Development of Enantioselective Imaging Method for Chiral Molecules by on-Tissue Chiral Derivatization and Ion Mobility Mass Spectrometry

Bioactive molecules are mostly chiral, and their enantiomers often exhibit different biological properties, including pharmacological effects and toxicity. Recent biochemical studies have revealed that certain trace-level chiral metabolites are associated with specific pathological conditions, including chronic kidney disease and metabolic disorders. This finding highlights the importance of enantioselective imaging techniques that can help visualize the spatial distribution and dynamic behavior of individual enantiomers. Although enantioselective biochemical analyses, such as those based on chromatography or electrophoresis, have proven effective in separating enantiomers, progress in enantioselective imaging methods has been limited. Ion mobility spectrometry/mass spectrometry imaging (IMS/MSI) has emerged as a powerful tool with the potential to enable the enantioselective imaging of minor chiral metabolites. However, suitable chemical structures that can achieve both sufficient resolving power for the target enantiomer in IMS and high ionization efficiency in MSI remain unclear. This review highlights the development of enantioselective imaging methods based on on-tissue chiral derivatization and IMS/MSI. After exploring suitable chiral derivatization reagents, we designed a new charged chiral tag that enabled complete separation of a pair of enantiomers by IMS, sensitive detection of D,L-2-hydroxyglutaric acid by mass spectrometry, and the visualization of their distribution in the mouse testis by IMS/MSI. This approach can be further expanded to analyze other chiral molecules and has great potential for unveiling the enantioselective distribution and dynamics of minor chiral metabolites in biological tissues.