Co-precipitation of Tobramycin into Biomimetically Coated Orthopedic Fixation Pins Employing Submicron-Thin Seed Layers of Hydroxyapatite

Implant migration, loosening and cut-out as well as nosocomial infections are current problems during surgery. New innovative strategies to overcome these issues are emphasized in today's research. The currentwork presents a novel strategy involving co-precipitation ofTobramycin with biomimetic hydroxyapatite (HA) formation to produce implant coatings that may ensure controlled local drug delivery to prevent early bacterial colonization of the implant. A sub-micron thin HA layer served as seed layer for the co-precipitation process and allowed for incorporation of Tobramycin in the coating from a stock solution of antibiotic concentrations as high as 20 mg/ml. Concentrations from 0.5 to 20 mg/ml Tobramycin and process temperatures of 37 °C and 60 °C were tested to assess the optimal parameters resulting in a thin Tobramycin delivering HA coating on discs and orthopedic fixation pins. The coating morphology and thickness as well as drugrelease profile were evaluated via scanning electron microscopy and high performanceliquid chromatography. The coatings were found to deliver pharmaceutically relevant amounts of Tobramycinover a period as of12 days. To the best of our knowledge, this is the longest release period ever observed for a fast-loaded biomimetic implant coating. The presented approach may form thefoundation for development of combination device/antibiotic delivery vehicles tailored to meet well-defined clinical needs combatting infections and ensuring fast implant in-growth.