The supramolecular hydrogel of a simple organic salt derived from a primary amine and a mono-sulfonic acid displayed a proton conductivity of 1.2 × 10−4 S cm−1.

An easy access to topical gels (both hydro- and organogels) derived from an anti-cancer prodrug namely 5-fluorouracil acetic acid (5-FuA) achieved by exploiting a simple salt formation strategy is reported for the first time.

The supramolecular synthon approach in the context of the crystal engineering rationale has been exploited to synthesize a new series of primary ammonium sulfonate salts derived from primary alkyl amines with varying alkyl chain lengths (A n = CH 3 −(CH 2 ) n −NH 2 ; n = 2−11, 13−15, 17) and naphthalene-2-sulfonic acid (N2S) as potential supramolecular gelators. The sulfonate salts A n N2S with n ≥ 9 showed the ability to immobilize a number of polar and nonpolar solvents including dimethyl sulfoxide/water, resulting in supramolecular gels which were characterized by dynamic rheology and transmission electron microscopy. Single-crystal X-ray diffraction studies carried out on eight such salts confirmed the presence of gel-inducing hydrogen bonded supramolecular synthons. Anti-bacterial studies (zone inhibition, turbidity, and tetrazolium assays) revealed that the salt A 14 N2S had the ability to kill the Gram-positive bacterium Staphylococcus aureus. Laser scanning confocal microscopy and flow cytometry data taken under various staining conditions suggested reactive oxygen species-mediated RNA depletion as the plausible cause of bacterial cell death in the presence of the gelator salt. Shear thinning of the aqueous gel of A 14 N2S along with its antibacterial activity indicated that it could be a potential candidate for topical application.

A series of primary ammonium monocarboxylate (PAM) salts derived from β-alanine derivatives of pyrene and naphthalene acetic acid, along with the parent acids, were explored to probe the plausible role of orthogonal hydrogen bonding resulting from amide⋅⋅⋅amide and PAM synthons on gelation. Single-crystal X-ray diffraction (SXRD) studies were performed on two parent acids and five PAM salts in the series. The data revealed that orthogonal hydrogen bonding played an important role in gelation. Structure-property correlation based on SXRD and powder X-ray diffraction data also supported the working hypothesis upon which these gelators were designed. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and cell migration assay on a highly aggressive human breast cancer cell line, MDA-MB-231, revealed that one of the PAM salts in the series, namely, PAA.B2, displayed anticancer properties, and internalization of the gelator salt in the same cell line was confirmed by cell imaging.

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