Monte Carlo Simulation of Enhanced Free Radical Generation Due to Presence of Gold Nanoparticle Under High Energy Photon Irradiation
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TU-IePD-TRACK 6-3 (Tuesday, 7/27/2021) 3:00 PM - 3:30 PM [Eastern Time (GMT-4)]
Purpose: Quantitative experimental characterization of free radical generation under high-energy photon irradiation, demonstrate enhancements in presence of gold nanoparticle (GNP). A concomitant free radical quenching effect leads to decreasing enhancement if nanoparticles are not precipitated immediately after irradiation. The two opposing effects are extremely difficult to decouple in experiment. In this study, Monte Carlo method is used to simulate those reaction processes in order to estimate the true amounts of free radicals generated in water radiolysis.
Methods: An in-house developed Monte Carlo model is based on a series of interaction probabilities, of which some are fixed based on established reaction parameters, some are set to adjustable parameters varied until a modeled outcome approaches that acquired through experiments. Statistics of different pathways of free radicals are tallied and analyzed as the results.
Results: Simulations for both pure water and GNP solutions were conducted to fit the measured data. Analysis of simulated data shows total amount of free radical generated with 30 nm diameter GNP in presence at 0.0005 mg/ml concentration is 265%±2% of that of pure water at all dose levels. About 37% of the free radicals are quenched by GNP. Excluding quenched, the ratio of released free radical is 159%±2%. The ratio of detected free radical amounts of two groups are dose dependent, similar to experimental result.
Conclusion: With Monte Carlo simulations we can successfully estimate the actual total amount of free radicals generated with the presence of GNP, including the fraction quenched, which is not easily measurable through experiments. The total free radical generation enhancement due to GNP compared to pure water is much higher than can be detected. The decreasing enhancements vs dose is due to faster decline of sensor molecule concentration in the presence of GNPs.
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