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The quality of MALDI Imaging analyses crucially depends on the matrix application protocols. Unfortunately, the currently used protocols have significant disadvantages that impair the robust and routine use of tissue imaging as analytical or even diagnostic approach. While pneumatic spray preparations provide high surface homogeneity and spatial resolution of the images, the process is manual and highly irreproducible. Depending of the degree of tissue wetting either the analyte molecules are badly incorporated into the matrix (too dry) or the spatial resolution is lost (too wet). Nano-spotting on the other hand provides quality spectra but as a sequential process it is slow, spatial resolution is limited by the spot raster (typical >100 μm) and perfect alignment with the mass spectrometer is critical.
We introduce an entirely new approach that combines the advantages of above methods and eliminates the disadvantages. In the new preparation device, matrix aerosol (< 50 μm droplets) is created by vibrational vaporization under controlled conditions that is gently deposited onto tissue sections. The entire microscope slide with multiple sections can be matrix coated in one setup. An optical sensor allows to monitor and to control all relevant preparation parameters at real-time: deposition periods, intervals, matrix layer thickness, wetness, drying rate, etc. This QC process built into the preparation process provides highly reproducible preparations over several slides and at different days. No user intervention is required in the fully automated process.
On tissue it was possible to achieve lateral resolutions down to 50 μm.