Abstract
Octacalcium phosphate (OCP) and hydroxyapatite (HAp) coatings were developed to control the degradation speed and to improve the biocompatibility of biodegradable magnesium alloys. Osteoblast MG-63 was cultured directly on OCP- and HAp-coated Mg-3Al-1Zn (wt%, AZ31) alloy (OCP- and HAp-AZ31) to evaluate cell compatibility. Cell proliferation was remarkably improved with OCP and HAp coatings which reduced the corrosion and prevented the H2O2 generation on Mg alloy substrate. OCP-AZ31 showed sparse distribution of living cell colonies and dead cells. HAp-AZ31 showed dense and homogeneous distribution of living cells, with dead cells localized over and around corrosion pits, some of which were formed underneath the coating. These results demonstrated that cells were dead due to changes in the local environment, and it is necessary to evaluate the local biocompatibility of magnesium alloys. Cell density on HAp-AZ31 was higher than that on OCP-AZ31 although there was not a significant difference in the amount of Mg ions released in medium between OCP- and HAp-AZ31. The outer layer of OCP and HAp coatings consisted of plate-like crystal with a thickness of around 0.1 μm and rod-like crystals with a diameter of around 0.1 μm, respectively, which grew from a continuous inner layer. Osteoblasts formed focal contacts on the tips of plate-like OCP and rod-like HAp crystals, with heights of 2–5 μm. The spacing between OCP tips of 0.8–1.1 μm was wider than that between HAp tips of 0.2–0.3 μm. These results demonstrated that cell proliferation depended on the micromorphology of the coatings which governed spacing of focal contacts. Consequently, HAp coating is suitable for improving cell compatibility and bone-forming ability of the Mg alloy.
Highlights
Magnesium and its alloys have great potential for use as biodegradable/bioabsorbable metallic implant materials, owing to their high specific strength and having a similar Young’s modulus (41–45 GPa) to bone (3–20 GPa).[1,2,3,4,5] For the practical use of Mg/Mg alloys as biodegradable orthopedic devices, such as bone fixation screws, plates and nails, it is important to appropriately control the degradation speed and to improve the bone-tissue compatibility properties, such as bone conductivity and bone integration.[2,6,7] Rapid and unpredictable corrosion of Mg/Mg alloy implants can cause unexpected loss of mechanical integrity in the surrounding tissue
We previously developed HAp and octacalcium phosphate (OCP) coatings for Mg/Mg alloys by a novel single-step chemical solution deposition method. [32,33,34,35,36,37,38] The type of Ca-P coating can be controlled with the pH of the treatment solution.[35,36]
Cell adhesion and proliferation behavior were examined on Octacalcium phosphate (OCP) and HAp coatings formed on AZ31 using human osteosarcoma MG-63 cells
Summary
Magnesium and its alloys have great potential for use as biodegradable/bioabsorbable metallic implant materials, owing to their high specific strength and having a similar Young’s modulus (41–45 GPa) to bone (3–20 GPa).[1,2,3,4,5] For the practical use of Mg/Mg alloys as biodegradable orthopedic devices, such as bone fixation screws, plates and nails, it is important to appropriately control the degradation (corrosion) speed and to improve the bone-tissue compatibility properties, such as bone conductivity and bone integration.[2,6,7] Rapid and unpredictable corrosion of Mg/Mg alloy implants can cause unexpected loss of mechanical integrity in the surrounding tissue. Rapid generation of corrosion products, such as H2 gas and OH– and Mg2+ ions, can cause the formation of a gas cavity, inflammation and a severe foreign. The pharmacological effect of Mg2+ ions is expected to promote healing of broken bone [8] or it may suppress inflammation.[9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
