Research On The Biocompatibility Of Mg-Zn-(β-TCP) Composite Material

Objective:This study investigated the biocompatibility degradation behavior and the impact on bone defect healing of Mg-6%Zn-(β-TCP) bio-compositthe, to preparation theory basic for preparation of new controllable degradation magnesium.Materials and methods:Mg-6%Zn-10%(β-TCP) bio-composite was successfully fabricated by means of powder metallurgy method, the concentration ofβ-TCP was 5%,10% and 15%; immersion test to study Mg-6% Zn-(β-TCP) composite corrosion performance; MTT assay method was used to evaluate the cytotoxicity of bio-composite to the rat fibroblast cells L929;to evaluate the in vivo biocompatibility and the impact on bone healing, Mg-6%Zn-10%(β-TCP) bio-composite was implanted to rabbit femur, biochemical measurement to monitor serum magnesium,serum calcium and serum zinc; 2,4,8 and 12 weeks post-implantation, the heart,liver, kidney and the soft tissues around implant were made into sections for histomorpHology analysis. Micro-CT was used to observe the fumer and the degradation of bio-composite. Bone formation around the implant was investigated by decalcified sections with HE stained using traditional light microscopy. The morpHology of remaining bio-composite were observed by SEM and analyzed by EDS.Results:Mg-6%Zn-5%(β-TCP),Mg-6%Zn-10%(β-TCP) Mg-6%Zn-15%(β-TCP) bio-composite are fabricated by means of power metallurgy method, which the elastic modulus is 21,24,36GPa,and are close to human bone(3-20GPa). Immersion test show that Mg-6%Zn-10%(β-TCP),Mg-6%Zn-15%(β-TCP) had better corrosion resistance. The MTT test shows the leaching liquor with 100%,50%,10% concentrations of Mg-6%Zn-10%(β-TCP) and Mg-6%Zn-15%(β-TCP) are nontoxic to L929.2,4,8 and 12 weeks post-implantation, the concentration of magnesium in serum is 1.65～1.85mmol/L (normal 0.88～2.22mmol/L), calcium in serum is 3.65～4.02mmol/L (normal 3.1～5.2mmol/L), zinc in serum is 86～96.4μmol/L(正常值norma76.5～170μmol/L);No obvious abnormalities and necrosis are observed in histopathological sections of the heart,liver, kidney and the soft tissues. Micro-CT show that bio-composite experienced gradual degradation over time. After 2 weeks, the bio-composite have clear edge; after 4 weeks, the bio-composite lose cleat edge, and the sample exhibiting pitting corrosion on the edge, the bone defect have healed, some new bone generate around the implant; after 8 weeks, samples have partly dissolved,and more new bone form to wrap the samples; after 12 weeks, Mg-6%Zn-10%(β-TCP) sample only have a little part of reservation,but the Mg-6%Zn-15%(β-TCP) sample are completely deformed, large amount of new bone generate in the area of sample. The area of bone and defect are obverted by decalcified sections with HE stained, newly formed bone can be observed around implant, some osteoblast and fibrous connective tissue are also observed. The product of the degradation on the surface of remaining implant is rough and crumbly, and show irregular-shaped cracks. The main component of the materials layer is Mg,O,P,Ca,Zn and so on.Conclusions:1.Mg-6%Zn-5%(β-TCP),Mg-6%Zn-10%(p-TCP) and Mg-6%Zn-15%(β-TCP) bio-composite was successfully fabricated by means of powder metallurgy method.2.1mmersion test show that Mg-6%Zn-10%(P-TCP),Mg-6%Zn-15%(β-TCP) had better corrosion resistance.3. The MTT test show the Mg-6%Zn-10%(β-TCP) and Mg-6%Zn-15%(β-TCP) are nontoxic to cell.4. The bio-composite gradual degradation after implant in vivo, and the products of degradation don't affect magnesium, calcium and zinc in serum. No obvious abnormalities are observed in histopathological sections of the heart, liver, kidney and the soft tissues, to prove the bio-composite have good in vivo biocompatibility, don't harm on bone defect healing and can improve newly bone generating. Mg-6%Zn-10%(β-TCP) bio-compasite have better corrosion resistance.