Toxicity assessment of nano-sized MAX phases: considerations for safe-by-design approaches

MAX phases are versatile materials with unique metallic and ceramic properties, utilized in aerospace, nuclear engineering, and high-temperature applications. A comprehensive assessment of the potential hazards and toxicity mechanisms is essential to ensure the safe utilization of these nanomaterials. In light of this, our study investigates the toxicity of two nano-sized MAX phases, Ti₂AlC and Ti₃AlC₂, to provide fundamental data for implementing the safe-by-design (SbD) approach. Cytotoxicity, genotoxicity, and ecotoxicity screening assays were conducted to identify environmental health and safety issues associated with these materials. The comparison with graphene oxide served as a reference nanomaterial in all toxicity tests. At a concentration of 1 mg L⁻¹, MAX phases showed approximately 20% cytotoxicity and a significant increase in DNA strand break marker and IL-6 level in BEAS-2B cells. However, at the same concentration, no significant toxicity was observed in C. elegans and zebrafish embryos. Overall, MAX phases exhibited non-negligible toxicity, with genotoxicity being the most notable endpoint. This study fills the knowledge gap between the prospective use of MAX phases in the biomedical field and their influence on the environment and human health. These findings underscore the importance of evaluating the potential hazards associated with nano-sized MAX phases and provide valuable insights for the implementation of SbD during their research, development, and design phases.