Exploring the Interactions between Gold Nanoparticles and Analytes through Surface-Assisted Laser Desorption/Ionization Mass Spectrometry.

[[abstract]]Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) is applied to provide strong evidence for the chemical reactions of functionalized gold nanoparticles (Au NPs) with analytes – Hg2R ions induced MPA Au NPs aggregation in the presence of 2,6-pyridinedicarboxylic acid (PDCA) and H2O2 induced fluorescence quenching of 11-MUA Au NDs. PDCA-Hg2R-MPA coordination is responsible for Au NPs aggregation, while the formation of 11-MUA disulfide compounds that release into the bulk solution is responsible for H2O2-induced fluorescence quenching. In addition to providing information about the chemical structures, SALDI-MS is also selective and sensitive for the detection of Hg2R ions and H2O2. The limits of detection (LODs) for Hg2R ions and H2O2 by SALDI-MS were 300nM and 250mM, respectively. The spot-to-spot variations in the two studies were both less than 18% (50 sample spots). Our results reveal that SALDI-MS can be used to study analyte-induced changes in the surface properties of nanoparticles