DESI-based imaging mass spectrometry in forensic science and clinical diagnosis

In the decades following the successful introduction of two soft ionization methods, viz., matrix-assisted laser desorption ionization (MALDI) and electrospray ionization ESI, several promising and practical techniques have been developed to perform ionization under ambient conditions. Desorption electrospray ionization (DESI) is one of the most popular ambient ionization methods and has been implemented in numerous fields. Imaging mass spectrometry (IMS) coupled with DESI is among the most successful of these applications, particularly in the fields of forensic science and molecular biology. Unlike MALDI based IMS which involves a matrix application process, sample preparation for DESI-IMS is a simple and minimal procedure that can be potentially performed by nonexperts, including hospital laboratory technicians. Moreover, DESI enables surface analysis of various materials under ambient conditions. Skin, glass, rubber, and even cotton can be analyzed using this ionization technique. Thus, DESI is versatile in situations typically encountered in forensic analysis. Rapid and facile DESI-based chemical detection and IMS are practical methods for forensic testing and clinical diagnosis.