Degradable implants based on magnesium and its alloys have been developed due to the problems of permanent orthopedic implants, such as the necessary of secondary surgeries, infection and prolonged inflammation. WE43 alloy has been eva‎luated as a suitable alloy for orthopedic implants due to its favorable and high mechanical corrosion properties. Over current research, plasma electrolytic oxidation /hydroxyapatite/poly Dopamine composite coating was suggested to modify surface , in order to solve the challenges such as the high rate of degradation, the low oesteointegration with and need to accelerate the growth and regeneration of bone around implant. First, plasma electrolytic oxidation coating deposited on the surface by different working parameter to discover the effect of frequency parameters (0.5, 0.8 and 1 kHz), coating time (5, 10 and 20 minutes) and working cycles (40-50, 50-20 and 40 70-70), on morphology, number and size of porosity. The optimize was contain frequency 0.8 KHz, time 10 minutes and duty cycle 40-50 with porosity 5.35± 0.2 and 15.31 ± 3. 0.0 μm. On the other hand, applying a bioactive coatings with controlled morphology resulted in osteoimunomodulation and led to improved ossteogenration. Therefore, the hydroxyapatite coating with a controlled plate-like morphology and random morphology Hydroxy apatite deposited on plasma electrolytic oxidation usng hot dip method, to discover the role of morphology on biological and physical properties. The results indicated an improvement in corrosion resistance by 20 times and an improvement in adhesion resistance in the case of plate-like morphology compare to randome like Hydroxy apatite. In the following, due to the impossibility of simultaneously obtaining hydroxyapatite and polydopamine coating as a secondary layer by hot dip method, the electrical deposition method was investigated. In order to optimize and control the morphology of the hydroxyapatite coating and composition, workiing parmeters such as deposition time (10, 20 and 30 minutes) and dopamine hydrochloride concentration (1, 2.5 and 5 mg/ml liter) was investingatied. The optimize samples sample was obtained at 20 minutes coating time and 1 mg/ml dopamine concentration. The resistance of the self-healing layer in this sample increased by 195 times on day 21 compared to day 1. Also, the lowest amount of hydrogen release after 7 days (about 5 ml/cm2) is related to this sample, which is 85% compared to the uncoated sample and 37% compared to the plasma electrolytic oxidation coated sample. Moreover, the results showed a significant improvement in the bioactivity and adhesion strength of the coating compared to the plasma electrolytic oxidation/ hydroxyapatite coated sample. All in all, plasma electrolytic oxidation /hydroxyapatite/polydopamine coating led to self-healing, control of degradation and hydrogen evolution rate. On the other hand, the results of cell adhesion and cell viability on the 3rd day related to the plasma electrolytic oxidation coating/hydroxyapatite/polydopamine coated sampele revealed , a significant difference and improved in viability up to 158% control compared to the samples with the plasma electrolytic oxidation /hydroxyapatite coated samples the electrolytic plasma oxidation coating. Furthermore, discovering the macrophage cell behavior over different samples indicated an increase in the expression of anti-inflammatory genes BMP2 and TGF-β and fast modulating of type 1 macrophages to type 2 following by controlling the morphology and composition by using. The plasma electrolytic oxidation/ hydroxyapatite/polydopamine led to osteoimmunomodulating properties along with the self-healing properties makes this coating suitable as a candidate for spinal implants.

مهشيد خرازيهاي اصفهاني , حسين صالحي

مسعود عطاپور

كيوان رئيسي , سعيد كرباسي