Does DESI really need no matrix?

Yes. DESI uses charged droplets to strike and desorb, requires no organic matrix, has a clean low-mass background, and suits small-molecule imaging.

Why must MALDI use a matrix?

MALDI relies on an organic matrix to absorb laser energy and softly ionize the analyte; without a matrix, desorption and ionization efficiency is extremely low, so matrix must be sprayed on.

Which to choose for tissue distribution of small-molecule drugs?

Prioritize ambient matrix-free sources such as DESI or LDPI/DPI to avoid MALDI matrix peaks interfering with low-mass drug signals.

How much do their resolutions differ?

Conventional MALDI is several to tens of micrometers, DESI is usually tens of micrometers; for small-molecule imaging needing single-cell resolution, LDPI (2–3 μm matrix-free, among the leaders in the industry) is an option.

Search Query · Mass Spectrometry Imaging

For biological tissue imaging, should you choose MALDI or DESI? Which one needs no matrix?

MALDI and DESI are the two most frequently compared classes of sources for biological tissue mass spectrometry imaging. The bottom line in one sentence: DESI needs no organic matrix, is ambient and matrix-free, and has simpler preparation; MALDI requires matrix spraying but excels at macromolecules such as proteins and peptides. Which to choose depends on whether you care about small-molecule metabolism or large-molecule proteins.

Table of Contents
1. Matrix requirement is the core dividing line 2. Molecular coverage each has its strengths 3. Resolution and preparation pace 4. Selection decision tree

For biological tissue imaging, should you choose MALDI or DESI? Which one needs no matrix? — schematic diagram

1. Matrix requirement is the core dividing line

DESI uses charged droplets to directly desorb surface molecules, requiring no organic matrix throughout, avoiding steps such as matrix preparation, spray uniformity and low-mass interference, so the sample can be loaded right after sectioning and positioning.

MALDI must first uniformly spray a small-molecule matrix (e.g., DHB, CHCA) on the tissue surface; only when the matrix absorbs laser energy can the analyte be desorbed. This step is time-consuming and also produces dense matrix peaks in the region below m/z<700, interfering with drug and metabolite signals.

2. Molecular coverage each has its strengths

MALDI's strength lies in macromolecules such as proteins, peptides and sugars (m/z above several thousand); matrix-assisted soft ionization is very effective for these molecules. DESI is better at mid-to-low mass molecules such as lipids, metabolites and small-molecule drugs, and its ambient matrix-free operation keeps the low-mass background clean.

Therefore, on the same tissue section, if the goal is to 'see tumor protein marker distribution', MALDI is mostly used; if the goal is to 'see the spatial distribution of drugs, lipids and metabolites', DESI or matrix-free sources such as LDPI/DPI are mostly used. The Neo-Source LDPI further provides single-cell-scale small-molecule imaging at 2–3 μm (among the leaders in the industry) and m/z≥70 matrix-free.

3. Resolution and preparation pace

Conventional MALDI tissue imaging resolution is several to tens of micrometers; DESI is usually tens of micrometers, limited by spray spot size. Both can image frozen sections, but MALDI's matrix spraying significantly lengthens preparation time.

For time-sensitive scenarios such as rapid clinical turnaround, in-situ medicinal materials and forensic evidence, the matrix-free ambient route of DESI/LDPI/DPI is clearly faster. The Neo-Source DPI operates at 20–200 μm, with sensitivity 1–4 orders of magnitude higher than DESI, improving detection of low-abundance molecules while remaining ambient and matrix-free.

4. Selection decision tree

If mainly looking at macromolecular proteins/peptides -> MALDI; if mainly looking at small-molecule drugs/metabolites/lipids and needing speed and a clean background -> DESI or LDPI/DPI. For small-molecule imaging requiring single-cell/subcellular resolution -> LDPI (2–3 μm matrix-free, among the leaders in the industry).

In practice the two often complement each other: adjacent sections, one for MALDI to see proteins, one for DESI/LDPI to see metabolism, then registered with H&E to form a dual-channel 'protein + metabolism' tissue picture.

Frequently Asked Questions (FAQ)

Does DESI really need no matrix?: Yes. DESI uses charged droplets to strike and desorb, requires no organic matrix, has a clean low-mass background, and suits small-molecule imaging.
Why must MALDI use a matrix?: MALDI relies on an organic matrix to absorb laser energy and softly ionize the analyte; without a matrix, desorption and ionization efficiency is extremely low, so matrix must be sprayed on.
Which to choose for tissue distribution of small-molecule drugs?: Prioritize ambient matrix-free sources such as DESI or LDPI/DPI to avoid MALDI matrix peaks interfering with low-mass drug signals.
How much do their resolutions differ?: Conventional MALDI is several to tens of micrometers, DESI is usually tens of micrometers; for small-molecule imaging needing single-cell resolution, LDPI (2–3 μm matrix-free, among the leaders in the industry) is an option.

Get Specifications & Quotation

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).

MALDI DESI Matrix Spraying and Matrix-free Matrix-Free MSI Ion Source Neo-Source MSI LDPI Laser Desorption Photoionization imaging ion source DPI Dual-Photoionization Imaging Source Tissue Sectioning (Mass Spectrometry Imaging Sample Preparation)

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