期刊
ACS APPLIED NANO MATERIALS
卷 1, 期 4, 页码 1595-1602出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsanm.8b00069
关键词
silver clusters; lipoic acid; antibiotic; analytical ultracentrifugation; electrospray ionization mass spectrometry; Ag-29
资金
- Welch Foundation [AX-1615, AX -1857]
- Margaret Batts Tobin Foundation, San Antonio, TX
- NSF [ACI-1339649, TG-MCB070039]
- NIH [R01GM120600]
- GENCI-IDRIS [2017-096829]
- DGAPA-UNAM [IN108817]
- Conacyt-Mexico [285821]
Here we report on the identification and applications of an aqueous 29-atom silver cluster stabilized with 12 lipoate ligands, i.e. Ag-29(R-alpha LA)12 or (29,12), wherein R-alpha LA = R-alpha-lipoic acid, a natural dithiolate. Its uniformity is checked by HPLC-ESI-MS and analytical ultracentrifugation, which confirms its small dimension (similar to 3 nm hydrodynamic diameter). For the first time, this cluster has been detected intact via electrospray ionization mass spectrometry, allowing one to confirm its composition, its [3-] charge-state, and the 8-electron shell configuration of its metallic silver core. Its electronic structure and bonding, including T-symmetry and profound chirality in the outer shell, have been analyzed by DFT quantum-chemical calculations, starting from the known structure of a nonaqueous homologue. The cluster is effective against Methicillin-Resistant Staphylococcus aureus bacteria (MRSA) at a minimum inhibitory concentration (MIC) of 0.6 mg-Ag/mL. A preformed Candida albicans fungal biofilm, impermeable to other antifungal agents, was also inhibited by aqueous solutions of this cluster, in a dose response manner, with a half-maximal inhibitory concentration (IC50) of 0.94 mg-Ag/mL. Scanning electron micrographs showed the post-treatment ultrastructural changes on both MRSA and C. albicans that are characteristic of those displayed after treatment by larger silver nanoparticles.
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