Responsive fluorophore aggregation provides spectral contrast for fluorescence lifetime imaging.

Fluorophores experience altered emission lifetimes when incorporated into and liberated from macromolecules or molecular aggregates; this trend suggests the potential for a fluorescent, responsive probe capable of undergoing self-assembly and aggregation and consequently altering the lifetime of its fluorescent moiety to provide contrast between the active and inactive probes. We developed a cyanobenzothioazole-fluorescein conjugate ( 1 ), and spectroscopically examined the lifetime changes caused by its reduction-induced aggregation in vitro . A decrease in lifetime was observed for compound 1 in a buffered system activated using the biological reducing agent glutathione, suggesting a possible approach for designing responsive self-aggregating lifetime imaging probes.