Controlling initial biodegradation of magnesium by a biocompatible strontium phosphate conversion coating

• Published in: Acta biomaterialia Vol. 10; no. 3; pp. 1463 - 1474
• Main Authors: Chen, X.B., Nisbet, D.R., Li, R.W., Smith, P.N., Abbott, T.B., Easton, M.A., Zhang, D.-H., Birbilis, N.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.03.2014
• Subjects: Alkaline Phosphatase - metabolism; Biocompatibility; Biodegradation; Cell Differentiation - drug effects; Coated Materials, Biocompatible - pharmacology; Coating; Coating effects; Conversion coating; Conversion coatings; Culture Media; Degradation; Electrochemical Techniques; Human mesenchymal stem cells; Humans; Hydrogen - analysis; Magnesium; Magnesium - pharmacology; Mesenchymal Stromal Cells - cytology; Mesenchymal Stromal Cells - drug effects; Mesenchymal Stromal Cells - enzymology; Microscopy, Electron, Scanning; Osteogenesis - drug effects; Phosphates; Phosphates - pharmacology; Photoelectron Spectroscopy; Strontium; Strontium - pharmacology; Strontium phosphate; Surface Properties; Temperature; X-Ray Diffraction; Biodegradation; Human mesenchymal stem cells; Magnesium; Strontium phosphate; Conversion coatings
• ISSN: 1742-7061; 1878-7568
• DOI: 10.1016/j.actbio.2013.11.016

A simple strontium phosphate (SrP) conversion coating process was developed to protect magnesium (Mg) from the initial degradation post-implantation. The coating morphology, deposition rate and resultant phases are all dependent on the processing temperature, which determines the protective ability for Mg in minimum essential medium (MEM). Coatings produced at 80°C are primarily made up of strontium apatite (SrAp) with a granular surface, a high degree of crystallinity and the highest protective ability, which arises from retarding anodic dissolution of Mg in MEM. Following 14days’ immersion in MEM, the SrAp coating maintained its integrity with only a small fraction of the surface corroded. The post-degradation effect of uncoated Mg and Mg coated at 40 and 80°C on the proliferation and differentiation of human mesenchymal stem cells was also studied, revealing that the SrP coatings are biocompatible and permit proliferation to a level similar to that of pure Mg. The present study suggests that the SrP conversion coating is a promising option for controlling the early rapid degradation rate, and hence hydrogen gas evolution, of Mg implants without adverse effects on surrounding cells and tissues.