Immobilization of glucose oxidase on rod-like and vesicle-like mesoporous silica for enhancing current responses of glucose biosensors

The use of rod-like and vesicle-like mesoporous SiO2 particles for fabricating high performance glucose biosensors is reported. The distinctively high surface areas of mesoporous structures of SiO2 rendered the adsorption of glucose oxidase (GOx) feasible. Both morphologies of SiO2 enhanced the sensitivities of glucose biosensors, but by a factor of 36 for vesicle-like SiO2 and 18 for rod-like SiO2, respectively. The greater enhancement of vesicle-like SiO2 can be accounted for by its higher specific surface area (509 m2 g−1) and larger total pore volume (1.49 cm3 g−1). Interestingly, the current responses of GOx immobilized in interior channels of the mesoporous SiO2 were enhanced much more than those of simple mixtures of GOx and the mesoporous SiO2. This suggests that the enhancement of current responses arise not only from the high surface area of SiO2 for high enzyme loading, but also from the improved enzyme activity upon its adsorption on mesoporous SiO2. Also compared were the performances of glucose biosensors with GOx immobilized on mesoporous SiO2 by physical adsorption and by covalent binding to 3-aminopropyltrimethoxysilane (APTMS) modified SiO2 using glutaraldehyde as the cross-linker. The covalent binding approach resulted in higher enzyme loading but lower current sensitivity than with the physical adsorption.