Speaker: Bindesh Shrestha, Waters

Topic: Biomedical Applications of MALDI and DESI Imaging using High-Resolution Ion Mobility Mass Spectrometry

Date: Monday, June 21th, 2021

Time: 1:00 PM EDT Presentation

Location: Webinar – see emails on June 10 and 17 for invite link. Join the mailing list

Abstract: In the last decade, both matrix-assisted laser desorption/ionization (MALDI) and desorption electrospray ionization (DESI) imaging mass spectrometry (MS) have been developed to spatially map small molecules, such as metabolites, lipids and drugs, on tissue. DESI often detects a complementary set of molecules to MALDI due to preferential ionization of those species in electrospray. In this presentation, biomedical applications using both imaging modalities, MALDI and DESI, will be shown. Multimodal imaging using both techniques widens the molecular coverage of many small molecules, such as drugs – with some analyte preferentially ionizing more robustly with one ionization technique versus another. Analysis of ions detected by DESI and MALDI on consecutive sections using similar solvent composition eluded to the complementary coverage of the two mechanistically different ionization sources. In addition to showing the benefits of multimodal imaging MS strategy, the advantages of integrating ion mobility separations during the imaging MS process will also be discussed. Ion mobility separation can isolate ions based on their collision cross-section. For example, imaging a specific lipid molecule on tissue is often challenging because of the large structural diversity of similar lipids present in the sample. Multipass ultrahigh-resolution ion mobility separation can improve the specificity of lipid imaging by DESI, allowing us to image isobaric ions separately. All imaging MS experiments were performed on quadrupole time of flight mass spectrometers, such as SYNAPT XS and Cyclic IMS, with traveling wave ion mobility separation and using High Definition Imaging (HDI) software.