Design And Fabrication Of Organic-inorganic Hybrid Carriers For Enzyme Immobilization Based On Bifunctinal Polymer

Design and preparation of organic-inorganic hybrid carrier have become hot issue and research frontier in many areas including enzyme engineering. Inspired by biomineralization, aiming at fully exploring and rationally extend the function of polymer materials, in this study, a kind of polymer with shape-forming and biomimetic mineralization inducing ability was screened, designed and synthesized. Employing these bifunctional polymers, different structured organic-inorganic carriers were fabricated and utilized for enzyme immobilization.β-Glucuronidase (GUS) was immobilized in CaCO3-Alg hybrid gel by an adsorption-encapsulation method. Alginate showed a strong shape-forming ability and its hydrogel matrix effectively prevented the leakage of enzyme. Meanwhile, alginate helped to maintain the mesoporous structure and adsorption ability of CaCO3 through inhibiting the recrystallization process. As a result, GUS loading efficiency, recycling and storage stability were all improved significantly.Inspired by the delicate structure of diatom cell, a novel and facile method for preparing organic-inorganic composite microcapsules was developed by a synergy of layer-by-layer (LBL) self-assembly and biomimetic mineralization. Protamine (Pro), a natural bifunctional polymer, was chosen as both a positive layer component and an inducer for silicification, providing a simple and efficient approach to form the cell membrane-like multilayer with a complete, uniform and robust cell wall-like silica shell. Catalase (CAT) is captured in the CaCO3 templates via co-precipitation and encapsulated in the composite capsules followed by dissolution of the templates. The encapsulation efficiency, harsh condition tolerance and long-term storage stability of the encapsulated enzyme were all notably improved due to the shielding effect of the inorganic shell.A novel bifunctional polymer, NH2-Alg(Ⅰ), was synthesized through an oxidation-amination-reduction process. NH2-Alg(Ⅰ) was then employed to induce the biomimetic mineralization from a silica precursor, Na2SiO3. The size and morphology of the resultant NH2-Alg(Ⅰ)/silica hybrid hydrogel could be controlled by the reaction conditions of co-precipitation process. Next, NH2-Alg(Ⅰ)/silica hybrid hydrogel was utilized for CAT immobilization. The encapsulated CAT exhibited an encapsulating efficiency as high as 100% as well as significantly improved thermal, pH, storage stability. Another novel bifunctional polymer with both a shape-forming function and a silicification-inducing functions, NH2-Alg(Ⅱ), was synthesized through a carbodiimide process using EDC and NHS. NH2-Alg(Ⅱ) could form hydrogel and induce silicification simultaneously, generating a robust hybrid hydrogel with dense structure and homogenously dispersed silica particles. The impregnated silica particles remarkably reduced the swelling of alginate hydrogel from 268% to 50%. The enzyme YADH after encapsulation in the hybrid hydrogel exhibited improved temperature, pH, recycling and storage stability.