A structural mass spectrometry strategy for the relative quantitation of ligands on mixed monolayer-protected gold nanoparticles.

Harkness KM, Hixson BC, Fenn LS, Turner BN, Rape AC, Simpson CA, Huffman BJ, Okoli TC, McLean JA, Cliffel DE
Anal Chem. 2010 82 (22): 9268-74

PMID: 20968282 · PMCID: PMC2980554 · DOI:10.1021/ac102175z

It is becoming increasingly common to use gold nanoparticles (AuNPs) protected by a heterogeneous mixture of thiolate ligands, but many ligand mixtures on AuNPs cannot be properly characterized due to the inherent limitations of commonly used spectroscopic techniques. Using ion mobility-mass spectrometry (IM-MS), we have developed a strategy that allows measurement of the relative quantity of ligands on AuNP surfaces. This strategy is used for the characterization of three samples of mixed-ligand AuNPs: tiopronin:glutathione (av diameter 2.5 nm), octanethiol:decanethiol (av diameter 3.6 nm), and tiopronin:11-mercaptoundecyl(poly ethylene glycol) (av diameter 2.5 nm). For validation purposes, the results obtained for tiopronin:glutathione AuNPs were compared to parallel measurements using nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS) without ion mobility separation. Relative quantitation measurements for NMR and IM-MS were in excellent agreement, with an average difference of less than 1% relative abundance. IM-MS and MS without ion mobility separation were not comparable, due to a lack of ion signals for MS. The other two mixed-ligand AuNPs provide examples of measurements that cannot be performed using NMR spectroscopy.

MeSH Terms (11)

Glutathione Gold Hydrophobic and Hydrophilic Interactions Ligands Magnetic Resonance Spectroscopy Mass Spectrometry Metal Nanoparticles Polyethylene Glycols Sulfhydryl Compounds Surface Properties Tiopronin

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