In this work, we demonstrated that the hydrogel obtained from a very simple and single synthetic molecule, N-heptyl-galactonamide was a suitable scaffold for the growth of neuronal cells in 3D. We evidenced by confocal microscopy the presence of the cells into the gel up to a depth of around 200 μm, demonstrating that the latter was permissive to cell growth and enabled a true 3D colonization and organization. It also supported successfully the differentiation of adult human neuronal stem cells (hNSCs) into both glial and neuronal cells and the development of a really dense neurofilament network. So the gel appears to be a good candidate for neural tissue regeneration. In contrast with other molecular gels described for cell culture, the molecule can be obtained at the gram scale by a one-step reaction. The resulting gel is very soft, a quality in accordance with the aim of growing neuronal cells, that requires low modulus substrates similar to the brain. But because of its fragility, specific procedures had to be implemented for its preparation and for cell labeling and confocal microscopy observations. Notably, the implementation of a controlled slow cooling of the gel solution was needed to get a very soft but nevertheless cohesive gel. In these conditions, very wide straight and long micrometric fibers were formed, held together by a second network of flexible narrower nanometric fibers. The two kinds of fibers guided the neurite and glial cell growth in a different way. We also underlined the importance of a tiny difference in the molecular structure on the gel performances: parent molecules, differing by a one-carbon increment in the alkyl chain length, N-hexyl-galactonamide and N-octyl-galactonamide, were not as good as N-heptyl-galactonamide. Their differences were analyzed in terms of gel fibers morphology, mechanical properties, solubility, chain parity, and cell growth.

In this work, we describe how a simple single low molecular weight gelator (LMWG) molecule – N-heptyl-D-galactonamide, which is easy to produce at the gram scale – is spun into gel filaments by a wet spinning process based on solvent exchange. A solution of the gelator in DMSO is injected into water and the solvent diffusion triggers the supramolecular self-assembly of the N-heptyl-D-galactonamide molecules into nanometric fibers. These fibers entrap around 97% of water, thus forming a highly hydrated hydrogel filament, deposited in a well organized coil and locally aligned. This self-assembly mechanism also leads to a very narrow distribution of the supramolecular fiber width, around 150 nm. In addition, the self-assembled fibers are oriented radially inside the wet-spun filaments and at a high flow rate, fibers are organized in spirals. As a result, this process gives rise to a high control of the gelator self-assembly compared with the usual thermal sol–gel transition. This method also opens the way to the controlled extrusion at room temperature of these very simple, soft, biocompatible but delicate hydrogels. The gelator concentration and the flow rates leading to the formation of the gel filaments have been screened. The filament diameter, its internal morphology, the solvent exchange and the velocity of the jet have been investigated by video image analysis and electron microscopy. The stability of these delicate hydrogel ropes has been studied, revealing a polymorphic transformation into macroscopic crystals with time under some storage conditions. The cell viability of a neuronal cell line on the filaments has also been estimated.

Three light-sensitive amphiphiles, based on azobenzene, have been synthesized as supramolecular gelators. A hydrophobic chain with an azobenzene group incorporated at different positions was click coupled to a maltose polar head by a copper(I)-catalysed azide–alkyne [3 + 2] cycloaddition. The liquid crystalline and gel properties of these azo-amphiphilic materials have been studied. Two of these azo-gelators containing maltose give rise to stable gels in water or in a mixture of water and DMSO at room temperature. The chiral supramolecular assemblies of these gelators have been characterised by NMR, electron microscopy and circular dichroism (CD). The light-response of azo-amphiphiles in supramolecular gels has been studied. Also azo-gels, which contained mixtures of the azo-amphiphilic compounds and a similar structural hydrogelator, have been investigated.

In the context of exploring new materials based on low molecular weight amphiphiles, we prepared a new series of photoresponsive gelators with azobenzene as photosensitive unit, D-maltose or poly(ethylene glycol) (PEG) as polar head, and L-phenylalanine as linker. The gelation properties of the final amphiphiles and the intermediate molecules have been studied in different solvents. Organogels are obtained for all of them, except for compound with PEG16 polar head. Gelation in polar solvents, as DMSO, was achieved. The morphology of supramolecular structures was characterized by electronic microscopy. The chiro-optical properties of gels, due to the supramolecular chirality imposed by the molecular chirality, were also studied. The modifications under irradiation have been monitored by UV-visible spectroscopy and electronic circular dichroism (ECD). Two of the obtained materials showed a gel–sol transition by irradiation with UV light and further thermal cis–trans isomerization to gel state at room temperature.