MALDI matrix sublimation versus spray coating in the FluoMALDI imaging pipeline

Area of Science:

• Mass spectrometry imaging
• Fluorescence microscopy
• Biomolecular analysis

Background:

• The FluoMALDI pipeline integrates slide-scanning fluorescence microscopy (SSFM) with matrix-assisted laser desorption/ionization (MALDI) imaging.
• This integration targets autofluorescent tissue structures for enhanced analysis.

Purpose of the Study:

• To systematically compare sublimation and spray coating matrix deposition methods within the FluoMALDI pipeline.
• To evaluate the impact of different MALDI matrices on tissue autofluorescence enhancement.
• To assess lipid detection efficiency and spatial distribution across MALDI ionization modes.

Main Methods:

• Comparison of sublimation and spray coating for six MALDI matrices (9-aminoacridine, norharmane, α-cyano-4-hydroxycinnamic acid, 2,5-dihydroxyacetophenone, 2,5-dihydroxybenzoic acid, sinapinic acid) on mouse brain, liver, and kidney tissues.
• Evaluation of autofluorescence enhancement in green, red, and far-red channels.
• Assessment of lipid detection efficiency (phosphatidylethanolamine, phosphatidylcholine) using MALDI-1 and MALDI-2 ionization modes.

Main Results:

• Norharmane matrix demonstrated consistent autofluorescence enhancement across deposition methods, with optimal channel-specific performance.
• Matrix crystal size did not significantly affect fluorescence enhancement.
• Sublimation generally yielded higher phospholipid detection efficiency than spray coating, particularly for PE(36:2) and PC(36:2).
• Lipid spatial distributions were consistent, but detection efficiency varied by matrix, tissue, and ionization mode.

Conclusions:

• Matrix selection and deposition method critically influence tissue autofluorescence, spatial resolution, and lipid detection in FluoMALDI imaging.
• Findings provide guidance for optimizing matrix deposition strategies based on specific research objectives in MALDI imaging.