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

Abstract

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. The increase in MS sensitivity was positively correlated with the number of repeated cycles. When ions were repeatedly accumulated for 25 cycles, the sensitivity of adenosine triphosphate detection was increased by 22-fold within 1.8 s. Our technique could stably detect low-abundance ions, especially MS ions, at the single-cell level, such as 5-methylcytosine hydrolyzed from sample equivalent to ∼0.2 MCF7 cell. The strategy presented in this study offers the possibility to aid single-cell analysis by enhancing MS detection sensitivity.

Towards Higher Sensitivity of Mass Spectrometry: A Perspective From the Mass Analyzers

“…Chem. 89, 2,275-2,281 (Si, et al, 2017). Copyright 2017 American Chemical Society; (B) The dual TIMS and Q-TOF tandem mass spectrometer.…”

“…A technique for repeated ion accumulation in the ion trap MS was developed to improve sensitivity (Si et al, 2017). The injected precursor ions were isolated and stored in the highpressure ion trap before CID (Figure 3A).…”

Electric modeling and characterization of pulsed high‐voltage nanoelectrospray ionization sources by a miniature ion trap mass spectrometer

“…Nano‐ESI can generate much smaller droplets and thus has a significant improved ionization efficiency, which is attributed to the reduced flow rate and smaller emitter in diameter (id 1 to approximately 10 μm) . Nano‐ESI is an economic ion source in terms of sample consumption, which is important for the comprehensive analysis of valuable and rare samples . On the other side, no nebulization gas is required in nano‐ESI, which simplifies the structure and operation of the ion source.…”

“…22,23 Nano-ESI is an economic ion source in terms of sample consumption, which is important for the comprehensive analysis of valuable and rare samples. 24,25 On the other side, no nebulization gas is required in nano-ESI, which simplifies the structure and operation of the ion source. In addition, nano-ESI also exhibits high tolerance of the suppression effects caused by salts and matrixes in complex samples.…”

Beyond the bulk: disclosing the life of single microbial cells

“…Low-abundant molecules could be concentrated with repeated ion accumulation in ion trap mass spectrometers to overcome this challenge (Si et al. 2017 ). This method was successfully validated for concentrating ATP up to 22-fold.…”