Automated Platform for
High-Resolution Tissue Imaging Using Nanospray Desorption Electrospray
Ionization Mass Spectrometry
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Abstract
An automated platform has been developed for acquisition
and visualization of mass spectrometry imaging (MSI) data using nanospray
desorption electrospray ionization (nano-DESI). The new system enables
robust operation of the nano-DESI imaging source over many hours by
precisely controlling the distance between the sample and the nano-DESI
probe. This is achieved by mounting the sample holder onto an automated <i>XYZ</i> stage, defining the tilt of the sample plane, and recalculating
the vertical position of the stage at each point. This approach is
useful for imaging of relatively flat samples such as thin tissue
sections. Custom software called MSI QuickView was developed for visualization
of large data sets generated in imaging experiments. MSI QuickView
enables fast visualization of the imaging data during data acquisition
and detailed processing after the entire image is acquired. The performance
of the system is demonstrated by imaging rat brain tissue sections.
Low background noise enables simultaneous detection of lipids and
metabolites in the tissue section. High-resolution mass analysis combined
with tandem mass spectometry (MS/MS) experiments enabled identification
of the observed species. In addition, the high dynamic range (>2000)
of the technique allowed us to generate ion images of low-abundance
isobaric lipids. A high-spatial resolution image was acquired over
a small region of the tissue section revealing the distribution of
an abundant brain metabolite, creatine, on the boundary between the
white and gray matter. The observed distribution is consistent with
the literature data obtained using magnetic resonance spectroscopy