Abstract
Hydroxyapatite coatings have been widely used to improve the corrosion resistance of biodegradable magnesium alloys. In this paper, in order to manufacture the ideal hydroxyapatite (HA) coating on the ZK60 magnesium substrate by hydrothermal method, formation mechanism of enhanced hydroxyapatite (HA) coatings, influence of pH values of the precursor solution on the HA morphology, corrosion resistance and cytotoxicity of HA coatings have been investigated. Results show that the growth pattern of the HA is influenced by the local pH value. HA has a preferential c-axis and higher crystallinity in the alkaline environment developing a nanorod-like structure, while in acid and neutral environments it has a preferential growth along the a(b)-plane with a lower crystallinity, developing a nanosheet-like structure. The different morphology and microstructure lead to different degradation behavior and performance of HA coatings. Immersion and electrochemical tests show that the neutral environment promote formation of HA coatings with high corrosion resistance. The cell culture experiments confirm that the enhanced corrosion resistance assure the biocompatibility of the substrate-coating system. In general, the HA coating prepared in neutral environment shows great potential in surface modification of magnesium alloys.
Highlights
Accepted: 22 December 2020Magnesium and its alloys have been considered promising candidates for bone implants due to their unique biocompatibility and biodegradation [1]
HA coatings were successfully prepared on ZK60 magnesium alloys using hydrothermal methods
HA coatings were successfully deposited on the ZK60 magnesium substrates using hydrothermal methods
Summary
Accepted: 22 December 2020Magnesium and its alloys have been considered promising candidates for bone implants due to their unique biocompatibility and biodegradation [1]. Magnesium can be degraded in vivo and avoid the secondary implant removal surgery. This makes them more suitable materials for bone implants than the titanium alloys, stainless steel or other bioinert materials [2,3]. Though the recommended daily intake for adults of magnesium is 240–420 mg/day, and the human body has a strong tolerance to magnesium ions [7], the rapid pH value increase and the hydrogen release during the degradation cause cell death and tissue inflammation [5,8]. The rapid degradation of magnesium-based material would cause a sharp decrease in the mechanical strength of the implant, which might lead to the implantation failure [9]
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