Extraction and Upconcentration of Adsorbates from Precisely Defined Area for Quantitative MALDI Mass Spectrometry Imaging

Mass spectrometry imaging (MSI) allows label-free detection of a wide range of biomolecules and simultaneously provides their spatial distributions. In particular, MSI by matrix-assisted laser desorption/ionization mass spectrometry (MALDI) has been widely used in biomolecule analysis. However, quantitation in MALDI-MSI is limited by matrix-deposition heterogeneity, analyte extraction area, and analyte-matrix cocrystallization. In this chapter, a microstructured PDMS stamp is utilized to precisely control the matrix deposition area and the analyte extraction area. We describe here simple steps-including stamp fabrication, matrix application, and data-acquisition guideline-for the quantitative analysis of adsorbed peptides on hydrophobic surfaces.