Unravelling the mechanisms of intracellular antioxidant activity of platinum nanozymes

Platinum nanoparticles (PtNPs) are considered promising nanomaterials for biomedical applications thanks to their formidable catalytic and antioxidant properties. To improve their therapeutic potential and to boost their applicability in nanomedicine, it is fundamental to understand the biological mechanisms that control PtNP interaction with cells and tissues. In this context, an important issue, still open and shared among other nanomaterials, is how internalized PtNPs, that are confined within endo-lysosomal compartments, can exert their activities within the cells. In this framework, here we overviewed the antioxidant and catalytic properties of PtNPs, that make them useful tools for theragnostic applications, and their interactions with cells. In particular, we focused the attention on the endocytic pathways of NPs and their intracellular localization and discussed the formation of inter-organelle contact sites as new and possible mechanisms of communications between cells and NPs, based on recent findings and never reported before. This brief review sheds light on possible new players in the process of nano-biointeractions at the intracellular level (i.e., the interorganelle contact sites), offering new insights about the mechanisms of action of PtNPs compared to previous works. In this context, we contemplated the opportunity to exploit this new mechanism of nano-biointeraction, e.g., by modulating the formation of inter-organelle contact sites and by targeting them to increase thepotential applications of PtNPs in biomedicine and theranostics.