Solvated electron-induced synthesis of cyclodextrin-coated Pd nanoparticles: mechanistic, catalytic, and anticancer studies

Herein, using in situ generated solvated electrons in the reaction media, a highly time-efficient, one-pot green approach has been employed to synthesize palladium (Pd) nanoparticles (NPs) coated with a molecular assembly of alpha-cyclodextrin (alpha-CD). The appearance of a shoulder peak at 280 nm in the UV-Vis absorption spectra indicated the formation of Pd NPs, which was further confirmed from their cubic phase XRD pattern. The nanomorphology varied considerably as a function of the dose rate, wherein sphere-shaped NPs (average size similar to 7.6 nm) were formed in the case of high dose rate electron-beam assisted synthesis, while nanoflakes self-assembled to form nanoflower-shaped morphologies in a gamma-ray mediated approach involving a low dose rate. The formation kinetics of NPs was investigated by pulse radiolysis which revealed the formation of Pd-based transients by the solvated electron-induced reaction. Importantly, no interference of alpha-CD was observed in the kinetics of the transient species, rather it played the role of a morphology directing agent in addition to a biocompatible stabilizing agent. The catalytic studies revealed that the morphology of the NPs has a significant effect on the reduction efficiency of 4-nitrophenol to 4-aminophenol. Another important highlight of this work is the demonstration of the morphology-dependent anticancer efficacy of Pd NPs against lung and brain cancer cells. Notably, flower-shaped Pd NPs exhibited significantly higher cancer cell killing as compared to spherical NPs, while being less toxic towards normal lung fibroblasts. Nonetheless, these findings show the promising potential of Pd NPs in anticancer treatment.

Automated summary

In this study, a one-pot green approach utilizing solvated electrons was used to synthesize palladium nanoparticles coated with alpha-cyclodextrin. The formation of Pd NPs was confirmed by UV-Vis absorption spectra and cubic phase XRD pattern. The morphology of the nanoparticles varied depending on the dose rate, with sphere-shaped NPs formed at high dose rate and nanoflake self-assembled nanoflower-shaped NPs formed at low dose rate. Pulse radiolysis revealed the formation of Pd-based transients induced by solvated electrons. Furthermore, the morphology of the NPs affected their catalytic efficiency in reducing 4-nitrophenol to 4-aminophenol and their anticancer efficacy against lung and brain cancer cells. Flower-shaped Pd NPs exhibited higher cancer cell killing while being less toxic to normal lung fibroblasts. These findings highlight the potential of Pd NPs in anticancer treatment.