High-Throughput Single Cell Proteomics Analysis with Nanodroplet Sample Processing, Multiplex TMT labeling, and Ultra-Sensitive LC-MS

Significance of the Topic

Analysis of proteins at the single cell level reveals cellular heterogeneity underlying development, disease progression, and therapeutic response. Mass spectrometry based proteomics offers an unbiased approach to quantify thousands of proteins in individual cells. However, challenges such as sample loss during preparation, low throughput, and limited sensitivity have hindered broad application of single cell proteomics in biomedical research.

Objectives and Study Overview

This study aimed to develop a high-throughput workflow combining nanodroplet sample processing, multiplexed isobaric labeling, and ultra-sensitive LC-MS to achieve comprehensive proteome coverage and accurate quantification in single mammalian cells. The authors benchmarked the platform across three cultured murine cell types (immune, epithelial, endothelial) to demonstrate its capacity for cell classification and quantitative robustness.

Methodology and Instrumentation

Single cells were isolated by fluorescence-activated cell sorting into nanowells on nanoPOTS chips. Each cell and a 5 ng carrier sample were denatured, reduced, alkylated, digested, and labeled in nanoliter volumes. Peptides were separated by nanoLC at 20 nL/min and analyzed using MS2 and SPS-MS3 methods with Real-Time Search on an Orbitrap Eclipse Tribrid mass spectrometer. Data were processed in Proteome Discoverer 2.4, focusing on protein identification, quantification reproducibility, and throughput.

Used Instrumentation

• nanoPOTS platform for nanodroplet processing
• Thermo Scientific UltiMate 3000 RSLCnano with 30 cm C18 column and integrated nanospray emitter
• Orbitrap Eclipse Tribrid mass spectrometer with Real-Time Search and SPS-MS3 capability
• Proteome Discoverer 2.4 software

Main Results and Discussion

The TMT10plex MS2 workflow identified up to 1 676 proteins and 8 234 peptides across 24 single cells, clearly distinguishing the three cell types by heat map and PCA. The SPS-MS3 approach with Real-Time Search analysis of 16 cells improved quantitative accuracy and differential protein coverage, yielding 2 346 proteins and 4 781 peptides. The optimized workflow achieved over 2 000 proteins quantified per batch of single cells with high reproducibility.

Benefits and Practical Applications

• Robust sample handling for sub-nanogram protein amounts with minimal losses
• High multiplexing throughput using TMT reagents for parallel analysis of up to 10 cells
• Improved quantification accuracy with SPS-MS3 and Real-Time Search
• Capability to classify cell types and detect rare subpopulations

Future Trends and Opportunities

The integration of nanodroplet platforms with advanced multiplexed labeling and intelligent MS acquisition is expected to expand to higher plexing, deeper coverage, and clinical specimens such as circulating tumor cells. Further enhancements in automation and data analysis for real-time decision making will drive applications in single cell diagnostics and drug discovery.

Conclusion

This study presents a high-throughput, ultra-sensitive single cell proteomics workflow that combines nanoPOTS processing, multiplex TMT labeling, and Orbitrap Eclipse analysis with Real-Time Search. The platform demonstrated robust protein coverage and quantitative accuracy across multiple cell types, paving the way for routine single cell proteome profiling in basic and translational research.

References

1. Zhu Y et al Angew Chem Int Ed 57 12370 2018
2. Budnik B et al Genome Biol 19 161 2018
3. Kelstrup CD et al J Proteome Res 18 1299 2019