Stimulated Raman Scattering Microscopy for Brain Imaging: Basic Principle, Measurements, and Applications

Stimulated Raman scattering (SRS) microscopy has proven to be a powerful imaging modality over the past decade due to its intrinsic capacity to provide a molecular fingerprint of the target specimen by detecting the vibrational energies associated with its chemical bonds. In fact, SRS automatically avoids the cumbersome process of attaching a fluorophore or fluorescence protein which may alter the intrinsic folding of the molecules due to its larger size and heavier molecular weight. Being a nonlinear imaging technique, SRS also enjoys other advantages such as pinhole-less three-dimensional optical sectioning, non-invasive observation, deep tissue penetration. Additionally, in contrast to coherent anti-Stokes Raman scattering (CARS), which is another coherent Raman technique, SRS signal is identical to spontaneous Raman spectra, linearly dependent on concentration, and free from non-resonant background. In this chapter, the basic principle of SRS microscopy and the corresponding advantages are elucidated. An overview of the advances in SRS measurements is also presented. Specifically, the recent progress in the instrumentation and chemistry related to both label-free and vibrational label-assisted SRS microscopy is reviewed with special emphasis on the brain imaging applications.