Aim. To investigate the effect of titanium dioxide (TiO2) nanoparticles (anatase form) with varying sulfur content on the functional activity of peripheral blood mononuclear cells (PBMCs) from healthy donors in vitro, based on the production of cytokines IL-1β, IL-4, IL-6, and TNF-α.

Materials and methods. The objects of the study were titanium dioxide (TiO2) nanopowders of the anatase crystalline form, with a particle size of 21-28 nm and varying sulfur content (0.04 %, 0.16 % and 0.83 %), developed at the I. M. Frantsevich Institute for Problems of Materials Science. Peripheral blood mononuclear cells (PBMCs) from healthy volunteer donors (n = 30) were incubated in vitro either without a stimulating agent, with the mitogen phytohemagglutinin (PHA), or in the presence of TiO2 nanoparticle suspensions (10 μL) at concentrations of 0.3 mg/mL, 3 mg/mL, and 30 mg/mL. Cytokine concentrations (IL-1β, IL-6, IL-4, and TNF-α) in the PBMC supernatants were measured using enzyme-linked immunosorbent assay (ELISA). The tests were performed using a Stat Fax-303 Plus ELISA reader.

Results. In vitro studies demonstrated that the nanomaterial at concentrations starting from 0.3 µg/mL, specifically TiO2 nanoparticles with 0.16 % and 0.83 % sulfur content, suppressed the functional activity of peripheral blood mononuclear cells, as evidenced by a statistically significant decrease in the production of cytokines IL-1β, IL-6, TNF-α, and IL-4 in donor samples (p < 0.05). This suggests a potential disruption of immune system function. In contrast, exposure to TiO2 nanoparticles containing 0.04 % sulfur at a concentration of 30 µg/mL resulted in a statistically significant reduction only in TNF-α production (p < 0.05), while IL-6, IL-1β, and IL-4 levels did not significantly differ from spontaneous cytokine production. Moreover, the data indicate that the immunomodulatory effect of TiO2 nanoparticles is closely related to their sulfur content: the higher the sulfur concentration, the more pronounced the suppression of key cytokine production (IL-1β, IL-6, TNF-α, IL-4). Overall, these results highlight the ability of sulfur-modified nanoparticles to exert differential effects on the immune response, ranging from neutral to potentially immunotoxic outcomes.

Conclusions. The functional activity of peripheral blood mononuclear cells, in terms of cytokine production (IL-1β, IL-6, TNF-α, IL-4), is suppressed by the tested TiO2 nanoparticles at specific concentrations, following the order: nano-TiO2 (0.04 % S) < nano-TiO2 (0.83 % S) < nano-TiO2 (0.16 % S). A sulfur content of 0.16 % or higher in TiO2 nanoparticles is associated with increased immunotoxicity. These findings suggest that the effect of TiO2 nanoparticles on cytokine production by peripheral blood mononuclear cells varies depending on the sulfur content, indicating a direct relationship between the chemical composition of the nanomaterial and its potential immunotoxicity.