Fabrication And Property Of Self-Assembled Composited Coatings On Magnesium Alloys

Magnesium(Mg)alloys have been widely applied in the fields of biomedical materials due to the notable biodegradability and biocompatibility.However,high corrosion rate as an inevitable obstacle hinders the extensive applications of Mg-based alloys.At the same time,it is susceptible to the bacterial adhesion and the formed biofilms can cause chronic infection of the issues.Therefore,it is of great importance to endow Mg alloys with good corrosion resistance and prevent them from bacterial infections for clinical applications.In this work,we constructed multilayer films on Mg alloys through the layer-by-layer(LbL)assembly technology,and thus endowed the substrates with multi-functionality including corrosion resistance,self-healing behavior,antibacterial property,drug release profile and so forth.First of all,in order to improve the corrosion resistance of Mg alloys,the spin-assisted LbL(SLbL)assembled polyvinylpyrrolidone(PVP)/polyacrylic acid(PAA)multilayer was developed on Mg substrate.Next,the self-healing multilayer based on SiO2/CeO2 nanoparticles(NPs)spin-spray LbL(SSLbL)assembly had been prepared on Mg alloys for good anticorrosion and self-healing performances.Besides,the heat treated(HT)gentamicin sulfate(GS)loaded poly(allylamine hydrochloride)(PAH)/PAA multilayer by means of SLbL assembly and HT methods was fabricated on Mg alloys for corrosion resistance,antibacterial property and drug release profile.Finally,polymethyltrimethoxysilane(PMTMS)modified silver NPs(AgNPs)/polyethyleneimine(PEI)LbL assembled composited coating fabricated using LbL assembly and poysiloxane modification improved the corrosion resistance,self-healing behavior and antibacterial activity of Mg alloys.The morphology.element composition,chemical component and intermolecular bonding mode of different coatings were characterized by SEM.F DS,XPS,XRD.FT-1R and so forth.The corrosion resistance of samples was tested using electrochemical and immersion tests.The adhesion strength between the coating and the substrate and the self-healing behavior were measured by nanoscale and nano-scratch indentations,and the antibacterial activity was gathered using the plate-counting method.The appearance and the release behavior of antibiotics were detected using UV-vis Furthermore,we also explained the formation mechanisms of films,and the corrosion and biodegradation behaviors in simulated body salt solutions(HBSS).The results showed that the PVP/PAA SLbL assembled multilayer enhanced the corrosion resistance and bonding strength of M g alloy substrate.Actually,during the spinning process.the adsorption and rearrangement of different charg ed polyelectrolytes were simultancously achieved in a very short period of time,in which the water molecules could be rapidly removed and the molar concentration of polyelectrolytes would be raised due to the eentrifugal fore and the air shear force during the spinning process.Then the eleetrostatic attraction?effeets between the opposite charged polyelectrolytes were enhanced.leadling to a denser and smoother coating.Besides,the SiO2/CeO2 NPs SSLbL assembld multilayer endowed Mg substrate good corrosion protection and self-repairing performance.The SiO2 NPs as the useful building units could be used as the physical barrier against corrosive medium and CeO2 NPs were chosen to act as the corrosion inhibitor to heal the physical damage of Mg-based substrate.The HT-PAH/PAA-GS multilayer had better corrosion resistance and antibacterial property due to the formation of anhydride bonding after thermal cross-linking,which also could prolong the release of GS.The PMTMS-AgNPs/PEI composited coating deposited on Mg alloys with corrosion resistance,self-healing behavior and antibacterial properties,as well as prolonging the release of Ag+from the coating toguarantee long-term antibacterial effects.Thus,LbL assembly technique could endow Mg alloys with multi-functionality including corrosion resistance,self-healing property,antibacterial performance and sustained release of antibiotics,and hence it is an ideal surface treatment technology of Mg alloys.