High hydrostatic pressure encapsulation of doxorubicin in ferritin nanocages with enhanced efficiency

- High hydrostatic pressure was first utilized for encapsulation of DOX in HFn.
- HHP, combined with additives, can completely inhibited aggregation.
- The HFn-DOX NPs showed similar structural features to the hollow cage.
- The HFn-DOX NPs demonstrated significant antitumor activity in vitro and in vivo.
- This HHP encapsulation strategy could economize on the consumption of DOX.

Human ferritin (HFn) nanocaging is becoming an appealing platform for anticancer drugs delivery. However, protein aggregation always occurs during the encapsulation process, resulting in low production efficiency. A new approach using high hydrostatic pressure (HHP) was explored in this study to overcome the problem of loading doxorubicin (DOX) in HFn. At the pressure of 500 MPa and pH 5.5, DOX molecules were found to be encapsulated into HFn. Meanwhile, combining it with an additive of 20 mM arginine completely inhibited precipitation and aggregation, resulting in highly monodispersed nanoparticles with almost 100% protein recovery. Furthermore, stepwise decompression and incubation of the complex in atmospheric pressure at pH 7.4 for another period could further increase the DOX encapsulation ratio. The HFn-DOX nanoparticles (NPs) showed similar morphology and structural features to the hollow cage and no notable drug leakage occurred for HFn-DOX NPs when stored at 4 °C and pH 7.4 for two weeks. HFn-DOX NPs prepared through HHP also showed significant cytotoxicity in vitro and higher antitumor bioactivity in vivo than naked DOX. Moreover, This HHP encapsulation strategy could economize on DOX that was greatly wasted during the conventional preparation process simply through a desalting column. These results indicated that HHP could offer a feasible approach with high efficiency for the production of HFn-DOX NPs.