Bond-selective imaging of 3D cellular nanostructures by interferometric scattering guided stimulated Raman scattering microscopy

Understanding the molecular composition of nanoscale cellular structures, such as extracellular vesicles and synapses, is critical for unraveling the mechanisms driving diverse biological processes. However, existing techniques face significant challenges: chemical labeling is often impractical, and conventional nanoscale imaging methods lack the specificity to resolve chemical bonds within these structures. To bridge this gap, we present an approach named interferometric scattering-guided stimulated Raman scattering microscopy (igSRS), which integrates the bond-selective capacity of stimulated Raman scattering imaging with the high sensitivity of interferometric scattering microscopy. By achieving a substantially enhanced signal-to-noise ratio, igSRS enables the visualization of chemical heterogeneity within individual extracellular vesicles and captures spectral features of nanostructures, such as synapses, in intact cells. Furthermore, igSRS's intrinsic optical sectioning capability allows for high-resolution, three-dimensional mapping of chemical distributions in complex systems like neurons. With high sensitivity and chemical specificity, igSRS offers transformative potential for a broad range of applications in biological and materials sciences.