Optical glucose sensor chip and method of manufacturing the same

Abstract

An optical glucose sensor chip includes a substrate, a pair of optical elements formed on a surface of the substrate for introducing light into the substrate and for emitting the light from the substrate, and a glucose sensing membrane formed on the surface of the substrate at a position between the optical elements. The sensing membrane includes a color reagent substrate, a first enzyme which oxidizes or reduces glucose, a second enzyme that generates a material which makes the color reagent substrate exhibit color by a reaction with a product obtained by oxidation or reduction of glucose, a nonionic cellulose derivative, and an ionic polymer into which a buffer is incorporated. At least one of the first and second enzymes is coated with the ionic polymer, and the color reagent substrate. The first and second enzymes, the buffer and the ionic polymer are supported by the nonionic cellulose derivative.

1 . An optical glucose sensor chip comprising:
 a substrate;   a pair of optical elements formed on a principal surface of the substrate for introducing light into the substrate and for emitting the light from the substrate; and   a glucose sensing membrane formed on the principal surface of the substrate at a position between the optical elements;   wherein the sensing membrane includes a color reagent substrate, a first enzyme which oxidizes or reduces glucose, a second enzyme that generates a material which makes the color reagent substrate exhibit color by a reaction with a product obtained by oxidation or reduction of glucose, a nonionic cellulose derivative, and an ionic polymer into which a buffer is incorporated,   at least one of the first and second enzymes is coated with the ionic polymer, and   the color reagent substrate, the first and second enzymes, the buffer and the ionic polymer are supported by the nonionic cellulose derivative.   
   
   
       2 . The sensor chip according to  claim 1 , wherein the first enzyme is glucose oxidase, the second enzyme is peroxidase and the color reagent substrate is at least one of 3,3,5,5-tetramethylbenzidine and N,N′-bis(2-hydroxy-3-sulfopropyl)tridine. 
   
   
       3 . The sensor chip according to  claim 1 , wherein the ionic polymer is a negative ionic polymer. 
   
   
       4 . The sensor chip according to  claim 3 , wherein the negative ionic polymer is a polymer containing at least one anionic group selected from the group consisting of a phosphate, a carboxylate and a sulfonate. 
   
   
       5 . The sensor chip according to  claim 1 , wherein the nonionic cellulose derivative is at least one selected from the group consisting of an alkyl cellulose, a hydroxyalkyl cellulose and a hydroxyalkylalkyl cellulose. 
   
   
       6 . The sensor chip according to  claim 1 , wherein the sensing membrane further contains a crosslinking high-molecular compound. 
   
   
       7 . The sensor chip according to  claim 6 , wherein the crosslinking high-molecular compound is a copolymer of a hydrophobic monomer and a hydrophilic monomer having at least one group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group and an ionic functional group. 
   
   
       8 . The sensor chip according to  claim 7 , wherein the copolymer of a hydrophilic monomer and a hydrophobic monomer is a copolymer of 2-methacryloyloxyethylphosphorylcholine and butylmethacrylate. 
   
   
       9 . The sensor chip according to  claim 1 , wherein the glucose sensing membrane further contains polyethylene glycol or ethylene glycol for endowing the membrane with water permeability. 
   
   
       10 . An optical glucose sensor chip comprising:
 a glass substrate;   a pair of optical elements formed on a principal surface of the glass substrate for introducing light into the glass substrate and for emitting the light from the glass substrate;   a light-reflecting path layer formed on the principal surface of the substrate on which the optical elements are formed and made of a resin having a higher refractive index than the substrate; and   a glucose sensing membrane formed on the light-reflecting path layer at a position between the optical elements;   wherein the sensing membrane includes a color reagent substrate, a first enzyme which oxidizes or reduces glucose, a second enzyme that generates a material which makes the color reagent substrate exhibit color by a reaction with a product obtained by oxidation or reduction of glucose, a nonionic cellulose derivative, and an ionic polymer into which a buffer is incorporated,   at least one of the first and second enzymes is coated with the ionic polymer, and   the color reagent substrate, the first and second enzymes, the buffer and the ionic polymer are supported by the nonionic cellulose derivative.   
   
   
       11 . The sensor chip according to  claim 10 , wherein the first enzyme is glucose oxidase, the second enzyme is peroxidase and the color reagent substrate is at least one of 3,3,5,5-tetramethylbenzidine and N,N′-bis(2-hydroxy-3-sulfopropyl)tridine. 
   
   
       12 . The sensor chip according to  claim 10 , wherein the ionic polymer is a negative ionic polymer. 
   
   
       13 . The sensor chip according to  claim 12 , wherein the negative ionic polymer is a polymer containing at least one anionic group selected from the group consisting of a phosphate, a carboxylate and a sulfonate. 
   
   
       14 . The sensor chip according to  claim 10 , wherein the nonionic cellulose derivative is at least one selected from the group consisting of an alkyl cellulose, a hydroxyalkyl cellulose and a hydroxyalkylalkyl cellulose. 
   
   
       15 . The sensor chip according to  claim 10 , wherein the sensing membrane further contains a crosslinking high-molecular compound. 
   
   
       16 . The sensor chip according to  claim 15 , wherein the crosslinking high-molecular compound is a copolymer of a hydrophobic monomer and a hydrophilic monomer having at least one group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group and an ionic functional group. 
   
   
       17 . The sensor chip according to  claim 16 , wherein the copolymer of a hydrophilic monomer and a hydrophobic monomer is a copolymer of 2-methacryloyloxyethylphosphorylcholine and butylmethacrylate. 
   
   
       18 . The sensor chip according to  claim 10 , wherein the glucose sensing membrane further contains polyethylene glycol or ethylene glycol for endowing the membrane with water permeability. 
   
   
       19 . A method of manufacturing an optical glucose sensor chip, comprising:
 preparing a glucose sensing membrane-forming coating solution by using any of: (a) a method in which at least one of a first enzyme that oxidizes or reduces glucose and a second enzyme that generates a material which makes a color reagent substrate exhibit color by a reaction with a product obtained by oxidation or reduction of glucose is mixed in advance with an aqueous solution containing an ionic polymer and a buffer, and the mixed solution is added to and mixed with the other enzyme, a color reagent substrate and a nonionic cellulose derivative; (b) a method in which the first and second enzymes are respectively mixed in advance with an aqueous solution containing an ionic polymer and a buffer, and the respective prepared mixed solutions are added to and mixed with a color reagent substrate and a nonionic cellulose derivative; or (c) a method in which both the first and second enzymes are mixed in advance with an aqueous solution containing an ionic polymer and a buffer, and the prepared mixed solution is added to and mixed with a color reagent substrate and a nonionic cellulose derivative;   forming a pair of optical elements on a substrate for introducing light into the substrate and for emitting the light from the substrate; and   applying the glucose sensing membrane-forming coating solution to a substrate area positioned between the optical elements, followed by drying to form a glucose sensing membrane.   
   
   
       20 . A method of manufacturing an optical glucose sensor chip, comprising:
 preparing a glucose sensing membrane-forming coating solution by using any of: (a) a method in which at least one of a first enzyme that oxidizes or reduces glucose and a second enzyme that generates a material which makes a color reagent substrate exhibit color by a reaction with a product obtained by oxidation or reduction of glucose is mixed in advance with an aqueous solution containing an ionic polymer and a buffer, and the mixed solution is added to and mixed with the other enzyme, a color reagent substrate and a nonionic cellulose derivative; (b) a method in which the first and second enzymes are respectively mixed in advance with an aqueous solution containing an ionic polymer and a buffer, and the respective prepared mixed solutions are added to and mixed with a color reagent substrate and a nonionic cellulose derivative; or (c) a method in which both the first and second enzymes are mixed in advance with an aqueous solution containing an ionic polymer and a buffer, and the prepared mixed solution is added to and mixed with a color reagent substrate and a nonionic cellulose derivative;   forming a pair of gratings on a substrate for introducing light into the substrate and for emitting the light from the substrate;   forming a light-reflecting path layer made of a resin having a higher refractive index than the substrate on a principal surface of the substrate on which the optical elements are formed; and   applying the glucose sensing membrane-forming coating solution to the part of the light-reflecting path layer positioned between the optical elements, followed by drying to form a glucose sensing membrane.