In vitro comparative study of composite coatings for magnesium-based bone implants

Abstract

This study provides a comparative assessment of the corrosion, morphology, and biological properties of four of the most promising coating methods for magnesium in biomedical applications, namely micro-arc oxidation (MAO), graphene oxide (GO)-containing MAO coating, MAO/sol-gel composite coating, and MAO/polycaprolactone (PCL) polymer dip coating approaches. Despite the abundance of research focused on these promising coating approaches, there is a notable lack of comparative studies evaluating their properties. To this end, the investigated composite coatings are ZK60+MAO, ZK60+MAO/GO, ZK60+MAO/Sol-gel, and ZK60+MAO/PCL composite coating. Several tests were used to assess various properties of the prepared groups such as in vitro corrosion characteristics, surface microhardness, adhesion strength, hydrophilicity, and cytotoxicity. The ZK60+MAO/Sol-gel composite coating demonstrated the highest in vitro corrosion resistance, surpassing both the ZK60+MAO and ZK60+MAO/PCL coating groups. Also, the addition of GO layered particles to the MAO coating electrolyte improved corrosion resistance to 0.21% over the immersion period and enhanced the biocompatibility. In addition, the ZK60+MAO/PCL composite coating exhibited the greatest biocompatibility compared to the other applied coatings, evidenced by the highest cell viability on average of 93% across all dilutions and a more hydrophilic surface by expressing a lower contact angle of 54.8°. Some discrepancies between the corrosion results from immersion tests and electrochemical corrosion tests were observed which emphasizes the importance of incorporating multiple corrosion testing methods in future corrosion studies. This study underscores the feasibility of producing biocompatible Mg-based implants with controlled corrosion properties through the application of diverse composite coatings.

Keywords

• Magnesium
• Coating
• Bone implants
• Corrosion
• In vitro