Biodegradable polymers exhibiting temperature-responsive sol-gel transition between room temperature and body temperature are expected to be applied as injectable polymer (IP) systems in biomedical applications. IP solution containing drugs or living cells can be injected by simple syringe injection at the target site in the body to form a hydrogel acting as a sustained drug releasing depot or a scaffold for tissue regeneration. For example, Lee et al. reported ABA-type triblock copolymer of poly(lactide-co-glycolide) and PEG as biodegradable injectable polymer [1]. We also reported several biodegradable IP systems exhibiting relatively high mechanical strength in gel state using block copolymers of polylactide and branched PEG [2]. These copolymers are usually sticky paste in dry state at room temperature, and it takes a long time to be dissolved in aqueous solution. On these issues, Jeong et al. reported solidification of the triblock copolymers containing poly(e-caprolactone) exhibiting temperature-responsive sol-gel transition [3]. But, the copolymers must be heated above melting temperature upon dissolution. In this study, we developed a very quick preparative method at room temperature for aqueous IP solution. We synthesized triblock copolymers of poly(e-caprolactone-co-glycolide) and PEG, PCGA-b-PEG-b-PCGA. The obtained copolymers could be freeze-dried to show powder form morphology in dry state at room temperature. We found that some of the best formulations composed of PCGA-b-PEG-b-PCGA and additives could be distributed in PBS to give suspension within 1 min at room temperature. The obtained suspension could be sucked by syringe and exhibited temperature-responsive sol-gel transition between room temperature and body temperature.Therefore, this system should be convenient for instant preparation at clinical scene.1) D. S. Lee et al., Macromol. Rapid Commun. 2001  , 22, 587.2) Y. Ohya et al., Adv. Funct. Mater. 2008  , 18, 1220.3) B. Jeong et al., Macromolecules 2005  , 38, 5260.

Quick preparative method and formulation for biodegradable injectable polymers exhibiting temperature-responsive sol-gel transition

247th National Meeting (2014)

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