Novel Bioorthogonal Theranostic Scaffold Enables on-Target Drug Release and Real Time Monitoring In Vivo.

Bioorthogonal chemistry-based prodrug strategy features spatiotemporally controlled release of therapeutic agent and/or imaging probe. However, the integration of diagnosis and therapy into a single molecule paired with a single bioorthogonal trigger remains a challenge. In this study, we devised a novel bioorthogonal theranostic scaffold amenable to the conjugation of various targeting agent and click-to-release reaction with the bioorthogonal prodrug to enable targeted drug liberation with concomitant fluorescence emission. Such one-stone-three-birds scaffold consists of a new fluorophore phenanthrodioxine (PDO) linked with a fluorescence masking group, tetrazine (Tz) which serves as a dual switch for the activation of fluorophore and drug. Further installation of a warhead of phenylboronic acid (PBA) ensures the targeted accumulation of the resultant PBA-PDO-Tz conjugate in tumor cells, thereby achieving on-demand activation of trans-cyclooctene-caged anticancer drug Doxorubicin with real-time monitoring and on-target cytotoxicity in live cells and an A549 xenograft mouse model. The targeted single trigger-dual response scaffold holds promise for precise theranostics applications in vivo.