Multifunctional iron oxide/silk-fibroin (Fe₃O₄-SF) composite microspheres for the delivery of cancer therapeutics

In this article, we report novel multifunctional iron oxide/silk-fibroin (Fe₃O₄-SF) microspheres synthesized by simple salting out process. These microspheres are used as the carriers of doxorubicin hydrochloride (a traditional anti-cancer drug), denoted as DOX-Fe₃O₄-SF. The results show that the drug loading capacity (LC) is 3.3% and the drug encapsulation efficiency (EE) could reach up to 76%. The DOX-loaded microspheres exhibit sustained and pH-sensitive release patterns. The total DOX release is measured to be about 60% at pH 5.5. More interestingly, RhB-labelled Fe₃O₄-SF microspheres exhibit a striking endocytosis, selectively accumulating in the cytoplasm compared to the free RhB. The endocytosis of DOX-Fe₃O₄-SF microspheres results in only ∼10% survival ratio of HeLa cells after 48 h. Furthermore, because of the remarkable biocompatibility of SF, Fe₃O₄-SF microspheres show no cytotoxicity toward HeLa cells compared to DOX-Fe₃O₄-SF. The results clearly indicate that Fe₃O₄-SF microspheres hold significant potential for drug loading and delivery into cancer cells to induce cell death.