Exploring the interactions between gold nanoparticles and analytes through surface-assisted laser desorption/ ionization mass spectrometry

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 - Hg⁺² 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-Hg²⁺-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 Hg²⁺ ions and H₂O₂. The limits of detection (LODs) for Hg²⁺ ions and H₂O₂ by SALDI-MS were 300nM and 250μM, 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.