Improved delivery system for celastrol-loaded magnetic FeO/α-FeO heterogeneous nanorods: HIF-1α-related apoptotic effects on SMMC-7721 cell.

FeO/α-FeO heterogeneous nanorods were prepared by a rapid combustion method with α-FeOOH nanorods as precursors. FeO/α-FeO heterogeneous nanorods with a saturation magnetization of 33.2 emu·g were obtained using 30 mL of absolute ethanol at a calcination temperature of 300 °C. Their average length was around 140 nm, and average diameter was about 20 nm. To improve the dispersion characteristics of the FeO/α-FeO heterogeneous nanorods in aqueous solution, citric acid and PEG were applied to modify the nanorod surface via the Mitsunobu reaction. The results showed that the hydrodynamic size range of FeO/α-FeO/CA-PEG-celastrol was 250-500 nm, the surface potential was -15 mV, and the saturation magnetization was approximately 23 emu·g. The drug loading capacity of FeO/α-FeO/CA-PEG was larger than the non-PEG modified version. FeO/α-FeO/CA-PEG-celastrol had slow-release characteristics and was sensitive to changes in pH. Application of a magnetic field significantly promoted the inhibition of SMMC-7721 human liver cancer cell growth after treatment with FeO/α-FeO/CA-PEG-celastrol. Celastrol and FeO/α-FeO/CA-PEG-celastrol increased the production of reactive oxygen species in SMMC-7721 cells and promoted apoptosis and apoptosis-related proteins (p53, Bax, Bcl-2) were also changed. In addition, the expression of hypoxia-inducible factor 1α (HIF-1α) was enhanced. We may conclude that celastrol-loaded magnetic FeO/α-FeO heterogeneous nanorods may be applied in the chemotherapy of human cancer with good biocompatibility and delivery.