Thermo-sensitive sol–gel transition of poly(depsipeptide-co-lactide)-g-PEG copolymers in aqueous solution

A series of biodegradable graft copolymers composed of poly(ethylene glycol) side-chains and a poly(depsipeptide-co-dl-lactide) backbone (PDG-dl-LA-g-PEG) were prepared as a novel thermo-gelling system. An aqueous solution of PDG-dl-LA-g-PEG (20 wt%) with a certain PEG length and composition showed instantaneous temperature-sensitive gelation at 33 °C. The sol–gel transition temperature (Tgel) could be controlled from 33 to 51 °C by varying the PEG length and compositions without a decrease in mechanical strength of the hydrogels. The 20 wt% hydrogel was eroded gradually in PBS at 37 °C for 60 days. This research provides a molecular design approach to create biodegradable thermo-gelling polymers with controllable Tgel and mechanical toughness.