Abstract
Magnesium alloys have great potential for developing orthopedic implants due to their biodegradability and mechanical properties, but the rapid corrosion rate of the currently-available alloys limits their clinical applications. To increase the corrosion resistance of the substrate, a protective ceramic coating is constructed by a micro-arc oxidation (MAO) process on ZK60 magnesium alloy. The porous ceramic coating is mainly composed of magnesium oxide and magnesium silicate, and the results from cell cultures show it can stimulate osteoblastic cell growth and proliferation. Moreover, gallic acid, a phenolic compound, was successfully introduced onto the MAO coating by grafting on hydrated oxide and chelating with magnesium ions. The gallic acid and rough surface of MAO altered the cell attachment behavior, making it difficult for fibroblasts to adhere to the MAO coating. The viability tests showed that gallic acid could suppress fibroblast growth and stimulate osteoblastic cell proliferation. Overall, the porous MAO coating combined with gallic acid offered a novel strategy for increasing osteocompatibility.
Highlights
Magnesium and its alloys are considered as the next-generation biomaterials for tissue repair and reconstruction [1,2,3]
The aim of this study is to examine the influence of immobilizing GA onto the micro-arc oxidation (MAO) coating with regard to corrosion resistance and osteocompatibility
Most of the surface modification needed to be carried out in aqueous solution and, the compactness of the protective coating might be destroyed. In this experiment, since GA could only be dissolved in absolute ethanol, the oxide layer would not react with water, break MAO coating’s structure, or generate cracks due to hydration and inflation
Summary
Magnesium and its alloys are considered as the next-generation biomaterials for tissue repair and reconstruction [1,2,3]. Recent research shows that magnesium ions can induce cellular adhesion and bone formation, which are important functions for building strong bone-implant interfaces [4,5]. In this respect, magnesium alloys are suitable candidates for bone grafting, due to their osteoinductive and osteoconductive effects [6]. The corrosion reaction that occurs on the surface will produce hydrogen bubbles that obstruct the initial cell adhesion [8] These adverse effects highlight the need to reduce the initial degradation rate and enhance its biocompatibility. Surface modification of magnesium is Materials 2017, 10, 696; doi:10.3390/ma10070696 www.mdpi.com/journal/materials
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