Study On Protein Adsorption Properties Of PEI Grafted Poly (Methyl Methacrylate)(PMMA) Magnetic Microspheres

Magnetic polymer microspheres due to small particle size,large specific surface and good dispersion.magnetic polymer microspheres have important theoretical and practical significance in the immobilization of enzymes.In this paper,poly(methyl methacrylate)(PMMA)magnetic microspheres were prepared and PEI were grafted onto their surface.We studied the adsorption properties and application of immobilized enzyme for the poly(methyl methacrylate)(PMMA)magnetic microspheres.The main contents of this paper are listed as below.Firstly,poly(methyl methacrylate)(PMMA)magnetic microspheres were prepared by suspension polymerization using methyl methacrylate as monomer and characterized by electron microscopy,It was found these microspheres to have good dispersion and sphericity,and the particle size distribution was between 10-25 ?m.Then the magnetic microspheres were esterified.The IR spectra showed that the surface of the microspheres with plenty of carboxyl groups.The chemical titration showed that the carboxyl content was 0.94 mmol/g.Secondly,(PEI 600,PEI 1800,PEI 70000)were grafted onto microspheres by using the carboxyl groups of the surface of the microspheres as functional groups.The effects of different molecular weights of PEI on the adsorption of protein were investigated and compared with those of not grafted PEI.The adsorption capacity of BSA was significantly increased after grafting of PEI,and the adsorption amount of BSA was the highest grafting of PEI 1800.The adsorption amount of PMMA esterified,PMMA-PEI 600,PMMA-PEI 1800,PMMA-PEI 70000 were 44 mg/g,54.1 mg/g,62.1 mg/g and 47.4 mg/g,respectively.The experiment was further studied the effect of the BSA concentration,medium pH,ionic strength and temperature on the adsorption of BSA by magnetic microspheres.The results showed that the increase of ionic strength could decrease the adsorption capacity of BSA,and the adsorption capacity of PMMA-PEI 1800 on BSA was 67mg/g at pH = 7.0 and 35 ?.In addition,adsorption-desorption experiments showed that PMMA-PEI 1800 had goodreproducibility.Thirdly,PMMA-PEI1800 magnetic microspheres as carrier were used to immobilize Candida rugosa lipase.The conditions of the immobilized enzyme were optimized,and the optimal temperature,optimum pH and thermal stability and pH stability of immobilized lipase were investigated.Compared with free enzyme,the optimum temperature,thermal stability and pH stability of immobilized enzyme were improved,and the temperature and pH range of immobilized enzyme were wider than that of free enzyme.The results show,when the amounts of lipase is 4 mg,pH = 7.0,temperature is 35 ?,the highest specific activity were observed.