CELLOBIOSE OXIDASE CROSS-LINKED IN A REDOX POLYMER MATRIX AT AN ELECTRODE SURFACE - A NEW BIOSENSOR

The properties of an enzyme electrode, based on cellobiose oxidase, CBO, crosslinked in a redox polymer (poly[(vinylpyridine)Os(bpy)2Cl2+/3+]/polyamine) matrix on a rotating disk electrode were studied. Effects on the steady state cellobiose response of pH, temperature, rotation rate and film thickness were investigated. The percentage of accessible redox couples remained constant, regardless of film thickness up to at least 2.5 mum, indicating full access to the outermost layer of the enzyme-polymer matrix. The apparent Michaelis constant K(m)' increased with increasing film thickness, owing to depletion of substrate in the film. The turnover number k2' decreased with increasing film thickness, indicating reaction limitation due to charge propagation through the film. Extrapolated to an infinitesimal film, the kinetic constants of the electrode mirror the enzyme kinetics in solution. The Arrhenius activation energy was determined to be 42 kJ mol-1 for the thickest electrode and 34 kJ mol-1 for the thinnest. The electrode is suited as a sensor for cellobiose, lactose and maltose as well as for cellotriose and corresponding oligosaccharides up to a degree of polymerization of at least six.