LuPO4:Nd3+ nanophosphors for dual-mode deep tissue NIR-II luminescence/CT imaging

lanthanide-doped phosphates luminescence materials have attracted increasing attention in biomedical applications. Among them, lanthanide-doped LuPO₄ nanophosphors have potentical for multimodal bioimaging due to good biocompatible and luminescence feasures and excellent X-ray absorption properties. However, research on the application of multimodal bioimaging using the lanthanide-doped LuPO₄ nanophosphors is still scarce. Here, dual-modal LuPO₄:Nd³⁺ nanophosphors with second near infrared (NIR-II) optical imaging and X-ray computed tomography (CT) imaging are reported. LuPO₄:Nd³⁺ nanoparticles (NPs) have been successfully prepared through a hydrothermal method under the chelator of critic acid. On the basis of the strong Nd³⁺ ion emission (at around 1064 nm), tissue penetration depths as large as 15 mm and the optical imaging in vivo have been demonstrated in the second near-infrared window, where absorption and scattering by human tissue are reduced drastically. Furthermore, the incorporation of Lu into the nanocystalline structure supplies strong X-ray absorption properties, making them promising for CT imaging as contrast agents. And, the nanophosphors exhibite relatively low toxicity and good biocompatibility for concentrations up to 800 mg L⁻¹, suggesting their safety for in vivo imaging. All these results suggested that the LuPO₄:Nd³⁺ nanoparticles can be regarded as potential candidates for dual-mode deep tissue NIR-II luminescence/CT imaging.