Characterization and Degradation Study of Calcium Phosphate Coating on Magnesium Alloy Bone Implant In Vitro

Abstract

Magnesium alloys have similar mechanical properties with natural bone, and they degrade within a certain time span. Therefore, magnesium alloys are suitable to be made as bone screws or plates. However, high susceptibility to corrosion has limited their applications in the orthopedic field. They would possess great medical functions if the degradation rates of magnesium alloys could be reduced. This paper describes approaches to form calcium phosphate coating on magnesium alloy (AZ31) to control the degradation rate. Samples of AZ31 were placed in the supersaturated calcification solution prepared with Ca(NO 3 ) 2 , NaH 2 PO 4 , and NaHCO 3 , and then, the calcium phosphate coating was formed. The composition, phase structure, and morphology of the coatings were investigated. The degradation behaviors of the naked and coated magnesium (Mg) alloys were studied in simulated body fluid. The results of this paper have shown that the coatings significantly decrease the degradation rate of the original Mg alloy, indicating that the Mg alloy with calcium phosphate coating is a promising degradable bone material.

Surface Modifications of Magnesium Alloys for Biomedical Applications

“…Different kinds of Ca-P coated AZ31 Mg alloy samples were immersed in SBF. 85 The degradation product and surface layer after immersion in SBF was shown in Fig. 2f.…”

Rapid coating of AZ31 magnesium alloy with calcium deficient hydroxyapatite using microwave energy

“…To date, several forms of calcium phosphate coating have been developed on magnesium and its alloys by various techniques, such as chemical precipitation [19,[27][28][29][30][31][32], electrodeposition [33][34][35], sol-gel [36] and hydrothermal method [37,38]. For example, Yang et al [29] produced hydroxyapatite (HA) coatings on AZ31 alloy by immersing the AZ31 substrate in supersaturated calcification solutions and applying heat treatments afterwards. Song et al [35] produced HA coatings on AZ91 alloy by electrodeposition with subsequent treatment in NaOH solution.…”

Electrochemical deposition of conducting polymer coatings on magnesium surfaces in ionic liquid

“…Alloying is an effective way to control the corrosion rate, but many Mg alloys contain toxic elements that may be released to the tissue [13]. Coatings have been applied to Mg implant, including microarc oxidation coatings [14], calcium phosphate coatings [15, 16] and hydroxyapatite coatings [17, 18]. These coatings can either influence the corrosion rate, or improve biocompatibility and tissue integration of the Mg-based implants [19].…”