Toxicological properties of two fluorescent carbon quantum dots with onion ring morphology and their usefulness as bioimaging agents

In the present work, two carbon quantum dots with onion ring morphology, C-NOR and C-NOR(Eu) with an average size of 40 nm differing in the absence or presence of Eu³⁺ as Lewis acids during their preparation were synthesized and fully characterized by several techniques. These nanoparticles can be internalized into human HeLa and Hep3B carcinoma cells where they exhibit interesting photoluminescent properties, in the same manner as in solution, confirming their utility as bioimaging agents. To address this possibility, a complete in vitro toxicological study has been performed here. Viability, proliferation, apoptosis and oxidative stress assessments upon limited or continuous exposure were done. It was observed that both nanoparticles did not show toxicity in both situations at low concentration, although some toxicity has been determined at higher concentrations under continuous exposure. These results support the possible use of C-NOR and C-NOR(Eu) nanoparticles as bioimaging agents.