Study On The Compatibility Of Ammonium Phosphate - Polyurethane Nanoparticles With Surface Modified Polyurethane And Its Properties

Ideal polymeric biomaterials which can be implanted into bodies should possess excellent blood compatiblity, histocompatibility and mechanical properties. At present, the most outstanding problems of biological materials are that they may cause blood clots, body infection and so on, which seriously restricts the development of new biological materials. Therefore, the research of developing anticoagulant polymer materials of biological has become the forefront of biomedical engineering and the key issues.Polyurethane (PU) is a kind of polymer containing amino acid groups, which is widely used in industrial and daily life. With relatively good biocompatibility, blood compatibility and mechanical properties, it has become an important materials that can contact directly with blood. So it was used in vascular grafts, interventional catheter, ventricular assist circulation system and artificial heart, etc. However, like other biomedical polymer materials, it also has the obvious induction thrombogenesi blood compatibility problems when polyurethane is used in human body.Improving the blood compatibility of polyurethane (as synthetic blood vessels) is a very important and key problem that has not yet been successfully solved. The researchers have been using many methods to solve the problems, such as using surface modification to solve this problem. Shen Jian (Nanjing university) group firstly used the ammonium phosphate, carboxyl amine, sulfonamides to modify the surface polymer (such as PU), which had a very significantly anticoagulant effect.In this paper, the method of precipitation is used to prepare the blood compatible Polyurethane (PU) composites, whose surface is modified with polyurethane ionomer nanoparticles (PUI-NPs). The mechanical properties and blood compatibility of modified PU are investigated.Compared to the unmodified PU, it can be seen that the surface of modified PU material uniformly distributs a large number of small protrusions by SEM. It shows that PUI-NPs nanospheres has been co-precipitation in the PU surface successfully and more evenly distributed in the PU surface. And it also further indicates the co-precipitation method is successfully. At the same time, the static contact angle tests show that the modified process slightly improves the hydrophilicity of the PU surface. The results of ATR-FTIR show that absorption peak of the modified PU at3460cm"1is caused by residues N-H groups on PUI-NPs surface. This result also indicates the PUI-NPs have already introducted successfully on the surface of the blank PU film. What’s more, the XPS spectra of PU/PU-NPs surface can be observed P2p peak at133.6eV. These all indicate PU-NPs nanospheres have been grafted successfully onto the PU surface.We mainly study the blood compatibility of material. The results of vitro hemolysis test shows that the hemolytic rate of modified and unmodified PU is less than5%, which are in line with international standards. And the recalcification time experiments show that, compared with the unmodified material, the recalcification time extens. It further indicates the modified composites have good blood compatibility. Futherly, the platelet adhesion experiment results show that anti-platelet adhesion capacity of the modification of polyurethane materials have been improved greatly. At the same time, the dynamic coagulation tests showed that the anticoagulant property of the modified materials is slightly higher than the raw materials to improve.In addition, the cytotoxicity assay results show that, compared with the unmodified PU toxicity, modified PU showed lower cytotoxicity after roling in living cells about24h and72h, and which is in full compliance with the medical standards of biological materials. The endothelial growth experiments show that, compared to unmodified PU, endothelial cells can growth better in the surface of modified PU.In order to get the available anti-clotting materials, we also studied the mechanical properties. The mechanical properties tensile experiments and SEM observations of fracture surface results show that not only the anticoagulant properties of modified polyurethane by co-precipitation method has been improved anticoagulant but also the mechanical properties of the PU is not affected at all. The mechanical properties of PU can still be maintained. The results of Rheological test further prove that the PUI-NPs and PU could form the covalent and hydrogen bonding interactions, and they also can form a slight cross-linking. And cross-linked structure is stable at different temperatures. Therefore, it is proved that the interfacial interaction between nanospheres with PU is strong, so it can be stable at different temperatures.On the basis of the above work, we prepared a new type of polyurethane/nano-composite materials which have good anticoagulant function and mechanical properties in both body and surface. And we expect that it can be widely used in biomedical engineering field.