Concentration- and Solvent-Induced Chiral Tuning by Manipulating Non-Proteinogenic Amino Acids in Glycoconjugate Supra-Scaffolds: Interaction with Protein, and Streptomycin Delivery

We showed solvent- and concentration-triggered chiral tuning of the fibrous assemblies of two novel glycoconjugates Z-P(Gly)-Glu and Z-F(4-N)-Glu made by chemical attachment of Cbz-protected [short as Z)] non-proteinogenic amino acids L-phenylglycine [short as P(Gly)] and 4-Nitro-L-phenylalanine [short as F(4-N)] with D-glucosamine [short as Glu]. Both biomimetic gelators can form self-healing and shape-persistent gels with a very low critical gelator concentration in water as well as in various organic solvents, indicating they are ambidextrous supergelators. Detailed spectroscopic studies suggested β-sheet secondary structure formation during anisotropic self-aggregation of the gelators which resulted in the formation of hierarchical left-handed helical fibers in acetone with an interlayer spacing of 2.4 nm. After the physical characterization of the gels, serum protein interaction with the gelators was assessed, indicating they may be ideal for biomedical applications. Further, both gelators are benign, non-immunogenic, non-allergenic, and non-toxic in nature, which was confirmed by performing the blood parameters and liver function tests on Wister rats. Streptomycin-loaded hydrogels showed efficacious antibacterial activity in vitro and in vivo as well. Finally, cell attachment and biocompatibility of the hydrogels were demonstrated which opens a newer avenue for promising biomedical and therapeutic applications.

Tuning Aqueous Supramolecular Polymerization by an Acid-Responsive Conformational Switch

Besides their widespread use in coordination chemistry, 2,2'-bipyridines are known for their ability to undergo cis-trans conformational changes in response to metal ions and acids, which has been primarily investigated at the molecular level. However, the exploitation of such conformational switching in self-assembly has remained unexplored. In this work, the use of 2,2'-bipyridines as acid-responsive conformational switches to tune supramolecular polymerization processes has been demonstrated. To achieve this goal, we have designed a bipyridine-based linear bolaamphiphile, 1, that forms ordered supramolecular polymers in aqueous media through cooperative aromatic and hydrophobic interactions. Interestingly, addition of acid (TFA) induces the monoprotonation of the 2,2'-bipyridine moiety, leading to a switch in the molecular conformation from a linear (trans) to a V-shaped (cis) state. This increase in molecular distortion along with electrostatic repulsions of the positively charged bipyridine-H+ units attenuate the aggregation tendency and induce a transformation from long fibers to shorter thinner fibers. Our findings may contribute to opening up new directions in molecular switches and stimuli-responsive supramolecular materials.

A facile preparation method for new two-component supramolecular hydrogels and their performances in adsorption, catalysis, and stimuli-response

In this study, we prepared a novel multifunctional two-component supramolecular hydrogel (T-G hydrogel) via two organic molecules in ethanol/water mixed solvents. In addition, we prepared gold nanoparticle/T-G (AuNPs/T-G) composite hydrogels using T-G hydrogel as a template for stabilizing AuNPs by adding HAuCl₄ and NaBH₄ during the heating and cooling process of T-G hydrogels. The morphology and microstructure of the as-prepared hydrogels were characterized using SEM, TEM, XRD, and FT-IR. The hydrogels prepared by solutions that contained different ethanol/water volume ratios exhibited different microstructures, such as sheets, strips, and rods. The obtained T-G hydrogels exhibited a sensitive response to pH changes in the process of sol–gel transformation and showed good adsorption properties for model organic dyes. In the presence of NaBH₄, the obtained AuNP/T-G composite hydrogels exhibited the excellent catalytic performance for 4-nitrophenol (4-NP) degradation. Thus, the current research provides new clues in developing new multifunctional two-component supramolecular gel materials and exhibits potential applications for wastewater treatment.

New two-component supramolecular hydrogels were prepared via a self-assembly process, demonstrating potential applications in adsorption and catalysis as well as sensor materials.

Mechanism of the formation of microphase separated water clusters in a water-mediated physical network of perfluoropolyether tetraol

Perfluoropolyether tetraol (PFPE tetraol) possesses a hydrophobic perfluoropolyether chain in the backbone and two hydroxyl groups at each chain terminal, which facilitates the formation of hydrogen bonds with water molecules resulting in the formation an extended physical network. About 3 wt% water was required for the formation of the microphase separated physical network of PFPE tetraol. The mechanism responsible for the microphase separation of water clusters in the physical network was studied using a combination of techniques such as NMR spectroscopy, molecular dynamics (MD) simulations and DSC. MD simulation studies provided evidence for the formation of clusters in the PFPE tetraol physical network and the size of these clusters increased gradually with an increase in the extent of hydration. Both MD simulations and NMR spectroscopy studies revealed that these clusters position themselves away from the hydrophobic backbone or vice versa. The presence of intra- and inter-chain aggregation possibility among hydrophilic groups was evident. DSC results demonstrated the presence of tightly and loosely bound water molecules to the terminal hydroxyl groups of PFPE tetraol through hydrogen bonding. The data from all the three techniques established the formation of a physical network driven by hydrogen bonding between the hydrophilic end groups of PFPE tetraol and water molecules. The flexible nature of the PFPE tetraol backbone and its low solubility parameter favour clustering of water molecules at the terminal groups and result in the formation of a gel.

Supramolecular gelatons: towards the design of molecular gels

The concept of supramolecular gelatons for the design of gels was proposed and described.

Supramolecular Chirality of the Two-Component Supramolecular Copolymer Gels: Who Determines the Handedness?

Natural supramolecular systems typically contain a wide variety of chiral molecules. Studying the chiral conflict within different supramolecular assemblies not only can be very helpful for understanding the inherent principles of supramolecular chirality but also can guide the preparation of many functional chiral soft matters. For assemblies containing only structurally similar molecules, supramolecular chirality is determined by enantiomeric excess of molecular building blocks. For supramolecular systems assembled by structurally different chiral molecules, however, the optical activity of the systems and the chiral conflict among different chiral molecules can be very complex. We found rather unexpected results regarding the chiral conflict within two-component supramolecular copolymer gels in this study. The handedness of the chirality of supramolecular copolymer gels, which were formed by the coassembly of bolaamphiphilic L-histidine derivatives and tartaric acids, was found to be dependent on the ordering molecular packing, instead of the preponderance of certain chiral molecules.

trans–cis Configuration regulated supramolecular polymer gels and chirality transfer based on a bolaamphiphilic histidine and dicarboxylic acids

Supramolecular polymer gels based on the co-assembly of bolaamphiphilic l-histidine(BolaHis) and dicarboxylic acids are dependent on the molar ratios, flexibility and cis–trans configuration of acid molecules.

High aspect ratio, processable coordination polymer gel nanotubes based on an AIE-active LMWG with tunable emission

A new TPE based low molecular weight gelator (LMWG) which displays both AIE and MCIE phenomena in gel state has been synthesized. LMWG self-assembles to form 1D nanofibers which undergo morphology transformation to coordination polymer gel (CPG) nanotubes upon metal ion coordination. CPG shows enhanced mechanical stability along with tunable emission properties.

A novel supramolecular polymer gel constructed by crosslinking pillar[5]arene-based supramolecular polymers through metal–ligand interactions

A novel heteroditopic A–B monomer was synthesized and used to construct linear supramolecular polymers utilizing pillar[5]arene-based host–guest interactions. Upon addition of Cu²⁺ ions, a supramolecular polymer gel formed through metal–ligand interactions.

Emission enhanced two-component gels for the detection of organic amine vapors

A two-component gelator with enhanced emission could be used to quantitatively detect and discriminate between aliphatic and aromatic organic amine vapors.

Cu(ii)-specific metallogel formation by an amido-anthraquinone-pyridyloxalamide ligand in DMSO–water

This study on the CuCl₂-induced and water-mediated metallogel formation by a pyridine containing anthraquinone-based ligand in DMSO provides significant insights on the relationship between the coordination geometry and metallo-gelation aptitude for a series of variably substituted pyridyloxalamide ligands.