Gold nanoparticles as assisted matrix for determining neutral small carbohydrates through laser desorption/ionization time-of-flight mass spectrometry

A method for the analysis of small neutral carbohydrates by surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) has been developed by using bare AuNPs as matrices. In comparison with citrate-capped and DDAB-capped AuNPs, bare AuNPs can capture the analytes on their surface; therefore, small neutral carbohydrates, which are difficult to ionize by matrix-assisted desorption/ionization mass spectrometry, could be cationized very efficiently by SALDI-MS with AuNPs as matrices. By using SALDI-MS in the positive ion mode, many molecular ions are obtained from monosaccharides and disaccharides. Without derivatization, the limits of detection at a S/N ratio of 3 are 82, 41, 144, and 151 nM for ribose, glucose, cellobiose, and maltose. In comparison with conventional organic matrixes (e.g., 2,5-dihydroxybenzoic acid), bare AuNPs as SALDI matrices offer many advantages, such as easy sample preparation, high ionization efficiency, and high shot-to-shot reproducibility. To validate the applicability of our method, a calibration curve is created from urine spiked with standard glucose (0.5-10 mM). We strongly believe that this approach can potentially be applied to diagnosis and glycomics.