A biosensor that is highly responsive and capable of rapid and highly sensitive quantification of a specific component contained in a sample is provided. The biosensor of this invention comprises: an electrically insulating base plate; an electrode system comprising a working electrode and a counter electrode disposed on the base plate; and a reagent system comprising an oxidoreductase which catalyzes the oxidation reaction of glucose, gluconolactonase and a buffer. The buffer is selected from the group consisting of phthalic acid and its salts, maleic acid and its salts, succinic acid and its salts, phospholic acid and its salts, acetic acid and its salts, boric acid and its salts, citric acid and its salts, glycine, tris(hydroxymethyl)aminomethane, piperazine-N,N′-bis(2-ethane sulfonic acid) and the like.
1. A method for measuring the concentration of glucose in a sample solution by using a biosensor comprising: an electrically insulating base plate;
an electrode system comprising a working electrode and a counter electrode disposed on said base plate; and
a reagent system comprising an oxidoreductase which catalyzes a reaction of oxidizing glucose to gluconolactone, gluconolactonase and a buffer, wherein said buffer is selected from the group consisting of phthalic acid and its salts, maleic acid and its salts, succinic acid and its salts, phospholic acid and its salts, acetic acid and its salts, boric acid and its salts, citric acid and its salts, glycine, tris(hydroxymethyl)aminomethane, piperazine-N,N′-bis(2-ethane sulfonic acid), N-(2-acetamide)iminodiacetic acid, N,N-bis(2-hydroxyethyl)-2-aminoethane sulfonic acid, 2-morpholinoethanesulfonic acid, imidazole, dimethyl glutaric acid, triethanolamine hydrochloride, collidine, N-tris(hydroxymethyl)methylglycine, and bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane,
wherein said reagent system further comprises an electron mediator, and
wherein the method comprises determining the concentration of glucose in a sample solution by measuring an oxidation current produced by the oxidation of an electron mediator that has been reduced as a result of oxidation of glucose.
2. The method in accordance with claim 1 , wherein said reagent system further comprises a hydrophilic polymer.
3. The method in accordance with claim 1 , wherein said oxidoreductase, gluconolactonase and buffer are, while being mixed, carried by the sensor.
4. The method in accordance with claim 1 , wherein said oxidoreductase and gluconolactonase are, while being separated from each other, carried by the sensor.
5. The method in accordance with claim 1 , wherein said gluconolactonase is originated from one selected from the group consisting of Escherichia coli , yeast, man, rat, swine, bovine, Aspergillus niger, Azotobacter vinelandii, Pseudomonas fluorescens, Zymomonas mobilis, Streptomyces coelicolor, Deinococcus radiodurans and Xylella fastidiosa.
6. The method in accordance with claim 1 , wherein the amount of the buffer carried by the sensor is 5 nmol/mm 2 or less.
7. The method in accordance with claim 1 , wherein the buffer has a buffering capacity in a range of pH 4 to 8.
8. The method in accordance with claim 1 , wherein said oxidoreductase is selected from the group consisting of glucose oxidase, PQQ dependent glucose dehydrogenase, NAD dependent glucose dehydrogenase and pyranose oxidase.
9. The method in accordance with claim 1 , further comprising a cover member that is disposed on the base plate to form a sample solution supply pathway to the electrode system between the cover member and the base plate.
10. The method in accordance with claim 1 , wherein said reagent system further comprises an amphipathic compound.
11. A method for measuring the concentration of glucose in a sample solution by using a biosensor comprising: an electrically insulating base plate;
an electrode system comprising a working electrode and a counter electrode disposed on said base plate; and
a reagent system comprising an oxidoreductase which catalyzes a reaction of oxidizing glucose to gluconolactone, gluconolactonase and a buffer, wherein said buffer is selected from the group consisting of phthalic acid and its salts, maleic acid and its salts, succinic acid and its salts, phospholic acid and its salts, acetic acid and its salts, boric acid and its salts, citric acid and its salts, glycine, tris(hydroxymethyl)aminomethane, piperazine-N,N′-bis(2-ethane sulfonic acid), N-(2-acetamide)iminodiacetic acid, N,N-bis(2-hydroxyethyl)-2-aminoethane sulfonic acid, 2-morpholinoethanesulfonic acid, imidazole, dimethyl glutaric acid, triethanolamine hydrochloride, collidine, N-tris(hydroxymethyl)methylglycine, and bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane,
wherein said reagent system further comprises an electron mediator, the method comprising the steps of:
supplying a sample solution including glucose to the biosensor for allowing the oxidoreductase to catalyze an oxidation of the glucose;
applying a voltage to the working electrode with respect to the counter electrode; and
measuring an oxidation current produced by the oxidation of the electron mediator that has been reduced as a result of oxidation of glucose in the sample solution.