Abstract
Present investigation focuses on development and detailed characterization of a new Mg alloy sample (BM) with and without coating of hydroxyapatite (BMH) and bioactive glass (BMG) by air plasma spray method. After detailed mechano-physico-chemical characterization of powders and coated samples, electrochemical corrosion and SBF immersion tests were carried out. Detailed in vitro characterizations for cell viability were undertaken using MG-63 cell line followed by in vivo tests in rabbit model for studying bone healing up to 60 days. Starting current density increases from BM to BMH to BMG indicating highest resistance towards corrosion in case of BMG samples, however BMH also showed highest icorr value suggesting slowest rate of corrosion than BM and BMG samples. Dissolution of calcium ion in case of BMH and BMG control formation of apatite phases on surface. Ca2+ ions of coatings and from SBF solution underwent reduction reaction simultaneously with conversion of Mg to MgCl2 releasing OH− in the solution, which increases pH. Viability and propagation of human osteoblast-like cells was verified using confocal microscopy observations and from expression of bone specific genes. Alkaline phosphatase assay and ARS staining indicate cell proliferation and production of neo-osseous tissue matrix. In vivo, based on histology of heart, kidney and liver, and immune response of IL-2, IL-6 and TNFα, all the materials show no adverse effects in body system. The bone creation was observed to be more for BMH. Although both BMH and BMG show rays of possibilities in early new bone formation and tough bone–implant bonding at interface as compared to bare Mg alloy, however, BMG showed better well-sprayed coating covering on substrate and resistance against corrosion prior implanting in vivo. Also, better apatite formation on this sample makes it more favourable implant.
Highlights
Magnesium alloys gathered special interest in recent years in context of structural lightweight applications in temporary implants because of their ability to be gradually dissolved, absorbed, consumed or excreted through urine [1, 2]
We have used a new Mg alloy with alloying elements of ~22.5% Zn and 0.5% Ca by wt. was used as substrate material
Statistical analysis of the in vivo immune response data was carried out using one-way analysis of variance (ANOVA) with a Tukey’s post hoc by ORIGIN software
Summary
Magnesium alloys gathered special interest in recent years in context of structural lightweight applications in temporary implants because of their ability to be gradually dissolved, absorbed, consumed or excreted through urine [1, 2]. High load bearing capacity and fracture toughness compared to existing biodegradable polymers made them more suitable as orthopaedic implant. The major obstacle against widespread application is their high corrosion rate [6, 7], which might be attributed to the presence of different impurity elements acting as active cathodic site when in solution. Presence of elements such as Fe, Ni, Cu and Co above their tolerance limit may significantly increase Mg corrosion [8]. Among the Mg alloy systems, Mg–Ca and Mg–Zn have shown a balance of properties, mechanical and corrosion resistance, suitable for biomedical applications [15]. It was suggested that surface coating of Mg-based implant has advantages of gradual
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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
