Utilization of L-serinyl derivate to preparing triple stimuli-responsive hydrogels for controlled drug delivery

Environmentally responsive hydrogels are widely used in various applications. Facile synthesis of multiply stimuli-responsive hydrogels is necessary. Herein, a triple pH-, thermo- and ion-sensitive hydrogel, shorted as HSP, was synthesized by aqueous radical polymerization using L-serinyl acrylate as a monomer and PEG 180 DMA as a crosslinker. The compositions and microstructures of HSP are characterized by FT-IR, 1 H NMR and SEM. The swelling ratio of HSP is the lowest at pH = 3.0 while increases sharply far away from this pH value. Meanwhile, HSP expands with elevated temperatures or ionic strengths, and reaches a plateau when they above 60 °C or 3.0 mol/L, respectively. In addition, these swelling processes are reversible under alternative changing in extern stimuli, and these cycles can be repeated at least 5 times. Furthermore, the release of sodium salicylate can be easily mediated by pH values, temperatures and ion concentrations, all above indicating that HSP is a promising material for controlled drug delivery.