| Background and Purpose Anterior cervical discectomy and fusion surgery has served as the standard by which cervical spondylosis judged as the result of its high rate of success for many years. The anterior screw-plate fixation truly enhances the cervical stability. However, the implant related complications such as instrument failure, dysphagia, foreign body sensation of throat, and sometimes even esophageal perforation have been hunting us for a long time. With the purpose of avoiding traditional implants related complications, bio-absorbable materials alternates have gained increasing attention recently. The ideal elastic modulus to human bone and compatibility to in vivo metabolism make magnesium alloy becomes a hotspot of recent studies. The previous biomechanical experiments have confirmed that the anterior cervical plate made of magnesium alloy obtain the similar biomechanical character comparing with titanium alloy plate. According to the ISO10993-5 and ISO10993-12, we carry out the cytotoxicity test of magnesium alloy in MG-63 cells and observe the expression level changes of type I collagen(Col-1), Osteocalcin(OC), osteopontin(OPN) and alkaline phosphatase(ALP) to explore the magnesium alloy biological compatibility and the effects it exerts to osteogenesis.Material and Method The extract is prepared according to the ISO standards 10993:5 and 10993:12. Magnesium alloy(Mg 2wt%Zn) specimens(provided by the Materials Science and Engineering College Zhengzhou University) is incubated in the minimum essential medium(MEM) under physiological conditions(5%CO2, 20%O2, 95% humidity, 37 ℃). And the osmolality, magnesium concentration and p H value of the extracts are measured before the test. The human osteosarcoma cell line MG63 is cultured in minimum essential medium(MEM) at 37 ℃ 5%CO2, 20%O2, 95% humidity. The study is divided into 2 groups: the blank control group and the experimental group. Cell proliferation activity is detected by CCK-8 method every 24 hours in the first 72 hours of extract cultivation. The alkaline phosphatase(ALP) is tested by colorimetry method. To evaluate the osteogenic ability of MG-63 cells, collagen type Ⅰ(Col-1), osteocalcin(OC) and osteopontin(OPN) is detected by the Western blot and qt-PCR.Results 1 CCK-8 test results In the experimental group, the survival rates of the cells in the concentrations below 5Xare significantly less than that above 10 X concentrations(P< 0.05). The survival rates of the cells in the groups above 5X concentrationsare not significantly different from the control group(P> 0.05). Osmolality and magnesium concentration are negatively correlatedwiththe survival rate of the cells. That meanshigher the Osmolalityand magnesium concentration come with a higher cytotoxicity. 2 ALP activity test results The MG-63 cells are cultured in 10 x dilution of magnesium alloy extract.The intracellular alkaline phosphatase expressions in the experimental group and blank control group show an upward trend along with the time(P < 0.05).And within the different group, alkaline phosphatase(ALP) expression presents significant differences at different time points respectively(P< 0.05). At the same time point, the expression of alkaline phosphatase in different groups is different(P< 0.05). The expression of alkaline phosphatase in the experimental group was lower than that in the blank control group(P< 0.05). 3 Expression levelsof OPN, OC and Col-1 5 days after MG-63 cells were cultured with 10 x dilution concentration of magnesium alloy extract, we collected the cells and extract proteins. OC, OPN and Col-1 are detected by Western blot and qt-PCR. Image analysis of the two groups is done by software. The expression levels of OC, Col-1 and OPN in the experimental group were significantly higher than that in the blank control group(P < 0.05).Conclusion 1.High concentrations of magnesium alloy Extracts inhibit the MG-63 cell proliferation;2.Mg-Zn alloy promotes the expression levels of Col-1, OC and OPN in MG-63 cells. |
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