Preparation and Characterization of Thermoresponsive PEG-Based Injectable Hydrogels and Their Application for 3D Cell Culture

We report here the synthesis of a series of ethylene glycol-based triblock copolymers containing a hydrophilic middle segment of poly(ethylene glycol) methyl ether methacrylate (PEGMA) and two temperature-responsive segments of diethylene glycol methyl ether methacrylate (DEGMA) at both ends via the reversible addition-fragmentation chain-transfer (RAFT) polymerization. While the corresponding temperature-responsive homopolymer (PDEGMA) and the diblock copolymer (PDEGMA-b-PPEGMA) could not form a gel, the triblock copolymers (PDEGMA-b-PPEGMA-b-PDEGMA) could form a physical gel at certain concentrations and at temperatures above the lower critical solution temperature (LCST). This sol-gel transition is fully reversible and can be repeated several times. Depending on the chain length of the middle block and two end blocks, a physical gel could be formed at a minimum polymer concentration of 5 wt %. In addition, a mechanically strong gel could be easily formed within 5 s at the maximum concentration of 20 wt % and at a temperature of 37 degrees C. Considering the good cell compatibility and soft rubbery nature of the triblock copolymers, they can potentially be used as injectable scaffold for cell culture and tissue engineering applications.