In situ analysis of single cell and biological samples with rGO-Cu functional probe ESI-MS spectrometry.

At present, probe electrospray ionization mass spectrometry is widely used in the single cell analysis. As the continuous expansion of requirements for detecting more metabolite species from single cells, the sensitivity and accuracy of the instrument and the enrichment capacity of the probes are in high demand. Therefore, a high efficiency functional probe electrospray ionization mass spectrometry (FPESI–MS) analysis platform is established. In this platform, nitrogen aggregation/gas heating system and reduced graphene oxide functional copper probe (rGO-Cu probe) are firstly reported. The nitrogen aggregation/gas heating system can promote desorption of the analytes from probe and aggregate the product ions into the ion cluster to increase the ion transport capacity and the detection efficiency. rGO-Cu probe formed huge specific surface area to enrich the analytes without sacrificing the electrical conductivity. The probe substrates were prepared by electrochemical etching, after rGO-functionalization, the tip diameter of all kinds of the probes were measured to be less than 100 nm, which is much smaller than the PC12 single cells. Graphene oxide cannot be completely reduced by electrochemical methods, thus the rGO-Cu probe can enrich the analytes through the huge surface area of the graphene thin layer, as well as the hydrogen bond and the electrostatic absorption of the surface oxygen-containing groups. Seven AD related neurotransmitters and sixteen biomarkers in PC12 single cells and twelve metabolites in serum of AD rats were successfully analyzed by using FPESI–MS, and this method is expected to be used in the rapid detection of metabolites in biological samples and living organism.