Larger pores dramatically enhance activity of an immobilized enzyme in mesoporous magnetic silica

Here, we report the influence of the pore size in biocatalysts based on magnetically responsive mesoporous silicas on the loading of an immobilized enzyme - glucose oxidase (GOx) - and the activity and reusability of the biocatalyst in d-glucose oxidation. The choice of the silica supports was determined by their commercial availability and drastically different pores sizes: 6 nm and 15 nm. In the former case, the pores are too small to accommodate GOx whose hydrodynamic diameter is 7.6 nm, while in the latter case, there is an ample room for immobilization of GOx inside the pores. Magnetic properties in both cases were imparted by the formation of magnetite nanoparticles in silica pores, whose presence did not alter the pore size distribution. We demonstrate that larger pores allow for higher enzyme loading capacity due to immobilization inside the pores, remarkable 100% relative activity, and enhanced stability in the repeated use due the conformational integrity of GOx in spacious pores. This study unambiguously shows advantages of supports with pores larger than the size of an enzyme for its immobilization in the biocatalyst synthesis.