Amplification of Reactive Oxygen Species Generation Under Gamma-Ray Irradiation for Gold Nanoparticle Mediated Radiation Therapy
N Charchi*, K Xie, A Ray, E Parsai, D Shvydka, University of Toledo Medical center, Toldeo, OH P Nath, University of Toledo
Presentations
TU-IePD-TRACK 6-2 (Tuesday, 7/27/2021) 3:00 PM - 3:30 PM [Eastern Time (GMT-4)]
Purpose: An approach of selective enhancement of the tumoricidal radiation effect with gold nanoparticles (AuNPs) have been successfully explored experimentally, both in-vivo and in-vitro. Significant amplification of reactive oxygen species (ROS) generation under irradiation in the presence of AuNPs is proposed as the main mechanism responsible for the biological effect. We have a two-fold purpose in this study: 1) finding a sensor suitable for quantitative characterization of ROS species in both aqueous media and cell cultures; 2) establishing a reliable protocol for fluorescence measurements with the sensor.
Methods: Radiolytic products such as hydroxyl radicals and hydrogen peroxide, generated under high-energy photon irradiation can be quantitatively characterized by fluorescence spectroscopy, providing a reliable sensor is identified. 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA) dissolved in DMSO (dimethyl sulfoxide) was used as a ROS sensor in experiments comparing radiolysis in pure water and 0.005mg/ml concentration AuNP solution (particle diameter 30nm, citrate coating). Samples in glass capillaries were irradiated under Ir-192 HDR treatment source (average energy ~380keV) to dose levels up to 100Gy. Fluorescence signal measurements were performed on irradiated samples within 1 hour after HDR treatment.
Results: The fluorescence intensity signals were normalized to those of the 0Gy, used as control in each experiment. The signal intensity increased with the dose for both aqueous and AuNP solutions, demonstrating AuNP-mediated ROS enhancement above 30% for higher doses. The sensor was found suitable for aqueous media only after cleavage in cell culture. The concentration of AuNPs used in the study leads to negligible physical dose enhancement. The same sensor was used with cells, demonstrating strong fluorescence signal after irradiation.
Conclusion: An experiment procedure for quantitative characterization of ROS species in both aqueous media and cell cultures using H2DCFDA was established and validated. Fluorescence signal enhancement is attributed to amplification in ROS production in presence of AuNPs.
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