Dual pH-/temperature-responsive and fluorescent hydrogel for controlled drug delivery

The purpose of this investigation is to develop a dual pH-/temperature-responsive and fluorescent hydrogel based on piperazine and Pluronic F127 (PF127). Firstly, polyurethane was synthesized using 1,6-hexamethylene diisocyanate, 1,4-bis(hydroxyethyl) piperazine, and PF127 by a step polymerization process. Erythrosine B (EB) is then incorporated into copolymers to offer a fluorescence property. The polyurethane-PF127-EB copolymer can spontaneously self-assemble into hydrogels with a great number of closely packed micelles, and the hydrogels also have the ability to undergo thermo-sensitive sol-gel phase transition above the critical gelation concentration. The gelation temperature can be adjusted near the physiological condition by modulating the - concentration of the copolymer in an aqueous medium. The acid--titration curves indicate a good pH-responsive property, and the UV-vis and fluorescence spectra exhibit strong self-fluorescence signals for hydrogels. As a result, the hydrogels not only can serve as drug carriers but can also be utilized as fluorescence imaging probes in biomedical applications.