Development of bioactive thermosensitive polymer–ceramic composite as bone substitute

The purpose of this study was to design a thermosensitive composite gel to be used as a bone graft substitute. This gel can provide a more suitable microenvironment by using the amphiphilic triblock copolymer (mPEG550PLGA1405) consisting of methoxy poly(ethylene glycol) (mPEG), poly(lactic-co-glycolic acid) (PLGA). An aqueous dispersion of mPEG550PLGA1405 mixed with different ratios of HAP/β-TCP (composite gel) underwent a sol–gel–sol transition as the temperature was increased from 4 to 70 °C. The particle size and critical micellization concentration (CMC) were increased by adding ceramics. During the in vitro degradation process, composite gels demonstrated a slight decrease in pH value, a slower degradation rate, less toxicity, and a higher cell survival rate. The biocompatibility of the composite gels was validated by hemolysis test. In vivo animal studies demonstrated both radiographic and gross bone union when the ratio of HAP/β-TCP was 7:3. Based on the results, we have developed novel thermosensitive composite gels as bone substitutes.

► Thermosensitive composite gelcomposed of mPEG–PLGA and HAP/β-TCPwas made.
► The gel is capable of sol-to-gel transition between 4 °C to 70 °C and of in-situ gelling.
► The composite gels do not acidify the surrounding environment.
► Higher hydroxyapatite contents help raise bone union rate.
► Bone union is examined through radiographic method.