Reversible sol-gel signaling system with epMB for the study of enzyme- and pH-triggered oligonucleotide release from a biotin hydrogel

A Co²⁺-selective and chirality-sensitive supermolecular metallohydrogel with a nanofiber network skeleton

This paper introduces a new metallohydrogel precursor that offers a peculiar gelation response to Co(2+) at pH 7-8. It is notable that the stability of this metallohydrogel is significantly dependent on its enantiomeric purity. In addition to the expected multi-stimuli responsive properties, including thixotropy, as well as re-assembly properties on adding HCl, this metallohydrogel possesses excellent self-healing behavior, which is uncommon in low-molecular-weight gelators. Electron microscopy (EM) studies revealed that the cryodried remains of this gel presented as well an organized three dimensional (3D) network of fibrils. This interesting metallohydrogel shows potential for developing new soft materials with drug delivery and catalysis properties.

Pb2+-specific metallohydrogel based on tryptophan-derivatives: preparation, characterization, multi-stimuli responsiveness and potential applications in wastewater and soil treatment

The gelator HAIP can self-assemble to form a metallohydrogel in the presence of Pb²⁺, and can simultaneously adsorb methylene blue.

pH sensitive smart gels of cetylpyridinium chloride in binary solvent mixtures: phase behaviour, structure and composition

Figure showing the effect of pH on CPC gel formation at 25 °C and fluorescence emission spectra of CPC solutions at pH ∼ 11.8.

Enzyme-triggered self-assembly of a small molecule: a supramolecular hydrogel with leaf-like structures and an ultra-low minimum gelation concentration

We report on the use of a phosphatase to assist the formation of leaf-like structures and a supramolecular hydrogel with an ultra-low minimum gelation concentration. The compound can gel water at a minimum gelation concentration of 0.01 wt%, which is the lowest gelation concentration reported up to now. The images obtained by transmission electron microscopy (TEM) reveal the existence of leaf-like structures serving as the matrix of the hydrogels. The stability of the hydrogels was studied and emission spectra were used to get information about the molecular packing in the leaf-like structures. Since lowering the concentration of the gelator decreases the toxicity of the resulting hydrogels, ultra-low concentration gels have potential uses as biocompatible biomaterials for, e.g., cell cultures, tissue engineering, and drug delivery.

Butadiene-based photoresponsive soft materials

The creation of stimuli-responsive materials offers considerable challenges in the area of material science. The use of light as an external stimulus has particular advantages because it can bring about rapid transformations in remote regions in a very precise manner. Naturally occurring photoresponsive systems provide the motivation for developing corresponding artificial systems using molecular self-assembly to address issues such as quantum efficiency, selectivity, and amplification. A practical strategy for developing photoresponsive materials is to utilize molecules that can undergo considerable change in shape on photoisomerization. Although the photoisomerization of polyenes between their linear all-trans isomer and bent cis isomers has been extensively investigated in solution and in organized media because of its relevance to naturally occurring photoresponsive systems, its use in developing artificial photoresponsive systems has not been well explored. This feature article provides an overview of photoresponsive soft materials such as liquid crystals and gels with special emphasis on our recent studies related to the use of the butadiene chromophore for the design of such materials. The role of molecular self-assembly in controlling the photochemical and photophysical properties of these molecules is also discussed.

New cholesterol-based gelators with maleimide unit and the relevant Michael adducts: chemoresponsive organogels

Compound 1 containing cholesteryl and maleimide units can gel a few organic solvents such as cyclohexane. It is interesting to note that the gel-sol transition can be triggered by addition of trace amounts of thiol and triethylamine. In this regard, we successfully demonstrate the proof of principle for designing chemoresponsive gels by incorporating the reactive groups into the gelators. Additionally, the Michael adducts 2 and 3 were prepared. Compounds 2 and 3 can also gel several organic solvents. The results also show that slight molecular structural variation has a large effect on the gelation ability of the compound. These organogels were characterized with SEM, AFM, CD, and XRD. Interestingly, gelation-induced CD spectra were observed for gels of 1, 2, and 3.

High-tech applications of self-assembling supramolecular nanostructured gel-phase materials: from regenerative medicine to electronic devices

It is likely that nanofabrication will underpin many technologies in the 21st century. Synthetic chemistry is a powerful approach to generate molecular structures that are capable of assembling into functional nanoscale architectures. There has been intense interest in self-assembling low-molecular-weight gelators, which has led to a general understanding of gelation based on the self-assembly of molecular-scale building blocks in terms of non-covalent interactions and packing parameters. The gelator molecules generate hierarchical, supramolecular structures that are macroscopically expressed in gel formation. Molecular modification can therefore control nanoscale assembly, a process that ultimately endows specific material function. The combination of supramolecular chemistry, materials science, and biomedicine allows application-based materials to be developed. Regenerative medicine and tissue engineering using molecular gels as nanostructured scaffolds for the regrowth of nerve cells has been demonstrated in vivo, and the prospect of using self-assembled fibers as one-dimensional conductors in gel materials has captured much interest in the field of nanoelectronics.

Detection of structure-switching in G-quadruplexes using end-stacking ability

G-quadruplex-forming ODNs containing nonpolar aromatic fluorophore moiety, A(PY) at the dangling ends undergo pi-stacking on surface of G-quadruplex, and the fluorescence change can be used to distinguish the structure-switching between the mixed parallel/antiparallel structure and antiparallel structure.

Probing the stable G-quadruplex transition using quencher-free end-stacking ethynyl pyrene-adenosine

Pyrene-modified adenosines in the dangling positions of G-rich oligodeoxynucleotides undergo pi-stacking in their G-quadruplex formation, but not in their single strands, which can be characterized by fluorescence lambda(max) changes that occur on stacking.