Preparation And Properties Of Magnesia Antibacterial Coating By Electrochemical Deposition On Titanium Surface

Objective:The optimum electrochemical deposition conditions of magnesium chloride solution were determined,and magnesium hydroxide and magnesium oxide coatings were prepared on titanium surface by this method,and the biological properties of the coatings at different deposition time were tested by antibacterial test and cytotoxicity test.Determine the most suitable coating to reduce clinical postoperative infection.Methods:Magnesium chloride solutions of different concentrations（0.1,0.2,0.3,0.4,05 M）were titrated with sodium hydroxide to determine the optimum p H value of the reaction.The optimal potential of the reaction was determined by linear volt-ampere scanning,and the optimum deposition voltage was obtained by voltage measuring instrument.After the electrodeposition parameters were determined,magnesium hydroxide coatings were prepared on the surface of pure titanium according to different deposition time and divided into groups（group A:0 h,group B:0.5 h,group C:1 h,group D:3 h,group E:6 h,group F:12 h）.The prepared magnesium hydroxide coating samples were calcined at 650℃to obtain new coating samples,and the new coating samples were divided into two groups again（group a:0 h,group b:0.5 h,group c:1 h,group d:3 h,group e:6 h,group f:12 h）.Weighing records after the sample preparation is completed.The surface morphologies of all samples were observed by scanning electron microscope,and the composition of coating elements was determined by energy spectrum scanning.The sample F and sample f with the longest deposition time and the thickest coating were analyzed qualitatively by X-ray diffraction.Through the degradation experiment in vitro,the relationship between degradation time and p H value of all samples within 24 hours was measured and evaluated.Through the antibacterial experiment in vitro,the plate counting method was used to detect and calculate the antibacterial properties of all samples against Staphylococcus aureus and Escherichia coli.Through cytological experiments in vitro,all samples were co-cultured with mouse osteoblasts.CCK-8 reagent was used to detect and calculate the cell survival rate of all coatings on the 1st,3rd and 5th day.Finally,according to the above results,the most suitable coating for clinical application is obtained.Results:When the concentration of magnesium chloride solution is 0.1 M,the optimum p H value for deposition is 9.5.Through the end of the smooth segment of the volt-ampere scanning curve,the optimum potential is-1.4V,and the voltage at both ends of the positive and negative electrodes is3.0 V,which is the optimum deposition voltage.The qualitative analysis of sample F and sample f by X-ray diffraction shows that the coating of sample F is composed of magnesium hydroxide and the coating of sample f is composed of magnesia.It was observed by scanning electron microscope that the particle-like material was uniformly distributed on the sample surface,and the particle distribution density increased with the increase of deposition time.When the deposition time was 12 h,the coating material was no longer granular,but fused to form a plate-like structure.The energy spectrum scanning results show that the coating coverage increases gradually with the increase of deposition time,which is mainly characterized by the disappearance of the peak value of titanium element and the increase of the peak value of oxygen element and magnesium element.After determining the p H value of all samples,it was found that the degradation was faster in the first 6 hours and slowly in the next 18hours,and the p H value of the samples increased with the increase of deposition time.In vitro antibacterial experiments show that magnesium hydroxide and magnesium oxide coating have antibacterial effect on Staphylococcus aureus and Escherichia coli,and the bacteriostatic rate increases with the deposition time of the coating.When the deposition time is less than 3 hours,the bacteriostatic rate of magnesia is significantly higher than that of magnesium hydroxide.When the deposition time is more than 6 hours,the bacteriostatic rate of both of them is close to 100%,and there is no significant difference.In vitro cell experiments showed that the two kinds of coating samples with deposition time of 0.5 h had low toxicity to mouse osteoblasts within 5 days,and even magnesium hydroxide promoted cell proliferation on the 5th day.The samples with deposition time of 1 h and 3 h showed higher cytotoxicity on the first day,and the cell survival rate increased gradually with the increase of culture days.The samples with deposition time of 6 h and 12 h were highly toxic to mouse osteoblasts within 5 days,and the cell survival rate was less than20%.In addition,when the deposition time was 0.5 h,1 h,6 h and 12 h,there was no statistical difference in the effect of magnesium hydroxide and magnesium hydroxide on cell survival rate,but the toxicity of magnesium hydroxide to mouse osteoblasts was significantly lower than that of magnesium hydroxide when the deposition time was 3 h.Conclusion:Mg（OH）₂ and Mg O coatings can be effectively prepared by electrochemical deposition.When the deposition time is 3 hours,the prepared Mg O coating has good antibacterial and cytotoxicity properties,and is better than Mg（OH）₂ coating.When the deposition time is 6 hours,the Mg O coating sacrifices part of the cell growth for strong antibacterial activity,which application depends on the needs of patients and the choice of clinicians.