Immobilization of enzymes in mesoporous materials: Controlling the entrance to nanospace

The immobilization behavior of lysozyme (LYZ) in mesoporous silicas (MPSs) with controlled morphologies has been investigated. The effects of entrance amount (EA) on the quantity and rate of immobilization of enzymes have been investigated due to the successful morphological control of MPSs. EA increases with the decrease of particle size of MPSs, leading to a significant improvement of immobilization ability. Rod-like SBA-15 (∼1-2 μm in length) shows a faster adsorption rate and larger immobilization amount than that for conventional SBA-15 (∼20 μm in length). It is observed that the adsorption rate of enzyme within MPSs is independent of the initial enzyme concentration. Increasing temperature favors a fast immobilization process of LYZ into MPSs. A maximum equilibrium adsorption amount of LYZ into rod-like SBA-15 is ∼500 mg/g at all temperatures under study (455°C). However, for conventional SBA-15, this maximum equilibrium adsorption amount cannot be observed within 48 h even at high temperature. A strong interaction between LYZ and MPSs is observed, resulting in very small amount of LYZ released by MPSs. Such conclusions may be important to understand the mechanism of protein immobilization within MPSs and potentially useful for applications of MPSs in biocatalysts or biosensors.