Au nanoparticles/ZnO nanorods as SALDI-MS substrate for on-plate enrichment and detection of glutathione in real samples

Abstract

• A SALDI-MS substrate was fabricated for on-plate selectively capturing, isolating and detecting thiols in complex samples. • The above capacities of the substrate were confirmed by detecting thiols in a mixed sample. • Glutathione in real samples was successfully detected with this substrate. As an important bio-thiol molecule, glutathione (GSH) plays key roles in various cellular activities. However, it is still a challenge to analyze GSH in complex samples because of severe signal suppression from high abundance of interferent. The most efficient approach to tackle this problem is to enrich target analytes on-plate from the complex samples by selectively capturing and isolating. Herein, the hierarchical substrates were synthesized for selective detection of GSH in real samples using surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). The structures are formed by homogeneously distributing Au nanoparticles (Au NPs) on ZnO nanorods (ZnO NRs). The Au NPs can selectively capture thiols through Au–S binding; ZnO NRs can not only efficiently absorb ultraviolet laser, but also isolate Au NPs–target compounds from complex samples as a carrier of Au NPs. Meanwhile, the Au–ZnO hybrid nanostructures can promote the hot electrons transfer at Au–ZnO interface and lead to higher desorption/ionization efficiency. The on-plate selective enrichment performance of the Au NPs/ZnO NRs as SALDI-MS substrates was demonstrated by successfully detecting GSH and l -Cysteine ( l -Cys) without interference peak in a mixed amino acids sample. The results in detecting GSH displayed high repeatability with relative standard deviation (RSD) of 4.91 % for substrate-to-substrate, good linearity (R 2 > 0.99), and high sensitivity with limit of detection (LOD) of 150 amol. Furthermore, the Au NPs/ZnO NRs substrate is applicable for analyzing practical samples, such as GSH in medicine and fruits, which demonstrates its potential in practical applications.