Visualizing specific enzyme activities in living systems is important in biomedical research, and Raman imaging probes are particularly suitable for simultaneous multiplexed detection of plural enzyme activities due to their narrow signal peak widths. Here, we present a molecular design strategy for enzyme-activity-detecting Raman probes based on control of aggregation. The probe itself is soluble and diffusive in aqueous solution due to its hydrophilic substrate moiety, but hydrolysis by the target enzyme affords a hydrophobic product that forms aggregates, thereby increasing the local dye concentration, which in turn results in a stronger Raman signal that enables visualization of the enzyme activity. We validated the molecular design by developing Raman probes targeting aminopeptidase, glycosidase and carboxypeptidase. The vibrational frequency can be shifted by isotope-editing, and the developed probes were successfully applied to visualize the activities of aminopeptidase and glycosidase in live cultured cells and spheroids. © 2025 The Authors. Published by American Chemical Society

Coumarin-hemicyanine (CHC) hybrid fluorophores bearing an intramolecular nucleophile have been reported as ratiometric fluorescent probes based on the equilibrium between the π-conjugated open and cyclic closed forms. Here, we report red-shifted CHC derivatives that can serve as scaffold dyes of activated fluorescent probes and activated Raman probes. We prepared a series of cyano-substituted CHC derivatives and found that substitution at C-4 of the coumarin moiety is effective in extending the absorption wavelength. The near-infrared (NIR) emission of these 4CN-CHC derivatives exhibits high tissue penetration. Dual-color imaging with 4CN-CHC enabled ratiometric monitoring of the lysosomal pH changes. Furthermore, the coherent anti-Stokes Raman scattering (CARS) signals of 4CN-CHC derivatives could be regulated by modifying the open/closed equilibrium, and the different patterns of CARS spectra enabled us to perform multicomponent imaging. Thus, these 4CN-CHC derivatives expand the repertoire of functional probes for NIR and multiplexed vibrational imaging. © 2025 The Authors. Published by American Chemical Society

9-cyanopyronin is a promising scaffold that exploits resonance Raman enhancement to enable sensitive, highly multiplexed biological imaging. Here, we developed cyano-Hydrol Green (CN-HG) derivatives as resonance Raman scaffolds to expand the color palette of 9-cyanopyronins. CN-HG derivatives exhibit sufficiently long wavelength absorption to produce strong resonance Raman enhancement for near-infrared (NIR) excitation, and their nitrile peaks are shifted to a lower frequency than those of 9-cyanopyronins. The fluorescence of CN-HG derivatives is strongly quenched due to the lack of the 10th atom, unlike pyronin derivatives, and this enabled us to detect spontaneous Raman spectra with high signal -to -noise ratios. CN-HG derivatives are powerful candidates for high performance vibrational imaging.