Characterization and evaluation of fluoridated apatites for the development of infection-free percutaneous devices

Abstract The wound healing process in the soft tissues adjacent to percutaneous implants induces “epithelial downgrowth”, and subsequently, a sinus tract around the device. This provides an optimal environment for bacterial colonization and proliferation. In an attempt to arrest downgrowth and achieve epithelial attachment to a device surface, we have sought to mimic the most common and successful percutaneous organ, the tooth. Since teeth are composed of partially and fully fluoridated forms of hydroxyapatite (HA), it was hypothesized that the surface properties of fluoridated apatites, fluorohydroxyapatite (FHA) and fluorapatite (FA), would improve epithelial cellular adhesion and differentiation when compared to HA and titanium (Ti) surfaces. In this study, the apatites (HA, FHA, and FA) were synthesized and characterized. Following a high-temperature sintering treatment of these apatites, keratinocyte and fibroblast adhesion and differentiation properties were analyzed in vitro , revealing a statistically significant increase in keratinocyte adhesion and terminal differentiation on FA surfaces sintered at 1050–1150 °C as compared to Ti or HA. Moreover, fibroblasts displayed enhanced adhesion on FHA surfaces. This data suggests that percutaneous devices coated with, or fabricated from, fluoridated apatites may induce improved epithelial cellular adhesion and differentiation, potentially limiting deeply penetrating epithelial downgrowth and resultant bacterial ingress.