A two-photon-activated prodrug for therapy and drug release monitoring

A light-activated cleavage strategy for the concomitant release of active drugs and generation of fluorescence changes is highly desirable. Herein a molecular prodrug featuring real-time monitoring of drug localization and release by manipulating fluorophores has been created by constructing a cleavable structure which comprises a photoremovable coumarinyl, an anticancer drug camptothecin, a cleavable linker and a near infrared fluorescent dye dicyanomethylene-4H-pyran (DCM). The fluorescence of coumarinyl and CPT is completely quenched by the DCM moiety via fluorescence resonance energy transfer (FRET). The internalization of the prodrug by cells and its subsequent intracellular location can be tracked by collecting the red fluorescence of DCM; while the release of active CPT as a result of one- or two-photon irradiation can be monitored by observing the newly emerged fluorescence of CPT under one- or two-photon excitation. The prodrug also shows highly controllable cytotoxicity toward HeLa cells and A549 cells, with low IC50 values of 4.01 and 2.53 μM, respectively, upon light irradiation and with much higher IC50 values (>40 μM) without light irradiation. This strategy may provide an approach for the development of light-activatable theranostic anticancer therapeutics.