Sublimation as a method of matrix application for mass spectrometric imaging

Area of Science:

• Analytical Chemistry
• Biophysics
• Materials Science

Background:

• Matrix-assisted laser desorption/ionization (MALDI) is a key technique for mass spectrometric imaging.
• Traditional matrix application methods, such as electrospray, can lead to uneven crystal formation and analyte delocalization.
• A need exists for reproducible, solvent-free matrix application methods for MALDI imaging.

Purpose of the Study:

• To investigate the sublimation properties of common MALDI matrices.
• To develop and validate a solvent-free matrix application technique for MALDI mass spectrometric imaging.
• To compare the performance of sublimation-applied matrix with traditional methods.

Main Methods:

• Common MALDI matrices (2,5-dihydroxybenzoic acid, 3,5-dimethoxy-4-hydroxycinnamic acid, alpha-cyano-4-hydroxycinnamic acid) were subjected to sublimation under reduced pressure and elevated temperature.
• The sublimated matrix was deposited onto tissue samples and phospholipid standards.
• Mass spectrometric imaging was performed on mouse brain tissue and standards using a Q-q-TOF mass spectrometer.

Main Results:

• Selected MALDI matrices undergo sublimation without decomposition.
• Sublimation provides a controlled, reproducible, and even deposition of small matrix crystals.
• MALDI imaging of phospholipid standards and mouse brain tissue using sublimation-applied matrix resulted in more intense, even signals and higher image quality compared to electrospray deposition.
• The technique eliminates analyte spreading associated with solvent-based methods.

Conclusions:

• Solvent-free sublimation is a viable and effective method for applying MALDI matrices for mass spectrometric imaging.
• This technique enhances image quality through even microcrystalline matrix deposition and reduced analyte delocalization.
• The sublimation method is inexpensive, reproducible, and improves upon existing matrix application techniques.