Tunable Hollow Bimetallic MnFe Prussian Blue Analogue as the Targeted pH-Responsive Delivery System for Anticancer Drugs

Owning to the improved ability of selectivity and penetration toward cancer cells, drug delivery systems (DDSs) play essential roles in chemotherapy for solid tumors. Herein, a series of bimetallic MnFe Prussian blue analogues (PBAs) with a tunable nanostructure was prepared by using sodium citrate (SC) as a structure regulator (represented by MnFe-PBA-SC). An advanced targeted drug delivery system was obtained by adding folic acid (FA) to the preparation system of MnFe-PBA-SC nanospheres (denoted as MnFe-PBA-SC-FA). The shape of pure MnFe PBA was changed from a typical nanocube to a hollow nanosphere when adding SC, leading to the formation of the core-shell nanospheres of the MnFe-PBA-SC-FA composite. The hollow nanostructures and intrinsic cavities in PBA can carry large amounts of doxorubicin (DOX), showing a high loading efficiency of MnFe-PBA-SC1.0-FA (91.8%), which was higher than that in MnFe-PBA-SC0.5 (63.2%). Additionally, the series of MnFe-PBAs showed pH-responsive drug release behaviors. A cell viability assay illustrated no remarkable cytotoxicity of MnFe-PBA-SC-FA against human breast cancer cells, Michigan Cancer Foundation-7 (MCF-7) cells, for 24 h. Confocal laser scanning showed that the MnFe-PBA-SC1.0-FA/DOX system significantly entered FA receptor-expressing MCF-7 cells in vitro and in vivo, while an increased DOX release was observed in the cytoplasm of the MCF-7 cells. In consequence, this novel anticancer delivery system based on bimetallic PBAs can be potentially applied to drug delivery.