Design And Fabrication Of Novel Dendritic Micro/Nano Magnetic Carriers And Their Application For Enzyme Immobilization

Dendritic magnetic micro/nano-carrier is a new materials which combines dendritic macromolecule and magnetic particle perfectly.It has many greatest strengths,for instance,low toxicity,good stability,good biocompatibility and it is rich in functional group density.So it has widely used for bio-pharmaceutical,catalysis,environmental conservation and other fields.In this paper,the dendrimer micro/nanocarriers with different structures and lengths of dendrimers were successfully prepared and used for the immobilization of Candida lipase and Penicillin acylase.And the performance of dendritic magnetic micro/nanocarriers and immobilized enzymes was systematically studied.The dendritic magnetic micro/nanocarriers were prepared to effectively solve the problem that there were limited numbers of functional groups on the surface of magnetic nanocarriers,which provided a technical reference for the immobilization of biomacromolecules used dendritic magnetic carriers.This thesis includes three parts as followed:1.Magnetic nanoparticles with good dispersibility were prepared by solvothermal method.Then dendrimers?PAMAM?were grafted onto the surface of the magnetic nanoparticles by using three kinds of amine reagents:diethylenetriamine?DETA?,ethylenediamine?EDA?and hexamethylenediamine?HMD?.The magnetic nanocarriers modified by dendrimers were obtained and the influence of the structure and length of the PAMAM chains on the immobilized lipase activity were detailed research.The results represented that the fourth-generation carriers modified by HMD?Gc-4/HMD?had a good effect on immobilized lipase.Furthermore,the activity of the immobilized lipase of Gc-4/HMD was 68.14%after 7 times of repeated use.2.The flower-like Fe₃O₄ microspheres with high specific surface area were prepared by improved solvothermal method,and the dendritic macromolecules were grafted on the surface of the magnetic microcarriers,and then the properties of the immobilized lipase were studied.The results indicated that Gc-2/HMD grafted with hexamethylene diamine was the best carrier for the immobilization of lipase.Under the optimal immobilization conditions,the immobilized lipases loading can reach 192.49 mg/g carriers and the activity remained above 2339.13 U/g protein.In addition,the immobilized lipase had excellent thermal stability in comparsion with free lipase,and after repeated use for 7 times,the relative activity still remained 68.83%.3.In order to extend the application of the novel dendritic magnetic micro/nanocarriers,water-based enzyme?Penicillin acylase?was immobilized on the dendrimer magnetic nanocarriers and microcarriers,respectively.Results show that the hexamethylenediamine grafted dendritic magnetic porous microspheres?Gc-2/HMD?enzyme showed excellent performance in immobilizing Penicillin acylase.Under the best conditions,the immobilized enzyme with excellent thermal stability and reusability.After 8 times of cycling,the relative activity remained 73.91%.