Corrosion resistance and antibacterial effects of hydroxyapatite coating induced by polyacrylic acid and gentamicin sulfate on magnesium alloy

Magnesium(Mg)alloys have attracted considerable research attention as potential biocompatible implant materials.However,the major barriers to the extended use of such medical devices are the possibility of high corrosion rate and implantassociated infections.To solve them,a novel polyacrylic acid(PAA)/gentamicin sulfate(GS)-hydroxyapatite(HAp)coating was synthesized by a one-step hydrothermal deposition method.Characteristics of functional coatings were investigated by SEM,FTIR and XRD.Corrosion properties of samples were evaluated by electrochemical and hydrogen evolution tests.Antibacterial activities of the coatings against Staphylococcus aureus(S.aureus)were measured by the plate-counting method.Results showed that the as-prepared HAp coating with dense and flawless morphologies could not only enhance the corrosion resistance of Mg alloys,but also improve the adhesion strength between the HAp coating and the substrate.In addition,the induction of the apatite coating during immersion confirmed the excellent mineralization ability of the HAp coating.Moreover,the obtained HAp coati ng possessed antibacterial properties and could prolong the release of GS.Thus,the PAA/GS-HAp coated Mg alloy could serve as a better candidate for biomedical applications with good anti-corrosion and antibacterial properties.

Advances in layer-by-layer self-assembled coatings upon biodegradable magnesium alloys

Magnesium(Mg)and its alloys are considered as ideal biodegradable materials due to their excellent mechanical properties and biocompatibility.In order to improve the surface properties to allow better adaptation to the surrounding tissue of the body,surface modification has played a significant role in satisfying multiple clinical requirements such as corrosion resistance,biocompatibility,and antibacterial ability.Here,layer-by-layer(LbL)self-assembly,which can be applied for biodegradable Mg alloys due to its extensive choice of usable units,holds great promise among all the surface techniques.In this review,the mechanisms of the driving force(i.e.,electrostatic interaction,hydrogen bonding,charge transfer interaction and covalent bonding),cuttingedge advances in preparation methods(e.g.,dipping,spraying,and spinning)and the functional properties(corrosion resistance,antibacterial activity,and biocompatibility)that could be achieved by the LbL coatings are summarized.A reasonable trend of the potential development of LbL for bioMg alloys is also proposed at the end of this article.

300 MPa grade biodegradable high-strength ductile low-alloy(BHSDLA)Zn-Mn-Mg alloys:An in vitro study

300 MPa grade biodegradable Zn-(0.6,0.8)Mn-(<0.1)Mg alloys with yield strengths>300 MPa and elongations>15%have been developed,which are designated as Zn06Mn006Mg(HE)and Zn08Mn005Mg(HE)in as-extruded state.They are the newest members of a small group of biodegradable Zn alloys with mechanical properties beyond the generally accepted benchmark for orthopedic implants.Immersed in simulated body fluid for 30 days,Zn06Mn006Mg(HE)and Zn08Mn005Mg(HE)exhibit corrosion rates of 38 and 53μm y^(-1),respectively.They show high antibacterial rates of 93%-97%against E.coli.In 25%-75%extracts of both the alloys,MC3T3-E1 cell viabilities for 1 day and 3 days are all over 100%,indicating complete cytocompatibility.In 100%extracts for 3 days,both alloys show non-toxicity.After a longtime room temperature storage of 72 weeks,natural embrittling alike Zn-Mg alloys does not happen.The Zn-Mn-Mg alloys still have mechanical properties exceeding the benchmark by a large margin.The in vitro study shows the newly developed BHSDLA Zn-Mn-Mg alloys are promising candidates for orthopedic implants.