A structural mass spectrometry strategy for the relative quantitation of ligands on mixed monolayer-protected gold nanoparticles.
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.
Department of Chemistry, Vanderbilt Institute of Chemical Biology, Vanderbilt Institute for Integrative Biosystems Research and Education, and Vanderbilt Institute of Nanoscale Science and Engineering, Vanderbilt University, 7330 Stevenson Center, Nashville, Tennessee 37235, United States.
Kellen M
KM
Harkness
Brian C
BC
Hixson
Larissa S
LS
Fenn
Brian N
BN
Turner
Amanda C
AC
Rape
Carrie A
CA
Simpson
Brian J
BJ
Huffman
Tracy C
TC
Okoli
John A
JA
McLean
David E
DE
Cliffel
D005978:Glutathione / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry / Q000379:methods*; D053768:Metal Nanoparticles / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013499:Surface Properties; D008625:Tiopronin / Q000737:chemistry
D008024:Ligands; D013438:Sulfhydryl Compounds; D011092:Polyethylene Glycols; D006046:Gold; D008625:Tiopronin; D005978:Glutathione