HIGH RESOLUTION IMAGING PLATFORM INCORPORATING MALDI AND DESI

Importance of the Topic

Imaging mass spectrometry enables spatially resolved chemical analysis. High resolution and accuracy are crucial for identifying small molecules such as lipids and metabolites within complex tissues. The integration of MALDI and DESI on a single high-performance platform addresses challenges in compound identification and throughput.

Objectives and Study Overview

This study demonstrates a multi-reflecting QTof instrument achieving up to 200,000 FWHM resolution and <500 ppb mass accuracy at scan rates up to 10 Hz. It evaluates the performance of both MALDI and DESI imaging modes for detailed tissue analysis.

Methodology and Instrumentation

• Sample Preparation: Porcine liver and mouse brain sections (18 µm for DESI, 12 µm for MALDI); DHB matrix applied via HTX™ M5 sprayer for MALDI; no additional preparation for DESI.
• Instrument: SELECT SERIES™ MRT multi-reflecting QTof analyzer.
• MALDI Settings: Continuous raster imaging, adjustable laser focus (130–10 µm), dual attenuator system, positive ion mode, scan rates up to 10 Hz.
• DESI Settings: DESI XS source with heated transfer line (450 °C), 95:5 MeOH:H₂O solvent at 1.5 µL/min, negative ion mode.
• Data Processing: HDI™ 1.6 and MassLynx™ 4.2 for visualization and spectral analysis; Lipostar™ MSI with 0.8 ppm tolerance against the LIPID MAPS database.

Key Results and Discussion

• MALDI imaging at 10 Hz produced pixel sizes from 130 to 10 µm with minimal oversampling; optimized laser focus and attenuation ensured consistent ablation widths.
• Mass resolution exceeded 190,000 FWHM with <500 ppb accuracy at the smallest pixel size.
• DESI imaging at 5 and 10 scans/sec on mouse brain showed no loss of image quality, resolution, or accuracy; signal intensity scaled with scan speed due to continuous sampling.
• Database searching enabled tentative identification of phosphatidylcholine lipids with sub-200 ppb mass deviations.

Benefits and Practical Applications

• Combined MALDI and DESI on one platform enhances workflow efficiency and versatility.
• High spatial resolution and mass accuracy improve confidence in metabolite and lipid identification within complex tissues.
• Flexible scan speeds and pixel sizes support a wide range of throughput and resolution requirements in research and QA/QC.

Future Trends and Prospects

Emerging developments may include integration of additional ambient ionization sources, further increases in scan rates without compromising data quality, and advanced data analysis with machine learning for automated compound annotation and spatial mapping.

Conclusion

The SELECT SERIES™ MRT platform delivers high-resolution, high-accuracy imaging for both MALDI and DESI workflows. Optimized parameters enable detailed molecular mapping at scan speeds up to 10 Hz and pixel sizes down to 10 µm, supporting robust metabolomic and lipidomic investigations.

Reference

No specific references were provided in the source text.