Study on direct Electrochemistry of glucose oxidase stabilized by cross-linking and immobilized in silica nanoparticle films

Glucose oxidase (GOD) in SiO2 nanoparticle films was cross-linked by glutaraldehyde (GA), forming GOD-GA-SiO2 films on the surface of pyrolytic graphite (PG) electrodes. GOD in the GOD-GA-SiO2 films showed a pair of well defined and quasi-reversible cyclic voltammetric peaks at -0.48 V vs. SCE in pH 7.0 buffers. Scanning electron microscopy of the films demonstrated that the interaction between GOD and GA/SiO2 would make the morphology of dry GOD-GA-SiO2 films very different from that of SiO2 and GOD-SiO2 films, IR spectroscopy confirms that the GODs in the films are indeed cross-linked through GA, and GA in the films greatly improves the film stability. UV-vis and IR spectroscopy suggest that the enzyme is not denatured by cross-linking in the films. The comparative bioelectrocatalytic study with free flavin adenine dinucleotide (FAD) in SiO2 films indicates that GOD in the films retains its biocatalytic activity toward glucose oxidation. All these results show that SiO2 nanoparticle films not only provide a favorable microenvironment for the native GOD to exchange electrons directly with underlying electrodes, but also supply a matrix for stabilizing GOD when combined with GA.