Noncovalent Theranostic Prodrug for Hypoxia-Activated Drug Delivery and Real-Time Tracking.

Real-time tracking of hypoxia-activated prodrugs (HAPs) delivery and the release process is of great significance for innovative medical treatments and drug development. Existing theranostic methods for HAPs activation imaging are based on the covalent approach, which suffered from complicated molecular design and tedious synthesis. In this work, a facile noncovalent strategy for constructing an hypoxia-activated theranostic prodrug has been proposed. An hypoxia-activated prodrug, NMAC4A, has been synthesized and bound with an NIR fluorophore CyNH2 through host-guest interaction to form the theranostic prodrug NMAC4A-CyNH2. Interestingly, the NIR fluorescence signal of CyNH2 can be effectively "turned off" after the formation of the stable theranostic prodrug NMAC4A-CyNH2. Because of the selective response to a tumor hypoxic microenvironment, NMAC4A-CyNH2 can realize the tumor-targeted drug delivery, accompanied by its NIR fluorescence "turn on". The synchronization of drug release and fluorescence "turn on" properties of NMAC4A-CyNH2 in an hypoxic microenvironment makes the fluorescence signal an effective tool for a precise tracing of the drug release process. Notably, NMAC4A-CyNH2 has been successfully applied to real-time image tracking of the drug delivery in vitro and in vivo. More importantly, the biodistribution of the theranostic prodrug's metabolites in a tumor and some major tissues have been mapped by mass spectrometry imaging at the molecular level, which further validated the effectiveness of NMAC4A-CyNH2 as a tumor-targeted drug delivery platform and NIR probe. This work will not only provide a promising tool for an hypoxia-activated drug delivery and real-time image tracking but also propose an effective design strategy for noncovalent theranostic prodrug construction.