Biomedix, Inc.

Shu-Hui Chen

Paul Shieh

Dingli Guo

Shek-Hong Lau

A sensor for the amperometric assay of cholesterol is provided which comprises a sensing electrode containing a first redox mediator and a reference electrode in simultaneous contact with a reagent strip containing a second redox mediator. The presence of the second redox mediator greatly amplifies the current flow produced by the presence of cholesterol and produces linear correlation of current flow with concentration over an extended range. The sensing electrode comprises a non-conductive support member having an electrically conductive layer containing the first redox mediator. The reference electrode is typically a Ag/AgCl electrode formed by coating an ink containing Ag/AgCl dispersed in a resin on a non-conductive base. The reagent strip is a porous or fibrous carrier, typically a paper, impregnated with a mixture containing the second redox mediator, cholesterol esterase, cholesterol oxidase, horseradish peroxidase, at least one surfactant and at least one stabilizer comprising an aqueous thickening agent. In one version of the sensor, the sensing electrode comprises a support member of polyester film coated with an electrically conductive graphite composition containing dimethylferrocene as the first redox mediator and the second redox mediator comprises 3,3',5,5'-tetramethylbenzidine. The sensor may be constructed in several physical forms. In one form, the sensing and reference electrodes are in the form of strips and the reagent strip is sandwiched between the electrically conductive layers of the electrodes with the reference electrode having a hole, through which the reagent strip is exposed, for the introduction of sample.

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Fremont, CA, United States of America

Shu-Hui Chen