A Dual-FRET-Based Versatile Prodrug for Real-Time Drug Release Monitoring and In Situ Therapeutic Efficacy Evaluation

A dual-Forster resonance energy transfer (FRET)-based versatile prodrug (V-prodrug), in which the fluorescence of both 5(6)-carboxylfluorescein (FAM) and doxorubicin (DOX) can be quenched by 4-(dimethylaminoazo)benzene-4-carboxylic acid (Dabcyl) with high quenching efficiency, is developed in this paper. The V-prodrug can selectively bind to the (v3) integrin overexpressed cancer cells through the Arg-Gly-Asp (RGD) targeting moiety. After that, the acid-mediated DOX release of the V-prodrug can be real-time monitored by the increase of the red fluorescence from DOX. Thereafter, DOX-induced cell apoptosis can also be in situ assessed by the fluorescence recovery of the FAM, due to the caspase-3-mediated Asp-Glu-Val-Asp (DEVD) peptide sequence cleavage. This novel prodrug provides a cascaded imaging of real-time drug release and subsequent cell apoptosis, which enables the in situ detection of the cancer response and the therapeutic efficacy evaluation of the prodrug.