Enzyme Encapsulated Hollow Microcapsules Prepared By Visible Light Induced Graft Polymerization

Enzyme-based catalytic technology has been widely used in various fields because of the advantages of environment-friend and mild reaction condition.However,there are some factors limiting the utilization of enzyme,including high cost,sensitivity to environmental changes such as pH and temperature,and difficulty to recycling them after reaction.Immobilization of the enzyme can effectively improve their stability,facilitate their recycling and reduce the cost,which are important for the continuous enzyme catalytic production.Exploring a novel enzyme immobilization strategy is a hot issue in the field of enzyme catalysis,which is of great significance for the development of highly efficient biocatalysis technology.In this thesis,according to the strategy to encapsulate enzymes in polymeric microcapsule by combination of visible light induced cross-linking graft polymerization and inorganic template was developed.The main results were listed here:1.Synthesis of enzyme-loaded calcium carbonate microspheres by biomimetic mineralization technology.Bovine serum albumin(BSA)was firstly used as a model protein to investigate the preparation of calcium carbonate microspheres.The relationship between the calcium carbonate microsphere structure,protein immobilization efficiency and loading ration in calcium carbonate with the change of the concentration of the CaCl2,Na2CO3 and protein was studied.Glucose oxidase(GOD)encapsulated calcium carbonate microspheres were prepared based on the optimal results of the BSA.It was found that when the enzyme concentration was in the range of 0.25-1.00 mg/mL,the enzyme immobilization efficiency was above 80%.The diameter of enzyme encapsulated microspheres is between 1-2?m.And the zeta potential of microparticle is negative(-11 mV)at pH=7,which is suitable for the subsequent reaction.2.Preparation of enzyme-loaded hollow microcapsules by visible light induced graft polymerization.First,the hydrogen donor polyethyleneimine(PEI)and the visible light photoinitiator thioxanthone catechol-O,O-diacetic acid(TX-Ct)were sequentially adsorbed on the surface of the calcium carbonate microparticles by electrostatic interaction.The adsorption amount of PEI and TX-Ct could be controlled by changing concentration of PEI and TX-Ct within a certain range.A cross-linked polymeric shell was prepared on the enzyme-loaded CaCO3 microparticles by visible light induced graft cross-linking polymerization of polyethylene glycol diacrylate(PEGDA).After the calcium carbonate template was removed by aqueous solution of ethylenediaminetetraacetic sodium salt,enzyme-loaded hollow microcapsule was prepared.The successful immobilization of enzyme in the microcapsules was confirmed by FTIR.The enzyme immobilization efficiency in microcapsules was above 90%.The glucose was used as a substrate for enzymatic reaction to investigate the activity of enzyme.The results showed that the stability of enzyme against high temperature and extreme pH was improved after immobilized comparing to free enzyme.The immobilized enzyme showed an excellent reusability and 75%of initial activity could be retained after 10 cycles of reuse.3.Based on the living characteristics of visible light induced graft polymerization,the dormant groups on the surface of the polymer microcapsules can be reactivated under visible light irradiation.And poly(sodium acrylate)could be successfully grafted on the surface of the microcapsules,which provided new reaction sites for further immobilization of other enzymes on the surface of the microcapsules.