Antibiotic-loaded poly-ε-caprolactone and porous β-tricalcium phosphate composite for treating osteomyelitis

A composite of poly-ε-caprolactone (PCL) loaded with gatifloxacine (GFLX), an antibiotic, and a β-tricalcium phosphate (βTCP) porous ceramic body was prepared by a solvent-free process in which no toxic solvent was used. GFLX mostly retained its bactericidal property after the processing. The composite of GFLX-loaded PCL and βTCP ceramic released GFLX for 4 weeks in Hanks’ balanced solution, and had sustained bactericidal activity against Streptococcus milleri and Bacteroides fragilis for at least 1 week. The composite of the GFLX-loaded PCL and βTCP ceramic was implanted in an osteomyelitis lesion induced by S. milleri and B. fragilis in the rabbit mandible. The osteomyelitis lesion expanded in the mesial–distal direction when no composite was implanted or when the lesion was treated with debridement only. The composite of GFLX-loaded PCL and βTCP showed efficacy in controlling infection at the bone defect formed by debridement, and supported bone tissue reconstruction at the bone defect. Twelve and 50 weeks after the implantation, the inflammation even disappeared. New bone formation was observed on the surface of the composite after 4 weeks. After 50 weeks, ingrowth of bone tissues with vascular channels was observed along the PCL and βTCP interface, which indicated degradation of PCL and/or βTCP ceramic at the ceramic/polymer interface followed by replacement by bone tissues. The GFLX concentrations in the serum and soft tissues were very low. Therefore, the composite of GFLX-loaded PCL and βTCP ceramic would help arrest osteomyelitis when it is used in addition to intravenous antibiotic administration, and help new bone formation and osteoconduction.