Thermo-sensitive sol-gel transition and mechanical properties of poly(Depsipeptide-co-lactide)-g-PEG copolymers

Thermo-gelling biodegradable polymers with a sol-gel transition point (T_gel) between room temperature and body temperature are expected to be useful for injectable polymer systems in biomedical applications such as drug delivery depot and scaffold for tissue engineering. In this study, a series of biodegradable graft-copolymers composed of PEG 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 the copolymer showed instantaneous temperature-sensitive gelation at 33°C. The T_gel could be controlled from 33 to 51°C by varying the PEG length and compositions without a decrease in mechanical strength of the hydrogels. This research provides a molecular design approach to creating biodegradable thermo-gelling polymers with controllable T_gel and mechanical toughness.