Facile Solvothermal Synthesis of Mesostructured Fe3O4/Chitosan Nanoparticles as Delivery Vehicles for pH-Responsive Drug Delivery and Magnetic Resonance Imaging Contrast Agents

We report a facile fabrication of a host-metal-guest coordination-bonding system in a mesostructured Fe3O4/chitosan nanoparticle that can act as a pH-responsive drug-delivery system. The mesostructured Fe3O4/chitosan was synthesized by a solvothermal approach with iron(III) chloride hexahydrate as a precursor, ethylene glycol as a reducing agent, ammonium acetate as a porogen, and chitosan as a surface-modification agent. Subsequently, doxorubicin (DOX), acting as a model drug (guest), was loaded onto the mesostructured Fe3O4/chitosan nanoparticles, with chitosan acting as a host molecule to form the (NH2ZnDOX)-D-II coordination architecture. The release of DOX can be achieved through the cleavage of coordination bonds that are sensitive to variations in external pH under weakly acidic conditions. The pH-responsive nature of the nanoparticles was confirmed by in vitro releases and cell assay tests. Furthermore, the relaxation efficiency of the nanoparticles as high-performance magnetic resonance imaging contrast agents was also investigated. Experimental results confirm that the synthesized mesostructured Fe3O4/chitosan is a smart nanovehicle for drug delivery owing to both its pH-responsive nature and relaxation efficiency.