Redox-responsive xanthene–coumarin–chlorambucil-based FRET-guided theranostics for “activatable” combination therapy with real-time monitoring

A FRET donor–acceptor xanthene–coumarin conjugate has been designed for redox-regulated synergic treatment of photodynamic therapy and chemotherapy with real-time monitoring. The “locked” FRET pair was selectively “unlocked” by biological reducing thiols via rupture of a sacrificial disulfide linker. A distinct change in fluorescence color and selective cancer cell toxicity were observed in vitro.