Immobilization of flavoproteins on silicon: effect of cross-linker chain length on enzyme activity

The effect of cross-linker chain length on the activities of choline oxidase (ChO) and glucose oxidase (GOx) immobilized on oxidized silicon wafers has been investigated for the cross-linkers N-succinimidyl 4-maleimido-butyrate (GMBS) and N-succinimidyl 6-maleimidocaproate (EMCS). Enzyme activities were determined with an indirect fluorometric assay based on the production of hydrogen peroxide. Immobilization of ChO or GOx onto oxidized silicon with either cross-linker resulted in an 86-99% loss in enzymatic activity relative to the soluble form of the flavoprotein. However, the different cross-linkers had distinctly different effects on enzyme activity: EMCS-immobilized GOx was four times more active than GMBS-immobilized GOx; EMCS-immobilized ChO had a sevenfold higher activity than GMBS-immobilized ChO.