Advantages of electrochemically deposited bioceramic-coating on magnesium implant for anti-corrosion and bone regeneration

Magnesium implants offer the advantages of biodegradability and absorbability after implantation in bone fractures. However, they cause delayed bone regeneration owing to their fast biodegradation rates. To address this issue, we attempted to utilize the bioactivity of bioceramic coatings and anti-corrosion property by doping Zn ions onto Mg implant surfaces. Zn-doped CaP bioceramic precipitation was induced on magnesium surfaces via electrochemical deposition in a mixed electrolyte of Ca(NO₃)₂ and NH₄H₂PO₄ with varying concentrations of Zn(NO₃)₂. As a result, in an electrolyte containing a low concentration of Zn(NO₃)₂, a uniform film layer, consisting of hydroxyapatite (HA) and calcium zinc phosphate hydrate (CZPD) bioceramics, was formed with approximately 30 μm of thickness. This layer improved the corrosion resistance of the Mg surface in simulated body fluids and promoted the formation of bioactive substrates. Higher concentrations of Zn(NO₃)₂ in the electrolyte led to an enhanced corrosion resistance with increasing Ca(OH)₂ precipitation. However, corrosion products were formed instead of bioactive substrates. Therefore, it was demonstrated that appropriate Zn(NO₃)₂ addition during electrochemical deposition induced stable osteoblast attachment and uniform formation of a new bone layer, delayed biodegradation with excellent corrosion resistance, and promoted bone regeneration through the formation of bioactive substrates during implantation.