Molecular Fingerprinting of Mouse Brain Using Ultrabroadband Coherent Anti-Stokes Raman Scattering (CARS) Microspectroscopy Empowered by Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS).

The Raman fingerprint spectral region provides abundant structural information on molecules. However, analyzing vibrational images within this region using coherent Raman imaging remains challenging due to the small Raman cross section and congested spectral features. In this study, we combined ultrabroadband coherent anti-Stokes Raman scattering (CARS) microspectroscopy across the spectral range of 500-4000 cm with multivariate curve resolution-alternating least-squares (MCR-ALS) to reveal hidden Raman bands in the fingerprint region. Applying this method to mouse brain tissue, we extracted information on cholesterol and collagen, leveraging their distinctive molecular signatures, as well as on key molecules such as lipids, proteins, water, and nucleic acids. Moreover, the simultaneous detection of second harmonic generation facilitated label-free visualization of organelles, including arachnoid membrane and Rootletin filaments.