Cellular uptake, induction of reactive oxygen species, and genotoxicity of differently sized cobalt oxide nanoparticles in human peripheral blood mononuclear cells in vitro

Cobalt (II, III) oxide nanoparticles (Co₃O₄-NPs) have potential applications in different technological and medical fields, including drug delivery and as novel anticancer treatments. However, widespread application could lead to a high-level direct human exposure, raising concerns about their genotoxic potential. This study aimed to evaluate the cytotoxicity and genotoxicity of Co₃O₄-NPs in human peripheral blood mononuclear cells (PBMCs) in vitro. Two sizes of Co₃O₄-NPs (10–30 nm and < 50 nm) were tested to understand any size-dependent differences in genotoxicity. The study measured NP uptake, reactive oxygen species (ROS) generation, cell viability, DNA strand breaks, micronuclei formation, and sister chromatid exchange to assess the cyto-genotoxic potential of Co₃O₄-NPs. Flow cytometric analysis revealed that Co₃O₄-NPs with a primary size of < 50 nm were more efficiently internalized by human PBMCs and induced higher ROS levels than 10–30 nm particles. Both nanoparticles’ sizes induced significant primary DNA damage at non-cytotoxic concentrations, often in a dose-dependent manner. Cytogenetic analysis demonstrated that Co₃O₄-NPs exert genotoxic effects, with < 50 nm NPs inducing more significant DNA damage and reduced cell viability than smaller nanoparticles. Additionally, interindividual differences in response to exposure to Co₃O₄–NPs were observed. The study findings suggest that Co₃O₄-NPs possess genotoxic potential in human PBMCs in vitro, raising safety concerns about their use. This highlights the need for comprehensive genotoxicity assessments of Co₃O₄-NPs in different cell types.