Thin magnesium layer confirmed as an antibacterial and biocompatible implant coating in a co-culture model

Implant-associated infections commonly result from biofilm-forming bacteria and present severe complications in total joint arthroplasty. Therefore, there is a requirement for the development of biocompatible implant surfaces that prevent bacterial biofilm formation. The present study coated titanium samples with a thin, rapidly corroding layer of magnesium, which were subsequently investigated with respect to their antibacterial and cytotoxic surface properties using a Staphylococcus epidermidis (S. epidermidis) and human osteoblast (hOB) co-culture model. Primary hOBs and S. epidermidis were co-cultured on cylindrical titanium samples (Ti6Al4V) coated with pure magnesium via magnetron sputtering (5 µm thickness) for 7 days. Uncoated titanium test samples served as controls. Vital hOBs were identified by trypan blue staining at days 2 and 7. Planktonic S. epidermidis were quantified by counting the number of colony forming units (CFU). The quantification of biofilm-bound S. epidermidis on the surfaces of test samples was performed by ultrasonic treatment and CFU counting at days 2 and 7. The number of planktonic and biofilm-bound S. epidermidis on the magnesium-coated samples decreased by four orders of magnitude when compared with the titanium control following 7 days of co-culture. The number of vital hOBs on the magnesium-coated samples was observed to increase (40,000 cells/ml) when compared with the controls (20,000 cells/ml). The results of the present study indicate that rapidly corroding magnesium-coated titanium may be a viable coating material that possesses antibacterial and biocompatible properties. A co-culture test is more rigorous than a monoculture study, as it accounts for confounding effects and assesses additional interactions that are more representative of in vivo situations. These results provide a foundation for the future testing of this type of surface in animals.