Surface Modification Of Titanium Plate And The Study Of Its Blood Compatibility

The titanium and its alloy have become one of the most prospective biological materials than other traditional medical metal materials due to their good mechanics performance, biological compatibility, resistance to corrosion, and outstanding workability. Titanium and its alloy are inert biomaterials. After implanting in vivo it will be enveloped by fibrous encystations, resulting in difficulty of forming strong union with biological tissues. Moreover, titanium alloys may contain chemical components harmful to human body, so the titanium. implanted in vivo may cause sensitization, cell mutation, carcinogenesis and so on. In this study we use the plasma chemical vapor deposition (PCVD) method and the liquid-phase plasma cathode to penetrate and to deposit carbon and nitrogen as the superficial film on the titanium plate. Then, we made biochemical modifications on the titanium plate in order to improve its blood compatibility.We have accomplished five major objectives in this study:(1) For improving blood compatibility of pure titanium, using Ar plasma to clean the substrate, the acetylene and argon are used to prepare DLC coatings on pure titanium by PCVD method. In the experiment, acetylene proportion and discharge power are detected. In ATR-FTIR spectrum there are peaks in 2885 cm^-1 and 2992 cm^-1correspondind to sp³ in the CH₃ symmetrical vibration absorption, and sp² in the CH₂ alkene vibration absorption. In Raman spectrum there are D peak in 1360 cm^-1 and G peak in 1550 cm^-1. In XPS spectrum only carbon element is detected. AFM result shows that the superficial appearance has been changed and the surface has been plated a kind of thin film. The corrosion experiment shows that corrosion-resistent property of the titanium with coatings is better than pure titanium. Change of contact angles is found after preparing DLC coatings on titanium. The haemolysis ratio measurement, plasma recalcification time (PRT) measurement, dynamic blood clotting test and platelet adhesion test show that the DLC films are helpful in enhancing the material to prevent blood clotting.(2) For improving blood compatibility of pure titanium, the liquid phase plasma is used to penetrate and to deposit carbon, nitrogen and titanium thin film on the titanium surface. We examined the effect of discharging current and the different process time on the coatings. XRD shows the titanium carbon nitrogen diffraction peaks, proving that the surface has the titanium carbon nitrogen formation. With the increase of electric current and the discharge time, the peaks also increase in height, indicating that the film thickness increase. In the XPS spectrum, the appearance of Ti, C and N element also suggests the formation of superficial ceramics titanium carbon nitrogen. Moreover, in air or in solution, titanium easily combines with oxygen, the surface has, high oxygen level. The cross section SEM image demonstrates that thickness of the films is approximately 60 mm, fully showing effect of this method. The EDX result does not include the oxygen, and N/C is consistent with the XPS result. The. SEM shows that the surface is of porous. nature. The corrosion experiment and hardness, experiment all indicate the performance of the pure titanium has been enhanced after treatment. The haemolysis ratio measurement, plasma recalcification time (PRT) measurement, dynamic blood clotting test and platelet adhesion test show that the titanium with penetrated carbon and nitrogen has good blood compatibility.(3) For improving the antithrombogenicity of titanium with DLC films, the samples are pretreated with the oxygen plasma, then it is subject to UV-induced grafted polyacrylamide (PAAm). Afterwards the treated sample is alcoholysized with polyethylene glycol, and polyethylene glycol is fixed to the surface. Effects of AAm concentration, plasma treatment power and time, UV irradiation time are investigated. The best reaction condition is gotten by orthogonal experiment method. The optimized condition is achieved at a plasma pretreatment power of 10 W, a pretreatment time of 5 min, the monomer AAm concentration of 30 wt%, and the UV irradiation time of 50 min. The surface properties and microstructure are characterized by XPS, ATR-FIIR and AFM. It is confirmed that PAAm and PEG are gradually fixed to the DLC films, indicating that the inorganic material has been connected with organic material. Results of platelet adhesion test show that antithrombogenicity of modified DLC films is improved clearly. The anti-thrombosis improvement is probably caused by the hydrophobic DLC films surface which is covered by the hydrophilic PAAm and polyethylene glycol spatial impedance to prevent protein adsorption.(4) For improving the biocompatibility of the titanium coating with penetrated carbon and nitrogen, we adopt the basic principle of molecular self-assembly. After combined with silicon tetrachloride in the surface, the sample is immersed in acetone and polyethylene glycol solution to adsorb the latter. The XPS and SEM show that the polyethylene glycol is successfully fixed to the material surface.(5) For improving the biocompatibility of pure titanium with carbon and nitrogen penetration, we use solid phase synthesis of polypeptides and fix glycine and phenylalanine progressively to the silanized sample. XPS and SEM show that the amino acid is bonded step by step to the material surface, and the samples are linked with the peptide chain.