A Structural Mass Spectrometry Strategy for the Relative Quantitation of Ligands on Mixed Monolayer-Protected Gold Nanoparticles

• Published in: Analytical chemistry (Washington) Vol. 82; no. 22; pp. 9268 - 9274
• Main Authors: Harkness, Kellen M, Hixson, Brian C, Fenn, Larissa S, Turner, Brian N, Rape, Amanda C, Simpson, Carrie A, Huffman, Brian J, Okoli, Tracy C, McLean, John A, Cliffel, David E
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15-11-2010
• Subjects: Analytical chemistry; Chemistry; Exact sciences and technology; Glutathione - chemistry; Gold; Gold - chemistry; Hydrophobic and Hydrophilic Interactions; Ions; Ligands; Magnetic Resonance Spectroscopy; Mass spectrometry; Mass Spectrometry - methods; Metal Nanoparticles - chemistry; Molecules; Nanoparticles; Polyethylene Glycols - chemistry; Spectrometric and optical methods; Sulfhydryl Compounds - chemistry; Surface Properties; Tiopronin - chemistry; Monolayer; Ethylene glycol; Gold; Ligand; Nanoparticle; Sample; NMR spectrometry; Mixture; Characterization; Signal; Ion mobility; Limitation; Mass spectrometry MS/MS; Ion spectrometry; Strategy; Mass spectrometry; Quantitative analysis; Glutathione
• ISSN: 0003-2700; 1520-6882
• 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.