Abstract
We report on strong X-ray-induced hydroxyl radical (. O H ) generation in an aqueous solution containing UV light pre-treated GdYVO4:Eu3+ nanoparticles (L-GdYVO). The methods of optical spectroscopy were used to detect . O H in the solutions. The complex nature of the mechanism of . O H generation has been revealed and discussed. The experimental data obtained indicate that the mechanism of . O H generation is associated with two main processes: (i) direct . O H generation with the participation of thermalized h+ formed at X-ray irradiation, and (ii) X-ray-facilitated jumps of h+ formed in the nanoparticles’ (NPs’) valence band at UV light pre-treatment and trapped in local levels formed by random scattering potential. At the same time, for GdYVO4:Eu3+ nanoparticles, which were not exposed to UV light before the X-ray irradiation (D-GdYVO), a strong radioprotective effect ascribed to the electron-donation properties of V4+ ions was observed. Thus, depending on the pre-treatment condition, we can change the redox properties of GdYVO4:Eu3+ NPs in an opposite direction, which makes this nanomaterial a unique theranostic agent for radiation therapy (RT) enhancement, allowing the problem of radiation therapy (RT)-resistant hypoxic tumours to be overcome.
Highlights
Radiation therapy (RT), i.e., the use of ionizing radiation for cancer treatment, has become one of the first-line treatment modalities in oncology [1,2,3,4]
This paper extends our work on GdYVO4 :Eu3+ NPs redox activity studies [23,24,25]
The obtained aqueous colloidal solution containing GdYVO NPs was characterized by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction analysis (XRD), dynamic light scattering (DLS) analysis, and UV-vis optical spectroscopy
Summary
Radiation therapy (RT), i.e., the use of ionizing radiation for cancer treatment, has become one of the first-line treatment modalities in oncology [1,2,3,4]. X-rays or γ-rays used for RT can destroy cancer cells either by directly damaging the nuclear material (DNA). By ionization/excitation of the water component of the cells. In the latter case, water is sequentially converted into a number of radicals and molecular products: hydrated electrons As photons interact with tumour tissues, severe side effects or even secondary cancers may be induced when healthy tissues are damaged [7,9]. The second challenge is innate or acquired radioresistance in a number of cancers (e.g., hypoxic tumours such as pancreatic cancer and glioblastoma) [9,10,11]. Solid tumours are Crystals 2020, 10, 370; doi:10.3390/cryst10050370 www.mdpi.com/journal/crystals
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