Synthesis and characterization of DOX-conjugated dendrimer-modified magnetic iron oxide conjugates for magnetic resonance imaging, targeting, and drug delivery

A tumor targeted and pH-responsive drug release system that is based on folic acid (FA) conjugated to poly(ethylene glycol) (PEG)-modified dendrimers (PAMAM) with doxorubicin (DOX) and superparamagnetic iron oxide (Fe3O4) (FA-PEG-PAMAM-DOX@IONPs) has been constructed and characterized. IONPs were stabilized by FA-PEG-G3.5 PAMAM dendrimers. The anticancer drug DOX was conjugated to the dendrimer segments of amino-stabilized IONPs using hydrazine as the linker via hydrazone bonds, which are acid cleavable and can be used as an ideal pH-responsive drug release system. The PEG moiety attached to the PAMAM@IONPs provides the conjugates with excellent solubility and stability in an aqueous medium, which may increase the circulation time. The attached FA could target the conjugates to the folate receptor (FR). These novel DOX-loaded conjugates have the potential to enhance the effect of MRI contrast and cancer therapy in the course of delivering drugs to the target sites.