This Application Note is based on data and analyses previously presented by Dr. Shannon Cornett and Dr. Jeremy Wolff, Bruker Daltonics.

Application & Background

MALDI imaging provides a wide molecular window into the makeup of biological tissue samples. The HTX SepQuant® dropletProbe, using Liquid Extraction Surface Analysis (LESA) technology, delivers a spatial component to the traditional 'omics' LC-MS strategies for large-scale compound analysis and identification. Bruker and HTX Technologies have combined the two techniques to create a solution for revealing greater information about chemical and biochemical processes within a sample.

CHALLENGE

MALDI imaging harnesses the reliability and reproducibility of MALDI to map the distribution of a wide variety of compound classes in thin samples without molecular labels. No other technology can map a wider range of compounds at high spatial resolution, but identifying the many hundreds of mapped species remains challenging. Tissue extraction coupled with ESI-based platforms can be used to identify thousands of compounds endogenous to the sample, but because spatial compartmentalization is lost during extraction, there is a degree of uncertainty when assigning a molecular identity to an ion image. What is needed is an extraction strategy that is able to link spatial information to the identified compounds so that ion images can be identified more confidently using both m/z and localization.

SOLUTION

The combination of MALDI imaging and SepQuant® dropletProbe's LESA technology creates a number of advantages for increasing the molecular information one can extract from serial sections of biological tissue as illustrated below. Bruker’s MALDI imaging system uses SCiLS Lab Core software as the standard tool for automatic segmentation and identifying co-localized molecular distributions from one section. SCiLS Lab Pro provides a complete suite of visualization and statistical tools for mining spatially significant molecular differences. Ions exhibiting significant distribution differences can be visualized in SCiLS Lab as a panel of images. The SepQuant® dropletProbe software applies a virtual grid of ~800um over the companion section and extracts analyte from each cell. The extracted solution is infused directly or injected onto a column and SepQuant® dropletProbeTM triggers the start of the online analysis. Data collected from the extracted spots is loaded into SCiLS lab and overlaid with the ion images.

Figure 1.  Orthologous mass spectrometry imaging techniques using MALDI imaging (A - D) and the SepQuant®  droplet Probe (A, E - G). A. Serial sections of tissue; B. HTX TM-Sprayer for MALDI matrix deposition; C. Bruker rapifleX MALDI mass spectrometer; D. SCiLS Lab MALDI images; E. Liquid microjunction extraction by the SepQuant®  droplet Probe for LC-MS analysis; F. Bruker timsTOF mass spectrometer; G. SCiLS Lab heatmaps.

Figure 1. Orthologous mass spectrometry imaging techniques using MALDI imaging (A - D) and the SepQuant® dropletProbe (A, E - G). A. Serial sections of tissue; B. HTX TM-Sprayer for MALDI matrix deposition; C. Bruker rapifleX MALDI mass spectrometer; D. SCiLS Lab MALDI images; E. Liquid microjunction extraction by the SepQuant® dropletProbe for LC-MS analysis; F. Bruker timsTOF mass spectrometer; G. SCiLS Lab heatmaps.