Star-Shaped Magnetic-Plasmonic Au@Fe3O4Nano-Heterostructures for Photothermal Therapy

Here we synthesize Au@Fe3O4 core@shell system with a highly uniform unprecedent star-like shell morphology with combined plasmonic and magnetic properties. An advanced electron microscopy characterization allows assessing the multifaced nature of the Au core and its role in the growth of the peculiar epitaxial star-like shell with excellent crystallinity and homogeneity. Magnetometry and magneto-optical spectroscopy revealed a pure magnetite shell, with a superior saturation magnetization compared to similar Au@Fe3O4 heterostructures reported in the literature, ascribed to the star-like morphology, as well as to the large thickness of the shell. Of note, Au@ Fe3O4 nanostars loaded cancer cells displayed magneto-mechanical stress under a low frequencies external alternating magnetic field (few tens of Hz). On the other hand, such a uniform, homogeneous, and thick magnetite shell enables the shift of the plasmonic resonance of the Au core to 640 nm, which is the largest red-shift achievable in Au@Fe3O4 homogeneous core@shell systems, prompting application in photothermal therapy and optical imaging in the first biologically transparent window. Preliminary experiments performed irradiating a stable water suspension of the nanostar and Au@Fe3O4 loaded cancer cell culture suspension at 658nm, confirmed their optical response and their suitability for photothermal therapy. The outstanding features of the prepared system can be thus potentially exploited as multifunctional platform for magnetic-plasmonic applications.