Picolyamine based pH/temperature sensitive hydrogels

pH/temperature-sensitive hydrogels have attracted increasing attention as drug/protein delivery systems. This study reports a new pH sensitive moiety of picolyamine (PCA) and its pentablock copolymer hydrogels made from triblock PCL-PEG-PCL and picolyamine oligomer (OPCA). The picolyamine monomer (PCAM) was synthesized using the picolyamine and methacryloyl chloride coupling reaction. OPCA was synthesized by conventional radical polymerization from PCAM. The pKa of the pH sensitive moiety, OPCA, was found to be 6.65. The moiety was used to couple with PCL-PEG-PCL to produce the pentablock copolymer, OPCA-PCL-PEG-PCL-OPCA. The sol-gel phase transition of the aqueous solution of this material was affected by the pH and temperature change. In addition, the gel phase region could be controlled by the molecular weight of OPCA, the PCL/PEG ratio and chain length of PEG. This material could be used as an injectable hydrogel for drug/protein delivery.