Development of Pico-ESI-MS for Single-Cell Metabolomics Analysis.

In this chapter, we introduced a Pico-ESI strategy for metabolomics analysis with picoliter-level samples. This Pico-ESI strategy was technically achieved by pulsed direct current electrospray ionization source (Pulsed-DC-ESI). This source could collect MS signals for a few minutes from a cell, enabling us to obtain large-scale MS data of metabolite IDs in single-cell analysis.

Detecting Low-Abundance Molecules at Single-Cell Level by Repeated Ion Accumulation in Ion Trap Mass Spectrometer.

Low-abundance metabolites or proteins in single-cell samples are usually undetectable by mass spectrometry (MS) due to the limited amount of substances in single cells. This limitation inspired us to further enhance the sensitivity of commercial mass spectrometers. Herein, we developed a technique named repeated ion accumulation by ion trap MS, which is capable of enhancing the sensitivity by selectively and repeatedly accumulating ions in a linear ion trap for up to 25 cycles.

Integrated Droplet-Based Microextraction with ESI-MS for Removal of Matrix Interference in Single-Cell Analysis.

Integrating droplet-based microfluidics with mass spectrometry is essential to high-throughput and multiple analysis of single cells. Nevertheless, matrix effects such as the interference of culture medium and intracellular components influence the sensitivity and the accuracy of results in single-cell analysis. To resolve this problem, we developed a method that integrated droplet-based microextraction with single-cell mass spectrometry.

Pulsed Direct Current Electrospray: Enabling Systematic Analysis of Small Volume Sample by Boosting Sample Economy.

We had developed pulsed direct current electrospray ionization mass spectrometry (pulsed-dc-ESI-MS) for systematically profiling and determining components in small volume sample. Pulsed-dc-ESI utilized constant high voltage to induce the generation of single polarity pulsed electrospray remotely. This method had significantly boosted the sample economy, so as to obtain several minutes MS signal duration from merely picoliter volume sample.

DNA methylation as a potential diagnosis indicator for rapid discrimination of rare cancer cells and normal cells.

The global DNA methylation degree may be a ubiquitous and early biomarker to distinguish cancer cells from benign cells. However, its usefulness in clinical diagnosis was scarcely demonstrated, because the cancer cells isolated from patients were usually very rare. Even if 10 mL of peripheral blood was sampled from a patient, only tens of cancer cells could be isolated.

Coupling a solid phase microextraction (SPME) probe with ambient MS for rapid enrichment and detection of phosphopeptides in biological samples.

In this study, we developed a probe-electrospray ionization method by coupling a SPME probe modified with nanosized TiO2 directly to nanoESI-MS for the phosphoproteome analysis, which demonstrated excellent selectivity and sensitivity for enrichment of phosphopeptides in complex biological samples.