Glutathione-Responsive Self-Assembled Magnetic Gold Nanowreath for Enhanced Tumor Imaging and Imaging-Guided Photothermal Therapy

Designing nanomaterials with advanced functions and physical properties to improve cancer diagnosis and treatment has been an enormous challenge. In this work, we report the synthesis of magnetic gold nanowreaths (AuNWs) by combining wet-chemical synthesis with layer-by-layer self-assembly. The presence of Au branches, small junctions, and central holes in AuNWs led to improved photothermal effect compared with Au nanoring seeds and thick Au nanoring with smooth surface. The self-assembly of exceedingly small magnetic iron oxide nanoparticles (ES-MIONs) on the surfaces of AuNWs not only effectively quenched the T₁-weighted magnetic resonance imaging (MRI) ability due to the enhanced T₂ decaying effect but also provided the responsiveness to glutathione (GSH). After intravenous injection, the T₁ signal of magnetic AuNWs initially in the "OFF" state can be intelligently switched on in response to the relatively high GSH concentration in tumor, and the formation of larger assemblies of ES-MIONs improved their tumor delivery compared to ES-MIONs themselves. Thus, the magnetic AuNWs showed higher MRI contrast than ES-MIONs or commercial Magnevist in T₁-weighted MR imaging of tumor. Furthermore, the magnetic AuNWs have absorption in near-infrared range, leading to strong photoacoustic signal and effective photoablation of tumor. Therefore, our GSH-responsive self-assembled magnetic AuNWs could enhance T₁-weighted MRI and photoacoustic imaging of tumor and be used for imaging-guided photothermal therapy.