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, ~1 H nuclear magnetic resonance(~1 H-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.

Chirality Transfer in Supramolecular Co-assembled Fibrous Material Enabling the Visual Recognition of Sucrose

Molecular recognition of simple sugars is crucial due to their essential roles in most living organisms.However,it remains extremely challenging to achieve a visual recognition of simple sugars like sucrose in water media under physiological conditions.In this article,the visual recognition of sucrose is accomplished by a chiral supramolecular hydrogel formation through the co-assembly of a two-component fibrous solution(l-phenylalanine based gelator co-diaminopyridine,LDAP)and sucrose.H-bonding between the amino group of LDAP and the hydroxyl group of sucrose facilitates the gelation by loading sucrose into the LDAP solution.The formed hydrogel showed an amplified inversion of circular dichroism(CD)signals as compared to the corresponding LDAP solution.In addition,the effective chirality transfer was accompanied by a bathochromic shift in UV-Vis and FL spectra of the gel.Such a simple and straightforward chiral co-assembled strategy to visually recognize sucrose will have the potential use of smart gelators in saccharides separation and proteomics to be further applied in medical diagnostics and cell imaging.