Surface characterization, in vitro and in vivo biocompatibility of Mg-0.3Sr-0.3Ca for temporary cardiovascular implant.
Magnesium-based alloys are attractive candidate materials for medical applications. Our earlier work showed that the ternary Mg-0.3Sr-0.3Ca alloy exhibits slower degradation rates than both binary Mg-Sr and Mg-Ca alloys. The ternary alloy immersed in simulated body fluid (SBF) forms a compact surface layer of corrosion products that we hypothesized to be a Sr-substituted hydroxyapatite (HA). The main objectives of the current work are to understand the bio-degradation mechanism of Mg-0.3Sr-0.3Ca, to identify the exact nature of its protective layer and to evaluate the in vitro and in vivo biocompatibility of the alloy for cardiovascular applications. To better simulate the physiological environment, the alloy was immersed in SBF which was daily refreshed. Raman spectroscopy and X-Ray photoelectron spectroscopy (XPS) confirmed the formation of a thin, Sr-substituted HA layer at the interface between the alloy and the corrosion products. In vitro biocompatibility evaluated via indirect cytotoxicity assays using HUVECs showed no toxicity effect and ions extracted from Mg-0.3Sr-0.3Ca in fact increased the viability of HUVECs after one week. In vivo tests were performed by implanting a tubular Mg-0.3Sr-0.3Ca stent along with a WE43 control stent into the right and left femoral artery of a dog. Post implantation and histological analyses showed no thrombosis in the artery with Mg-0.3Sr-0.3Ca stent after 5weeks of implantation while the artery implanted with WE43 stent was extensively occluded and thrombosed. Microscopic observation of the Mg-0.3Sr-0.3Ca implant-tissue interface confirmed the in situ formation of Sr-substituted HA on the surface during in vivo test. These results show that the interfacial layer protects the surface of the Mg-0.3Sr-0.3Ca alloy both in vitro and in vivo, and is the key factor in the bio-corrosion resistance of the alloy.
Light Metals and Advanced Magnesium Materials, Mining and Materials Engineering, McGill University, Montreal, Qc, H3A 0C5, Canada; Biointerface Lab, Mining and Materials Engineering, McGill University, Montreal, Qc H3A 0C5, Canada. Electronic address: mandana.bornapour@mail.mcgill.ca.
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Bornapour
Biointerface Lab, Mining and Materials Engineering, McGill University, Montreal, Qc H3A 0C5, Canada.
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Mahjoubi
Department of Anatomy and Cell Biology, McGill University, Montreal, Qc, H3A 0C7, Canada.
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Vali
Department of Cardiac Surgery and Surgical Research, McGill University, Montreal, Qc H3G 1A1, Canada.
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Shum-Tim
Biointerface Lab, Mining and Materials Engineering, McGill University, Montreal, Qc H3A 0C5, Canada.
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Cerruti
Light Metals and Advanced Magnesium Materials, Mining and Materials Engineering, McGill University, Montreal, Qc, H3A 0C5, Canada.
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Pekguleryuz
D000497:Alloys / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D020099:Coated Materials, Biocompatible / Q000494:pharmacology*; D004285:Dogs; D005263:Femoral Artery / Q000378:metabolism / Q000601:surgery*; D006801:Humans; D008274:Magnesium / Q000494:pharmacology; D008422:Materials Testing; D015607:Stents; D013324:Strontium / Q000494:pharmacology; D013499:Surface Properties
D000497:Alloys; D020099:Coated Materials, Biocompatible; D008274:Magnesium; D002118:Calcium; D013324:Strontium
Biocompatibility; Biodegradation; Cardiovascular stent; Magnesium; Substituted hydroxyapatite