Abstract
The objective of this study was to discuss the thermosensitive hydrogel methoxy polyethylene glycol-co-poly(lactic-coglycolic acid) (mPEG–PLGA) amphiphilic diblock copolymers mixed with different weight ratio strontium carbonate for osteoporosis treatment. A series of amphiphilic diblock copolymer was synthesized by ring-opening polymerization of mPEG,D,L-lactide and glycolide. The initial ratio of monomers in PLGA was LA/GA=78/22. Blending strontium carbonate into the polymer solution with weight ratio (Gel:Strontium carbonate =G1S0, G5S1, G3S1 and G1S1). The copolymer was characterized via ¹H-NMR, FT-IR and GPC. The physical properties of a series of composite gels, including the critical micelle concentration (CMC), particle sizes, rheological behavior, morphology of composite gels, and sol–gel transition, were characterized in vitro. These results revealed that addition of strontium carbonate do not significantly interfere with gel-forming mechanisms. As the temperature increased, micelle aggregation was observed by DLS and TEM. As results of sol-gel transition, 20 wt% hydrogel of the gelling temperature below body temperature 37 ° C, and its gelation temperature approximately 25 °C . In vitro pH change test showed that the strontium carbonate can react with hydrogen ions, which effectively raise the pH value. Raising pH value caused degradation to slow, thus achieving long-term release. The concentration of strontium ions released on the first day reached effective concentration to treat osteoporosis. Higher cell viability was observed in the composite gels with more strontium carbonate, as shown in the MTT assay and the live and dead stain. Based on the above results, mixing mPEG–PLGA with strontium carbonate may hold greater promise than mPEG–PLGA alone for osteoporosis therapy.