Layer-by-layer assembled hyaluronic acid/chitosan-coated Fe₃O₄@rGO nanoparticles: Synthesis and characterization for doxorubicin delivery in breast cancer cells

Magnetic nanoparticles (MNPs) are of significant interest for biomedical applications. Among them, Fe₃O₄ nanoparticles are widely used. However, they suffer from oxidation and reduced magnetization under physiological conditions. To overcome this limitation, Fe₃O₄@rGO (FR) nanoparticles were synthesized via a solvothermal method and optimized for 20 h reaction time. For further functionalization, the MNPs were coated with a multilayered polymeric shell consisting of alternating hyaluronic acid (HA) and chitosan (CHI) layers through a Layer-by-Layer (LbL) assembly method, with doxorubicin (DOX) embedded directly within the HA layers for controlled release, and referred to as FR-HC@DOX. In this design, rGO enhances structural stability, HA provides CD44-mediated targeting ability, and CHI improves biocompatibility. The LbL technique allows for precise control of coating thickness and uniform layer deposition, enhancing drug-loading efficiency and ensuring controllable release profiles. The optimized FR-HC@DOX maintained sufficient magnetic response (M_s = 26.04 emu/g) after drug loading, which is substantially higher than most reported polymer-coated Fe₃O₄ systems that typically drop below 20 emu/g. These magnetic nanocarriers also exhibited strong pH sensitivity (∼100 % release at pH 5.5 vs 13 % at pH 7.4) and showed potent anticancer activity in MCF-7 cells while remaining biocompatible in MCF-12A healthy control cells at concentrations up to 80 μg/mL. This study presents a new approach by combining rGO embedded/coated Fe₃O₄ with multilayer HA/CHI coatings, creating a magnetic nanocarrier that improves the stability of Fe₃O₄, is controllable, pH-responsive, and targeted drug release. These results position the system as a distinctive and effective nanoplatform for magnetically guided, tumor-targeted chemotherapy.