrane is hydrophobic and has a small charge. It is considered that this reaction is schematically shown in FIG. In FIG. 4, the hydrophilic ions 19 are repelled by the membrane because the membrane is hydrophobic. There is a concentration gradient of amphipathic ions in the A solution 15 and the B solution 16 sandwiching the membrane (here, the concentration of the A solution 15 is lower than that of the B solution 16), and the charge contained in the membrane 10 If the polarity of the charge of the group 11 is opposite to that of the amphipathic ion 17, the potential difference V between the A solution 15 and the B solution 16

[0012]

(Equation 1)

Occurs. Here, k is a sensitivity coefficient that maximizes the Nernst gradient (RT / zF), and C0 and C are the concentrations of amphipathic ions in the A solution 15 and the B solution 16, respectively. If the potential difference V is known, the concentration ratio between the A solution 15 and the B solution 16 is known, and the concentration of the B solution 16 is known when the A solution 15 is set to the reference concentration. Since the charge contained in the film is small, there is no chance that the amphipathic ions are adsorbed on the film surface and the reproducibility is good. In addition, since the film is hydrophobic, there is no elution of the film material into the solution to be measured. .

[0014]

FIG. 2 shows a flowchart of a first embodiment of the manufacturing method of the present invention. The first embodiment is an example of copolymerization in an aqueous solution, and the procedure is as follows. 7 g of vinyl chloride (main agent), 0.07 g of sodium acrylamide 2-methylpropanesulfonate (secondary agent) and 0.07 g of ammonium persulfate as a catalyst (polymerization initiator) in 20 ml of 0.75% sodium dodecyl sulfate (emulsifier) aqueous solution Emulsion polymerization at 50 ° C. for about 12 hours. The copolymer is washed with water. (Removal of catalyst, emulsifier, etc.) Dissolve in tetrahydrofuran (THF). About 1 solution dissolved in tetrahydrofuran (THF)
Wash dropwise with 1 l of distilled water. Washing is performed three times. After washing, dry. 2 g of the dried sample and Elvaloy 742 (ELVALO)
Y742: manufactured by DuPont: Elvaloy, ELVALOY
Is EI DuPont de Nimores and CO
3 g) (plasticizer) are dissolved in 20 ml of THF. The dissolved matter is filtered. After filtration, spread on a glass plate to evaporate the solvent. A film having a thickness of about 0.1 mm was obtained by the method described above.

FIG. 1 schematically shows the structure of the obtained film.
It is considered that the obtained film 10 has a structure in which the polymer 12 having the charged group 11, the polymer 13 having no charged group 11, and the plasticizer 14 are entangled. Polymer 1 having charged group 11 in FIG. 1
The chemical formula of 2 is shown in Chemical formula 1.

[0016]

Embedded image

In the above process, when the solvent is evaporated by spreading it on a glass plate after filtration, if the solvent is slowly evaporated, a small hole called a microchannel (having a diameter of several tens to several hundreds) can be obtained.
(about μm) does not occur, but if microchannels occur, they allow permeation of counter-ions, so if they occur, annealing treatment is performed. The annealing treatment is performed under reduced pressure (~ 0.
(1 mmHg), just below the softening temperature of the membrane (40-50
C.) for 6 to 24 hours.

Using a solution obtained by dissolving PVC in THF as an adhesive, the obtained film was attached to a PVC pipe, and the inner solution (100 m
M potassium chloride solution) to prepare a sensor, and an experiment was performed using the measurement system shown in FIG. In addition, the detection of a bitter substance is more stable when the bitter substance is added to the internal solution.

The measuring system includes a sensor 23 in a container 23 containing a solution to be measured (1 mM potassium chloride solution + taste substance) 22.
0, the inner solution (100 mM potassium chloride solution) 21 of the sensor 20 and a saturated potassium chloride solution 28 containing a reference silver-silver chloride (Ag-AgCl) electrode 27 are connected to a salt bridge 25.
The solution to be measured 22 and the silver-silver chloride electrode 29 for measurement
And a saturated potassium chloride solution 30 containing the same, and connected by a salt bridge 26. A magnetic stirrer 24 is provided in the solution to be measured to make the concentration of the taste substance uniform. The entire measurement system is housed in a shield box 31. The membrane potential was measured with an electrometer not shown.

The reagents include quinine hydrochloride (hereinafter referred to as quinine) as a bitter taste and sodium chloride (N
aCl), hydrochloric acid (HCl) as sour, sucrose as sweet, sodium L-glutamate as umami
MSG) was used. For the measurement of the response of the five basic taste substances, the potential response was read about 2 minutes after the reagent was dropped and stirred, and the membrane potential was plotted against the logarithmic concentration. Measurement is 3
It was done repeatedly. The electric potential was measured with an electrometer having an input resistance of 10 13 Ω or more based on the internal solution.

FIG. 6 shows the five basic taste substance responses. The horizontal axis in FIG. 6 defines the concentration of the tastant in the solution to be measured, and the vertical axis defines the membrane potential at the lowest concentration of the tastant to be measured as 100% because the initial value fluctuated about ± 10 mV around +45 mV. In addition, the concentration characteristics of the taste substance with respect to the membrane potential are displayed relatively. △ indicates quinine, は indicates sodium chloride, ◎ indicates hydrochloric acid, は indicates sucrose, and ◇ indicates MSG measurement results.

This membrane has a weak response to sucrose (sweet), MSG (umami), and electrolytes such as sodium chloride (saltiness) and hydrochloric acid (sourness). In contrast, a strong response is seen with quinine (bitterness), which is strongly hydrophobic. Further, as can be seen from the figure, the reproducibility of the measurement for bitterness is good.

FIG. 3 shows a flowchart of a second embodiment of the manufacturing method of the present invention. The second embodiment is an example of copolymerization in an organic solvent, and the procedure is as follows. 10 g of vinyl chloride (main agent), 0.05 g of sodium aryloxyphenylsulfonate (secondary agent) and 0.3 g of azobisisobutyronitrile as a catalyst in THF50.
The reaction is carried out at 60 ° C. for about 8 hours to obtain a copolymer. The copolymer is washed with water. (Removal of catalyst and the like) Dissolve in tetrahydrofuran (THF). About 1 solution dissolved in tetrahydrofuran (THF)
Wash dropwise with 1 l of distilled water. Washing is performed three times. After washing, dry. 2 g of the dried sample and 3 g of Elvaloy HP441 (manufactured by DuPont) are mixed and dissolved in 20 ml of THF. The dissolved matter is filtered. After filtration, spread on a glass plate to evaporate the solvent. Thus, a film having a thickness of about 0.05 mm was obtained. Second
The ratio of the copolymer, the plasticizer and the common solvent is about 2: 3: 10 to 20 in the process of Example.

The chemical formula of the polymer having a charged group contained in the film obtained in the second embodiment is shown in Chemical formula 2.

[0025]

Embedded image

In the first embodiment and the second embodiment, vinyl chloride is used as a main ingredient. However, other examples include those shown in Table 1.

[0027]

[Table 1]

Further, examples of the auxiliary agent include those shown in Table 2.

[0029]

[Table 2]

As described in the section of action, the polarity of the charge of the charged group contained in the membrane needs to be opposite to the amphipathic ion to be detected. Taste substances exhibiting bitterness include cations and anions, and in order to detect both, a membrane containing a charged group of each polarity may be prepared.

[0031]

As described above, according to the present invention, a durable taste sensor film having good characteristics, for example, as a taste sensor, particularly a bitter sensor, can be obtained. An increase in the number of types of sensors leads to an increase in the amount of information for determining taste and the like. Since it has a structure in which a functional group is directly bonded to a polymer chain, there is no problem such as elution of lipid. That is, when performing measurement in multiple channels using a plurality of types of membranes, the membranes eluted from each other are not contaminated, and the lifetime (durability) of the membrane itself is extended. Further, in this method, by changing the ratio between the main agent and the auxiliary agent, the amount of the film charge can be easily changed, and thus various types of films can be adjusted.

[Brief description of the drawings]

FIG. 1 is a schematic view of a cross section of a hydrophobic polymer film for a taste sensor of the present invention.

FIG. 2 is a flowchart showing a first embodiment of a method for producing a hydrophobic polymer film for a taste sensor according to the present invention.

FIG. 3 is a flowchart showing a second embodiment of the method for producing a hydrophobic polymer film for a taste sensor according to the present invention.

FIG. 4 is a schematic diagram illustrating a reaction of a hydrophobic polymer membrane for a taste sensor according to the present invention to an amphipathic ion (bitterness).

FIG. 5 is a diagram showing a measurement system for examining a basic taste response of the hydrophobic polymer film for a taste sensor of the present invention.

FIG. 6 is a diagram showing a basic taste response of the hydrophobic polymer film for a taste sensor of the present invention.

[Explanation of symbols]

 1 step (step of obtaining a copolymer) 2 step 3 step 4 step 5 step 6 step (step of obtaining a mixed solution) 7 step 8 step (step of evaporating a common solvent from the mixed liquid) 10 film (hydrophobicity for taste sensor) 11 charged group 12 polymer having a charged group 13 polymer 14 plasticizer 15 A liquid 16 B liquid 17 amphiphilic ion 18 hydrophilic ion 19 hydrophilic ion 20 hydrophilic ion 21 inner liquid 22 solution to be measured 23 Container 24 Magnetic Stirrer 25 Salt Bridge 26 Salt Bridge 27 Standard Silver-Silver Chloride Electrode 28 Saturated Potassium Chloride Solution 29 Measurement Silver-Silver Chloride Electrode 30 Saturated Potassium Chloride Solution 31 Shield Box

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-238263 (JP, A) JP-A-3-54446 (JP, A) JP-A-7-5147 (JP, A) JP-A-63-1988 222248 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 27/00-27/49

Claims (2)

(57) [Claims] 1. A hydrophobic polymer membrane for a taste sensor, comprising a polymer (12) having a charged group (11) in a part of its molecular structure. 2. A step (1) of obtaining a copolymer by copolymerizing a main agent composed of an alkene having no charged group and an auxiliary agent composed of an alkene having a charged group, comprising the steps of: A method for producing a hydrophobic polymer film for a taste sensor, comprising: dissolving in a common solvent to obtain a mixed solution (6); and evaporating the common solvent from the mixed solution (8).