N Charchi¹*, P Nath², K Xie³, E Parsai⁴, A Ray⁵, D Shvydka⁶, (1) University of Toledo Medical center, Toldeo, OH, (2) University Of Toledo, ,,(3) ,,,(4) University of Toledo Medical Center, Toledo, OH, (5) University Of Toledo, ,,(6) University of Toledo Health Science Campus, Toledo, OH

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  N Charchi

PO-GePV-T-435 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: Gold nanoparticles (GNPs) enhance the effect of radiation in biological models, primarily through greater production of reactive oxygen species (ROS), which are mostly responsible for cell inactivation under x-ray sources. GNPs exhibit some level of toxicity and the tendency to aggregate in the presence of salt, inherently present in any biological media. Development of suitable polymer coatings is therefore necessary for their practical use. GNPs surface coatings however may interfere with ROS production affecting the surface charge. In this study we investigate the feasibility of utilizing polyvinyl alcohol (PVA), a biocompatible and nontoxic polymer, for GNPs coating and measure ROS generation under 6MV x-ray irradiation.

Methods: The experiment was conducted in a cell-free medium comparing ROS generation in samples containing 0.05mg/ml GNPs coated with 0.1 and 1% PVA irradiated with a 6MV using a linac for various dose levels. X-rays mediated water radiolysis and associated radiolytic compounds were produced by one-electron redox processes (radiation-oxidation chemical reactions) at the PVA coated GNP surface. Fluorescence microscopy was used to quantify the ROS generated after irradiation in the medium using Dihydrorhodamine-123(DHR123) fluorescent sensor, activated in the presence of ROS.

Results: The PVA coated GNPs showed ~25% increase in the production of ROS compared to aqueous solution containing PVA nanoparticles at similar concentration. However, when compared to water without PVA, the increase in ROS production from PVA coated GNPs was <5%. These results can be attributed to quenching of the ROS by PVA.

Conclusion: Ionizing radiation interacts with coated GNPs, changing their catalytic effects and surface charge, which is important for ROS formation. Although PVA effectively prevented GNP aggregation in media, our findings reveal that it also quenches the created ROS, likely due to interaction between the coating and DHR123 sensor thus making the composite system less suitable for GNP-enhanced radiation therapy application.

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