Fundamental Study and Method Development for Surface-based Laser Desorption Ionization Imaging Mass Spectrometry

Abstract

By providing both the chemical identity and the spatial organization of each component in biological samples, Imaging Mass Spectrometry (IMS) becomes an emerging tool in clinic and pharmacological study. Most work in IMS has been focused on protein and peptide mapping in biological samples to take advantage of effective analyte ionization in MALDI-MS, and also partially due to the limitation of MALDI-MS in small molecule detection. The focus of my research is to develop novel tools to image spatial distribution of small molecules in biological samples. A surface-based mass spectrometric imaging method, i.e. Desorption/Ionization on Silicon (DIOS), was used for biological surface analysis in the concept-proof investigation. More over, possible proton transferring pathways and impact of local chemical environment have been systematically investigated in the fundamental understanding of ionization mechanism of SALDI-MS. Based on the finding on the SALDI mechanism, a hybrid ionization approach, ME-SALDI has been developed by combing the strength of the conventional MALDI matrix and SALDI, where the improved detection sensitivity with reduced matrix-analyte interference and the improved imaging capability through analysis of mouse brain and heart sections has been demonstrated. In addition, the impact of vacuum stability of matrix in ME-SALDI-IMS applications has been examined. A solvent free, homogenous and reproducible sublimation method has been developed for ionic matrix in ME-SALDI, by which improved vacuum stability and MS detection have been achieved. Furthermore, a new generation of meso-porous oxide substrate was developed as a novel ME-SALDI substrate with a superior storage stability, extended detectable mass range and robust substrate preparation.