Ambient Molecular Imaging and Depth Profiling of Live Tissue by Infrared Laser Ablation Electrospray Ionization Mass Spectrometry

• Published in: Analytical chemistry (Washington) Vol. 80; no. 12; pp. 4575 - 4582
• Main Authors: Nemes, Peter, Barton, Alexis A, Li, Yue, Vertes, Akos
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.06.2008
• Subjects: Acanthaceae - chemistry; Acanthaceae - metabolism; Acanthaceae - ultrastructure; Analytical chemistry; Aphelandra; Biochemistry; Chemistry; Exact sciences and technology; Ions; Lasers; Mass spectrometry; Microscopy, Electron, Scanning; Molecules; Plant Leaves - chemistry; Plant Leaves - metabolism; Plant Leaves - ultrastructure; Spectrometric and optical methods; Spectrometry, Mass, Electrospray Ionization - methods; Spectrophotometry, Infrared - methods; Scanning electron microscopy; Metabolomics; Atmospheric pressure; Metabolite; Electrospray; Chemical ionization; Biological compound; In vivo; Tissue; Sensitivity; Depth resolution; Imaging; Depth profile; Water content; Database; Feasibility; Laser ablation technique; Mass spectrometry
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac8004082

Mass spectrometry in conjunction with atmospheric pressure ionization methods enables the in vivo investigation of biochemical changes with high specificity and sensitivity. Laser ablation electrospray ionization (LAESI) is a recently introduced ambient ionization method suited for the analysis of biological samples with sufficient water content. With LAESI mass spectrometric analysis of chimeric Aphelandra squarrosa leaf tissue, we identify the metabolites characteristic for the green and yellow sectors of variegation. Significant parts of the related biosynthetic pathways (e.g., kaempferol biosynthesis) are ascertained from the detected metabolites and metabolomic databases. Scanning electron microscopy of the ablated areas indicates the feasibility of both two-dimensional imaging and depth profiling with a ∼350 µm lateral and ∼50 µm depth resolution. Molecular distributions of some endogenous metabolites show chemical contrast between the sectors of variegation and quantitative changes as the ablation reaches the epidermal and mesophyll layers. Our results demonstrate that LAESI mass spectrometry opens a new way for ambient molecular imaging and depth profiling of metabolites in biological tissues and live organisms.