A smart bioresponsive nanosystem with dual-modal imaging for drug visual loading and targeted delivery

Most of present studies are focusing on improving cancer therapy effect by synthesizing new carriers or drugs, while little attention is paid to develop new drug loading patterns and improve the efficiency. Herein, a novel and smart nanosystem that not only realized targeted delivery and responsive degradation but also achieved facilely visual drug loading and release, was reported for the first time. To build this system, highly fluorescent carbon quantum dots (CQDs) were synthesized and served as an effective indicator and carrier to achieve visual doxorubicin (DOX) loading by the strong fluorescence resonance energy transfer (FRET) interactions between them. Biodegradable nano-MnO2 was then synthesized by biomineralization with folic acid modified bovine serum albumin, which was employed as the other fluorescence quencher for CQDs and DOX and established the other FRET system to visually monitor drug loading. The double-FRET nanosystem could be specifically ingested by cancer cells and responsively degraded by intracellular H+/H2O2 or glutathione. Meanwhile, this triggered drug release behavior was visually detected after gradual dissociation of the two FRET systems by monitoring the fluorescence and magnetic resonance changes. More importantly, both in vitro and in vivo experiments demonstrated that the novel nanosystem exhibited much better cancer therapy effects than pure DOX, and we also reported its first experimental example to treat cancer migration. This work established a new pattern to improve and monitor drug loading, delivery and release, and demonstrated its good performance in cancer therapy and anti-migration.