The Interaction Between Biomacromolecules And Material Surfaces

The responsivity of interactions between biomacromolecules and matrix in response to biological signals is one of the core processes of biological activities and functions. The type and amount of adsorbed biomacromolecules on the surface play an important role in determining the ultimate biocompatibility and biofunctionality of a given material when exposing to a biological environment. Therefore, investigation of the interaction of biomacromolecules and surfaces of biofunctional materials are of great theoretical interest for the construction of biofunctional materials, protein separation and purification technology, bio-detection technology and so on.In this research, vinyl groups were first introduced to polyurethane (PU) surfaces by a simple chemical method and then three different surfaces including hydrophilic polymer-modified polyurethanes surfaces, hydrophobic polymer-modified polyurethanes surfaces and stimuli-responsive polymer-modified polyurethanes surfaces were constructed by surface-initiated radical polymerization with various vinyl monomers. The interactions between the three different surfaces and proteins were investigated. On the other hand, to fabricate bioactive surfaces, proteins (lysozyme) were immobilized on Surface Plasmon Resonance (SPR) sensor by chemical grafting method. The interactions between lysozyme and regioselectively sulfated chitosan were studied by SPR. The detailed research works were introduced as follows:1. C-C double bonds were first introduced to polyurethane (PU) surfaces by a simple chemical method and then surface-initiated radical polymerization was conducted with various vinyl monomers. The interactions between fibrinogen and these modified PU surfaces were studied. Results of water contact angle and X-ray photoelectron spectroscopy (XPS) showed that vinyl groups were successful introduced to PU surfaces for further surface-initiated radical polymerization. Fibrinogen adsorption experiments showed that hydrophilic polymer (poly (2-hydroxyethyl methacrylate) (PHEMA)) and hydrophobic polymer (poly (1H,1H,2H,2H-heptadecafluorodecyl acrylate) (PFMA)) modified PU surfaces exhibited good protein resistance. 2. The effect of molecular weight (MW) of surface grafted poly(N-isopropylacrylamide) (PNIPAAm) on protein adsorption and cell adhesion was investigated systematically. PNIPAAm-grafted polyurethane (PU) surfaces of varying graft molecular weight (MW) were prepared via conventional radical polymerization. The MW was controlled by adjusting the vinyl monomer concentration. Adsorption of three typical proteins (human serum albumin (HSA), fibrinogen (Fg), and lysozyme (Lys)) with different sizes and charges on the modified surfaces at different temperature was evaluated using a radio-labeling method. Adsorption of blood plasma on the modified surfaces at 37℃was measured using a radio labeling method and immune blot analysis respectively. The results suggested the graft MW played an important role in the interaction of PU-PNIPAAm surface with proteins. As the MW increased, the adsorption of proteins decreased gradually reaching aplateau value at MW above 7.9×104. Compared to the unmodified PU, the surface grafted with PNIPAAm of MW 14.6×104 reduced the adsorption of Fg and HAS in PBS by 91%and 86%at 37℃respectively. Moreover, the surfaces with higher MW PNIPAAm showed minimal adhesion of cells presumably due to the absence of cell-adhesive proteins on the surfaces.3. Lysozyme (Lys) immobilized surfaces were prepared and their interactions with regioselectively sulfated chitosan were studied by SPR. The results showed that sulfated chitosan concentration played an important role in the interaction of Lys with sulfated chitosan. As the concentration increased, the binding capacity of Lys with sulfated chitosan increased and association rate constant decreased, while the dissociation rate constant increased. Moreover, structural differences of sulfated chitosan have greater impacts on their following binding. The order of the binding capacity between regioselectively sulfated chitosan and Lys is 6-O-sulfated chitosan (6S)> 2-N-6-O-sulfated chitosan (26S)> 3,6-O-sulfated chitosan (36S)> 2-N-3,6-O-sulfated chitosan (236S). The results indicated that the lysozyme binding activity of chitosan sulfates was not simply determined by sulfur content or electrostatic interaction, while sulfated groups on different positions may play an important role in the interaction between lysozyme and sulfated chitosan.