Synthesis and Characterization of Doxorubicin Loaded pH-Sensitive Magnetic Core–Shell Nanocomposites for Targeted Drug Delivery Applications

In order to improve the effects of medical therapy for cancer, we prepared magnetic nanocomposites (Fe 3 O 4 @SiO 2 –NH–NH 2 ) as doxorubicin (DOX) carriers via two different schemes. Scheme (I): the carriers were synthesized from magnetic silica nanoparticles (Fe 3 O 4 @SiO 2 ) via layer by layer modification, scheme (II): the carriers were obtained from amino-modified magnetic silica nanoparticles (Fe 3 O 4 @SiO 2 –NH 2 ) synthesized by one-step, and followed by surface modification. In order to load DOX effectively, the surface of the carriers were further modified to make the surface with a large number of hydrazine bonds which can form a pH-sensitive bond (hydrazone bond) with DOX. The two kinds of carriers both exhibited a size around 80 nm, high stability and superparamagnetic behavior. However, DOX-loaded carriers (Fe 3 O 4 @SiO 2 –DOX(2)) performed relatively poorer performance in terms of drug loading and releasing (the loading efficiency of DOX decreased from 67.33% to 42.15%, while the releasing efficiency of DOX decreased from 66.16% to 62.23% within 72 h at pH 4.0). Water-soluble tetrazolium salts (WST-1) assays in cancer cells (Hela) demonstrated that the Fe 3 O 4 @SiO 2 –DOX presented high anti-tumor activity, while the carriers were nearly nontoxic. Thus, the results suggested that the magnetic nanocomposites synthesized by the two different methods both can be employed to deliver DOX, while the carriers obtained via the first method may perform better and would be applied in the field of cancer therapy in the future.