Outer-Frame-Degradable Nanovehicles Featuring Near-Infrared Dual Luminescence for in Vivo Tracking of Protein Delivery in Cancer Therapy

In vivo monitoring of cargo protein delivery is critical for understanding the pharmacological efficacies and mechanisms during cancer therapy, but it still remains a formidable challenge because of the difficulty in observing nonfluorescent proteins at high resolution and sensitivity. Here we report an outer-frame-degradable nanovehicle featuring near-infrared (NIR) dual luminescence for real-time tracking of protein delivery in vivo. Upconversion nanoparticles (UCNPs) and fluorophore-doped degradable macroporous silica (DS) with spectral overlap were coupled to form a core–shell nanostructure as a therapeutic protein nanocarrier, which was eventually enveloped with a hyaluronic acid (HA) shell to prevent protein leakage and for recognizing tumor sites. The DS layer served as both a container to accommodate the therapeutic proteins and a filter to attenuate upconversion luminescence (UCL) of the inner UCNPs. After the nanovehicles selectively accumulated at tumor sites and entered cancer cells, intracellular hyaluronidase (HAase) digested the outermost HA protective shell and initiated the outer frame degradation-induced protein release and UCL restoration of UCNPs in the intracellular environment. Significantly, the biodistribution of the nanovehicles can be traced at the 710 nm NIR fluorescence channel of DS, whereas the protein release can be monitored at the 660 nm NIR fluorescence channel of UCNPs. Real-time tracking of protein delivery and release was achieved in vitro and in vivo by NIR fluorescence imaging. Moreover, in vitro and in vivo studies manifest that the protein cytochrome c-loaded nanovehicles exhibited excellent cancer therapeutic efficacy. This nanoplatform assembled by the outer-frame-degradable nanovehicles featuring NIR dual luminescence not only advances our understanding of where, when, and how therapeutic proteins take effect in vivo but also provides a universal route for visualizing the translocation of other bioactive macromolecules in cancer treatment and intervention.