MALDI mass spectrometry imaging in microscope mode with infrared lasers: bypassing the diffraction limits

Anal Chem. 2014 Jan 7;86(1):321-5. doi: 10.1021/ac403421v. Epub 2013 Dec 10.

Abstract

This letter demonstrates the use of infrared matrix-assisted laser desorption/ionization coupled with microscope mode mass spectrometry imaging. It is aimed to explore the use of intrinsic water in tissue as a matrix for imaging at spatial resolutions below the diffraction limit of the employed IR optics. Stigmatic ion optics with a magnification factor of ~70 were used to project the spatial distribution of produced ions onto a detector while separating ions with different mass-to-charge ratios using a time-of-flight mass spectrometer. A pixelated detector was used to simultaneously record arrival time and impact position. A previously described dried-droplet sample system of 2,5-dihydroxybenzoic acid (DHB) and 5 peptides covered by a copper grid for defined surface structure was used to benchmark the light- and ion-optical setup for spatial resolution and mass spectrometric performance. A spatial resolving power of 9.8 μm, well below the optical limit of diffraction (14 μm for the given setup), was established. After, frozen cryo-sections from a biological model system were measured by exploiting the endogenous water content as a matrix. Principal component analysis enabled a clear distinction between distinct tissue regions identified by both light microscopy and MS imaging.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Infrared Rays*
  • Lasers* / statistics & numerical data
  • Liver / chemistry
  • Liver / cytology
  • Osmeriformes
  • Random Allocation
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / methods*