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 Ca(2+) 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.