Effects of gatifloxaine content in gatifloxacine-loaded PLGA and ß-tricalcium phosphate composites on efficacy in treating osteomyelitis.

Composites of gatifloxacin (GFLX)-loaded poly (lactic-co-glycolic) acid (PLGA) and ß-tricalcium phosphate (ßTCP) containing 0, 1, and 10 wt % GFLX (0, 1, and 10 wt % GFLX composites), and GFLX-loaded PLGA containing 1, 5, and 10 wt % GFLX (1, 5, and 10wt % GFLX-PLGA) as controls were fabricated and characterized in vitro and in vivo. On in vitro evaluation, the 10 wt % GFLX composite released GFLX over at least 28 days in Hanks' balanced solution and exhibited clinically sufficient bactericidal activities against Streptococcus milleri and Bacteroides fragilis from 1 h to 10 days. The 0, 1, and 10 wt % GFLX composites and 10 wt % GFLX-PLGA were implanted in bone defects created by debridement of osteomyelitis lesions induced by S. milleri and B. fragilis in the mandible of rabbits (n = 5). Four weeks after implantation of the 10 wt % GFLX composite, inflammation in the debrided area disappeared in all the rabbits, while inflammation remained in all the rabbits after implantation of the 0 wt % GFLX composite and 10 wt % GFLX-PLGA, and in three rabbits after implantation of the 1 wt % GFLX composite. Bone formation appears to be less intense for the 10 wt % GFLX composite than for the 1 wt % GFLX composite probably owing to the rapid degradation of the 10 wt % GFLX composite. These findings show that the GFLX composite is effective for the local treatment of osteomyelitis.

Gatifloxacine-loaded PLGA and ß-tricalcium phosphate composite for treating osteomyelitis.

Gatifloxacine (GFLX)-containing poly(lactide-co-glycolide) (PLGA) was introduced to the pores and surfaces of porous ß-tricalcium phosphate (ßTCP) granules by melt compounding whereby no toxic solvent was used. The granular composite of GFLX-loaded PLGA and ßTCP released GFLX for 42 days in Hanks' balanced solution and exhibited sufficient in vitro bactericidal activity against Streptococcus milleri and Bacteroides fragilis for at least 21 days. For in vivo evaluation, the granular composite was implanted in the dead space created by the debridement of osteomyelitis lesion induced by S. milleri and B. fragilis in rabbit mandible. After a 4-week implantation, the inflammation area within the debrided area was markedly reduced accompanied with osteoconduction and vascularization in half of the rabbits, and even disappeared in one of the six rabbits without any systemic administration of antibiotics. Outside the debrided area, inflammation and sequestrum were observed but the largest of such affected areas amounted to only 0.125 times of the originally infected and debrided area. These findings showed that the granular composite was effective for the local treatment of osteomyelitis as well as an osteoconductive scaffold which supported and encouraged vascularization.

Antibiotic-loaded poly-epsilon-caprolactone and porous beta-tricalcium phosphate composite for treating osteomyelitis.

A composite of poly-epsilon-caprolactone (PCL) loaded with gatifloxacine (GFLX), an antibiotic, and a beta-tricalcium phosphate (betaTCP) 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 betaTCP 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 betaTCP 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 betaTCP 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 betaTCP interface, which indicated degradation of PCL and/or betaTCP 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 betaTCP ceramic would help arrest osteomyelitis when it is used in addition to intravenous antibiotic administration, and help new bone formation and osteoconduction.

Fibronectin-calcium phosphate composite layer on hydroxyapatite to enhance adhesion, cell spread and osteogenic differentiation of human mesenchymal stem cells in vitro.

Fibronectin (Fn) and type I collagen (Col) were immobilized on a surface of a hydroxyapatite (HAP) ceramic by coprecipitation with calcium phosphate in a supersaturated calcium phosphate solution prepared by mixing clinically approved infusion fluids. These proteins and the calcium phosphate precipitate formed a composite surface layer. As a result, the proteins were immobilized firmly as not to be released completely for 3 d in a physiological salt solution. When human mesenchymal stem cells (hMSCs) were cultured on a HAP ceramic in a differentiation medium supplemented with dexamethasone, beta-glycerophosphate and ascorbic acid, hMSCs spread well within 1 h. The alkaline phosphatase (ALP) activity of hMSCs cultured on the Fn-calcium phosphate composite layer significantly increased compared with that of hMSCs cultured on the untreated HAP ceramic. On the other hand, Col did not increase the ALP activity of hMSCs and no synergy between Fn and Col was observed. Therefore, the Fn-calcium phosphate composite layer formed on the HAP is useful for the enhancement of the spreading and osteogenic differentiation of hMSCs in vitro.