Supramolecular Hydrogelators and Hydrogels: From Soft Matter to Molecular Biomaterials

Abstract

In this review we intend to provide a relatively comprehensive summary of the work of supramolecular hydrogelators after 2004 and to put emphasis particularly on the applications of supramolecular hydrogels/hydrogelators as molecular biomaterials. After a brief introduction of methods for generating supramolecular hydrogels, we discuss supramolecular hydrogelators on the basis of their categories, such as small organic molecules, coordination complexes, peptides, nucleobases, and saccharides. Following molecular design, we focus on various potential applications of supramolecular hydrogels as molecular biomaterials, classified by their applications in cell cultures, tissue engineering, cell behavior, imaging, and unique applications of hydrogelators. Particularly, we discuss the applications of supramolecular hydrogelators after they form supramolecular assemblies but prior to reaching the critical gelation concentration because this subject is less explored but may hold equally great promise for helping address fundamental questions about the mechanisms or the consequences of the self-assembly of molecules, including low molecular weight ones. Finally, we provide a perspective on supramolecular hydrogelators. We hope that this review will serve as an updated introduction and reference for researchers who are interested in exploring supramolecular hydrogelators as molecular biomaterials for addressing the societal needs at various frontiers.

Low-Molecular-Weight Gels: The State of the Art

“…There are many reviews that already provide this information. [1][2][3]5,68 Rather here we mainly focus on one example where the process of gelation has been used to lead to significantly different outcomes. This example is hydrogelators; this could be one reason why sufficient data exist on the formation of gels under different conditions because, compared with organic solvents, water as a solvent opens up many additional parameters, including variations in ionic strength, pH, and the addition of background salts.…”

“…The gels arise from the self-assembly of small molecules into long, anisotropic structures, most commonly fibers. [1][2][3][4][5] At a sufficiently high concentration, these fibers entangle or otherwise form cross-links, leading to the network that is able to immobilize the solvent through surface tension and capillary forces. 1,2 These gels differ from permanently covalently cross-linked polymer gels because the cross-linking can be reversed by the input of energy, for example, by heating.…”

Hybrid supramolecular gels of Fmoc-F/halloysite nanotubes: systems for sustained release of camptothecin

“…Compared to polymeric hydrogels, supramolecular hydrogels offer different advantages, such as sol-gel reversibility under the action of different stimuli and the possibility of tailoring their properties to a given application by making small changes in the gelator structure. [30][31][32] Among hydrogelators, peptides have received much consideration. [33][34][35] However, their substantial drawbacks are their high cost and complicated chemical syntheses that require long purification processes.…”

Peptide hydrogel in vitro non‐inflammatory potential

“…One such class of LMWH are short synthetic peptides, which are of significant interest as they can be synthesised using standard chemical routes and therefore be obtained with high definition and high purity. In addition, being built out of natural amino acids, they can be designed to be biocompatible and biodegradable and can be metabolised by the body 10, 11, 12…”