Multi-responsive supramolecular hydrogels based on merocyanine–peptide conjugates†
Stimuli-responsive hydrogels are “smart” materials with diverse applications. We now report short peptide conjugates with merocyanine (MC) that are able to form stimuli-responsive hydrogels. Systematic investigation reveals that merocyanine is a highly effective promoter for the self-assembly of its oligopeptide conjugates. Hydrogels formed by MC–peptide conjugates showed responses towards light and heat, and their sol–gel phase transition could be manipulated by the reverse photochromism of the corresponding spiropyran moiety. Impressively, a MCI–RGD conjugate formed a supramolecular hydrogel with responses to multiple stimuli, including visible light irradiation, pH change and the presence of Ca2+ ions. An erasable photo-lithograph on the MCI–RGD hydrogel was demonstrated using visible light to write and heat-and-cool treatment to erase for multiple rounds without significant loss of sensitivity.