Broadband Collision-Induced Dissociation Mass Spectrometry Imaging.

Abstract

This study demonstrates the first application of broadband collision-induced dissociation (bbCID) to mass spectrometry imaging (MSI) for the identification of untargeted metabolites in human tissues. The methodology integrates bbCID with laser ablation-remote atmospheric pressure photoionization/chemical ionization (LARAPPI/CI), enabling the simultaneous acquisition of precursor and fragment ion distributions during MSI for many compounds simultaneously. In this approach, an infrared (IR) laser is used to ablate biological material, which is then ionized in the gas phase by a combination of photoionization and chemical ionization at atmospheric pressure. The method was validated using reference compounds, including thymidine and commonly used synthetic dyes, to assess ionization efficiency, fragmentation behavior, and spatial colocalization of precursor and fragment ions. Subsequently, bbCID-MSI was applied to clinical tissue samples of human bladder and kidney cancer. For the bladder cancer tissue, higher intensities of heptadecanoic acid, docosahexaenoic acid (FA(22:6)), docosapentaenoic acid (FA(22:5)), and FA(16:0) were observed in tumor regions, whereas proline was more abundant in adjacent nontumorous area. In renal cell carcinoma, cancerous regions exhibited elevated levels of polyunsaturated fatty acids such as arachidonic acid (FA(20:4)) and adrenic acid (FA(22:4)), while creatine and serine were enriched in healthy tissue zones. These findings highlight the utility of bbCID-MSI for spatially resolved metabolite analysis and its potential to reveal biologically relevant metabolic alterations associated with cancer.