Design of Gold Hollow Nanorods with Controllable Aspect Ratio for Multimodal Imaging and Combined Chemo-Photothermal Therapy in the Second Near-Infrared Window.

Gold nanoparticles (AuNPs) exhibit great potential for biological applications due to their good biocompatibility and tunable localized surface plasmon resonance (LSPR) properties. Currently, although tuning the aspect ratio of a solid structure or designing a hollow structure has been performed to regulate the LSPR properties of AuNPs, the method of preparing hollow anisotropic AuNPs has rarely been reported. In this study, we designed gold hollow nanorods (AuHNRs) with controllable aspect ratios by a Se-doping Te nanorod-templated method with the assistance of l-cysteine. UV-vis-NIR spectra showed that AuHNRs with an aspect ratio of about 3 could have a LSPR peak in the second near-infrared (NIR-II) window, which is only half of the value required by traditional Au nanorods. Moreover, AuHNRs are nontoxic and capable of loading drugs. In vivo experiment revealed that AuHNRs can be used as contrast agents in multimodal imaging, including photothermal imaging, photoacoustic imaging, and computed tomography imaging, as well as in chemo-photothermal combined therapy of tumor in the NIR-II window. Because light in the NIR-II window has remarkable advantages over that in the first near-infrared (NIR-I) window in biomedical applications, AuHNRs can be used as promising NIR-II-window-responsive multifunctional nanoagents.