Fabrication of Biosensors with the use of Electrodes Immobilizing Plural Kinds of Enzymes

(1)利用Au电极固定胆固醇氧化酶和胆固醇酯制备胆固醇传感器氨基乙醇在金电极上的化学吸附提供了其致密的自组装单分子层。以戊二醛为交联剂，将胆固醇氧化酶和胆固醇酯酶共价固定在电极上。在含有硫堇作为电子介体的电解质溶液中，将所得电极在相对于SCE为0V下极化。结果发现，注射游离胆固醇或胆固醇酯酶产生的氧化电流和值稳步增加，增加在基板。根据这些实验结果，我们建立了一个实用的方法，精确测定浓度的游离胆固醇和胆固醇酯酶与使用制备的胆固醇传感器。(2)用Au电极固定尿酸酶和电子媒介物的尿酸传感器的制作用与上述相同的方法也制备了固定尿酸酶（尿酸氧化酶）的Au电极。如果使用含有适当电子介体的电解质溶液，则电极用作尿酸传感器。利用氧化还原聚合物作为电子介质，制备了固定尿酸酶和电子介质的Au电极。在这种情况下，能够在溶液中不添加任何其他物质的情况下测定溶液中尿酸的浓度。此外，通过自组织融合的自组装单分子层的烷烃乙醇和磷脂形成的人工双层被用来与电子介质一起固定膜蛋白之一的尿酸酶。双层电极作为尿酸传感器具有极高的底物选择性。

(1) Fabrication of Cholesterol Sensors using Au electrodes immobilizing Cholesterol Oxidase and Cholesterol EsteraseChemical adsorption of aminoethanethiol on a gold electrode provided its densely packed self-assembled monolayer. Cholesterol oxidase and cholesterol esterase were covalently immobilized on the electrode with use of glutaraldehyde as a cross-linking agent. The resulting electrode was polarized at 0 V vs. SCE in an electrolyte solution containing thionin as an electron mediator. It was found that injection of free cholesterol or cholesterol esterase gave generation of oxidation currents and the value increased steadily with an increase in the substrate. From these experimental results, we established a practical methodology of precise determination of concentration of free cholesterol and cholesterol esterase with the use of the prepared cholesterol sensors.(2) Fabrication of Uric Acid Sensors using Au electrodes immobilizing Uricase and Electron MediatorAn Au electrode immobilizing uricase (uric acid oxidase) was also prepared by the same method as that mentioned above. The electrode worked as a uric acid sensor if an electrolyte solution containing an appropriate electron mediator was used. Preparation of Au electrode on which uricase and electron mediator were immobilized was achieved by using a redox polymer which can work as an electron mediator for uricase. In this case, concentration of uric acid in solution was able to be determined without addition of any other substances in the solution. Furthermore, an artificial bilayer formed by self-organized fusion of a self-assembled monolayer of alkanethiol and phospholipid was used to immobilize uricase that is one of membrane proteins together with electron mediators. The bilayer electrodes worked well as the uric acid sensor possessing an extremely high substrate selectivity.