Combined membrane emulsification with biomimetic mineralization: Designing and constructing novel organic-inorganic hybrid microspheres for enzyme immobilization

The organic-inorganic hybrid composites displayed great potential for biotechnological and biomedical application. In this research, a novel and facile method for preparing organic-inorganic hybrid microspheres was developed by a synergy of membrane emulsification and biomimetic mineralization. The gelatin solution (water phase) was mixed with the liquid paraffin (oil phase) at 60 °C and a coarse W/O emulsion was produced by magnetic stirring. The coarse emulsion was extruded through a Shirasu Porous Glass (SPG) membrane, and then was slowly dropleted into the pre-hydrolyzed tetraethoxysilane (TEOS), which acted as silicon precursor. The biomimetic mineralization was occurred in situ under the catalysis of gelatin, while silica was formed around the gelatin emulsion droplets, resulting in the final gelatin/silica hybid microspheres. These microspheres were characterized by a variety of techniques, including SEM, TEM, EDS, TGA/DTA, and DSC. The gelatin/silica hybrid microspheres present a mass fraction of the inorganic component as high as 46%, while their glass (Tg) and melting (Tm) transition temperature raised by 9 °C and 40 °C, respectively. Catalase (CAT) was immobilized in the obtained novel gelatin-silica hybrid microspheres as the model enzyme. Due to the protective effect of carriers, the pH tolerance stability, storage and recycling stability of the immobilized CAT were all improved in comparison with free CAT.