Magnetic Molecularly Imprinted Polymer And Its Application In Protein Separation And Purification Process

Molecular imprinting is a technique for tailoring polymers with complementary size,shape and functional sites to specific molecules.Covalent imprinting,non-covalent imprinting and semi-covalent imprinting methods have been invented.Molecularly imprinted polymers have the advantages of specific recognition capabilities,low preparation costs,material resistance to high temperature and pressure,a wide range of pH applications and the ability to be reused multiple times.They have been successfully applied in many fields,but while most of the successful examples are based on small molecules as templates,research on large biological molecules,especially protein imprinted materials,has lagged behind.The first reason is that the large size of the proteins hinders the transfer of the template molecules into the polymer;the second reason is that the complex structure of the proteins makes the polymer preparation conditions particularly prone to inactivate them,making the molecularly imprinted polymer less selective.Also traditional methods of eluting template proteins usually use high concentrations of surfactants,strong acids or bases,which can also alter the structure of the protein and make it biologically inactive.Achieving gentle extraction of proteins is of great importance to expand the application of imprinted polymer materials in the field of biomolecular separation.This thesis addresses the above problem by introducing FeCo magnetic nanorods into molecularly imprinted polymers.FeCo nanoalloys,magnetically responsive molecularly imprinted hydrogels and magnetically responsive molecularly imprinted porous membranes were synthesised,respectively:(1)Synthesis of FeCo nanowires(FeCo NWs)and testing of their magnetic properties:FeCo NWs were prepared by electrochemical deposition using anodic aluminium oxide(AAO)templates,and the synthesis of FeCo alloys was demonstrated using SEM,EDS,HRTEM,XPS and other characterisation methods.By investigating the relationship between the electrochemical deposition time and the length of FeCo NWs,it was learned that they form a general linear relationship and that the length-to-diameter ratio of FeCo NWs can be controlled by controlling the deposition time.By investigating the magnetic properties of FeCo NWs obtained at different deposition times,it was demonstrated that the magnetic properties of FeCo NWs are dominated by shape anisotropy and that the preparation of magnetic nanowires with different coercivity can be achieved by controlling the deposition time.The presence of gold hinders the application of FeCo NWs in other fields as the AAO template in the experiment requires gold spraying to make its electrodeposition smoother.In this study.FeCo NWs were successfully applied to molecularly imprinted polymers by the action of an ultrasonic cell crusher to give a good dispersion of FeCo NWs.(2)Molecularly imprinted hydrogels(MIH)were prepared to solve the problem of encapsulation of protein macromolecules,and the loose and porous structure of the hydrogels provided convenient conditions for protein mass transfer.MIH was synthesized using acrylamide as the functional monomer.N-N’-methylenebisacrylamide as the cross-linking agent and ammonium persulphate as the initiator,and the principle of free radical polymerization.The hydrogels were characterized by SEM with pore sizes up to 10 μm.The adsorption kinetics and isothermal adsorption experiments were carried out to test the adsorption performance of the hydrogels.The MIH was shown to have a good specific adsorption capacity.To further verify this fact,single selective adsorption experiments and competitive adsorption experiments were carried out on the hydrogels,and the results proved that MIH has a strong specific recognition ability.After introducing FeCo NWs into the hydrogel system and placing them in an atmosphere with different magnetic field strengths to elute the template,MIH then combined to adsorb the template protein.The experimental results indicated that the magnetic nanowires worked well in a magnetic field atmosphere with a mild detergent to elute the template protein,which well protected the protein activity and achieved a mild extraction of the protein.(3)Combining membrane separation with molecular imprinting,the surface imprinting technique was used on a porous membrane carrier to achieve continuous filtration separation on the one hand,avoiding the tedious step of recovering the imprinted polymer and making the separation more convenient:on the other hand,the porous structure of the membrane increased the specific surface area of the imprinted layer and improved the adsorption and separation efficiency.In this paper,molecularly imprinted membranes(MIM)and molecularly imprinted membranes with FeCo NWs(MIM-FeCo)were prepared by using cellulose acetate membranes as carriers,methyl methacrylate as functional monomer,ethylene glycol dimethacrylate as crosslinker,ammonium persulphate and sodium bisulphite as initiators and bovine serum proteins as template molecules for surface polymerisation under nitrogen protection.The adsorption properties of the imprinted membranes were tested in kinetic and isothermal adsorption experiments,and the adsorption of the imprinted membranes was determined to be in accordance with the Freundlich model by fitting the adsorption model.Competition adsorption experiments and permeation experiments were carried out to investigate the specific selectivity of MIM in more depth.The results demonstrate the high specificity of MIM for the continuous filtration separation of template proteins.