ZnO&HAp Modified Magnesium Implant With Broad Spectrum Antibacterial Properties And A Unique Minimally Invasive Defined Degrading Capability

Background and Objective:As a new generation of orthopedic metallic material,magnesium?Mg?have attracted a great deal of attention due to its biodegradability and potential for avoiding second sugery.However in practical applications,magnesium implants would be excessively degraded before the fracture has completely healed,resulting in a surgical failure.On the other hand,since bacterial infection is also one of the leading causes of surgical failure.ZnO&HAp based membrane was proposed to improve the antibacterial properties and anticorrosion capability of the magnesium?Mg?implant,simultaneously.More importantly,the concept of minimally invasive surgery was introduced to define the degradation timing of the as-modified magnesium implant.With the aid of a Kirschner wire,the as prepared membrane could immediately change from the“protective layer”to the“degradation accelerator”of the implant material.The subsequent studies implied that this membrane could be a promising avenue to create a biocompatible and lightweight implant material with a valuable personal customized degradable timing capability.In this present paper,a new type of ZnO and HAp composite coating on magnesium surface has been systematically studied.By comparing with pure magnesium and magnesium coated with single HAp film,the antibacterial and corrosion resistance of the three materials were analyzed.And the biocompatibility of the materials was evaluated.The experimental results show that:Firstly,we fixed that the concentration of Zn?CH₃COO?₂ and C₆H₁₂N₄ in the experimental reaction solution were 60 mol/m³ and the reaction time was set at 2hours.Under these conditions,the synthetic HAp coating showed sufficient corrosion resistance as well as excellent antibacterial properties.For the sake of controllable degradation characteristics,we designed a material soaking experiment for 30 days.There was no significant difference in the weight loss rate between the Mg-HAp and the Mg-HAp-ZnO in the first 10 days.After wrecking the coating,we could found that the weight loss rate of the Mg-HAp-ZnO group were remarkably increased,while the weight loss rate of the Mg-HAp group were less than 10%in30th day.This result indicated that we have successfully realized the controllable degradation characteristics of Mg-HAp-ZnO in vitro.In order to investigate the corrosion resistance and antibacterial properties of Mg-HAp-ZnO in vivo,we conducted the following experiments.First,we divided the samples into 4 groups:Pure Mg,Mg-HAp-ZnO?two groups?and MgO.These samples were implanted into the tergal muscles of the rabbits to observe their biodegradation.When one group of Mg-HAp-ZnO coating was partially scratched?named as Mg-HAp-ZnO??,the degradation rate began to rise.On the 8th week,the degradation rate of Mg-HAp-ZnO?group was obviously higher than that of Mg-HAp-ZnO group.This phenomenon was consistent with our assumption.In the in vivo antibacterial experiment,to increase the ratio of infection,three different implants were soaked in the solution of S.aureus before operation.After 2 weeks,we immersed these implants,which were taken out from mice,into sterile PBS.According to the plate counting method,the hydroxyapatite coating had no obvious antibacterial property,while Pure Mg and Mg-HAp-ZnO possessed great antibacterial properties compared to Mg-HAp?***,p<0.001?.We could also intuitively detected that the incision of Mg-HAp group had not healed yet,and the incision of Pure Mg and Mg-HAp-ZnO had healed without redness or swelling.However,there was a large bubble formation under the skin of the rat incision of Pure Mg group.We explored both cytotoxicity and hemolysis tests.We found that the cell viabilities of the three groups of materials were basically higher than 80%,with no statistical difference.In the hemolysis experiment,the hemolysis rates of the Mg-HAp-ZnO group was significantly less than 5%.