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.