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

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 <i>Staphylococcus epidermidis</i> were each cultured on cylindrical Ti samples coated with a thin layer of Mg/Mg₄₅Zn₅Ca, applied <i>via</i> magnetron sputtering. Uncoated titanium samples served as controls. <i>S. epidermidis</i> was quantified by counting colony forming units. The biofilm-bound fraction was isolated <i>via</i> ultrasonic treatment, and the planktonic fraction <i>via</i> centrifugation. Biofilm-bound <i>S. epidermidis</i> 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.