Silica nanotubes for lysozyme immobilization.

Silica nanotubes were synthesized and used as enzyme immobilization carriers. The immobilization profiles were described by the adsorption of lysozyme molecules from aqueous solution onto the hydrophilic silica surface. The driving force of the adsorption, structure changes in the immobilized lysozyme molecules, and enzymatic activities were investigated. A study of the zeta potentials of silica with and without the immobilized lysozyme showed that there was an increase in the isoelectric point with the increase in the loading amount of lysozyme. FTIR spectra indicated that protein secondary structure was maintained well in the immobilized molecules. It was observed that enzymatic activities first increased and then decreased with increasing surface coverage of silica nanotubes by lysozyme, which suggested that the overlap and aggregation of lysozyme molecules reduced enzymatic activities of the adsorbed lysozyme molecules at high surface coverage.