LuAG:Pr-porphyrin based nanohybrid system for singlet oxygen production: Toward the next generation of PDTX drugs.

A highly prospective drug for the X-ray induced photodynamic therapy (PDTX), LuAG:Pr@SiO-PpIX nanocomposite, was successfully prepared by a three step process: photo-induced precipitation of the LuAlO:Pr (LuAG:Pr) core, sol-gel technique for amorphous silica coating, and a biofunctionalization by attaching the protoporphyrin IX (PpIX) molecules. The synthesis procedure provides three-layer nanocomposite with uniform shells covering an intensely luminescent core. Room temperature radioluminescence (RT RL) spectra as well as photoluminescence (RT PL) steady-state and time resolved spectra of the material confirm the non-radiative energy transfer from the core Pr ions to the PpIX outer layer. First, excitation of Pr ions results in the red luminescence of PpIX. Second, the decay measurements exhibit clear evidence of mentioned non-radiative energy transfer (ET). The singlet oxygen generation in the system was demonstrated by the 3'-(p-aminophenyl) fluorescein (APF) chemical probe sensitive to the singlet oxygen presence. The RT PL spectra of an X-ray irradiated material with the APF probe manifest the formation of singlet oxygen due to which enhanced luminescence around 530 nm is observed. Quenching studies, using NaN as an O inhibitor, also confirm the presence of O in the system and rule out the parasitic reaction with OH radicals. To summarize, presented features of LuAG:Pr@SiO-PpIX nanocomposite indicate its considerable potential for PDTX application.