Achieving Single-Cell Resolution via Desorption Electrospray Ionization Mass Spectrometry Imaging (DESI-MSI) on...

Area of Science:

• Analytical Chemistry
• Biotechnology
• Molecular Imaging

Background:

• Desorption electrospray ionization (DESI) is a key ambient mass spectrometry imaging (MSI) technique.
• Minimal sample preparation and preservation of native chemical states are advantages of DESI.
• Achieving single-cell resolution with DESI has been limited by ionization and ion transmission efficiencies.

Purpose of the Study:

• To develop and present four distinct implementations for achieving single-cell resolution using DESI MSI.
• To optimize experimental parameters and integrate modular hardware for enhanced DESI performance.
• To demonstrate the capability of DESI-based single-cell MSI for analyzing metabolites in heterogeneous cell populations.

Main Methods:

• Four distinct platforms were developed, integrating DESI XS sources with various mass spectrometers (Waters Synapt G2-Si, Thermo LTQ Orbitrap XL, Thermo Exploris 240, Thermo Orbitrap Fusion Lumos).
• Key parameters such as heating temperature, sprayer-to-surface distance, and solvent flow rate were optimized.
• Modular hardware integration, including motorized stages and ion-source interfaces, was employed.

Main Results:

• All four platforms successfully enabled MSI of metabolites in single cells from heterogeneous populations.
• Integration with Orbitrap systems enhanced mass resolution and spatial resolution.
• The combination of DESI XS and Exploris 240 achieved the smallest pixel size (2.7 μm × 10 μm) and detected the most molecular features.

Conclusions:

• A flexible and reproducible framework for adapting DESI across different platforms for high-resolution ambient MSI was established.
• Distinct chemical differences between neighboring cells under native conditions were revealed.
• The developed methods significantly advance the capability of DESI for single-cell chemical analysis.