Comparative Influence of Dendron and Dicarboxylate Coatings on the Hyperthermia Performances of Cubic and Spherical Magnetic Nanoparticles

Surface functionalization of magnetic nanoparticles, commonly used for their biocompatibility in biomedical applications, plays a critical role in optimizing iron oxide nanoparticles (IONPs) for magnetic hyperthermia (MH), a promising modality in cancer therapy. In this study, we provide the first comprehensive comparison of hyperbranched dendron coatings versus linear dicarboxylate ligands on IONPs, revealing their contrasting impacts on heating efficiency under varying magnetic field amplitudes (H). Dendron-coated IONPs outperform dicarboxylate-coated ones at low fields (H < 25 kA/m) due to reduced dipolar interactions and enhanced Brownian relaxation. Conversely, dicarboxylate coatings excel at high fields (H > 25 kA/m) by enabling magnetically aligned chains, which amplify hysteresis losses. Our work also introduces an approach to dynamically modulate the heating efficiency of IONPs by applying a static DC magnetic field (H_DC) in conjunction with the alternating magnetic field (AMF). We observed a coating-dependent response to H_DC in the parallel configuration (H_DC aligned with AMF), the specific absorption rate (SAR) increased by ~620 W/g_Fe for cubes and ~370 W/g_Fe for spheres at high AMF amplitudes (H > 30 kA/m) for dicarboxylate-coated IONPs. This enhancement arises from magnetically aligned chains (visualized via Transmission Electron Microscopy), which amplify extrinsic anisotropy and hysteresis losses; in contrast, for dendron-coated IONPs, their SAR values decreased under H_DC (up to ~665 W/g_Fe reduction for cubes in the perpendicular configuration), as the thick dendron shell prevents close interparticle contact, suppressing chain formation and fanning rotation modes. These findings underscore the significance of surface functionalization in enhancing the therapeutic efficacy of magnetic nanoparticles.