Polyvinyl alcohol/magnesium phosphate composite coated Mg-Ca alloy for biodegradable orthopaedic implant applications

Magnesium-Calcium (Mg-Ca) alloys are suitable candidate materials for developing degradable metallic implants. However, the degradation rate of these alloys in the physiological environment needs to be controlled to avoid the loss of mechanical integrity of the implant and hydrogen gas pocket formation. In this work, the degradation rate of low Ca containing Mg alloy was controlled using polyvinyl alcohol (PVA)/magnesium phosphate (Mg-P) composite coating. The sample surfaces were subjected to hydrothermal treatment prior to coating. Mg-P was developed using magnesium nitrate [Mg(NO3)(2) center dot 6H(2)O] and diammonium phosphate [(NH4)(2)HPO4] as precursors were dispersed in PVA solution prior and was spin coated on the sample surfaces. The in vitro biodegradation and biomineralization of the samples were tested in supersaturated simulated body fluid (SSBF). The immersion test results showed that composite coating on hydrothermally pretreated samples reduced the degradation rate and enhanced biomineralization in the physiological environment. The hydrothermal treatment made the coating-substrate interface stable. The combination of hydrothermal pretreatment and PVA/Mg-P composite coating can be used as a surface modification technique to enhance biomineralization and control the rapid degradation rate of Mg alloys in the physiological environment.