Co-precipitation of Tobramycin into Biomimetically Coated Orthopedic Fixation Pins Employing Submicron-Thin Seed Layers of Hydroxyapatite
Jan H. Sorensen, Mirjam Lilja, Maria Astrand, Torben C. Sorensen, Philip Procter, Maria Stromme and Hartwig Steckel
Affiliation: Division for Nanotechnology and Functional Materials, The Angstrom Laboratory, Uppsala University, Box 534, 751 21 Uppsala, Sweden.
The migration, loosening and cut-out of implants and nosocomial infections are current problems associated
with implant surgery. New innovative strategies to overcome these issues are emphasized in today’s research. The current
work presents a novel strategy involving co-precipitation of tobramycin with biomimetic hydroxyapatite (HA) formation
to produce implant coatings that control local drug delivery to prevent early bacterial colonization of the implant. A submicron-
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 for a thin tobramycin-
delivering HA coating on discs and orthopedic fixation pins. The morphology and thickness of the coating and the
drug-release profile were evaluated via scanning electron microscopy and high performance liquid chromatography. The
coatings delivered pharmaceutically relevant amounts of tobramycin over a period of 12 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
could form the foundation for development of combination device/antibiotic delivery vehicles tailored to meet
well-defined clinical needs while combating infections and ensuring fast implant in-growth.
Keywords: Co-precipitation, tobramycin, hydroxyapatite, biomimetic coating, drug release.
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