Covalent immobilization and SECM analysis in feedback mode of glucose oxidase on a modified oxidized silicon surface

Covalent immobilization of glucose oxidase (GOx) on oxidized silicon (SiO2) surfaces is detailed in view of producing interfaces with a simple, controlled and reproducible procedure that could be used in bioanalytical applications as those based on SECM detection. The procedure is based first on the formation of an amino-terminated propyl layer on a SiO2 substrate followed by addition and cross-linking of a polyoxyethylene bis(diglycidylether) and GOx mixture. The epoxide groups of the cross-linker react with amino groups allowing both the cross-linking with the enzyme (reaction with the free amino groups of the lysine residues) and the covalent attachment of the enzyme layer on the amino groups bound to the surface. SECM in feedback mode analysis provides a characterization of the modified surface and the measurement of the enzymatic activity depending on the concentrations of glucose and mediator. Kinetics analysis indicates that GOx maintains a large enzymatic activity and that the active enzymes remain reachable after their incorporation in the layer with the advantages of a robust immobilization.