Physicochemical properties and toxicological assessment of modified CdS nanoparticles

Cadmium sulfite (CdS) nanoparticles (NPs) modified with different stabilizing agents (2-mercaptopropionic acid or 2MPA, 3-mercaptopropionic acid or 3MPA, and l-cysteine or cys) were designed to be used as luminescent probes. The toxicity and inflammatory response of luminescent CdS NPs (average diameter between 2 and 3 nm) was evaluated “in vitro” using human lung epithelial cells (BEAS-2B). Also, mucociliary function changes or injuries were assessed by mucociliary transport (MCT) and ciliary beat frequency (CBF) measurements using frog palates. Toxicity assays showed that Cd concentrations above 1.0 mg L⁻¹ were toxic to BEAS-2B, while Cd associated to NPs was not toxic at the concentrations tested (fivefolds that of Cd toxicity). Cadmium at toxic levels of 2.5 mg L⁻¹ significantly induced the release of both cytokines, IL-6 and IL-8, conversely none toxic levels (2.5 mg L⁻¹) of 2MPA-CdS nanoparticles showed similar effects. However, cys-CdS and 3MPA-CdS NPs did not induce the secretions of either IL-6 or IL-8 by lung epithelial cells at the same Cd concentration of 2.5 mg L⁻¹. Conversely, significant reduction in the secretion of these two pro-inflammatory cytokines was observed. The MCT and CBF results revealed no impairment on mucociliary behavior except a very slight change in mucus viscosity by 3MPA-CdS NPs. These findings highlight the potential of 3MPA-CdS and cys-CdS NPs for future biomedical research, and encourage further histopathological and metabolic studies in order to strengthen that possibility.