A Ca-P coating consisting of biodegradableβ-tricalcium phosphate[β-TCP,β-Ca3(PO4)2]accepted for medical application was coated on a biodegradable AZ31 alloy by chemical deposition to improve the corrosion resistance.The good bonding strength of the coating is obtained.The results show that the corrosion potential of the Ca-P coated AZ31 alloy increases significantly,and MG63 cells show good adherence,proliferation and differentiation on the surface of the coated alloy.The Ca-P coating might be an effective way to improve the surface bioactivity of magnesium alloys.
A new concept for development of metallic biomaterials is proposed in this article, i.e., a certain bio-function can be realized for a metal implant through continuous release of a designed bio-functional metal element from surface of the metal implant in the body environment. This creative idea has been verified to be possible by several different in vitro and in vivo experimental evidences on the Cu-bearing stainless steels and magnesium based metals. It was indicated that a trace amount of Cu release from the Cu-bearing steels could have obvious bio-functions of reduction of the in-stent restenosis （ISR）, anti-bacterial infection, inhibiting the inflammatory cells and even promoting the early osteogenesis. Furthermore, the degradation of magnesium based metals in bones could promote the new bone formation, enhance the bone mineral density for the osteoporosis modeled animal, and even have strong anti-bacterial ability and strong cytotoxicity to bone tumor cells due to the enhancement of pH. Special bio-function with satisfied load-bearing capacity for metallic biomaterials will bring higher application values for the implant made of this novel material. This is an attractive direction for research and development with many challenges, but the final success will be much beneficial to the majority of patients.
Magnesium （Mg） based metals possess unique features of biodegradation that can be used for different purposes. In this study, two tumor cells, MG63 and KB, were cultured directly on a pure Mg with and without MAO coating to evaluate their cytotoxic effects on the tumor cells. It was found that both MG63 cells and KB cells adhered better on the surface of the coated Mg samples than those on the pure Mg samples. However, the survivals of two kinds of tumor cells were obviously inhibited on both Mg samples with and without coating, compared with that on the pure titanium. In addition, the survival of MG63 cells was more susceptive to the Mg degradation compared with the KB cells. Thus, the application of such effect should take account of that the degradation of Mg based metal may result in different cytotoxic effect on different cells.
Qiang Wang1aShi JinXiao LinYang ZhangLing RenKe Yang
In the present study, a Si-containing coating was fabricated on AZ31B Mg alloy. Cytocompatibility of the coated alloy was evaluated by both indirect and direct contact methods, respectively. Effects of a number of incubation variables on the sensitivity and reproducibility of the hemolysis test were also examined by using positively and negatively responding biomaterials. Cytocompatibility testing results indicated that cell condition, cell adherence, cell proliferation and extracellular matrix secretion of the coated alloy were improved compared with those of the uncoated alloy for different extraction and co-culture time. The hemolysis test suggested that hemolysis testing conditions were critical to determine the hemolysis of the alloy. It was also found that 1 day in vitro degradation of the uncoated AZ31B alloy had no destructive effect on erythrocyte. As for the coated AZ31B alloy at any time point, the hemolysis rate was much lower than 5%, the safe value for biomaterials. These in vitro experimental results indicate that the Si-containing coating is effective to improve the cytocompatibility and hemolysis behaviors of AZ31B alloy during its degradation.
A composite coating was fabricated on pure magnesium by hydrothermal treatment in order to reduce its degradation in body environment. The coating was character- ized by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The XRD pattern showed that the main composition of the coating was a mixture of CaSiO3, MgSiO3 and Mg（OH）2. Electrochemical test showed that the corrosion current den- sity （icor~） of the coated magnesium was decreased by about two orders of magnitude compared with that of the bare magnesium, and the EIS measurement also showed that the corrosion resistant performance of the coated magnesium was significantly enhanced. Meanwhile, weight loss test showed that the weight loss of the coated magnesium was lower than that of the bare magnesium. Hence, the present study indicated that the composite coating could greatly slow down the degradation of pure magnesium.
Yanjin LULili TANHongliang XIANGBingchun ZHANGKe YANG
A biodegradable Ca-P coating mainly consisting of β-tricalcium phosphate （β-TCP） was fabricated on pure magnesium via the chemical deposition in a simulated Hank’s solution. The method significantly accelerated the coating formation on magnesium. Moreover, the morphology, phase/chemical composition, the coating formation mechanism as well as degradation behavior in phosphate buffered saline （PBS） solution were in- vestigated. Scanning electron microscopy （SEM） images showed that the coating had three layers and X-ray diffraction （XRD） patterns showed that the coating mainly contained Ca3（PO4）2 and （Ca,Mg）3（PO4）2. Elec- trochemical test showed that the corrosion current density （Icorr） of the coated Mg was decreased by about one order of magnitude as compared to that of pure magnesium. The immersion test indicated that the coating could obviously reduce the degradation rate.
Yanjin LuLili TanHonglia. ng XiangBingchun ZhangKe YangYangde Li
