Open AccessTetrahedral (T) Closed-Shell Cluster of 29 Silver Atoms & 12 Lipoate Ligands, [Ag29(R-α-LA)12](3−): Antibacterial and Antifungal Activity
Author(s) -
Priscilla Lopez,
Humberto H Lara,
Sean Mullins,
David M. Black,
Heidi M. Ramsower,
Marcos M. Alvarez,
Tayler L. Williams,
Xóchitl López-Lozano,
HansChristian Weissker,
Adrián Muñoz García,
Ignacio L. Garzón,
Borries Demeler,
José L. López-Ribot,
Miguel Yacaman,
Robert L. Whetten
Publication year - 2018
Publication title -
acs applied nano materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.227
H-Index - 29
ISSN - 2574-0970
DOI - 10.1021/acsanm.8b00069
Subject(s) - chemistry , electrospray ionization , aqueous solution , minimum inhibitory concentration , crystallography , cluster (spacecraft) , mass spectrometry , osmium , fast atom bombardment , nuclear chemistry , stereochemistry , antimicrobial , chromatography , organic chemistry , computer science , ruthenium , programming language , catalysis
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-α-LA) 12 or (29,12), wherein R-α-LA = R-α-lipoic acid, a natural dithiolate. Its uniformity is checked by HPLC-ESI-MS and analytical ultracentrifugation, which confirms its small dimension (~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 (IC 50 ) 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.