Multimodal imaging and photothermal therapy were simultaneously achieved in the core–shell UCNR structure by using single near-infrared light

Abstract

Core–shell nanostructures consisting of plasmonic materials and lanthanide-doped upconversion nanoparticles (UCNPs) show promising applications in theranostics including bio-imaging, diagnosis and therapy. However, some challenges still remain in the synthetic control because of the non-coordination between energy transfer and photothermal therapy (PTT). Herein, we developed a novel type of thermal-fluorescent core–shell hybrid nanocomposite incorporating rare-earth Yb³⁺ and Er³⁺ ion doped GdOF as the shell and gold nanorods (GNRs) as the core, creating upconversion nanorods (UCNRs) of GNRs@GdOF:Yb³⁺,Er³⁺. In order to facilitate the absorption or excretion of UCNRs in vivo, we designed gold nanorods with lower aspect ratios by reducing the amount of CTAB in the growth solution. More importantly, under 980 nm near-infrared (NIR) light irradiation, the green and red emissions of GdOF:Yb³⁺,Er³⁺ generally overlap with the visible absorbance of GNRs; by altering the contents of Yb³⁺ and Er³⁺ ions appropriately, the localized surface plasmon resonance (LSPR) absorption of low aspect ratio GNRs under 980 nm NIR laser excitation can be enhanced for improving the PTT efficiency. Furthermore, in vitro and in vivo assays reveal that the composite has excellent bio-compatibility and cancer therapy efficiency. This multi-functional nanocomposite, which possesses upconversion luminescence and photothermal and biocompatibility properties, shows strong potential for application in bio-imaging and photothermal anti-cancer therapy.