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Highly Efficient FRET System Capable of Deep Photodynamic Therapy Established on X-ray Excited Mesoporous LaF3:Tb Scintillating Nanoparticles

Tang, Yong’an, Hu, Jun, Elmenoufy, Ahmed H., Yang, Xiangliang
ACS Applied Materials & Interfaces 2015 v.7 no.22 pp. 12261-12269
X-radiation, crystallization, energy transfer, irradiation, luminescence, nanocomposites, nanoparticles, neoplasms, photochemotherapy, photosensitizing agents, porous media, singlet oxygen
Photodynamic therapy (PDT) for deep-seated tumor is largely impeded by the limited penetration depth of excitation light in tissue. X-ray is considered as an ideal energy source to activate photosensitizers (PSs) located deep within the body with the assistance of scintillating nanoparticles (ScNPs). However, the efficacy under this concept is not satisfying due to the low scintillating luminescence and weak energy transfer from ScNPs to PSs. Here, mesoporous LaF₃:Tb ScNPs were successfully synthesized by a facile hydrothermal process to act as PS carriers and X-ray energy transducers, owing to their good ionizing radiation stopping power and high luminescence efficiency. The formation mechanism of porous structure was elucidated in detail with classical crystallization theory. After a systematic investigation, LaF₃:Tb ScNPs with optimized scintillating luminescence were obtained for loading Rose Bengal (RB) to establish an efficient FRET system, owing to their excellent spectral match. The FRET efficiency between ScNPs and RB was calculated to be as high as 85%. Under irradiation, enhanced ¹O₂ generation induced by LaF₃:Tb-RB nanocomposites via FRET process was detected. This LaF₃:Tb-RB FRET system shows great potential to be applied in X-ray stimulated PDT for deep-seated tumors in the future.