2D hybrids based on graphene oxide and palladium nanozymes for multimodal theranostics

Graphene oxide (GO)/palladium (Pd) nanocomposites have shown a great potential as multifunctional nanoparticles with plasmonic, photothermal and enzyme-like behavior for multimodal theranostics. In this work, different types of hybrid 2D GO/Pd nanosystems were synthesized, with the size of the 2D nanomaterials being controlled by the precursor concentrations as well as different chemical functionalities, including GO vs. reduced-thiolated GO (rGOSH), N-doped reduced GO (rGO-NX), mixed organic/inorganic matrix. 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. The GO/Pd hybrids were tested in terms of photocatalysis experiments of H2 evolution and photothermal response. The assessment of nanozyme features for the GO/Pd nanoplatforms unveiled a strong enhancement of hydrogen evolution and broad antioxidant activities, as scrutinized respectively by photocatalysis experiments and MitoSOX and SOD-like activity, respectively. The bio-interface response of systems was evaluated on both tumor cells and healthy cells. 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 MTT assay and wound scratch test confirmed the antitumor efficiency of all Pd-based samples in inhibiting tumor growth and monitoring cell migration, respectively. In particular, cells treated with GO-PdNP hybrids with larger sizes showed higher cell viability and migration rate in healthy cells (3T3 line). This makes them promising candidates as nanozyme-theranostic platforms for cancer treatment. The results pointed to a significant reduction of tumor growth and thus the promising potential of the developed GO/Pd 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).