Efficacy of Zinc-, Copper-, and Silver-Doped Fluorapatite as Bacteriophobic Surfaces for Percutaneous Osseointegrated...

Percutaneous osseointegrated (OI) prosthetic systems offer superior exoprosthetic docking compared with traditional socket-based attachments; however, their clinical success remains limited by high superficial infection rates. These infections arise primarily from the absence of a stable epithelial seal at the implant-skin interface, permitting bacterial colonization of the stoma, particularly by Staphylococcus aureus (S. aureus). Fluorapatite (FAp) coatings have previously demonstrated potential to enhance epithelial integration, yet additional antimicrobial functionality could limit bacterial colonization on the device. This study investigated metal doping as a strategy to create dual-functional FAp surfaces that resist bacterial adhesion for percutaneous OI applications. Zinc-, copper-, and silver-doped FAp were synthesized in-house using a validated precipitation method and comprehensively characterized. Sintered discs were evaluated for S. aureus adhesion and cytocompatibility to keratinocytes. Fourier transform infrared confirmed retention of the hexagonal apatite structure across all doping compositions. X-ray diffraction revealed secondary phases at higher dopant levels. SEM showed dopant-dependent microstructural changes. Only copper-doped FAp (1%-5%) reduced S. aureus adhesion by >3 log-folds. However, copper-doped surfaces exhibited reduced cytocompatibility to keratinocytes, highlighting a tradeoff between anti-bacterial adhesion efficacy and epithelial attachment affinities. These findings indicate that lower copper doping levels warrant further investigation to achieve keratinocytes adhesion for percutaneous implant coating applications.