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Magnesium alloys are ideal materials in clinical applications for their excellent mechanical properties, while potential cytotoxicity with rapid degradation limits their clinical applications. Moreover, it is also important for implants to avoid inflammation caused by bacterial infections in the early stage of implantation. Therefore, copper-doped anhydrous calcium phosphate nanoparticles were fabricated by the hydrothermal method and dispersed in a dicalcium phosphate dihydrate (DCPD)/Polycaprolactone (PCL) composite coating to improve its bacteriostatic properties, corrosion resistance, and biocompatibility in this paper. The impedance of the DCPD/PCL/Cu-doped anhydrous calcium phosphate (Cu-ADCP) composite-coated sample is 1 order of magnitude higher than that of the bare magnesium alloy, and the corrosion current density decreases by 2 orders of magnitude, indicating that the composite coating incorporating nanoparticles can effectively enhance the corrosion resistance. The in vitro cell experiments show its biocompatibility with sustained growth in cellular activity and increased alkaline phosphatase activity. Most importantly, the embedded copper-doped nanoparticles significantly improve the antibacterial properties of the composite coating. Compared with the composite coating with almost no antibacterial ability, the antibacterial rate reached 96 and 98% for Escherichia coli and Staphylococcus aureus , respectively, after the nanoparticles were embedded, making them a promising choice for orthopedic applications. [ABSTRACT FROM AUTHOR]

As potential degradable biomaterials, magnesium (Mg) alloys have development prospects in the field of orthopedic load-bearing, whereas the clinical application has encountered a bottleneck due to a series of problems caused by its rapid corrosion. In this study, strontium-substituted calcium phosphate (CaP) coatings with different structures were prepared on the surface of the Mg matrix by a simple one-step electrodeposition method at different temperatures, which enhanced the poor corrosion resistance of the Mg matrix. The coated sample prepared at 65 °C reduced the corrosion current density by 3 orders of magnitude and increased the impedance by nearly 2 orders of magnitude compared with bare Mg alloy, thanks to its dense fibrous structure similar to that of natural bones. Although the coating composition varies with different preparation temperatures, CaP, as an inorganic component similar to natural bone, has good cytocompatibility. Doping the right amount of strontium, which is a trace element in human bones, is beneficial to stimulate osteoblast differentiation, inhibit the activity of osteoclasts, and induce the formation of bone tissues. This provides a new option for modifying the Mg alloy with CaP coatings as a base.

Magnesium (Mg) alloys, a degradable material, have been studied for medical applications due to their excellent mechanical and chemical properties. However, their applications are limited by rapid corrosion. In this work, stearic acid and sodium stearate were used to treat the silane-induced calcium phosphate dihydrate coating to improve its protection for the Mg alloy further without changing the bone-like structure of calcium phosphate. The different effects of stearic acid treatment and sodium stearate treatment were compared. Electrochemical test and immersion test results confirmed that the corrosion resistance of the stearic acid-treated composite coating was greatly enhanced with a reduced corrosion current density by 3 orders of magnitude and hydrogen evolution reduced to 1/25 after 14 days. The stearic acid-treated coating also exhibited improved in vitro biocompatibility corroborated by promoted cell viability and better cell morphology.