# Unravelling the Properties of Fluorescent Ammonium Salts to Obtain Thixotropic Hydrogels with Antitumoral Activity

## TL;DR

This paper introduces fluorescent hydrogels that can both image and kill cancer cells, with improved performance when using gluconate as an anion.

## Contribution

The study introduces novel fluorescent ammonium salts with thixotropic hydrogel properties and antitumoral activity.

## Key findings

- Fluorescent ammonium salts with gluconate anions showed enhanced cellular uptake and cytotoxicity against cancer cells.
- Hydrogels release gelator into aqueous media, enabling ammonium salts to exert cytotoxic effects.
- Gluconate-based salts trigger oxidative stress and apoptotic cell death in cancer cells.

## Abstract

Novel
fluorescent and thixotropic hydrogels, based on
naphthalimide
salts differing for both the cation and anion structure, were obtained
and applied as promising bioimaging and antitumoral agents. First,
the photophysical behavior of the salts was analyzed through UV–vis
and fluorescence investigation at variable solvent and concentration,
together with the determination of the relative fluorescence quantum
yield in water. Organic salts were also tested as gelators, and the
resulting soft materials, obtained in H2O, H2O/DMSO mixtures, and glycerol, were characterized by rheological
measurements and fluorescence and resonance light scattering analyses.
Morphology of gel phases was examined via scanning electron microscopy.
To assess their therapeutic potential, the salts were tested for cytotoxicity
and selectivity against a panel of cancer and normal cell lines using
the MTT assay. Their performance as bioimaging agents was also evaluated.
Remarkably, all salts exhibited strong fluorescence, and their cytotoxicity
effects were closely linked to their chemical structure. Notably,
the replacement of bromide with gluconate as an anion significantly
enhanced cellular uptake, cytotoxicity, and selectivity toward cancer
cells. Release experiments revealed that the mechanism of action of
the hydrogel can be ascribed to the release of gelator into aqueous
media, enabling the ammonium salts to exert a cytotoxic effect. Collectively,
our findings support a mechanism of action in which gluconate-based
salts are internalized more efficiently by cancer cells, thereby triggering
oxidative stress, mitochondrial dysfunction, and apoptotic cell death.
These results highlight gluconate-based salts as dual-function materials
with promising applications in both cancer therapy and bioimaging.