Study On Biocompatibility And Entrance Mechanism Of Zinc And Copper Into Coatings Developed On Ti6A14V Alloys In Solutions Containng Phytic Acid

In recent years,titanium alloys have become an ideal functional structural material for surgical implants due to their low density,high specific strength,low elastic modulus,excellent biocompatibility and processibility.However,as an implant material,titanium alloy has two main disadvantages,namely,poor biological activity and no antibacterial property.Micro-arc oxidation(MAO)surface modification can not only retain the original excellent properties of titanium alloys,but also effectively enhance their biological activity.The electrolyte composition is a main factor of influencing the performance of prepared oxide film.Phosphorus is the main element that makes up the bone,so phosphates have good biological activity.Zinc and copper are trace elements of natural bone and play an important role on bone development.In addition,zinc and copper have antibacterial property.However,their contents must be strictly controlled,and the excess amounts can cause deleterious effects.In this paper,phytic acid,an environment-friendly organic phosphorus-containing substance,was used as a basic electrolyte.Based on the bionics principle,copper-containing and zinc-containing substances were added to prepare MAO coatings containing phosphorus,zinc,and copper and zinc.The biocompatibility of the MAO film prepared in a solution only containing phytic acid was investigated.The entrance mechanism of zinc and zinc copper into the oxide film was revealed.In addition,the influence of zinc content in MAO coating on the biocompatibility was clarified.The achieved results are as follows:(1)Anodic coatings were prepared by MAO on the surface of titanium alloys in a base solution only containing phytic acid.The results show that compared with untreated control,the MAO treated titanium alloy achieves cytocompatibility in viability,adhesion,proliferation and differentiation of mouse MC3T3-E1 pre-osteoblasts.Due to good biocompatibility,the results indicate that MAO-treated Ti6A14V alloys in phytic acid solutions can be used as implants for orthopedic applications.(2)An orthogonal experiment of four factors with three levels was used to study the effects of EDTA-ZnNa2,KOH and phytic acid concentraton on Zn and P contents.Some conclusions are as follows:? The Zn element in MAO coating combines with P element and exists in the form of Zn3(PO4)2.P enters the MAO coatings mainly through a diffusion mechanism.?The sequence of processing factors on the Zn content of MAO coating is phytic acid concentration>KOH concentration>EDTA-ZnNa2 concentration>treatment time.With the increasing phytic acid concentration,the Zn amount in anodic coatings increases.The order on phosphorus content is phytic acid concentration>KOH concentration>treatment time>EDTA-ZnNa2 concentration.?Phytic acid is beneficial for the development of MAO coatings,while KOH inhibits the coating formation.With the increase of phytic acid concentration or the decrease of KOH concentration,the contents of Zn and P in MAO coating show a similar increasing trend.?The fabricated MAO samples containing Zn amounts in the range of 2.86-8.81wt.%achieve good biocompatibility and can be used as biomaterials.(3)The orthogonal experiment of four factors with three levels was used to analyze the mechanism of Cu and Zn entering the oxide film.Some results are achieved:?Copper in the oxide film mainly exists in the form of Cu or Cu2O,and coooer amount increases with the increasing KOH concentration.Zinc is mainly present in the oxide film in the form of Zn3(PO4)2 and is related to phytic acid concentration.?Copper salts can inhibit zinc from entering the oxide film,indicating that zinc and copper compete with each other into the oxide film.