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Live imaging of biomolecules with high specificity and sensitivity as well as minimal perturbation is essential for studying cellular processes. Here, we report the development of a bioorthogonal surface-enhanced Raman scattering (SERS) imaging approach that exploits small Raman reporters for visualizing cell-surface biomolecules. The cells were cultured and imaged by SERS microscopy on arrays of Raman-enhancing nanoparticles coated on silicon wafers or glass slides. The Raman reporters including azides, alkynes, and carbondeuterium bonds are small in size and spectroscopically bioorthogonal (background-free). We demonstrated that various cell-surface biomolecules including proteins, glycans, and lipids were metabolically incorporated with the corresponding precursors bearing a Raman reporter and visualized by SERS microscopy. The coupling of SERS microscopy with bioorthogonal Raman reporters expands the capabilities of live-cell microscopy beyond the modalities of fluorescence and label-free imaging. [ABSTRACT FROM AUTHOR]

Alkynes can be metabolically incorporated into biomolecules including nucleic acids, proteins, lipids, and glycans. In addition to the clickable chemical reactivity, alkynes possess a unique Raman scattering within the Raman-silent region of a cell. Coupling this spectroscopic signature with Raman microscopy yields a new imaging modality beyond fluorescence and label-free microscopies. The bioorthogonal Raman imaging of various biomolecules tagged with an alkyne by a state-of-the-art Raman imaging technique, stimulated Raman scattering (SRS) microscopy, is reported. This imaging method affords non-invasiveness, high sensitivity, and molecular specificity and therefore should find broad applications in live-cell imaging. [ABSTRACT FROM AUTHOR]

Direct detection of glycans on live cells using surface‐enhanced Raman scattering (SERS) has been shown. A bioorthogonal Raman reporter was directly installed onto the monosaccharide analogs. Once metabolically incorporated into cell surface glycans, the Raman reporter was detected using SERS (see picture). [ABSTRACT FROM AUTHOR]

Raman detection of glycans on surfaces of live cells has been achieved, as described in the Communication by Z.‐Q. Tian, X. Chen, and co‐workers on page 7266 ff. A bioorthogonal Raman reporter (for alkyne, azide, and nitrile groups, or carbon–deuterium bonds) was installed onto the monosaccharide analogues, which were metabolically incorporated into cell surface glycans. The Raman reporter is detected using surface‐enhanced Raman scattering with the aid of gold nanoparticles. [ABSTRACT FROM AUTHOR]