Gold-Nanoparticle-Supported Silicon Plate with Polymer Micelles for Surface-Assisted Laser Desorption/Ionization Mass Spectrometry of Peptides

We developed surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) using nanocomposite films of cationic diblock copolymer micelles [poly(styrene-b-N-methyl-4-vinyl pyridinium iodide)] and ammonium citrated Au nanoparticles (AuNPs) on silicon. The nanocomposite film on silicon was suitable for use as a material for matrix-free LDI-MS of peptides due to its low matrix background from Au clusters and high ionization efficiency; this plate successfully ionized angiotensin I, and also insulin in the proton adduct forms, in contrast to methods using only AuNPs and those using nanocomposite films of cationic polymer in conjunction with Au NPs. The high ionization efficiency is discussed from the viewpoint of nanoparticle distribution controlled by polymers on the plate (aggregates vs. nonaggregates).