Research Of Corrosion Degradation Performance And Biocompability Of Tartaric Acid (TA) Coating On Biomedical Metal Magnesium

New biodegradable materials have attracted much attention in the field of biomedicine,because of its ease of degradation in the human body fluid environment.The ideal biodegradable materials can degrade at a controllable speed and completely disappear after the treatment period,avoiding potentially the second surgical procedure.Biodegradable magnesium as well as its alloys have been widely investigated for biodegradable implants applications,because of its ease of corrosion,good mechanical properties,and unquestionable biosafety.However,the too fast corrosion rate leads usually to byproducts of hydrogen gas,locally increased pH valve and premature mechanical failure of the implants,both of which limit the use of magnesium in clinic use.In this work,Tartaric acid(2,3-Dihydroxybutanedioic acid)was selected to deposit on magnesium for biodegradable implant applications.On one hand,tartaric acid molecules can be absorbed on the surface of magnesium substrate so as to reduce the exposure of the active site.On the other hand,the Tartaric acid molecules were surface-immobilized on the alkaline pretreated Mg and then spontaneously deposited with participation in a chelating reaction with Mg ions.An organometallic-like compound layer was thus formed,which was used as an effective barrier to prevent the attack of corrosive environment.Besides,excellent biocompatibility of tartaric acid can meet the needs of materials for biomedical applications.Therefore,using tartaric acid to modify the surface of magnesium can not only control the corrosion rate but also improve the biocompatibility of the substrate material.The surface morphology(SEM),chemical composition(FTIR)and bonding energy(XPS)results showed a homogeneous and compact TA coating(1.25?m thick)formed on Mg surface by surface-immobilizing and subsequent chelating reaction.Electrochemical corrosion of Ecorr,icorr and EIS showed that TA coating provided a barrier to against attack of the anion,thus have a good protection of magnesium electrolyte solution.In vitro immersion degradation investigations demonstrated that the HEDP coated Mg exhibited significantly slower corrosion rate than untreated Mg in phosphate buffered saline(PBS)solution.Particularly,Mg-OH@15 TA exhibited the best modification result,that is to say,15 g/L tartaric acid deposited on the surface of magnesium will drastically improve the resistance against corrosion and provide maximum protection for substrate material.Moreover,the tartaric acid coated Mg exhibits osteo-compatible in that it induces not only bioactivity of bone-like apatite(HA or OCP)precipitation but also promotes osteoblast cells adhesion and proliferation.The well-controlled biodegradable and biocompatible TA coating for magnesium would probably be put into clinical application for bone implant.