CeYTbF3–Photoran complex for X-ray-Induced photodynamic therapy: energy transfer and cellular toxicity

Abstract

Ce0.5Y0.35Tb0.15F3 nanoparticles conjugated with the chlorin e6 photosensitizer Photoran were studied as a potential system for X-ray-induced photodynamic therapy. Under 266 nm excitation, the luminescence spectra contained a broad Ce3+ band at 280–400 nm and characteristic Tb3+ lines at 487, 540, 583, and 619 nm. Addition of Photoran shortened the Tb3+ luminescence lifetime, indicating nonradiative energy transfer to the photosensitizer. The transfer efficiency reached 67% at 55 μL/mL Photoran solution. After colloid dilution, the luminescence lifetime did not recover, confirming formation of stable conjugates. Analysis using Dexter expressions and the Reisfeld approximation showed that transfer occurred predominantly through a dipole–dipole Förster mechanism.

The nanoparticle powder was treated with low-pressure helium plasma. X-ray diffraction revealed no substantial crystal-structure changes, whereas the zeta potential changed from (+17.4 ± 0.5) to (−0.17 ± 0.13) mV and luminescence quenching in the presence of Photoran decreased.

Cytotoxicity was evaluated by the MTT assay using A549 human lung adenocarcinoma cells. After X-ray irradiation, cell viability in the presence of the conjugates was (51.5 ± 2.3)% at 100 kV and (66.1 ± 1.8)% at 200 kV. The increase in viability at higher tube voltage may result from lower X-ray absorption by the nanoparticles. The conjugate produced the strongest cytotoxic effect compared with its individual components, likely due to X-ray energy conversion by the nanoparticles, transfer to Photoran, and generation of reactive oxygen species. These findings confirm formation of stable Ce0.5Y0.35Tb0.15F3–Photoran conjugates with efficient energy transfer and pronounced X-ray-induced cytotoxicity.

Speaker

Akhmetzyanova Kamila
Kazan (Volga Region) Federal University
Russia

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