Ten-Fold Expansion MALDI Mass Spectrometry Imaging of Tissues and Cells at 500 nm Resolution

Abstract

Achieving high spatial resolution in matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) is crucial for detailed molecular mapping in biological tissues and cells. However, conventional MALDI-MSI platforms are typically limited to spatial resolutions of 5-20 m, restricting their ability to visualize fine subcellular structures. Here, we present a novel ten-fold expansion MALDI-MSI (10X ExMSI) method that attains 500 nm spatial resolution without the need for specialized optics or customized instrumentation. By physically expanding biological samples using a swellable hydrogel matrix, our method maintains high retention and broadens the detection range of lipids, ensuring comprehensive lipid profiling. We demonstrated the effectiveness of 10X ExMSI by visualizing intricate subcellular structures within mouse brain tissues, including individual nuclei, astrocytes, Purkinje cells, and, notably, dendritic arborizations-features previously unresolvable using mass spectrometry imaging. Applying 10X ExMSI to single-cell analysis of cultured cells revealed detailed spatial distributions of lipids at the subcellular to organelle level. Notably, the method is fully compatible with standard commercial MALDI-MSI platforms, enabling widespread adoption without significant additional investment. The 10X ExMSI offers a transformative tool for high-resolution molecular imaging, opening new avenues for molecular analysis in diverse biological and biomedical fields, including neuroscience, pathology, and cellular biology.