Enhanced imaging of endogenous metabolites by negative ammonia assisted DESI/PI mass spectrometry

In this work, endogenous metabolites in mouse brain tissue were imaged by negative desorption electrospray ionization (DESI), ammonia assisted DESI (aa-DESI), DESI/post-photoionization (DESI/PI), and ammonia assis-ted DESI/PI (aa-DESI/PI) mass spectrometry imaging (MSI) strategies. The combined effect of ammonia additive and post-photoionization was found to play an important role in the enhancement of sensitivity and coverage for endogenous analytes under ambient conditions. Compared with DESI, aa-DESI/PI can provide increased signal intensities for metabolites up to 37.1-fold, as well as the imaging of nine more small metabolites (m/z < 350) (26 for aa-DESI/PI and 17 for DESI) in mouse brain tissue. The results of Pearson correlation analysis and KEGG pathway analysis showed that the enhanced imaging strategy of aa-DESI/PI can facilitate the study of endoge-nous metabolic pathways and molecular networks. Moreover, the imaging results of mouse tumor tissue demonstrated the promising application of aa-DESI/PI in tumor research.

Automated summary

In this study, different mass spectrometry imaging techniques were used to image endogenous metabolites in mouse brain tissue, and the combined effect of ammonia additive and post-photoionization was found to enhance sensitivity and coverage. Compared to DESI, aa-DESI/PI showed increased signal intensities and more imaging targets, and it facilitated the study of endogenous metabolic pathways and molecular networks, with promising applications in tumor research.