Insights into the MALDI Process after Matrix Deposition by Sublimation Using 3D ToF-SIMS Imaging

Area of Science:

• Biochemistry
• Analytical Chemistry
• Biophysics

Background:

• Matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS) is crucial for mapping biomolecules in tissues.
• Homogeneous matrix deposition is vital for high-quality MALDI-IMS data, with sublimation being effective for lipid imaging.

Purpose of the Study:

• To investigate the MALDI process for lipids using sublimation matrix deposition.
• To understand lipid migration dynamics at the tissue-matrix interface in 3D.

Main Methods:

• 3D time-of-flight secondary ion imaging mass spectrometry (3D TOF-SIIM) was employed to analyze the matrix-tissue interface.
• Experiments varied matrix thickness and analyzed lipid migration over time.

Main Results:

• Lipids migrate from the tissue into the sublimated matrix layer via diffusion.
• Triacylglycerols and phospholipids exhibit slower migration than diacylglycerols and monoacylglycerols, influenced by time and matrix thickness.
• Lipid migration into the matrix depends on the lipid's fluidity; cholesterol migration requires fluid lipids and appears to enhance lipid fluidity.

Conclusions:

• Lipid diffusion into the matrix is a key mechanism in sublimation-based MALDI-IMS.
• Lipid properties like fluidity and interactions with other lipids (e.g., cholesterol) significantly impact their spatial distribution in MALDI-IMS.
• This understanding aids in optimizing MALDI-IMS protocols for lipid analysis.