Preparation Of Injectable Antibiotic DBM And Treatment Of Experimental Infected Bone Defects With Injectable Antibiotic DBM

Objective: To evaluate the effects of tobramycin on MC3T3-E1, develop injectableantibiotic DBM, and evaluate the constructive characteristics, biocompatibility andvalidity of preventing bone infection and repairing bone defects of the injectableantibiotic DBM.Methods:1. Evaluate the effect of tobramycin on MC3T3-E1cell viability and function.MC3T3-E1cells were treated with varying concentrations of tobramycin over a periodof1,3,6d, harvesting them after each time period and performing assays to test theirviability(trypan blue exclusion test), metabolic function(MTT assay), Alkalinephosphatase (ALP) activity, expression of ALP, COL â…  and Smad1and cellmembrane viability (LDH). Alkaline phosphatase staining and calcium staining werealso assessed. Cell recovery in the absence of tobramycin was evaluated.2. Construction of injectable antibiotic DBM with varying concentrations of tobramycin.To construct injectable antibiotic DBM with varying concentrations of tobramycin(25mg/ml,50mg/ml,75mg/ml and100mg/ml) and investigate the difference oftobramycin release rate, swelling ratio, degradation rate, and antibacterial activity invitro, and tobramycin release rate in muscle bag of mouse between groups.3. Characteristics of injectable antibiotic DBM. Gelation time of thermogelling chitosanwas tested by tube inverting method. SEM observation, cytotoxicity test, andintramusculary implanting test of injectable antibiotic DBM were performed.4. Treatment of experimental infected bone defects with injectable antibiotic DBM.Injectable antibiotic DBM were implanted in contaminated unicortical defect of rabbits.The validity of preventing bone infection and repairing bone defects were assessed byclinical, radiological, histological, gross examination, bacterial load assay, and highperformance liquid chromatography(HPLC) analysis of tobramycin concentration.Results:1.Tobramycin of high concentration inhibit MC3T3-E1cell viability and metabolicfunction, ALP activity, expression of ALP, COLâ…  and Smad1and cell membrane viability. Cells, which had been treated with lower concentration of tobramycin, showedbetter viability and function in the absence of tobramycin.2. The injectable antibiotic DBM with50mg/ml tobramycin performed better in gelstate maintain and controlled-release, and showed average function of antibacterialactivity in vitro, and tobramycin release rate in vivo.3. Injectable antibiotic DBM showed a3D structure with varying pores, grade0toâ… cytotoxicity, and good biocompatibility in vivo.4. Animals implanted with injectable antibiotic DBM all survived without weight lossand high serum concentrations. At4weeks,52.6%tobramycin were conserved in theinjectable antibiotic DBM. Bacterial load assay and radiological analysis showed bestresults in all groups. The degradation of implants matched with new bone formation.Conclusion:1. Tobramycin delivery should avoid local excessive drug concentrations.2. Suitable tobramycin concentration for injectable antibiotic DBM is50mg/ml.3. Injectable antibiotic DBM had good biocompatibility and physical characteristic.4. Injectable antibiotic DBM is a good local antibiotic delivery system, which couldprevent bone infection and repair bone defects.