GLUCOSE OXIDASE/LIPID MIXED LB-FILMS ON A PT ELECTRODE APPLICATION AS SENSOR MODEL

Abstract

Glucose oxidase (GOD)/lipid Langmuir-films on the air/water interface were prepared and investigated. The enzyme molecules were adsorbed by a preformed pure or mixed lipid monolayer from the aqueous subphase of the Langmuir-trough. The following types of lipids and their mixtures were used: lecithine, lecithine/ cetyltrimethylammonium bromide (CTAB), CTAB-modified methylmethacrylate monomer, stearic acid and stearic acid/CTAB. GOD was found to adsorb the strongest on positively charged lipid monolayers. It is due to the negative charges dominating the protein molecule at pH 7.0. The enzyme retains its enzymatic activity in adsorbed layers. The transfer of one to ten lipid-protein monolayers onto Pt-electrodes under 20-40 mN/m surface pressure was performed by the Langmuir-Blodgett method. As a result the biosensor was obtained with a measuring range from 0.5-5.0 mM glucose. The current output was found to depend on the number of transferred lipid-protein monolayers and on the surface pressure at which the transfer was carried out. The best electrode characteristics were found with glucose oxidase adsorbed on monolayers of the CTAB-modified methylmethacrylate monomer.