Development of an Automatic Ultrasonic Matrix Sprayer for Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging.

Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) has emerged as a powerful tool for studying the spatial distribution of various types of molecules. Matrix deposition is a critical step for obtaining high-quality imaging data. An automatic device named SoniCoat was fabricated based on an ultrasonic nozzle driven by a pizeoelectric ceramic for matrix coating in the present study. Compared with the minihumidifier developed previously by our group for matrix deposition, SoniCoat realized automation, and the ultrasonic nozzle of this device is easy to clean and less likely to get clogged, indicating a longer life. Compared with commercial and homemade instruments such as the TM-Sprayer and electrospray matrix coating device, our newly developed device achieved a good nebulization effect without the need for high-pressure gas flow and high voltage. Matrix deposition by SoniCoat generated more homogeneous matrix crystals with diameters of about 10 µm and reduced the occurrence of molecular diffusion to a greater extent, compared with the results by TM-Sprayer. Repeatable high-spatial-resolution MS imaging data were obtained with the help of SoniCoat. Furthermore, the newly developed device can also be successfully applied for in situ derivatization.