AMPEROMETRIC BIOSENSORS USING POLY-L-LYSINE POLY(STYRENESULFONATE) MEMBRANES WITH IMMOBILIZED ENZYMES/

Enzyme electrodes for L-lactic acid, choline and glucose were prepared by immobilizing lactate oxidise, choline oxidase and glucose oxidase into polyion complex membranes, respectively: an aqueous solution cont aining poly-L-lysine and each enzyme was placed on a glassy carbon ele ctrode, then an aqueous solution of poly(4-styrenesulfonate) was added to the polycation/enzyme mixture and dried. The anodic current (at 1 V vs. Ag/AgCl) of each enzyme electrode increased after the addition o f the corresponding analyte, due to the electrolytic oxidation of the hydrogen peroxide produced through the oxidase-catalyzed reaction in t he membrane. The membrane showed permselectivity based on the solute s ize with the molecular cut-off of 110. For the L-lactate and choline-s ensing electrodes, the permselectivity was effective in reducing the i nterferential response as compared to the response for the analyte: th e permeation of interferents such as L-ascorbic acid, uric acid and ac etaminophen, was restricted, whereas the analyte permeated easily to u ndergo the enzymatic reaction. in the case of the glucose oxidase/poly ion complex layer, the restriction of glucose transport resulted in th e enzyme electrode suitable for the determination of the analyte in hi gh concentrations. Each enzyme electrode was highly stable, e.g., the glucose-sensing electrode could be used for more than 20 weeks.