Photoresponsive Supramolecular Hydrogel Co-assembled from Fmoc-Phe-OH and 4,4′-Azopyridine for Controllable Dye Release

Photoresponsive hydrogels have been attractive because they can provide precise spatial and temporal control for molecule release, whereas the conventional preparation of photoresponsive hydrogels generally involves complex chemical synthesis steps or specific conditions which limits their practical applications. Herein, a new photoresponsive hydrogel is facilely prepared via co-assembly of two simple molecules, Fmoc-Phe-OH and Azp, without chemical synthesis. The co-assembly mechanism, morphology, and photoresponsiveness of (Fmoc-Phe-OH)-Azp hydrogel are investigated by circular dichroism (CD), ultraviolet-visible (UV-Vis), fluorescence, 1H nuclear magnetic resonance (¹H-NMR), attenuated total internal reflection Fourier transform Infrared (ATR-FTIR) spectroscopy, and scanning electron microscopy (SEM). Furthermore, the enhanced release of encapsulated sulforhodamine B (SRB) dye molecules can be achieved via UV light irradiation. The enhanced dye release amount can be controlled by manipulating photoirradiation time. This study provides a facile way to prepare photoresponsive hydrogel which holds great potential for controllable drug release.