In Vitro and Ex Vivo Biocompatibility, Biomolecular Interactions, and Characterization of Graphene Quantum Dots and Its Glutathione-Modified Variant for Qualitative Cell Imaging.

This study explores the biological effects and imaging potential of graphene quantum dots (GQDs) and their nitrogen-doped, glutathione-modified form (GQDs-GSH) in human cell models. We evaluated the cell viability, hemolysis potential, and irritation effects of these nanomaterials, showing that both GQDs and GQDs-GSH maintained 100% cell viability in the range of 16.25-260 μg mL-1, caused minimal RBC hemolysis (<9%), and presented low irritation scores in HET-CAM assays. Interaction studies revealed distinct binding behaviors with biomolecules: GQDs used a static quenching mechanism with human serum albumin (HSA), while GQDs-GSH exhibited a mixed static and dynamic interaction. Additionally, GQDs-GSH exhibited a stronger affinity for calf thymus DNA (ctDNA) without disturbing the DNA secondary structure. Fluorescence microscopy-based apoptotic cell staining assays indicated the adherence potential of both GQDs and GQDs-GSH. GQDs tended to accumulate more prominently in regions associated with apoptotic bodies, whereas GQDs-GSH tended to localize on the membranes of spheroid-shaped cells.