Glucose biosensor based on the layer-by-layer self-assembling of glucose oxidase and chitosan derivatives on a thiolated gold surface.

The work proposed here deals with the design and characterization of biorecognition layers for the amperometric glucose determination based on the self-assembling of new chitosan derivatives, Nafion and glucose oxidase onto thiolated gold electrodes. The supramolecular multistructure is obtained by deposition of a layer of chitosan derivative (quaternized or hydrophobic) onto the gold surface modified with the sodium salt of 3-mercapto-1-propansulfonic acid, followed by the deposition of a layer of Nafion (as anti-interference barrier) and by the alternate deposition of the chitosan derivative and glucose oxidase (as biocatalytic layer). The influence of the deposition time and concentration of polyelectrolytes, organization and number of layers, and nature of the chitosan derivative on the sensitivity and selectivity of the bioelectrode is examined and optimized in order to obtain a rational design of the biosensor. The system is studied electrochemically from the oxidation at 0.700 V of the hydrogen peroxide enzymatically generated using gold as substrate, and spectrophotometrically from the protein absorption at 277 nm using quartz as substrate. The selected biosensor containing five quaternized chitosan/glucose oxidase bilayers exhibits very good analytical performance with a sensitive ((4.9+/-0.2) x 10(2) nA mM(-1)) and highly selective response (0% interference for maximum physiological levels of ascorbic acid and uric acid), demonstrating that the alternate electrostatic adsorption of conveniently selected polyelectrolytes allows noticeable improvements in the selectivity and sensitivity of a biosensor.