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Innovations in light microscopy have tremendously revolutionized the way researchers study biological systems. Although fluorescence microscopy is currently the method of choice for cellular imaging, it faces fundamental limitations such as the bulky fluorescent tags and limited multiplexing ability in the era of “omics”. Here I will present two chemical imaging strategies, respectively. First, we devised a live-cell Bioorthogonal Chemical Imaging platform suited for probing the dynamics of small bio-molecules, which cannot be effectively labeled by bulky fluorophores. This scheme couples the emerging stimulated Raman scattering microscopy with tiny and Raman-active vibrational probes (e.g., alkynes, nitriles and stable isotopes including 2H and 13C). Exciting biomedical applications such as imaging fatty acid metabolism related to lipotoxicity, glucose uptake and metabolism, drug trafficking, protein synthesis in brain, DNA replication, protein degradation, RNA synthesis and tumor metabolism will be presented. Second, we invented a super-multiplex optical imaging technique. We developed electronic pre-resonance stimulated Raman scattering (epr-SRS) microscopy, achieving exquisite vibrational selectivity with high versatility and sensitivity. Chemically, we created a unique vibrational palette consisting of novel dyes bearing conjugated and isotopically-edited triple bonds, each displaying a single epr-SRS peak in the cell-silent spectra window. Up to 24 resolvable colors are currently achieved with great potential for further expansion. Using this approach, we monitored DNA and protein metabolism in neuronal co-cultures and brain tissues. This super-multiplex optical imaging approach promises to facilitate untangling the intricate interactions in complex biological systems, and can also find broad applications in photonics and biotechnology in general.
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