Short-wave near-infrared emissive GdPO4: Nd3+ theranostic probe for in vivo bioimaging beyond 1300 nm

The optical probes working in the second near-infrared (NIR-II) window have attracted increasing research interest for their advantages of high tissue penetration depth, low autofluorescence, and unprecedentedly improved imaging sensitivity and spatial resolution. Therefore, it is of great significance to design a new nanoplatform by integration of NIR-II optical imaging and drug delivery functions. Herein, a multifunctional nanoplatform based on GdPO4:Nd3+ yolk-shell sphere was developed for dual-modal in vivo NIR-II/X-ray bioimaging and pH-responsive drug delivery. The in vivo NIR-II bioimaging and real-time tracking presented that these probes were mainly accumulated in liver and spleen. Moreover, owing to the large X-ray absorption coefficient of Gd3+, these probes are successfully used as superior X-ray imaging agents than iobitridol. The in vivo toxicity assessments demonstrate the low biotoxicity of the GdPO4:Nd3+ spheres in living animals. More importantly, apart from the excellent dual-modal bioimaging, these yolk-shell-structured probes were also used as ideal nanotransducer for pH-responsive drug delivery of doxorubicin (DOX). These findings open up the opportunity of designing theranostic nanoplatform with integration of imaging-based diagnosis and therapy.