Calcitonin-Loaded Thermosensitive Hydrogel for Long-Term Antiosteopenia Therapy.

Effective antiosteopenia therapy can be achieved by designing long-term protein/peptide drug delivery systems for bone trabecula restoration. Here we show that a complex of salmon calcitonin and oxidized calcium alginate (sCT-OCA) was prepared and loaded into a thermosensitive copolymer hydrogel for long-term antiosteopenia treatment. The triblock copolymer, poly(d,l-lactic acid-co-glycolic acid)-b-poly(ethylene glycol)-b-poly(d,l-lactic acid-co-glycolic acid) (PLGA-PEG-PLGA) exhibited sol-gel transition at body temperature. The sustained release of sCT from the in situ gelling system was determined by both the degradation of the hydrogel and the decomposition of the sCT-OCA complex. This system showed sustained effects in reducing serum calcium and bone trabecula reconstruction in the treatment of glucocorticoid-induced osteopenia in rats for approximately 30 days after a single subcutaneous injection, which may shed light on antiosteopenia therapy in the future.