On the mechanism of radiation sensitization by gold nanoparticles under X-ray irradiation of oxygen-free aqueous organic solutions: A spin trapping study

In this study we have probed the role of different enhancement mechanisms of the nanosensitizers in the X-ray irradiated oxygen-free model aqueous organic systems containing “bare” gold nanoparticles (AuNPs) using the spin-trapping technique with electron paramagnetic resonance detection. The observed enhancement effect was found to be ca. 1.67 wp−1 for the AuNPs with an average diameter of 18 nm and 45 kVp X-rays. The comparison with Monte Carlo simulation shows that the sensitizing effect of AuNPs in the X-ray irradiated oxygen-free aqueous organic systems could be attributed to the increasing absorbed dose due to high absorption cross-section of gold atoms. It implies that the radiation-chemical yield of hydroxyl radicals responsible for the oxidative damage in the absence of oxygen remains virtually unchanged in the presence of AuNPs. Also, no clear evidence was found for the dose rate effects upon variation of this parameter by more than an order of magnitude (0.06–1.21 Gy/s). In practical sense, these results urge the development of new efficient approaches for the radiation treatment of hypoxic media using nanoparticles.