2D hybrids of palladium nanozymes and graphene oxide as a new multimodal theranostic platform

Multifunctional nanoparticles with enzyme-like behavior represent an emerging paradigm in theranostics. Concerning cancer nanomedicine, recent studies have shown the great potential of palladium (Pd) nanozyme for chemodynamic therapy, by the generation of endogenous chemicals such as reactive oxygen species (ROS) through their oxidase and peroxidase activities or by relieving the hypoxia of a tumor microenvironment through their catalase or superoxide dismutase (SOD) activity, with a potent antitumor effect that directly induces tumor cell death. In this work, hybrid nanoplatforms made of Pd nanospheres and graphene oxide (GO) nanosheets were prepared by the green reduction of PdCl2 in the presence of polyvinylpyrrolidone as a stabilizing agent. The physicochemical properties were scrutinized by using UV-visible and Raman spectroscopies, atomic force microscopy, zeta-potential and hydrodynamic light scattering. Theoretical DFT calculations paralleled the experimental studies. On the catalytic side, Pd-GO hybrids were tested in terms of photocatalysis experiments of H2 evolution. The assessment of nanozyme features for the Pd- GO unveiled a strong enhancement of hydrogen evolution and broad antioxidant activities, as scrutinized respectively by photocatalysis experiments and MitoSOX and SOD-like activity, respectively.Proof-of-work in vitro cell experiments on human prostate cancer cells (PC-3 line) and mouse embryonic fibroblast cells (3T3 line) cells were carried out in terms of cytotoxicity (MTT assay), inhibition of cell migration (wound scratch test) and organelle perturbation (colocalization studies by confocal microscopy). The results pointed to a significant reduction of tumor growth and thus the promising potential of the developed Pd-GO hybrid nanozymes in cancer therapy. This work has been partially funded by the European Union (NextGeneration EU), through the MUR- PNRR project SAMOTHRACE (ECS00000022) and by the University of Catania (PIAno di inCEntivi per la RIcerca di Ateneo 2020/2022 GRABIO_Linea di intervento 2).