The Surface Modification Of Magnetic Microspheres And Study On The Interaction Of It And Protein By Microcalorimetry

Magnetic Polymer Microsphere (MPM ) is a kind of novel functional materials with magnetism and special structure, which is composed of polymer and inorganic magnetic materials. The microsphere can behave superparamagnetism besides properties of magnetic polymer materials. It can not only be endowed with functional groups on surface by copolymerization or surface chemical modification, such as -COOH, -OH, -CHO, -ArCH₂Cl, -NH₂ and so on, so it can be coupled with a lot of biological active material like protein, antibody, antigen etc, but also be separated quickly and easily from mixtures by exterior magnetic field. Therefore, since 1970's, as a new type of functional material, it has gained broad applications in cell separation, protein purification, immunoassays, immobilized enzyme and target delivery of drug.In this paper, on the basis of summarizing the research fruits of magnetic polymer microspheres worldwide, the polystyrene magnetic microspheres of nuclear shell structure with monodispersity, strong magnetic responsivity and great capacity of coupling protein was prepared by improved micro-suspension polymerization. The preparation and surface modification of magnetic microspheres by copolymerization of Styrene, maleic anhydride, acrylic acid in the presence of organic solvent and the reaction mechanism were investigated emphatically. Some influencing factors, such as stir and ultrasonic dispersion, polymerization temperature, the amount of initiator, surfactant and the scale of Fe₃O₄/St etc. were discussed respectively. Some properties such as microsphere structure, particle size, magnetic properties and the content of functional group were characterized. The magnetic content of the carboxyl-modified polystyrene microsphere by copolymerization of CBA can reach to 17.65 %. So far, the carboxyl-modified polystyrene microsphere is prepared by improved micro-suspension copolymerization of CBA, which has not found in any literature.Before the action of MPM and protein is studied, the effect of Selenium and Cadmium on the growth metabolism of Escherichia coli was studied by microcalorimetry at different concentrations. According to the thermogenesis curves of the action of Se and Cd on Escherichia coli, much useful information, both qualitative and quantitative, were obtained directly and easily. So microcalorimetric method is of great significance to synthesize, select druggery and study on the action of MPM and protein .For the application study of MPM, the interaction of MPM and protein was studied by microcalorimetry mainly and ultraviolet spectrum and fluorescentspectrometry method. Such influencing factors as the adsorption temperature, the concentration of MPM and BSA, the action time were surveyed. Furthermore, the interaction of MPM prepared by Bangs Co. Ltd in America and BSA was also studied by microcalorimetric and ultraviolet spectrum. The experiment results indicated, the adsorption of BSA of the carboxyl-modified polystyrene microsphere by copolymerization of CBA can reach to 566.8mgBSA/g microsphere. The adsorption amount increased greatly, and it exceeded the 67.8mgBSA/g microsphere obtained by Wang Shenglin^[59] and est. The characteristics of the MPM prepared by ourselves are similar with that of Bangs Co. Ltd in America, and the mechanism of action of MPM and BSA obtained by microcalorimetric are accordant with that by usual spectroscopic methodology. But microcalorimetric method can be a more accurate and visualized, microscale and automatical, straight-forward and simple than usual spectroscopic methodology, and we can obtain correlative thermodynamics and dynamics information by studying the coupling difference between different surface-modified MPM and BSA. The study on the interaction of MPM and BSA by different methods is becoming very popular with scholars^[56], but the study of the interaction of MPM and BSA by microcalorimetric has not found in any literature in the world.