Detection of cholesterol through electron transfer to cholesterol oxidase in electrode-supported lipid bilayer membranes

Cholesterol oxidase is immobilized in lipid bilayer membranes assembled on tin-doped indium oxide electrode surfaces to sequester cholesterol from solution and to follow cholesterol oxidation via electrochemical reduction of hydrogen peroxide. The inner leaflet of the bilayer is chemically bound to the electrode surface through a thiol functionality at the polar headgroup end of the lipid. The outer lipid leaflet, containing cholesterol oxidase, is formed using a deoxycholate dialysis procedure. Continuous solution flow experiments, where the flow is changed from buffer solution containing no cholesterol to a buffer solution containing cholesterol, show currents for the reduction of hydrogen peroxide generated by the enzyme. The data indicate that cholesterol oxidase is immobilized on the electrode in an active state. The data are also consistent with energetically favored collection of cholesterol from solution by the electrode-supported lipid bilayer membrane.