Matrix precoated targets for direct lipid analysis and imaging of tissue

We have developed targets precoated with matrix for imaging lipids in tissues using matrix-assisted laser desorption ionization mass spectrometry (MALDI MS). Thin tissue sections (rat kidney and mouse or rat brains) were placed onto 1,5-diaminonaphthalene precoated targets (prepared beforehand by a protocol utilizing sublimation) and were washed with ammonium formate solution. After a brief drying period, the target slides were imaged by MALDI MS. The resulting images from these sections were of equivalent quality to those obtained using the usual postcoating approach, such as sublimation and spraying, in terms of the sharpness of substructures in the images demonstrated by imaging at spatial resolutions of 100, 10, and 5 μm. Matrix precoated targets have a shelf life of more than 6 months when kept in a dark, nonhumid environment such as a nontransparent desiccator.