RESUMO
Breast cancer is a major cause of death among women worldwide. Resistance to conventional therapies has been observed in HER2-positive breast cancer patients, indicating the need for more effective treatments. Small interfering RNA (siRNA) therapy is an attractive strategy against HER2-positive tumors, but its success depends largely on the efficient delivery of agents to target tissues. In this study, we prepared a magnetic hybrid nanostructure composed of iron oxide nanoparticles coated with caffeic acid and stabilized by layers of calcium phosphate and PEG-polyanion block copolymer for incorporation of siRNA. Transmission electron microscopy images showed monodisperse, neutrally charged compact spheres sized <100 nm. Dynamic light scattering and nanoparticle tracking analysis revealed that the nanostructure had an average hydrodynamic diameter of 130 nm. Nanoparticle suspensions remained stable over 42 days of storage at 4 and 25 °C. Unloaded caffeic acid-magnetic calcium phosphate (Caf-MCaP) nanoparticles were not cytotoxic, and loaded nanoparticles were successfully taken up by the HER2-positive breast cancer cell line HCC1954, even more so under magnetic guidance. Nanoparticles escaped endosomal degradation and delivered siRNA into the cytoplasm, inducing HER2 gene silencing.