Biocompatibility of TiO2 and TiO2/heparin coatings on NiTi alloy

NiTi shape memory alloy has been used widely as implanted material; however, possible release of Ni ions may cause toxic, allergic, and potentially carcinogenic effects in a physiological environment. In order to solve this problem, we notice that, as shown by previous studies, anticoagulant heparin is a better material for improving blood biocompatibility. Thus a promising way is to develop new TiO2/heparin coatings on NiTi shape memory alloy, for the purpose of reducing possible release of toxic Ni ions and hence improve hemocompatibility. In this regard, we have fabricated four kinds of hemocompatible coatings: sol-gel TiO2, heating TiO2, sol-gel TiO2/heparin and heating TiO2/heparin on NiTi shape memory alloy. Various measurements have been done against this new material, including FE-SEM, XRD and contact angle tests (used to monitor surface characters), as well as hemolytic tests, dynamic clotting time experiments, platelet binding tests, cell morphology, MTT, ALP and RT-PCR (utilized to investigate blood- and cell-compatibility). Our results reveal that this new material of heparin loaded coatings, as expected, is able to improve the hemocompatibility of NiTi surgical alloy material. Moreover, RT-PCR measurements indicate that the best coating for cell growth is the heating TiO2/heparin. Our results suggest that deposition of TiO2 and heparin coating on the surface of a NiTi alloy sample is a promising method to improve its hemocompatibility.