Commercially available graphene quantum dots (GQDs) are promising nanomaterials for applications in research and preclinical diagnostics, drug delivery, and bioimaging. Their bioactivity is highly dependent on dose, route of exposure, duration, cell type, uptake mechanisms, tissue and cellular distribution, and physicochemical properties. This study aimed to evaluate genotoxic, cytotoxic, and cytostatic endpoints of blue- (B-GQDs) and green-emitting (G-GQDs) GQDs in human blood and salivary leukocytes. GQDs were tested at concentrations ranging from 2.5 to 100 µg/mL using distinct treatment periods. Fourier transform infrared spectroscopy (FTIR), trypan blue exclusion, comet, and cytokinesis-block micronucleus cytome (CBMN cyt) assays were performed. FTIR analysis revealed that G-GQDs, unlike B-GQDs, exhibit an absorption band typically associated with amine functional groups, which may contribute to their pronounced genotoxic effects. Peripheral blood mononuclear cells and salivary leukocytes showed higher sensitivity to G-GQDs compared to whole blood samples. Although no cytotoxic effects were observed, both GQDs induced significant DNA damage, with G-GQDs demonstrating greater genotoxic potential. These findings demonstrate that GQDs can induce DNA damage in the absence of detectable cytotoxic effects under the conditions tested, highlighting the importance of considering both physicochemical properties and cellular models in the safety assessment of nanomaterials.

Abstract Anti-proliferative effects of halogenated boroxine – K2(B3O3F4OH) (HB) – have been confirmed in multiple cancer cell lines, including melanoma, but the exact mechanism of action is still unknown. This study aimed to determine its cytotoxic effects on human Caucasian melanoma (GR-M) cell growth in vitro as well as on the expression of cell death-related genes BCL-2, BECN1, DRAM1, and SQSTM1. GR-M and peripheral blood mononuclear (PBM) cells were treated with different HB concentrations and their growth inhibition and relative gene expression profiles were determined using the Alamar blue assay and real-time PCR. HB significantly inhibited cell growth of both GR-M and PBM cells but was even more effective in GR-M melanoma cells, as significant inhibition occurred at a lower HB concentration of 0.2 mg/mL. GR-M BCL-2 expression was significantly downregulated (P=0.001) at HB concentration of 0.4 mg/mL, which suggests that HB is a potent tumour growth inhibitor. At the same time, it upregulated BCL-2 expression in normal (PBM) cells, probably by activating protective mechanisms against induced cytotoxicity. In addition, all but the lowest HB concentrations significantly upregulated SQSTM1 (P=0.001) in GR-M cells. Upregulated BECN1 expression suggests early activation of autophagy at the lowest HB concentration in SQSTM1 cells and at all HB concentrations in PBM cells. Our findings clearly show HB-associated cell death and, along with previous cytotoxicity studies, reveal its promising anti-tumour potential.