Study On Biocompatibility Of Antibacterial Coatings Of AZ91D Magnesium Alloy Based Calcium Phosphate/Chitosan Composite

Magnesium and magnesium alloy with good biological and mechanical properties, could degrade inside the living body and thereby avoid the pain on the patient caused by the second operation. However, magnesium and magnesium alloy, as the bone implanting materials, have two disadvantages. Firstly, its rapid degradation inside the living body results in the poor performance of biological property. Secondly, in the implantation process, it could cause bacterial infection. Therefore, how to enhance the corrosion resistance and antibacterial property of magnesium and magnesium alloy is still a problem to be resolved.Regarding the shortcoming of Magnesium and magnesium alloy mentioned above, corrosion resistant antibacterial layer was built on the surface of AZ91D magnesium alloy. On the basis of the former research "Preparation of AZ91D Magnesium Alloy Based Calcium Phosphate/CNTs/Chitosan Bone Implant Material Using the Electrophoretic Deposition (EPD) Combined with Phosphate Buffer Solution (PBS) Conversion Process", antibacterial metal ions Zn2+,Cu2+were added during the process of electrophoretic deposition to study the biological activity, degradation behavior and antibacterial property of AZ91D Magnesium Alloy Based composites implant material in the simulated body fluid (m-SBF).First of all, single factor experimental method was adopted to optimize the Loading quantity of Zn2+,Cu2+in order to determine the most ideal dosage to prevent the mechanical property of materials from being affected. The best preparation technology of AZ91D Magnesium Alloy Based CaP-CNTs-Zn-CS composites film was 0.05g of the Zn(NO3)2 additive quantity. The best preparation technology of AZ91D Magnesium Alloy Based CaP-CNTs-Cu-CS composites film was 0.05g of the Cu(NO3)2 dosage.Secondly, the difference of biological activity and degradation behavior of materials soaked in the simulated body fluid during various periods were studied. Infrared analysis, Raman analysis, XRD, canning electron microscope, energy spectrum analysis were adopted to study material surface composition and morphology. The electrochemical experiment was carried out to study corrosion behavior of materials. The mechanics experiment was done to study mechanical properties of materials. Inductively coupled plasma atomic emission spectrometry was adopted to measure the different concentrations of ions in the m-SBF solution. The results showed that the bone implant material had good biological property, and the release time of Zn2+,Cu2+ was about 14 days.Last, experiment was conducted on the resistance of AZ91D Magnesium Alloy Based antibacterial composite film against the White staphylococcus and Escherichia coli. The size of Bacteriostasis Circle surrounding the material could directly showed the intensity of its antibacterial property. The result shows that the size of Bacteriostasis Circle of the two kinds of bacterial was the largest on the first day. The size of Bacteriostasis Circle on the film of Cu2+ and Calcium Phosphate/Chitosan/CNTs composites was (23.4±1.1)mm when it endured the invasion of White staphylococcus group, while the size of Bacteriostasis Circle was (20.6±1.8)mm when it endured the invasion of Escherichia coli group. Calcium Phosphate/Chitosan/CNTs film generates no Bacteriostasis Circle when it suffered from the invasion of either bacteria. As time going, the diameter of Bacteriostasis Circle on the film of Cu2+and Calcium Phosphate/Chitosan/CNTs composites was reducing. After being invaded by the White staphylococcus group for 16 days, the Bacteriostasis Circle disappeared, while after being invaded by the Escherichia coli group for 13 days, the Bacteriostasis Circle disappeared, but yet no bacterial grew in the medium contacting with the films in both two groups. The result of the bacteria colony count test matches the result of Bacteriostasis Circle test. The White staphylococcus and Escherichia coli still grew after it contacted with the Calcium Phosphate/Chitosan/CNTs film, but the two kinds of bacteria dramatically reduced after they contactd with the film of Cu2+ and Calcium Phosphate/Chitosan/CNTs composites. The calculation revealed that antibacterial ratio of the film of Cu2+ and Calcium Phosphate/Chitosan/CNTs composites against White staphylococcus was 92.27% and the antibacterial ratio of the film of Cu2+ and Calcium Phosphate/Chitosan/CNTs composites against Escherichia coli was 85.84%.