Innovations in light microscopy have tremendously revolutionized the way researchers study biological systems with subcellular resolution. In particular, fluorescence microscopy with the expanding choices of fluorescent probes has provided a comprehensive toolkit to tag and visualize various molecules of interest with exquisite specificity and high sensitivity. Although fluorescence microscopy is currently the method of choice for cellular imaging, it faces fundamental limitations for studying the vast number of small biomolecules. This is because common fluorescent labels, which are relatively bulky, could introduce considerable perturbation to or even completely alter the native functions of vital small biomolecules. Hence, despite their immense functional importance, these small biomolecules remain largely undetectable by fluorescence microscopy.
To address this challenge, a bioorthogonal chemical imaging platform has recently been introduced. By coupling SRS microscopy with tiny and Raman-active vibrational probes (e.g., alkynes and stable isotopes), bioorthogonal chemical imaging exhibits superb sensitivity, specificity, and biocompatibility for imaging small biomolecules in live systems. A broad spectrum of small biomolecules, including ribonucleosides and deoxyribonucleosides, amino acids, fatty acids, choline, glucose, cholesterol, and small-molecule drugs can be imaged in live biological systems ranging from individual cells to animal tissues and model organisms. Importantly, this platform is compatible with live-cell biology, thus allowing real-time imaging of small-molecule dynamics. Moreover, further chemical and spectroscopic strategies are developed for multicolor bioorthogonal chemical imaging, a valuable technique in the era of “omics”.
L. Wei, F. Hu, Z. Chen, Y. Shen, L. Zhang and W. Min. “Live-cell bioorthogonal chemical imaging: stimulated Raman scattering microscopy of vibrational tags”, Acc. Chem. Res. 49, 1494 (2016).
L. Wei, F. Hu, Y. Shen, Z. Chen, Y. Yu, C. Lin, M. Wang and W. Min. “Live-cell imaging with alkyne-tagged small biomolecules by stimulated Raman Scattering”, Nature Methods, 11, 410 (2014).
Z. Chen, V. C. Cornish* and W. Min*. “Chemical tags: inspiration for advanced imaging techniques”, Curr. Opin. Chem. Biol. 17, 637 (2013).
