Spatial lipidomics and metabolomics of multicellular tumor spheroids using MALDI-2 and trapped ion mobility imaging

Lipids and metabolites are small biological molecules that act major roles in cellular functions. Multicellular tumor spheroids (MCTS) are a highly beneficial three-dimensional cellular model for cancer research due to their ability to imitate numerous characteristics of tumor tissues. Increasing studies have performed spatial lipidomics and metabolomics in MCTS using matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI). However, these approaches often lack the sensitivity and specificity to offer a comprehensive characterization of lipids and metabolites within MCTS. In this study, we addressed this challenge by utilizing MALDI combined with laser-induced postionization (MALDI-2) and trapped ion mobility spectrometry (TIMS) imaging in H295R adrenocortical MCTS. Our results showed that MALDI-2 could detect more lipids and metabolites in MCTS than the traditional MALDI. TIMS data revealed a successful separation of many isomeric and isobaric ions of lipids and metabolites with different locations (e.g., proliferative region and necrotic region) within MCTS, suggesting an enhanced peak capacity for spatial lipidomics and metabolomics. To further identify these isomeric and isobaric ions, we performed MS/MS imaging experiments to compare the differences in signal intensities and spatial distributions of product ions. Our data highlight the strong potential of MALDI-2 and TIMS imaging for analyzing lipids and metabolites in MCTS, which may serve as valuable tools for numerous fields of biological and medical research.