Multifunctional ferritin nanocages for bimodal imaging and targeted delivery of doxorubicin into cancer cells

Recently, drug delivery systems with tumor-targeting potential have been highly desirable for improving the efficacy and applicability of drugs. With its cage structure, apoferritin (AFn) is very suitable as a drug carrier. This study describes an alternative strategy for the delivery of an anticancer drug (DOX) by encapsulating it in the cavity of AFn. The encapsulation (AFn/DOX) was achieved by manipulating the pH-dependent unfolding-refolding process of AFn at pH 2.0 and 7.4, respectively. Carbon dots (Cdots) were selected as the fluorescent probe attached to the surface of AFn nanoshells, which were of low toxicity and had good fluorescent properties. Cdots were synthesized by a simple and green strategy for imaging by using both down and upconversion fluorescence. Targeted drug delivery and multimodal imaging based on magnetic fields can be used advantageously to integrate tumor diagnosis and treatment. In this system, AFn/DOX was decorated onto the surface of iron oxide nanoparticles (IONPS), which can greatly improve the biocompatibility of IONPS. The work provides a promising strategy for tumor diagnosis by fluorescence and MR imaging. Furthermore, the pH-sensitive AFn/DOX release of the drug from the AFn nanoshells was also observed by varying the pH during the treatment both in vitro and in vivo. The system also can selectively kill cancer cells in highly localized regions via its excellent magnetically targeted abilities.