posted on 2024-01-05, 20:10authored byRory T. Steven, Amy Burton, Adam J. Taylor, Kenneth N. Robinson, Alex Dexter, Chelsea J. Nikula, Josephine Bunch
Mass spectrometry
imaging (MSI) allows for the spatially resolved
detection of endogenous and exogenous molecules and atoms in biological
samples, typically prepared as thin tissue sections. Desorption electrospray
ionization (DESI) is one of the most commonly utilized MSI modalities
in preclinical research. DESI ion source technology is still rapidly
evolving, with new sprayer designs and heated inlet capillaries having
recently been incorporated in commercially available systems. In this
study, three iterations of DESI sprayer designs are evaluated: (1)
the first, and until recently only, commercially available Waters
sprayer; (2) a developmental desorption electro-flow focusing ionization
(DEFFI)-type sprayer; and (3) a prototype of the newly released Waters
commercial sprayer. A heated inlet capillary is also employed, allowing
for controlled inlet temperatures up to 500 °C. These three sprayers
are evaluated by comparative tissue imaging analyses of murine testes
across this temperature range. Single ion intensity versus temperature
trends are evaluated as exemplar cases for putatively identified species
of interest, such as lactate and glutamine. A range of trends are
observed, where intensities follow either increasing, decreasing,
bell-shaped, or other trends with temperature. Data for all sprayers
show approximately similar trends for the ions studied, with the commercial
prototype sprayer (sprayer version 3) matching or outperforming the
other sprayers for the ions investigated. Finally, the mass spectra
acquired using sprayer version 3 are evaluated by uniform manifold
approximation and projection (UMAP) and k-means clustering.
This approach is shown to provide valuable insight that is complementary
to the presented univariate evaluation for reviewing the parameter
space in this study. Full spectral temperature optimization data are
provided as supporting data to enable other researchers to design
experiments that are optimal for specific ions.