Surface Modification Of NiTi Alloy By Layer-by-layer Assembly

NiTi alloy has been extensively used as medicinal materials, such as a departmentof stomatology, department of gynaecology,orthopaedic, cardiovascular,and soon,mainly due to its unique shape memory effect, high corrosionresistance,super-elastic propertyand good biocompatibility. The Ni ion release andinterfacial situations of NiTi alloy substrate limited the applications of NiTi alloy in thefield of medicinal materials. Layer-by-Layer assembly technique(LBL technique) is asimple and convenient method to help the surface modification of NiTi alloy.In thisstudy, LBL technique is used by us to construct polyelectrolyte multilayer films onNiTi alloy materials surfaces,in order to reduce Ni ion release and promotebiocompatibility. The main contents of this study are listed as follows:①The TiN coating on NiTi alloy was prepared via a filtered arcing ion platetechnique for the present study.Then Polyethylene imine (PEI) was used to obtain aprecursor layer. DS/Chi multilayer films were achieved by such LBL self-assemblytechnique. X-ray diffraction(XRD),Scanning electron microscopy(SEM), EDS andinductively coupled plasma mass spectrometry (ICP-MS) were used to investigatecharacterization of materials surfaces.The results indicated that DS/Chi multilayer filmssuccessfully form on the NiTi-TiN substrate,and TiN/LBL composite coating caneffectively decrease diffusion of Ni ion from NiTi alloy.At the same tiome, osteoblastswere seeded onto native and treated NiTi alloys surfaces, and to determine proliferationability of osteoblasts, cell morphology and differentiation ability of osteoblasts. Theresults indicated that compared with that of NiTi-TiN and native NiTi, proliferationability of NiTi-TiN-LBL samples is better(p <0.05), and showed significantly highestnumbers of osteoblasts. ALP activity of NiTi-TiN-LBL samples showed statisticallysignificant difference(p <0.01). DS/CHI multilayer films are beneficial forbiocompatibility on NiTi alloy.②Dopamine was used to obtain a precursor layer. Gel/Chi/Gel/VEGF multilayerfilms were achieved by such LBL self-assembly technique. The field-emission scanningelectron microscopy (FE-SEM), atomic force microscope (AFM) and contact anglemeasurement were employed to observe surface characterization of the samples. Theexperimental results showed that the multilayers of Gel/Chi/Gel/VEGF weresuccessfully deposited onto the surface of NiTi substrates. In the meantime, The human umbilical cord vein endothelial cells (HUVECs) were seeded onto native and treatedNiTi alloys surfaces, and to determine proliferation ability of HUVECs, cellmorphology, cell migration, NO and PGI2release production. The results showed thatcompared with deposited Gel/Chi multilayers onto NiTi and native NiTi, proliferationability of deposited Gel/Chi/Gel/VEGF multilayers onto NiTi is better(p <0.05or p <0.01). and showed significantly highest numbers of HUVECs. DepositedGel/Chi/Gel/VEGF multilayers substrates were beneficial for the migration of HUVECs.In addition, deposited Gel/Chi/Gel/VEGF multilayers substrates displayed significantlyhigher NO release (p <0.01) and PGI2release(p <0.05or p <0.01). SoGel/Chi/Gel/VEGF multilayer films are beneficial for biocompatibility on NiTi alloy.