Cholesterol sensor containing electrodes, cholesterol dehydrogenase, nicotinamide adenine dinucleotide and oxidized electron mediator

Abstract

A cholesterol sensor for quantitative determination of cholesterol is provided containing an electrode system and a reaction reagent system. The electrode system contains a measuring electrode such as a carbon electrode and a counter electrode, and the reaction reagent system contains cholesterol dehydrogenase, nicotinamide adenine dinucleotide and an oxidized electron mediator. Electron mediators include ferricyanide, 1,2-naphthoquinone-4-sulfonate, 2,6-dichlorophenol indophenol, dimethylbenzoquinone, 1-methoxy-5-methylphenazinium sulfate, methylene blue, gallocyanine, thionine, phenazine methosulfate and Meldola's blue. Diaphorase, cholesterol esterase and a surfactant may also be present. The electrode system is on an insulating base plate, and the base plate has a covering member containing a groove that is a sample supplying channel which extends from an end of the base plate to the electrode system. A reaction layer containing the reagent system in dry form and a layer of a hydrophilic polymer is provided on the base plate or the covering member, or on both the electrode system and covering member so as to be exposed to the sample supplying channel. During operation, the electron mediator is reduced in conjunction with oxidation of cholesterol in a sample by cholesterol dehydrogenase, and an amount of current required to electrochemically re-oxidize the electron mediator is directly proportional to a quantity of cholesterol present in the sample.