The Blood Compatibility Research Of Dacron Modified By Plasma Surface Modification

Blood compatibility plays an important role in biomaterials and medical implants whose surface characteristics often decide the anticoagulant properties. So, surface modification is an important and useful way to improve blood compatibility of materials. In this paper, the poly(ethylene terephthalate, PET) films were modified using two kinds of plasma surface modification. One is gas plasma surface modification, which three kinds of gas(Ar, N₂,O₂) were used to modify the materials' surface. The surface free energy, surface hydrophilicity and blood compatibility of these modified PET films were studied and the influence of processing conditions (power, treatment time , gas flow, gas sorts) on these proprieties were studied as well. Another way is plasma grafting that the poly(ethylene glycol, PEG) of different molecular weights was grafted on PET films and further heparin was immobilized on surface of these grafted PEG samples in order to improve blood compatibility of materials.The results of contacting angle and the attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photon spectroscopy (XPS) measurement indicated that chains of PEG and heparin were grafted on PET films successfully.Two kinds of surface modification all can improve the hydrophilicity of materials. The water-contacting angle of two kinds of modification samples decreased from 85.5 degree to 13.6 degree and 38.7 degree respectively. At the same time, surface free energy increased from 38.9mN/m to 63.1mN/m and the polar part increased from 2.3mN/m to 25.9mN/m. Interface free energy between materials and water decreased from 30.7mN/m to under 15mN/m. But the surface modified by plasma gas had a markedly aging effect.The study of blood compatibility in vitro suggested that pure gas plasma treatment cannot improve blood compatibility markedly and plasma grafting can enhance blood compatibility of materials. The result of platelet adhesion tests in vitro indicated that the number of platelet adsorbing on the materials' surface decreased largely and platelet did not aggregate and distort. Blood compatibility became better at first and further became worse with the increase of molecular weight of the grafted PEG. Blood compatibility of immobilized heparin samples became worse than grafting PEG. The result of coagulant factor tests revealed that the activated partially thromboplastin time (APTT) of the plasma grafting samples was longer than unmodified PET films. APTT of P6K was 51.5 seconds and its blood compatibility was the best one among these samples, but the APTT of unmodified PET was only 36.5 seconds. The changes of the prothrombin time (PT) and thrombin time (TT) were not distinct, so the materials cannot markedly influence extrinsic coagulant system. The change of APTT significantly indicated that the modified surface of PET films could influence markedly intrinsic coagulant system.The platelet adhesion test of PET films whose surface was pre-coated with fibrinogen and albumin indicated that the surface of adsorbing albumin can distinctly inhibit platelet adhesion and aggregation and possessed favorable blood compatibility, but the adsorbing fibrinogen surface could enhance platelet adhesion and aggregation. The competitive adsorption relationship of plasma protein (fibrinogen and albumin) adsorbing on materials surface was analyzed on the basis of surface energy and interface free energy. The result indicated that PET films grafted PEG long chain molecular possessed characteristic of preferential adsorbing albumin and this adsorption tendency of grafted PEG6000sample was most distinct.