Hollow mesoporous structured MnFe₂O₄ nanospheres: A biocompatible drug delivery system with pH-responsive release for potential application in cancer treatment

In this paper, a novel pH-responsive drug delivery system based on hierarchical hollow mesoporous MnFe₂O₄ nanospheres was developed for potential application in cancer treatment. The well-defined hollow mesoporous MnFe₂O₄ nanospheres were directly fabricated via a facile one-step solvothermal approach without the involvement of additional templates. A mechanism of inside-out Ostwald ripening was suggested to account for the formation of hollow mesoporous nanostructures. The morphology, crystal structure, chemical composition, magnetic properties, thermal stability and mesoporous characteristics of the fabricated MnFe₂O₄ nanospheres were comprehensively assessed based on various analysis techniques. The resulting hollow mesoporous MnFe₂O₄ nanospheres with a high biocompatibility were able to be served as a nanocarrier for loading and delivering of anticancer drug doxorubicin (DOX). In vitro drug release study revealed that DOX release from DOX-loaded MnFe₂O₄ nanospheres was significantly restrained in pH 7.4 phosphate buffer solution (PBS), while it was markedly accelerated in pH 4.5 PBS. The results of cytotoxicity assay and inverted biological microscopy demonstrated that the DOX-loaded MnFe₂O₄ nanospheres were more cytotoxic against HepG2 cells than MnFe₂O₄ nanospheres due to the evident inhibition effect of released DOX from the constructed drug delivery system. Therefore, the developed pH-responsive delivery system will have a great potential for its practical application in cancer treatment.