Low-Temperature Thermal Evaporation (LTE) in MALDI Mass Spectrometry Imaging (MSI)

LTE is a novel dry deposition method for applying organic matrix compounds in MALDI-MSI to achieve better control over the matrix layer and ensure a high-quality, uniform matrix crystal coating. The evaporator system, equipped with LTE sources, facilitates precise deposition at low evaporation temperatures and high-vacuum conditions (<5x10-5 mbar). The reproducible LTE deposition method for DHB and DAN matrices at 80°C ensures controlled deposition rates of homogeneous submicrometer-sized matrix crystals over tissue samples. Notably, using <99% pure matrices does not compromise lipid analyte ionization or MS image quality compared to >99% pure matrices. Tissue sections coated with DAN or DHB matrix stored at -80°C for 2 weeks yield consistent MALDI-MSI results. Comparisons with the traditional spray-coating method demonstrate LTE's superiority in detecting more lípids and metabolites, yielding higher signal intensities, and producing higher-quality MALDI images with reduced analyte diffusion.