Bioimaging supported by nanoparticles requires low cost, highly emissive and photostable systems with low cytotoxicity. Carbon dots (C-dots) offer a possible solution, even if controlling their properties is not always straightforward, not to mention their potentially simple synthesis and the fact that they do not exhibit long-term photostability in general. In the present work, we synthesized two C-dots starting from citric acid and tris (hydroxymethyl)-aminomethane (tris) or arginine methyl ester dihydrochloride. Cellular uptake and bioimaging were tested in vitro using murine neuroblastoma and ovine fibroblast cells. The C-dots are highly biocompatible, and after 24 h of incubation with the cells, 100% viability was still observed. Furthermore, the C-dots synthesized using tris have an average dimension of 2 nm, a quantum yield of 37%, high photostability and a zeta potential (ζ) around −12 mV. These properties favor cellular uptake without damaging cells and allow for very effective bioimaging.

The emergence of SARS-CoV-2 variants requires close monitoring to prevent the reoccurrence of a new pandemic in the near future. The Omicron variant, in particular, is one of the fastest-spreading viruses, showing a high ability to infect people and evade neutralization by antibodies elicited upon infection or vaccination. Therefore, the search for broad-spectrum antivirals that can inhibit the infectious capacity of SARS-CoV-2 is still the focus of intense research. In the present work, hyperbranched poly-L-lysine nanopolymers, which have shown an excellent ability to block the original strain of SARS-CoV-2 infection, were modified with L-arginine. A thermal reaction at 240 °C catalyzed by boric acid yielded Lys-Arg hyperbranched nanopolymers. The ability of these nanopolymers to inhibit viral replication were assessed for the original, Delta, and Omicron strains of SARS-CoV-2 together with their cytotoxicity. A reliable indication of the safety profile and effectiveness of the various polymeric compositions in inhibiting or suppressing viral infection was obtained by the evaluation of the therapeutic index in an in vitro prevention model. The hyperbranched L-arginine-modified nanopolymers exhibited a twelve-fold greater therapeutic index when tested with the original strain. The nanopolymers could also effectively limit the replication of the Omicron strain in a cell culture.

The class of diamino-naphthalene exhibits antioxidant properties, which are partly related to the relative positions of the two amino groups. This study demonstrates how the reactivity of one of these compounds, 1,5-diamino-naphthalene (DAN), can be adjusted by introducing a single amide bond through a simple thermal coupling with l-pyroglutamic acid (PyroGlu). The solventless thermal reaction between PyroGlu and DAN at 160 °C yielded a new mono-pyroglutanilide compound (PyroDAN) that was characterized using various analytical techniques, including a thermal and infrared analysis, HRMS (ESI), and one- (1D) and two-dimensional (2D) NMR. The optical properties were investigated using UV-Vis and fluorescence spectroscopy. Additionally, two chemical standard assays were used to measure both the antioxidant and pro-oxidant properties of PyroDAN. The molecule has shown nearly negligible pro-oxidant activity, while a mild antioxidant activity is still retained. These findings indicate that the transformation of DAN into a mono-pyroglutanilide derivative breaks the original molecular symmetry and effectively modifies the electronic distribution of the aromatic system, suppressing the oxidant properties while keeping a mild antioxidant activity. Furthermore, the tuneable fluorescent properties of PyroDAN—the mild antioxidant activity and the inhibition of the cytologically harmful pro-oxidant properties—suggest promising applications in bioimaging and other biological fields.

Se rods decorated with SnO₂ nanoparticles have been synthesized via a facile hydrothermal approach to bridge the gap between ultraviolet-only and visible-only photocatalysis and to enhance reactive oxygen species generation under visible illumination. Structural and morphological analyses using X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy have confirmed the coexistence of cassiterite SnO₂ particles intimately interfaced with trigonal selenium rods. Diffuse-reflectance spectroscopy revealed a long absorption tail extending into the 400–550 nm range. Under 450 nm sample illumination, the composite produced singlet oxygen in higher yields than either bare SnO₂ or Se, as evidenced by the indocyanine green assay. The system alone does not produce free radicals, as shown by the terephthalic acid test; however, the addition of rhodamine B acts as an effective sensitizer, enabling hydroxyl radical generation. Photodegradation tests using rhodamine B have shown that the SnO₂–Se system outperforms both its single components, Se and SnO₂, as a catalyst. The synergistic interplay underscores the potential of SnO₂–Se heterostructures in photochemical applications under visible light.