Gels, formed by three-dimensional, elastic networks whose interstitial spaces are filled with liquid, present many useful properties (e.g., response to external stimuli1) and applications in various areas (e.g., bioanalysis, chemical sensing, food processing, cosmetics, drug delivery, and tissue engineering2). Motivated by the existing and potential applications of gel materials, researches on gels have expanded rapidly in the past two decades. Among the studies of gels, supramolecular gelators have been the focus of increasing research attention over the past two decades. Initially small molecular organogelators, which are low-molecular-mass molecules that self- assemble into fiber-like supramolecular polymeric networks that encapsulate organic solvents to form organogels, have received a lot of attention Then, small molecules that self-assemble to form gel in water was emerged The demonstration of self-assembled oligopeptides,5 which gel in water and provide hydrogels for biomedical applications (e.g., as scaffolds to promote the growth of neurons, to induce biomineralization, or to assist cell adhesion), has stimulated recent research efforts on low-molecular-weight hydrogelators Hydrogels made from small molecules also respond to many properties commonly observed in hydrogels made from natural or synthetic polymers, such as responses to pH change, thermal perturbation, and ligand-receptor interaction and their formation can be trigged by these stimuli. Recently, Messersmith et al reported using an enzyme to crosslink polymers to induce hydrogelation, which is believed to be advantageous in biomedical application of hydrogels. Similar methodologies, however, have yet to be explored with hydrogels formed by the self-assembled supramolecular polymeric nanofibers.
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