Comparative study of solid silica nanoparticles and hollow silica nanoparticles for the immobilization of lysozyme

In this study, three different morphology silica materials, i.e. hollowsilica nanotubes, hollowsilica nanospheres and solid silica nanoparticles were prepared and then employed as supports for immobilization of lysozyme. The produced silica materials were characterized by transmission electron microscopy (TEM), FTIR and BET. The comparative study of three silica materials for the immobilization of lysozyme indicated that the amount of immobilized lysozyme on solid silica nanoparticles was 186 mg/g silica, and while that of immobilized lysozyme within hollow silica nanotubes and hollow silica nanospheres could, respectively, reach up to 351 mg/g silica and 385 mg/g silica. Among the three types of silica supports, it was obvious that the hollow silica nanospheres represented the highest immobilization ability, whereas the specific activity of immobilized lysozyme on silica nanospheres (1.38×10^6 unit/g) was slightly lower than that of immobilized lysozyme on silica nanotubes (1.46×10^6 unit/g). This unexpected phenomenon is more likely to be due to the relatively airtight structure of hollow silica nanospheres. Compared to solid silica nanoparticles, silica materials with hollow structure and large pore size would facilitate the enzymatic immobilization.