Abstract
Noble metal-based nanomaterials have shown promise as potential enzyme mimetics, but the facet effect and underlying molecular mechanisms are largely unknown. Herein, with a combined experimental and theoretical approach, we unveil that palladium (Pd) nanocrystals exhibit facet-dependent oxidase and peroxidase-like activities that endow them with excellent antibacterial properties via generation of reactive oxygen species. The antibacterial efficiency of Pd nanocrystals against Gram-positive bacteria is consistent with the extent of their enzyme-like activity, that is {100}-faceted Pd cubes with higher activities kill bacteria more effectively than {111}-faceted Pd octahedrons. Surprisingly, a reverse trend of antibacterial activity is observed against Gram-negative bacteria, with Pd octahedrons displaying stronger penetration into bacterial membranes than Pd nanocubes, thereby exerting higher antibacterial activity than the latter. Our findings provide a deeper understanding of facet-dependent enzyme-like activities and might advance the development of noble metal-based nanomaterials with both enhanced and targeted antibacterial activities.
Highlights
Noble metal-based nanomaterials have shown promise as potential enzyme mimetics, but the facet effect and underlying molecular mechanisms are largely unknown
Transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) images of the samples indicate that the synthesized Pd nanocrystals displayed cubic and octahedral geometries with an average edge length of around 10 nm (Fig. 1a, b)
The HRTEM images, corresponding to Fast Fourier Transform (FFT) patterns taken from individual nanocrystals and X-ray diffraction patterns, confirmed that the Pd cubes and Pd octahedrons exhibited the expected {100} and {111} facets, respectively (Fig. 1c–f and Supplementary Fig. 1a)
Summary
Noble metal-based nanomaterials have shown promise as potential enzyme mimetics, but the facet effect and underlying molecular mechanisms are largely unknown. The emergence of new infectious diseases and the continuous increase in bacterial drug resistance present serious problems for the preservation of public health In this regard, engineered nanostructures have emerged as one of the most promising antibacterial agents due to their high surface-to-volume ratio and their exceptional—either intrinsic or chemically incorporated—antibacterial activity[4,5,6]. It is worth noticing that the surface morphology of NP has an important role in regulating their various catalytic activities[30,31,32] and the enzyme-mimetic activity of noble metal-based NPs could be controlled by tuning their exposed facets. It is highly anticipated that the antibacterial activities of noble metal-based NPs could be regulated by tuning their exposed facets
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