Tetracyanoquinodimethane mediated glucose sensor based on a self-assembling alkanethiol/phospholipid bilayer

Abstract

An amperometric tetracyanoquinodimethane (TCNQ) mediated biosensor for glucose is described, based on a self-assembling alkanethiol/phospholipid bilayer laid down onto a gold surface. Gold was sputter deposited onto chromium coated silicon wafers to a thickness of 200 nm. A monolayer of alkanethiol was allowed to self-assemble from an ethanolic solution of dodecanethiol onto a freshly cleaned gold electrode in an overnight incubation. The monolayer was characterized by ellipsometric, impedance and cyclic voltammetry measurements (capacitance = 1·60 ± 0·06 μF/cm 2, and thickness 1·34 ± 0·15 nm). A mixture of phospholipid liposomes containing free amino groups was placed on the monolayer and allowed to incubate overnight. The self-assembly of a phospholipid monolayer from the phospholipid solution onto the alkanethiol monolayer, resulted in the formation of a bilayer. The formation of bilayer was again characterized by impedance and cyclic voltammetry measurements (capacitance = 0·98 ± 0·09 μF/cm 2, and thickness = 1·85 ± 0·22 nm). TCNQ has been incorporated into the liposomes before the formation of the bilayer. Glucose oxidase was cross-linked with the amino-groups of the phospholipids using bis [2-(sulphosuccinimiidooxicarbonyloxy)ethyl] sulphone. TCNQ which was incorporated in the bilayer acted as an efficient mediator to regenerate glucose oxidase. Cyclic voltammetry of the modified electrode and a response curve for the glucose sensor are reported.