Toxic or non-toxic: a critical assessment of the contradictory results for selected graphene family materials

The toxicity of graphene, graphene oxide, and reduced graphene, selected members of graphene family materials (GFMs), has been widely investigated, yet reported biological effects remain highly inconsistent, limiting reliable hazard assessment. Here, we synthesize current evidence to examine how intrinsic material properties and methodological factors contribute to these discrepancies. Published studies were critically evaluated with particular attention to physicochemical characteristics, synthesis and post-processing histories, sonication protocols, and interactions with commonly used in vitro toxicity assays. The literature reveals that reported cytotoxic, genotoxic, and antimicrobial effects vary widely, ranging from pronounced dose-dependent toxicity to negligible or even beneficial biological responses. A major driver of these contradictions is pervasive interference of these selected GFMs with colorimetric, fluorometric, and luminometric assays, arising from adsorption, fluorescence quenching, optical masking, and catalytic effects, often compounded by insufficient experimental controls. Variations in oxidation state, defect density, surface chemistry, lateral size, and sonication-induced structural modification strongly influence both biological behaviour and assay artefacts, while additional confounders such as endotoxin contamination and residual impurities are rarely assessed. Overall, the evidence indicates that many contradictory toxicity outcomes reflect differences in material properties and assay interference rather than true biological inconsistency, underscoring the need for rigorous material characterisation and the adoption of interference-free or label-free testing strategies to generate reliable and reproducible toxicity data for these graphene materials.