| In this study, the surfaces of polyurethane films were modified by poly(ethylene glycol) (PEG) and PEG-derivatives, and blood compatibility of resulting surfaces was investigated. Various PEG and PEG-derivatives were grafted to polyurethane surfaces by covalent bonds. The effect of factors including end-group, molecular weight, grafting density, orientations of PEG-derivatives on protein adsorption to modified surfaces were studied.It was observed that the protein adsorption of PEG and monomethyl poly(ethylene glycol))(MPEG) modified surfaces increased after a decreasing with the molecular weight of PEG or MPEG increasing. PEG(M_n=400,2000)-grafted and MPEG(M_n=350,2000)-grafted surfaces possessed lower value of protein adsorption than that of other surfaces. It means that the protein adsorption is greatly influenced by graft density and chain length of PEG or MPEG.Both Monobenzyloxy poly(ethylene glycol)(BPEG) with PEG or BPEG with MPEG modified surfaces were achieved by filling back the PEG and MPEG to BPEG grafted the surfaces. Although this kind of surfaces possessed higher graft density than the surfaces modified by BPEG only for 12h , it shows higher water contact angle and protein adsorption. We further studied the effect of reaction time on hydrophilicity and protein adsorption of BPEG modified surface. The hydrophilicity and protein adsorption increased after decreasing to a minimum value with the reaction time increase.Another important innovative point in our research is to prepare a bioactive surface by conjugating a special amino acid which is highly affinitive to plasminogen through a PEG-spacer. In this system, PEG could suppress the non-specific protein adsorption while the amino acid could bind plasminogen to degrade fibrin in an evolving clot.It is hoped that our research will benefit to the researchers who are working in the field of blood compatible materials, and we also hope that this successful idea can be applied to other biomaterials surface.
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