Molecular photoswitches can change their conformation upon irradiation with light and convert this molecular movement into macroscopic changes of sophisticated materials. By combining state-of-the-art azobenzenes with supramolecular low-molecular-weight gelators, based on cyclic dipeptides, photomodulation of hydrogels was achieved. Photochromic amino acids with structures related to the natural L-phenylalanine were an essential element. The supramolecular hydrogels are multi-responsive towards pH, ions, temperature, and, in particular, light. Hereby the gelator Fâ-PAP-DKP-Lys can be turned into a sol upon irradiation with green light and within this transition a drug, for example an antibiotic, was released. The further improved supergelator Clâ-PAP-DKP-Lysâ is reversibly switchable with red and violet light in the range of 0.2-0.5 % in an isotonic Ringer's solution. At a concentration of 1 %, the hydrogel consisting of Clâ-PAP-DKP-Lysâ remains stable in a boiling water bath. Thus, we envision that the enhanced stability of the supramolecular assembly of Clâ-PAP-DKP-Lysâ and orthogonal biocompatibility of Fâ-PAP-DKP-Lys, could enable further applications, spanning from regenerative medicine to electronic devices, besides our future vision towards photopharmacology.weiterlesen