Enhancing metabolite coverage in MALDI-MSI using laser post-ionisation (MALDI-2)

Area of Science:

• Metabolomics
• Mass Spectrometry Imaging
• Biochemistry

Background:

• Matrix-assisted laser desorption/ionisation mass spectrometry imaging (MALDI-MSI) is crucial for understanding metabolic alterations in heterogeneous tissues.
• Conventional MALDI-MSI has limitations in metabolite coverage and sensitivity, particularly for low molecular weight (LMW) metabolites.

Purpose of the Study:

• To investigate the benefits of coupling laser post-ionisation (MALDI-2) with MALDI-MSI for spatial metabolomics.
• To assess the improvements in metabolite coverage and detection sensitivity for LMW metabolites (< 600 m/z).

Main Methods:

• Application of negative ion mode MALDI-2 coupled with MALDI-MSI to mouse kidney and liver tissues.
• Comparison of MALDI-2 performance against conventional MALDI-MSI using specific matrices (e.g., N-(1-naphthyl) ethylenediamine dihydrochloride).
• Analysis of datasets using the METASPACE platform and co-localisation analysis for tumour-specific metabolites.

Main Results:

• MALDI-2 nearly doubled the number of on-tissue specific mass features in mouse kidney tissue compared to conventional MALDI.
• MALDI-2 enhanced detection sensitivity and enabled imaging of LMW metabolites (e.g., uridine) previously undetectable.
• MALDI-2 identified 34 unique metabolite m/z features in kidney tissue not consistently annotated in public datasets.
• In liver tissue with metastatic breast cancer, MALDI-2 detected six tumour-specific metabolites and increased signal intensities up to 20-fold for others (e.g., glutamate).

Conclusions:

• MALDI-2 offers significant improvements in sensitivity and metabolite coverage for spatial metabolomics.
• This technique provides unprecedented insights into metabolic heterogeneity in complex biological samples.
• MALDI-2 represents a powerful advancement for metabolite imaging in research and diagnostics.