Diffusion, adsorption and reaction of glucose in glucose oxidase enzyme immobilized mesoporous silica (SBA-15) particles: Experiments and modeling

Abstract

Glucose oxidase (GOD) enzyme is widely used as a sensing molecule for glucose and is thus immobilized in different porous hosts for sensing applications. We have synthesized different morphologies of mesoporous silica (SBA-15) host particles and impregnated GOD in it. Rod and cuboid shaped SBA-15 particles having internal pore diameters of 6.8 and 11.4nm respectively, were synthesized, in order to measure enzyme activity. The latter primarily determines the performance of a glucose sensor. In this quest, we therefore developed a mathematical model to predict variation of glucose concentration with time, by considering diffusion, adsorption and reaction rates of glucose by immobilized GOD. The model was validated with our own experiments, by fitting diffusion coefficient of glucose inside mesopores and the competitive product inhibition constant of GOD. The validated model indicates that, specific activity of GOD immobilized in SBA-15 is lower at higher GOD loading. Thus, this provides insight into the effect of pore-confinement on diffusion and reaction kinetics of the substrate (glucose) by an immobilized enzyme (GOD). Understanding the interplay of chemical transport and reaction kinetics issues in a porous solid nanoparticle host (SBA-15) can lead to superior detection and measurement of glucose concentration.