Quantitative relationship between microdosimetric quantities and plasmid DNA damage induced by auger electrons

Area of Science:

• Radiological Physics and Radiation Biology
• Nanodosimetry and Radiation Chemistry

Background:

• Understanding the physical mechanisms of radiation-induced DNA damage is crucial for radiation protection and therapy.
• Auger electrons (AEs) deposit energy at the nanometer scale, posing unique challenges for microdosimetric analysis.
• Microdosimetric quantities like lineal energy are potential physical predictors of initial DNA damage.

Purpose of the Study:

• To investigate the microdosimetric characteristics of Auger electrons (AEs).
• To evaluate microdosimetric quantities (yF and yD) as physical predictors of initial DNA damage.
• To assess the universality of these predictors across different radiation types (AEs, protons, alpha particles).

Main Methods:

• Monte Carlo simulations using OpenTOPAS to calculate frequency-mean lineal energy (yF) and dose-mean lineal energy (yD).
• Simulations were performed in spherical water targets (10-500 nm radii) for monoenergetic electrons (3-15 keV).
• DNA damage yields (strand breaks, double-strand breaks) were quantified using TOPAS-nBio with a plasmid DNA model.

Main Results:

• AEs showed site-radius dependency for yF and yD in 10-100 nm targets.
• Strong power-law correlations (R² ≥ 0.94 for yF, R² ≥ 0.89 for yD) were observed between microdosimetric quantities and DNA damage yields.
• A continuous microdosimetric-damage relationship was found for low-energy electrons, protons, and alpha particles; yF was a more sensitive predictor for AEs at low lineal energies (<10 keV/µm).

Conclusions:

• Microdosimetric quantities yF and yD effectively reflect nanoscale energy deposition patterns related to DNA strand break induction.
• The established microdosimetry-damage relationship is applicable to low-energy AEs, protons, and alpha particles.
• Frequency-mean lineal energy (yF) serves as a more sensitive physical predictor for initial DNA damage induced by Auger electrons in specific energy ranges.