Ion-Tolerant, Injectable, and Biocompatible Pyrene-Amino Acid Supramolecular Hydrogels for Antimicrobial Applications in Saline Media.

Herein, we report an ion-tolerant supramolecular hydrogel formed from a pyrene-conjugated amino acid in an electrolytic (saline) aqueous medium with a minimum gelator concentration of 1.8 mM. The hydrogel exhibits thermoreversible and thixotropic behavior, undergoing reversible gel-sol transitions in response to thermal and mechanical stimuli. Spectroscopic and microscopic studies reveal that cooperative π-π stacking of pyrene units and directional hydrogen-bonding interactions from the amino acid backbone drive the self-assembly process. UV-visible and fluorescence analyses confirm the formation of J-type aggregates, while AFM demonstrates a concentration-dependent transition from spherical aggregates to an interconnected fibrous network. Circular dichroism spectroscopy indicates efficient transfer of supramolecular chirality, leading to left-handed helical assemblies that are disrupted at elevated temperatures. X-ray diffraction reveals an ordered lamellar packing with a characteristic π-π stacking distance of ∼0.38 nm. Rheological investigations confirm the viscoelastic and thixotropic nature of the hydrogel. Importantly, the hydrogel exhibits good biocompatibility and effective antibacterial and antifungal activity, highlighting its potential as an injectable, ion-resilient soft material for antimicrobial applications, localized drug delivery, and tissue engineering under physiological saline conditions.