Synthesis of Lanthanide-based scintillator@MOF nanocomposites for X-ray-induced photodynamic therapy

Multifunctional nanocomposites comprising a set of diverse nanoparticles are highly desirable for realizing on-demand therapy with minimized adverse effects. X-ray-induced photodynamic therapy (X-PDT) has reformed conventional PDT for deep-seated tumor by utilizing penetrating X-rays, but its application faces the challenge of efficiently integrating scintillator with photosensitizer. To this end, core-shell nanocomposites rationally integrating NaGdF4: Tb@NaGdF4: Ce@NaLuF4 nanoparticles with Hf-porphyrin metal–organic frameworks (MOFs) by surface-assisted epitaxial-growth strategy, have been proposed and synthesized for X-PDT. Herein, NaGdF4: Tb@NaGdF4: Ce@NaLuF4 nanoparticles demonstrate strong X-ray attenuation coefficient and bright green light emission, serving as efficient scintillator to activate the photosensitizer. The porphyrin in MOFs can absorb and further be activated by the emission of lanthanide-based scintillator, playing the role of photosensitizer to generate a significant amount of singlet oxygen. Moreover, the uniform nanocomposites with regular core-shell structure enables the maximization of energy transfer between scintillator and MOFs, and inherent pores of MOFs facilitate the diffusion of reactive oxygen species (ROS) out of the MOF interior to boost PDT efficacy. Besides, the existence of heavy atoms such as Gd, Lu, and Hf can significantly enhance the radiation sensitization, facilitating the production of ROS. This work presents a novel strategy for fabricating lanthanide-based scintillator@MOFs nanocomposites for efficient X-PDT and is anticipated to promote the theranostic applications of nanocomposites.