Study On The Antibacterial Properties Of Nano-magnesium Oxide Films Prepared On The Surface Of Pure Titanium

Objective:By controlling the time of magnetron sputtering,nano-MgO films with different thicknesses were prepared on the surface of pure titanium,and their antibacterial effects in vitro were evaluated.Methods:In this study,a round titanium sheet with a diameter of 14 mm and a thickness of 3 mm was used as the research model,and the sheets were divided into 4 groups after grinding and polishing.The experimental groups were divided into MgO-Ⅰ group(100nm),MgO-Ⅱgroup(200nm)and MgO-Ⅲ group(300nm)according to the thickness of the nano-MgO films deposited on the surface by magnetron sputtering,the untreated titanium sheet was the control group(Ti group).Scanning electron microscope(SEM)was used to observe the surface morphology of each group of samples,X-ray energy dispersive spectroscopy(EDS)was used to analyze the surface elements of each group of samples,and X-ray diffraction(XRD)was used to analyze the phase of each group of samples.The surface roughness of each group of samples was analyzed by atomic force microscopy(AFM),and the water contact angle of each group of samples was measured by a contact angle meter.The release amount of magnesium ions in MgO-Ⅰ,MgO-Ⅱ and MgO-Ⅲ groups was detected by inductively coupled plasma emission spectrometer.The effects of different thicknesses of nano-magnesium oxide films on the surface of pure titanium on the growth of Porphyromonas gingivalis were investigated by colony counting and bacterial morphology observation.Meanwhile,the cytotoxicity of nano-magnesium oxide films on MC3T3-E1 cells was detected by CCK-8 method.Results:1.Scanning electron microscope observation of the surface of each group of samples found that the surfaces of the three groups of MgO-I,MgO-II and MgO-III were covered with nano-magnesium oxide films,and only scratches were visible on the surface of the Ti group.The EDS analysis results show that Mg and O elements can be detected in MgO-Ⅰgroup,MgO-Ⅱ group and MgO-Ⅲ group,and there are no other impurity elements.The results of XRD shows that only Ti diffraction peaks are seen in Ti group and MgO-I group.Besides Ti diffraction peaks,MgO diffraction peaks also appear on the surface of MgO-II and MgO-III groups.2.The roughness of the Ti group measured by AFM was the smallest(39.07±2.8nm),which was significantly different from the other three groups(P<0.05).The roughness of the MgO-Ⅰ group increased slightly(49.93±3.89nm),which was also significantly different from the MgO-Ⅱ group(70.4±4.73nm)and the MgO-Ⅲ group(78.23±3.84nm)(P< 0.001).There was no significant difference between the MgO-Ⅱ group and the MgO-Ⅲ group(P>0.05).3.The water contact angle on the surface of the Ti group was the largest(56.82±2.66),which was significantly different from the other three groups(P<0.05).The water contact angle on the surface of MgO-Ⅰ group(37.83±0.59)and MgO-Ⅱ group(36.42±0.67)decreased,but there was no significant difference between them(P>0.05),but it was different from that of MgO-Ⅲ group(28.44±1.48)(P>0.05).,there was a statistically significant difference in the contact angle(P<0.05).4.Magnesium ions on the surface of MgO-Ⅰ group,MgO-Ⅱ group and MgO-Ⅲ group were released explosively on the first day,and the release rate of each group was relatively fast at the beginning,and the release rate gradually decreased with the passage of time.slow.On the third day,the release of magnesium ions in the MgO-Ⅰ group began to decrease and basically disappeared.The release of magnesium ions in the MgO-II group continued to become slow until the fifth day,and there was still a small amount of magnesium ions released later.Magnesium ions were released continuously in the MgO-III group,and the release of magnesium ions could still be detected from 7 to 14 days.5.Compared with Ti group,the average antibacterial rate of MgO-Ⅰ group against Porphyromonas gingivalis reached 78.14%,and the average antibacterial rate of MgO-Ⅱgroup and MgO-Ⅲ group was higher,which were 87.16% and 99.86%.There were significant differences in the average bacteriostatic rate among the groups(P<0.001).6.On the surface of the Ti group,the bacterial morphology was complete and the bacteria grew well,and the surface of the MgO-I group began to appear broken bacteria.The number of bacteria on the surface of MgO-II group and MgO-III group was significantly reduced,and most of the bacteria were ruptured without complete structure.7.The MC3T3-E1 cells were used for cytotoxicity detection,and the cell viability in three time periods of 24 h,48h and 72 h was tested respectively.There was no significant difference in the cell viability between the groups(P>0.05),indicating that the three thicknesses of nanometer Magnesium oxide films were not cytotoxic.Conclusion:Nanometer magnesium oxide films with different thicknesses were prepared on the surface of pure titanium by magnetron sputtering,which can effectively inhibit the growth of Porphyromonas gingivalis.In this experiment,300 nm thick nano-magnesium oxide can basically completely inhibit the growth of Porphyromonas gingivalis.