Effect of mixing ceramics with a thermosensitive biodegradable hydrogel as composite graft

The composite of methoxy polyethylene glycol (mPEG) and poly(lactic-co-glycolic acid) (PLGA) thermosensitive hydrogel mixed with various portions of hydroxyapatite (HAP) or β-tricalcium phosphate (β-TCP) were used as bone graft substitutes. The physical properties of a series of composite gels, including the critical micelle concentration (CMC), particle sizes, zeta potential, rheological behavior, morphology of composite gels, and sol-gel transition, were characterized in vitro. These composite gels could form a gel at body temperature and could be controlled easily at room temperature, but showed only a small decline in pH, to between 6.33 and 6.66, whereas mPEG-PLGA gel without ceramic exhibited a more significant decrease in pH over a period of 5 days. The dissolution of ceramics results in an increase in the concentration of calcium and phosphate, which can buffer the degradation of mPEG-PLGA. Higher cell viability was observed in the composite gels with more bioceramics, as shown in the MTT assay and the live and dead stain. Mixing mPEG-PLGA with HAP or β-TCP may hold greater promise than mPEG-PLGA alone for repairing bone defects.