Fast corroding, thin magnesium coating displays antibacterial effects and low cytotoxicity

Abstract

Bacterial colonisation and biofilm formation are characteristics of implant-associated infections. In search of candidates for improved prosthetic materials, fast corroding Mg-based coatings on titanium surfaces were examined for their cytotoxic and antimicrobial properties. Human osteoblasts and Staphylococcus epidermidis were each cultured on cylindrical Ti samples coated with a thin layer of Mg/Mg₄₅Zn₅Ca, applied via magnetron sputtering. Uncoated titanium samples served as controls. S. epidermidis was quantified by counting colony forming units. The biofilm-bound fraction was isolated via ultrasonic treatment, and the planktonic fraction via centrifugation. Biofilm-bound S. epidermidis was significantly decreased by approximately four to five orders of magnitude in both Mg- and Mg₄₅Zn₅Ca-coated samples after seven days compared to the control. The osteoblast viability was within the tolerance threshold of 70% stated in DIN EN ISO 10993-5:2009-10 for Mg (~80%) but not for Mg₄₅Zn₅Ca (~25%). Accordingly, Mg-coated titanium was identified as a promising candidate for an implant material with antibacterial properties and low cytotoxicity levels. The approach of exploiting fast corrosion contrasts with existing methods, which have generally focused on reducing corrosion.

Keywords:

• Implant-associated infections
• antibacterial coatings
• magnesium
• Staphylococcus epidermidis
• human osteoblasts

Acknowledgements

The authors thank Prof. Andreas Podbielski for providing laboratory facilities and Mrs Kathleen Arndt (Institute of Medical Microbiology, Virology and Hygiene, University Medicine Rostock) for her support with experiments. Furthermore, the authors thank Dr Marcus Frank, Mr Wolfgang Labs, Mr Gerhard Fulda (EMZ Rostock, University Medicine Rostock), Mr Philipp Pisowocki (Department of Orthopaedics, University Medicine Rostock) and Mrs Regina Lange (Institute for Electronic Appliances and Circuits, University Rostock) for their assistance with scanning electron microscopy.