Abstract
In the field of orthopedics, magnesium (Mg) and magnesium-based composites as biodegradable materials have attracted fundamental research. However, the medical applications of magnesium implants have been restricted owing to their poor corrosion resistance, especially in the physiological environment. To improve the corrosion resistance of Mg/HA/TiO2 nanocomposites, monolayer MgO and double-layer Si/MgO coatings were fabricated layer-by-layer on the surface of a nanocomposite using a powder metallurgy route. Then, coating thickness, surface morphology, and chemical composition were determined, and the corrosion behavior of the uncoated and coated samples was evaluated. Field-emission scanning electron microscopy (FE-SEM) micrographs show that an inner MgO layer with a porous microstructure and thickness of around 34 μm is generated on the Mg/HA/TiO2 nanocomposite substrate, and that the outer Si layer thickness is obtained at around 23 μm for the double-layered coated sample. Electrochemical corrosion tests and immersion corrosion tests were carried out on the uncoated and coated samples and the Si/MgO-coated nanocomposite showed significantly improved corrosion resistance compared with uncoated Mg/HA/TiO2 in simulated body fluid (SBF). Corrosion products comprising Mg(OH)2, HA, Ca3(PO4)2, and amorphous CaP components were precipitated on the immersed samples. Improved cytocompatibility was observed with coating as the cell viability ranged from 73% in uncoated to 88% for Si/MgO-coated Mg/HA/TiO2 nanocomposite after nine days of incubation.
Highlights
In recent years, following the biodegradability of magnesium (Mg) alloys in the physiological body environment, their excellent biocompatibility especially osteopromotion, as well as the similar mechanical properties to human bone has led to biodegradable magnesium alloys and magnesium-based composites being considered for use as orthopedic implant materials over other traditional metallic materials [1,2,3,4,5,6,7,8]
The X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Field-emission scanning electron microscopy (FE-Scanning electron microscopy (SEM)) results confirmed that monolayer MgO and double‐layer Si/MgO as the protective coatings bonded onto the surface of that monolayer MgO and double-layer Si/MgO as the protective coatings bonded onto the surface
Potentiodynamic polarization, electrochemical impedance spectroscopy, and immersion immersion tests supported that the anticorrosion ability of Mg/HA/TiO2 was improved significantly tests supported that the anticorrosion ability of Mg/HA/TiO2 was improved significantly after surface after surface modification
Summary
In recent years, following the biodegradability of magnesium (Mg) alloys in the physiological body environment, their excellent biocompatibility especially osteopromotion, as well as the similar mechanical properties to human bone has led to biodegradable magnesium alloys and magnesium-based composites being considered for use as orthopedic implant materials over other traditional metallic materials [1,2,3,4,5,6,7,8]. In addition to the high corrosion rate, the low bioactivity of magnesium implants such as the ability to form hydroxyapatite (HA) is another challenging problem, which needs to be resolved before utilization in clinical applications [11,12,13,14] To overcome this drawback, several surface modification techniques, i.e. electrochemical deposition [15,16], polymer treatment [17,18], chemical deposition [19,20], and micro-arc oxidation (MAO) techniques [21,22,23], have been introduced to improve the degradation rate and bioactivity of magnesium and its alloys [9,24]. The cytotoxicity tests indicated that Mg/10HA extract showed no toxicity to L-929 cells
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