Investigation On Degradation Behavior Of Calcium Phosphate Coating Modified Magnesium In Eye Environment:in Vitro And In Vivo

Magnesium and magnesium alloys have received wide attention in clinical applications because of their excellent biodegradability,biosafety and biocompatibility,However,magnesium alloys as eye implant materials have been rarely reported in recent years.In this paper,Hydroxyapatite(HA),Calcium hydrogen phosphate(DCPD)and Calcium hydrogen phosphate/Stearic acid(DCPD+SA)calcium phosphate coatings were prepared on magnesium substrate by liquid phase deposition.The corrosion behavior of calcium phosphate coating modified magnesium in vivo and in vitro was studied,and the feasibility of modified magnesium as a candidate material for human eye aqueous humor drainage device was explored.Electrochemical experiments showed that the corrosion potential of magnesium modified by HA,DCPD and DCPD+SA calcium phosphate coatings in simulated eye environment increased 1180 m V,1306 m V and 1322 m V respectively,the corrosion current density reduced by 2 orders of magnitude,and the corrosion rate decreased by25 times,3 times and 10 times,respectively.In the immersion experiment,it was found that with the continuous immersion,the concentration of Mg^2+,Ca²⁺and P⁵⁺ions in the corrosion medium decreased gradually,and the weight loss of the specimens increased slowly.Local galvanic corrosion and pitting corrosion are the main corrosion modes in the immersion process,and the surface of the sample is gradually covered with corrosion products in the form of Mg(OH)₂,Mg CO₃,Mg O and calcium phosphate.After soaking for 30 days,the corrosion rate of HA was the lowest,followed by DCPD+SA,DCPD and pure magnesium,indicating that calcium phosphate coating improved the corrosion resistance of magnesium alloy in simulated eye environment.MTT and LDH experiments showed that calcium phosphate coating could reduce the cytotoxicity of magnesium alloy in eye fibroblasts and improve cell activity.The animal eye implantation experiment showed that calcium phosphate coating could slow down the inflammatory reaction of magnesium alloy in vivo and showed excellent biocompatibility and biosafety,while the corrosion of magnesium alloy in vivo was faster than that in vitro,especially the edge corrosion rate of magnesium alloy in vivo was faster,and the surface of the sample was significantly delaminated,the corrosion products were mainly composed of Ca,Mg and P.Eight weeks after operation,HA and DCPD+SA still maintained high integrity,followed by DCPD,and pure magnesium was the most serious,indicating that calcium phosphate coating can effectively improve the corrosion resistance of magnesium alloy under the eyes of New Zealand rabbits and ensure that magnesium alloy can maintain good aqueous humor drainage during its service period,which is expected to develop into a new generation of degradable aqueous humor drainage device material for curing glaucoma.