Use Of Quartz Crystal Microbalance (QCM) For Study Of Adsorption Of Protein Onto Surface Of Chitoan And Its Derivates

When biomaterials are contacted with the tissue, a variety of complicated bioreactions could be activated. In these multiple-events, the protein adsorption is the first occurrence which is of great importance for the anti-thrombosis of implanted materials and the induction of biological functions. For different applications,it is required that the surface absorb different amounts of protein or different kinds of proteins. The interaction between cell and surface of biomaterial is induced by the interaction between protein of cell surface and surface of biomaterial. The research of protein adsorption behavior is significant in the research of biocompatible materials. Chitosan is linear cationic polysaccharide with a series of unique chemical properties and biofunctions. Chitosan can be modified with its active hydroxyl and amino groups. Its derivates have a great potential in the application of biomedical engineering. In this work, Polyvinylpyrrolidone which exhibits excellent water-solubility and biocompatibility was grafted onto chitosan in order to improve the hydrophilcity and reduce the amount of adsorbed proteins. Quartz Crystal Microblance(QCM) was applied in the study of interactions between the surface of chitosan and its derivates and proteins. The research works are as follows:The graft copolymerization of vinylpyrrolidone (NVP) onto chitosan under nitrogen atmosphere with ammonium persulfate served as the initiator, and FT-IR, element analysis characterized the graft copolymer. All study results demonstrate that PVP has been grafted onto chitosan. The work investigated factors that affect the grafting reaction i.e. grafting percentage, grafting efficiency as well as the initiating system, initiator concentration, monomer concentration, chitosan concentration, reaction temperature and reaction time. The optimum reaction conditions for high grafting percentage and grafting efficiency were as follows: reaction temperature 70℃, reaction time 2h, initator concentration 6mmol/L, chitosan concentration 5g/L, monomer concentration 0.4 g/L.We investigated the adsorption behavior of proteins on chitosan membrane surface. The results show the amount of adsorbed proteins is related to pH, ionic strength of solution, protein concentration and protein composition. The maximum amount of adsorbed proteins increases with the increasing ionic strength of solution. Moreover, the amount of adsorbed proteins increases further with the increasing protein concentrations. For different proteins, the amount of adsorbed proteins with high molecular weight is higher than that of low molecular weight. The adsorption of bovin serm albumin (BSA) and γ-globumin (γ-G) on membranes of alkyl derivative of chitosan were investigated. The alkyl chain length exerts an effect on the adsorption amounts. The hydrophilicity of N-alkyl chitosan and the pH value induced electrostatic interaction variations are important influencing factors.The adsorption of bovin serm albumin (BSA) on membranes of chitosan-graft- vinylpyrrolidone and chitosan-blend-poly vinylpyrrolidone were investigated. It is demonstrated that the amount of the adsorbed proteins on chitosan-graft- polyvinylpyrrolidone membrane surface is less than that of chitosan or chitosan-blend-poly vinylpyrrolidone membrane surfaces at equal conditions. BSA was observed to absorb on all membrane surfaces according to langmuir's adsorption isotherm. The amount of adsorbed BSA was observed not positively in proportion to concentration of BSA. The work discussed the kinetic of the adsorption behavior of BSA on chitosan and its derivates. In the early stage of protein adsorption, it is assumed that the reaction of protein adsorption on the surface forms meta-stable complex compound. The amount of adsorbed protein depends on the amount of the complex. The attachment constant rate k1, detachment constant rate k-1, association constant Ka could be calculated. The attachment detachment constants increased in the following order: CS>CS-blend-PVP>CS-g-PVP. The detachment constants in...