Alkyne-tag Raman imaging and sensing of bioactive compounds

An alkyne is an unsaturated hydrocarbon characterized by the presence of at least one C≡C bond. Alkyne groups generate a strong Raman peak in the cellular-silent region, a region between 1,800 and 2,800 cm⁻¹ where endogenous molecules do not produce a Raman signal. As a result, alkynes are regularly used as tags to label and visualize small molecules in live cells using Raman microscopy, a method referred to as alkyne-tag Raman imaging (ATRI). ATRI has been applied to various compounds to enable their cellular localization and, recently, alkyne-tagged compounds have been used as Raman sensors to detect intracellular biomolecules, such as metal ions or reactive oxygen species. ATRI has unique advantages over existing methods for localizing small molecules intracellularly, such as enabling super-multiplex detection and incurring a smaller impact on labelled compounds. In this Primer, we describe the principles and key techniques involved in ATRI, including the design of alkyne-tagged molecules, sample preparation and the set-up of Raman microscopes. We showcase the demonstration and application of ATRI, encompassing the development of responsive alkyne-tagged compounds for sensing biomolecules. Finally, we discuss the limitations and potential applications of ATRI, shedding light on the future possibilities of this method.