Multi-responsive supramolecular hydrogels based on merocyanine–peptide conjugates

Abstract

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.

Negatively photochromic organic compounds: Exploring the dark side

“…89 Solvent dependent negative photochromism was also noted for mononitrospiropyrans derived from 5-amino Fischer's base with the mononitrospiropyran -Schiff base dyad 16 90 and supramolecular hydrogels based on mononitrospiropyranpeptide conjugates 17 (Figure 8). 91 The matrix also has a significant impact on the routine photochromic switching of the parent spiropyran 1 which can be modified to exhibit negative photochromism when it is entrapped in the rigid channels of a zinc ion-rich metal organic framework 92 and covalent linking of 6-hydroxyspyropran to the polymer backbone of an acrylate copolymer stabilised the coloured zwitterionic form which could be reversibly bleached upon irradiation. 93 Temporary negative photochromism was imparted into two long chain substituted mononitrospiropyrans 18 and 19, in thin films, upon protonation with HCl.…”

Effect of polar amino acid incorporation on Fmoc-diphenylalanine-based tetrapeptides

“…17 In addition to the RGD sequence, other epitopes, typically laminin and collagen-based, have promoted cell adhesion in peptide hydrogels. [18][19][20][21] Recent work has shown that the spacing between adjacent cell adhesive epitopes is important for the adhesion of endothelial cells. 22 Although control over epitope incorporation and spacing throughout a scaffold is useful for enhancing adhesion, in many cases the surface presentation of the desired peptide sequence is unknown.…”

Supramolecular biofunctional materials

“…Ultrasound, an efficient approach to promote dissolution or dispersion of molecules (usually) in a solvent, is also widely used for preparing supramolecular hydrogels by disrupting, redistributing, and rebuilding the stacking of small molecules, making the hydrogels more homogenous. [59, 60] Light-controlled self-assembly requires the presence of light sensitive motifs, such as tetrazole,[61, 85] merocyanine,[86] α-carboxy-2-nitrobenzyl (CNB),[87] and azobenzene. [88] Although light is a physical stimulus, chemical reactions and structural changes, in most cases, also occur to initiate the light-triggered sol-gel or gel-sol transition, and the resulting conformation of the molecules typically favor more compact stacking when a hydrogel forms.…”