Core–Shell Lanthanide Upconversion Nanophosphors as Four-Modal Probes for Tumor Angiogenesis Imaging

Abstract

Multimodality imaging overcomes the shortage and incorporates the advantages of different imaging tools. Lanthanide-based nanoprobes are unique and have rich optical, magnetic, radioactive, and X-ray attenuation properties; however, simple doping of different lanthanide cations into one host can result in a material with multifunction but not the optimized properties. In this study, using NaLuF₄:Yb,Tm as the core and 4 nm of ¹⁵³Sm³⁺-doped NaGdF₄ (half-life of ¹⁵³Sm = 46.3 h) as the shell, we developed a lanthanide-based core–shell nanocomposite as an optimized multimodal imaging probe with enhanced imaging ability. The lifetime of upconversion luminescence (UCL) at 800 nm and relaxation rate (1/<i>T</i>₁) were at 1044 μs and 18.15 s^–1·mM^–1, respectively; however, no significant decrease in the attenuation coefficient was observed, which preserved the excellent X-ray imaging ability. The nanomaterial NaLuF₄:Yb,Tm@NaGdF₄(¹⁵³Sm) was confirmed to be effective and applicable for UCL imaging, X-ray computed tomography (CT), magnetic resonance imaging, and single-photon emission computed tomography (SPECT) <i>in vivo</i>. Furthermore, the NaLuF₄:Yb,Tm@NaGdF₄(¹⁵³Sm) nanoparticles were applied in tumor angiogenesis analysis by combining multimodality imaging of CT, SPECT, and confocal UCL imaging, which shows its value of multifunctional nanoparticles NaLuF₄:Yb,Tm@NaGdF₄(¹⁵³Sm) in tumor angiogenesis imaging