MALDI Mass Spectrometry Imaging sample preparation with wet-interface
matrix deposition for lipid analysis.
Abstract
RATIONALE: Sample preparation is one of the most crucial steps for MALDI
mass spectrometry imaging (MALDI-MSI). The scientists beginning their
adventure with this technique may be overwhelmed by the variety of
matrices, solvents, concentrations, the ways of their applications, and
the lack of widely available knowledge about the influence of these
parameters on the results. Here we would like to present our experiences
with detailed aspects of matrices deposition, hopefully helpful for the
scientific community. METHODS: In our article, we have tested several
MALDI matrices applied by the SunCollect® system: wet-interface matrix
deposition in the context of lipids analysis. Among them:
2,5-dihydroxybenzoic acid (DHB), norharmane, N-(1-naphthyl)
ethylenediamine dihydrochloride (NEDC), 9-aminoacridine (9AA). We have
optimized the number of matrix layers and nozzle settings in terms of
spectra intensity and the overall quality of obtained ion maps. RESULTS:
Our research presents the influence of the number of matrix layers and
nozzle settings on the results and allows for choosing the optimal
parameters for the analyses. In positive ionization mode, DHB matrix
could be chosen as the first selection. In the negative ionization mode,
DAN matrix produces higher peak intensity in a lower mass range and
seems to provide more information than 9AA. We recommended NEDC for
particular tasks such as glucose analysis. Comparably to remaining
matrices, norharmane significantly changes received ion maps.
CONCLUSIONS: Dealing with such a great amount of data allows us to
notice an interesting conclusion: the obtained ion picture for a
particular ion could differ dramatically with changing the matrix, the
solvent composition, or even the number of matrix layers. This must be
considered when interpreting the result and forces us to compare the
results obtained with different matrices with extreme caution.