Antibiotic releasing hydroxyapatite beads

Synthesis hydroxyapatite (HAP), similar to bone or tooth mineral composition, was developed for bone grafts in dental and orthopedic applications. Common skin microorganisms, such as Staphylococcus aureus and Staphylococcus epidermidis, have been associated with bone graft-related infections. We investigated whether an antibiotic controlled-releasing HAP device would reduce bacterial organisms at the operated site. Cefotiam (CTM) was used as a model antibiotic since it possesses activity against Staphylococcus aureus and Staphylococcus epidermidis. To control the release rate of CTM, egg phosphatidylcholine (EPC) was loaded into a HAP bead (diameter : 8.48 mm, weight : 531 mg). The EPC-HAP beads were placed in CTM aqueous solutions(4-25 mg/ml) under atmospheric pressure. A bead containing CTM solution in its internal pores was referred to as a “wet CTM-EPC-HAP bead”. In vitro release studies demonstrated that the release rate of CTM decreased with the increase of EPC load. One wet CTM-EPC-HAP bead was implanted in the skin pocket made in a rat, and inoculated with Staphylococcus aureus or Staphylococcus epidermidis (10⁷CFU/ml). Wet CTM-EPC-HAP beads showed less Staphylococcus aureus and Staphylococcus epidermidis in comparison with the control HAP beads two days after inoculation. These studies suggest that antibiotic controlled-releasing HAP delivery can decrease infections at the operated site of patients undergoing bone grafts.