Photoswitchable Nanofiber–Nanoparticle Transformation in a Cosolvent Gel–Sol System

Photoresponsive gel–solution (gel–sol) transitions endow supramolecular peptide gels with a powerful ability to release on-demand cargos in a controllable manner. Photophysical peptide gelators were reported for this purpose, but their gel–sol transitions were not sufficient. An anthracene–peptide conjugate gelator, which enables photochemically regulated gel–sol switches, has not been reported. In this work, we report an anthracene–peptide gelator Nap-Phe-Phe-Lys(anthracene)-OH (Mo-Nap-An) which, under 365 nm laser irradiation, is efficiently converted to its dimer Di-Nap-An, accompanied by a gel–sol transition (or nanofiber–nanoparticle transformation from the microperspective) in a tetrahydrofuran/water cosolvent (THF/H2O = 40/60, v/v). Reversely, upon 254 nm light irradiation, Di-Nap-An is converted to Mo-Nap-An, switching the solution to gel. This work provides a facile bottom-up strategy of "smart" photogelator design for efficient and photochemical control of gel properties.