Preparation Of The Anti-TB Drug Loaded Scaffolds And Their Drug Release Behaviors And Osteogenic Potential

Bone tuberculosis, caused by the bacteria mycobacterium tuberculosis,continues to present a formidable challenge to humans. The most common method in treating serious bone TB cases is infection foci debridement. Meanwhile, bone repair and long-term antitubercular drug therapy are necessary after the debridement of infected bone. However, to achieve effective local drug concentrations, patients have to take excess drug to obtain high blood drug concentration, which might cause serious toxic effect to normal tissues and organs, especially liver and kidney. A long-term drug delivery system was needed to satisfy the needs of both bone regeneration and antituberculous drug therapy. In this study, several long-term single/multiple antitubercular drug-loaded polylactone scaffolds were designed and prepared, and their drug release behaviors and bone regeneration capacities were investigated systematically.Firstly, a kind of novel block polylactone, i.e. polycaprolactone-b-poly (L-lactide-co-glycolide) (b-PLGC) copolymer, was synthesized by two steps of ring-opening polymerization.It showed much difference from corresponding r-PLGC copolymers in thermal behaviors, hydrophility/hydrophobicity and drug release behaviors. Therefore, RFP-loaded b-PLGC/β-TCP composite scaffolds were prepared by physical blending, and the scaffolds were characterized by tests such as scanning electron microscopy and thermal gravity analysis to reveal their morphology, pore structure, the amount of β-TCP, mechanical properties and drug release behavior. At the same time, biocompatibilities of those drug-loaded composite scaffolds were studied by cell culture experiments. The evaluation of drug-loaded scaffold inducing bone regeneration was conducted with a critical-sized segmental defect in the forelimb of rabbit. The results showed that RFP/b-PLGC/β-TCP scaffold had demonstrated a long-term sustained release behavior of hydrophobic RFP both in vitro and in vivo,and RFP concentrations obtained in blood and tissue surrounding the implant could reach a high value, which was above the effective level required for TB treatment and could sustained at least 84 days. Meanwhile, RFP/b-PLGC/β-TCP scaffold showed good biocompatibility and osteogenesis capability. In a word, RFP/b-PLGC/β-TCP scaffold should have the great potential to combine recovering the residual cavity and the drug therapy for effective bone TB treatment.Secondly, water-soluble isoniazid (INH)loaded TCP@gelatin composite microspheres were prepared by the method of oil-in-water emulsion. Their morphology, the amount of β-TCP in microspheres and drug release behavior were characterized by tests such as scanning electron microscopy and thermal gravity analysis, etc. A sustained released of INH from composite microspheres was obtained at least for 30 days. Then, INH-loaded microspheres/b-PLGC scaffold was prepared by the combination of TCP@gelatin composite microspheres and b-PLGC scaffold. And its morphology, pore structure, the amount of TCP and drug release behavior were characterized by tests such as scanning electron microscopy and thermal gravity analysis, etc. The results showed that the water-souble INH was successfully loaded into polylactone scafflold, and the initial burst release of INH from the scaffold was greatly reduced in comparison with directly blending INH/b-PLGC scaffold. It was good to find that INH could be sustainedly released from INH-TCP@GM/b-PLGC scaffold as long as 84 days.Finally, the two aforementioned methods were combined to prepare scaffold containing both INH and RFP at the same time. Sustained release of both INH and RFP from the scaffold was obtained for a period as long as 84 days. The results suggested a new and promising method for developing long-term multiple drug therapy to treat severe bone tuberculosis. Obvisouly, the preparing strategy for multi-drug loaded scaffold can be extended to other oil soluble and water soluble drugs in addition to RFP and INH.Thus, it maybe applicable to the treatment of other disease which needs long-term multiple drug therapy.