Rheology, small-angle X-ray scattering (SAXS), and dynamic light scattering (DLS) analysis, zeta potential measurement, scanning electron microscopy (SEM), and micro-FTIR and absorbance spectroscopy were used to enlighten the controversial literature about LAPONITE® materials. Our data suggest that pristine LAPONITE® in water does not form hydrogels induced by the so-called “house of cards” assembly, but rather forms Wigner glasses governed by repulsive forces. Ionic interactions between anisotropic LAPONITE® nanodiscs, sodium polyacrylate and inorganic salts afforded hydrogels that were transparent, self-standing, moldable, strong, and biocompatible with shear-thinning and self-healing behavior. An extensive study on the role of salts in the gelification process dictates a trend that relates the valence of cations with the viscoelastic properties of the bulk material (G′ values follow the trend, monovalent < divalent < trivalent). These hydrogels present G′ values up to 5.1 × 10⁴ Pa, which are considered high values for non-covalent hydrogels. Hydrogels crosslinked with sodium phosphate salts are biocompatible, and might be valid candidates for injectable drug delivery systems due to their shear-thinning behavior with rapid self-healing after injection.

A series of new hybrid fluorescent Biginelli compounds, including a Monastrol derivative, were designed and synthesized with good yields. The photophysical studies revealed dual fluorescence emission, attributed to excited enol forms (E*) and tautomeric (K*) species, respectively, due to the ESIPT mechanism. The cytotoxic activity of all compounds was evaluated against MCF-7, Caco-2 and PC3 cancer cell lines and PNT2 normal prostate cells. The fluorescent Monastrol derivative 8f was the most active with cytotoxic activity very similar to cisplatin, whereas derivative 8c was the most selective towards the PC3 prostate cancer cells. The confocal laser scanning microscopy images of PC3 and MCF-7 cancer cell lines were acquired after incubation of the fluorescent Biginelli hybrids 8c and 8f, respectively, demonstrating efficient cellular uptake of both compounds and strong fluorescence within the intracellular medium. These results show that the new hybrid 3,4-dihydropyrimidin-2-(thi)ones are dual-function bioactive compounds that act both as fluorescent probes and antineoplastic agents.