AFADESI builds on DESI by introducing an auxiliary gas flow: a high-speed air/nitrogen jet strikes the tissue surface, desorbing molecules in-situ into the gas phase, which then collide with charged droplets produced by electrospray to complete ionization. The gas flow improves desorption efficiency and sampling stability, giving stronger and more reproducible signals.
This process takes place under ambient, open conditions. Samples require no vacuum introduction and no MALDI matrix spraying, so it belongs to a label-free, low-prep imaging route that helps preserve the in-situ molecular distribution.
A typical setup consists of a gas nozzle, an electrospray capillary, and a sampling interface; their spatial geometry determines desorption-ionization coupling efficiency. During sampling, the tissue section or living surface is scanned point by point, a mass spectrum is acquired per pixel, and the result is reconstructed into an ion image.
Compared with standalone DESI, AFADESI's gas-flow assistance lowers the surface flatness requirement and signal fluctuation, making it better suited for continuous imaging of larger fields of view or irregular surfaces, and is one of the DESI-family variants oriented toward stable imaging.
AFADESI can image peptides, proteins, lipids, and metabolites, covering mid-to-high polarity molecules; its ambient matrix-free nature offers advantages for small molecules and living-surface sampling. Spatial resolution is limited by the spray spot and scan step size, typically on the order of tens of microns.
For scenarios requiring subcellular resolution, AFADESI is not the strongest choice and TOF-SIMS or transmission MALDI should be considered; for ambient, in-situ, low-prep needs, it is a robust option in the DESI route.
AFADESI, LDPI, and DPI all belong to ambient matrix-free imaging but differ in ionization mechanism: AFADESI relies on electrospray liquid-phase ionization, while LDPI/DPI rely on photochemical/dual-photoionization. For polar, easily liquid-phase-ionized molecules, AFADESI and the DESI system are more natural; for matrix-free high-sensitivity needs, DPI can be compared.
Selection should combine analyte polarity, whether living-surface sampling is needed, and the host platform (Orbitrap, Q-TOF, and other ambient interfaces); Neo-Source LDPI/DPI can also serve as an alternative or supplementary module for ambient matrix-free imaging.
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).