A functionalizable reverse thermal gel based on a polyurethane/PEG block copolymer

Injectable reverse thermal gels have great potentials as biomaterials for tissue engineering and drug delivery However most existing gels lack functional groups that can be modified with biomolecules that can guide cell/material interactions We created an amine-functionalized ABA block copolymer poly (ethylene glycol)-poly(serinol hexamethylene urethane) or ESHU This reverse thermal gel consists of a hydrophobic block (B) poly(serinol hexamethylene urethane) and a hydrophilic block (A) poly (ethylene glycol) The polymer was characterized by GPC FTIR and H-1 FTNMR. Rheological study demonstrated that ESHU solution in phosphate-buffered saline initiated phase transition at 32 degrees C and reached maximum elastic modulus at 37 degrees C The in vitro degradation tests performed in PBS and cholesterol esterase solutions revealed that the polymer was hydrolyzable and the presence of cholesterol esterase greatly accelerated the hydrolysis The in vitro cytotoxicity tests carried out using baboon smooth muscle cells demonstrated that ESHU had good cytocompatibility with cell viability indistinguishable from tissue culture treated polystyrene Subcutaneous implantation in rats revealed well tolerated accurate inflammatory response with moderate ED-1 positive macrophages in the early stages which largely resolved 4 weeks post-implantation We functionalized ESHU with a hexapeptide Ile-Lys-Val-Ala-Val-Ser (IKVAVS) which gelled rapidly at body temperature We expect this new platform of functionalizable reverse thermal gels to provide versatile biomaterials in tissue engineering and regenerative medicine (C) 2010 Elsevier Ltd All rights reserved