The most typical is a 10–20 μm cryo-section mounted on an ITO/conductive slide and uniformly sprayed with matrix. Tissue must be fixed quickly to prevent molecular migration; plants, microbial colonies and dried blood spots can also be MALDI-MSI subjects.
Sample preparation determines success or failure: untimely fixation or uneven matrix is directly reflected in the image; see sample-prep requirements for details.
MALDI has high ionization efficiency for proteins (several kDa to tens of kDa), peptides, lipids and glycans, which is its main strength; these large molecules are harder to cover with matrix-free sources.
For small-molecule drugs and metabolites, because matrix peaks occupy the low-mass region, MALDI is not the first choice; matrix-free sources such as LDPI (m/z≥70 low background) and DESI are more suitable.
In a word: large molecules look to MALDI, small molecules with a low background look to matrix-free sources. If a study includes both proteins and metabolites, the two sources can complement each other, or imaging can be done separately on continuous sections of the same frozen block.
This is also the core logic of ion source selection—matching the source to the molecule's mass window.
At project launch, first confirm the target molecule's mass range: for >m/z 1000 prefer MALDI; for 100–1000 with a low background, evaluate LDPI/DESI.
Matching sample and molecule matters more for success than the instrument brand; it is recommended to validate with a small standard sample before scaling up.
To obtain detailed specifications, compatible models, or a quotation for the MSI LDPI / DPI full series imaging ion sources, visit the Neo-Source official website, or contact the official team for compatibility advice tailored to your mass spectrometer (Agilent / SCIEX / Thermo and other mainstream MS).