Airbrushing, matrix solution

For a few tissue samples, the matrix deposition can be performed manually. A matrix solution is sprayed onto the tissue section with a hand-held thin layer chromatography (TLC) sprayer or an artist airbrush. The reproducibility of manual matrix deposition is an issue. When the manual sprayer is used, the MALDI target plate with the tissue section is held vertically about 15-25 cm from the sprayer nozzle. It is recommended to spray multiple coats of matrix across the tissue section and each coating cycle consists of passing the sprayer two to hve times across the tissue section and allowing the tissue to dry for about 1-5 min. This process is usually repeated between 10 and 20 cycles. 

Airspray coating, in which the matrix solution is sprayed over the sample with a pneumatic airbrush. Several coatings are applied and the sample is dried between applications. 

Pour approximately 1.0 mL of the solvent for the matrix solution into the airbrush. 

Pour the prepared matrix solution into the airbrush and spray onto the tissue section on the ITO slide glass. 

The matrix solution was sprayed over the tissue surface using a 0.2-mm nozzle caliber airbrush (Procon Boy FWA Platinum Mr. Hobby, Tokyo, Japan). 

Use the airbrush in a hood or other enclosed environment to avoid inhaling aerosolized matrix solution. Spray parameters will need to be adjusted based on air currents and other factors. In the fume hood, try holding the airbrush perpendicular to the MALDI plate at a distance of 35 cm and adjust the flow rate of matrix so that most of the matrix solvent evaporates before reaching the plate. However, a certain amount of solvent is crucial for extracting peptides firom tissue samples to yield detectable signals. 

---