Lipidomic Analysis of Mouse Brain to Evaluate the Efficacy and Preservation of Different Tissue Preparatory Techniques by IR-MALDESI-MSI

Numerous preparatory methods have been developed to preserve the cellular and structural integrity of various biological tissues for different -omics studies. Herein, two preparatory methods for mass spectrometry imaging (MSI) were evaluated, fresh-frozen and sucrose-embedded, paraformaldehyde (PFA) fixed, in terms of ion abundance, putative lipid identifications, and preservation of analyte spatial distributions. Infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI)-MSI was utilized to compare the preparatory methods of interest with and without the use of the conventional ice matrix. There were 2.5-fold and 1.6-fold more lipid species putatively identified in positive- and negative-ion modes, respectively, for sucrose-embedded, PFA-fixed tissues without an ice matrix relative to the current IR-MALDESI-MSI gold-standard, fresh-frozen tissue preparation with an exogenous ice matrix. Furthermore, sucrose-embedded tissues demonstrated improved spatial distribution of ions resulting from the cryo-protective property of sucrose and paraformaldehyde fixation. Evidence from these investigations supports sucrose-embedding without ice matrix as an alternative preparatory technique for IR-MALDESI-MSI.

Automated summary

Two preparatory methods for mass spectrometry imaging (MSI), fresh-frozen and sucrose-embedded, paraformaldehyde (PFA) fixed, were evaluated in terms of ion abundance, putative lipid identifications, and preservation of analyte spatial distributions. Sucrose-embedded, PFA-fixed tissues without an ice matrix showed significantly higher numbers of putatively identified lipid species in positive and negative ion modes compared to the traditional gold-standard fresh-frozen tissue preparation with an exogenous ice matrix. Sucrose-embedded tissues also demonstrated improved spatial distribution of ions. These findings support sucrose-embedding without ice matrix as an alternative preparatory technique for IR-MALDESI-MSI.