Zheng Kaiyuan, Setyawati Magdiel I, Leong David Tai, Xie Jianping
Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, 117585, Singapore.
School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798, Singapore.
Bioact Mater. 2020 Oct 8;6(4):941-950. doi: 10.1016/j.bioactmat.2020.09.026. eCollection 2021 Apr.
The size of metal nanoparticles (NPs) is crucial in their biomedical applications. Although abundant studies on the size effects of metal NPs in the range of 2-100 nm have been conducted, the exploration of the ultrasmall metal nanoclusters (NCs) of ~1 nm in size with unique features is quite limited. We synthesize three different sized gold (Au) NCs of different Au atom numbers and two bigger sized Au NPs protected by the same ligand to study the size influence on antimicrobial efficacy. The ultrasmall Au NCs can easily traverse the cell wall pores to be internalized inside bacteria, inducing reactive oxygen species generation to oxidize bacterial membrane and disturb bacterial metabolism. This explains why the Au NCs are antimicrobial while the Au NPs are non-antimicrobial, suggesting the key role of size in antimicrobial ability. Moreover, in contrast to the widely known size-dependent antimicrobial properties, the Au NCs of different atom numbers demonstrate molecule-like instead of size-dependent antimicrobial behavior with comparable effectiveness, indicating the unique molecule-like feature of ultrasmall Au NCs. Overcoming the bacterial defenses at the wall with ultrasmall Au NCs changes what was previously believed to harmless to the bacteria instead to a highly potent agent against the bacteria.
金属纳米颗粒（NPs）的尺寸在其生物医学应用中至关重要。尽管已经对2-100纳米范围内金属纳米颗粒的尺寸效应进行了大量研究，但对尺寸约为1纳米、具有独特特性的超小金属纳米团簇（NCs）的探索却相当有限。我们合成了三种不同金（Au）原子数的不同尺寸的金纳米团簇以及两种由相同配体保护的较大尺寸的金纳米颗粒，以研究尺寸对抗菌效果的影响。超小金纳米团簇能够轻松穿过细胞壁孔隙进入细菌内部，诱导活性氧生成，从而氧化细菌膜并干扰细菌代谢。这解释了为什么金纳米团簇具有抗菌作用而金纳米颗粒没有，表明尺寸在抗菌能力中起关键作用。此外，与广为人知的尺寸依赖性抗菌特性不同，不同原子数的金纳米团簇表现出类似分子的抗菌行为而非尺寸依赖性抗菌行为，且效果相当，这表明超小金纳米团簇具有独特的类似分子的特性。用超小金纳米团簇克服细菌细胞壁防御，将之前认为对细菌无害的物质转变为对抗细菌的高效剂。
