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

Objective.This study investigated the microdosimetric characteristics of auger electrons (AEs) and their DNA damage-related physical properties, specifically evaluating the microdosimetric quantity as a physical predictor of initial DNA damage across different radiation types.Approach.Monte Carlo simulations using OpenTOPAS were conducted to calculate the frequency-mean lineal energy (y_F) and the dose-mean lineal energy (y_D) in spherical water targets (radii: 10-500 nm) for monoenergetic electrons (3-15 keV). DNA damage yields were quantified using TOPAS-nBio with a linear plasmid DNA model. The correlations between microdosimetric quantities and DNA damage were analyzed not only for AEs but also for protons and alpha particles to assess the universality ofy_Fandy_Das potential biological predictors.Main results.AEs demonstrated a pronounced site-radius dependency for bothy_Fandy_Dwithin the 10-100 nm target region. Across these biologically relevant nano-scale targets, both strand break (SB) and double-SB (DSB) yields exhibited strong power-law correlations with microdosimetric quantities (R²⩾ 0.94 fory_FandR²⩾ 0.89 fory_D). Low-energy electrons, protons, and alpha particles aligned along a continuous microdosimetric-damage relationship despite differences in particle identity. Specifically,y_Fprovided a more sensitive physical predictor thany_Dfor Auger electron-induced initial DNA damage in the low-lineal-energy region below 10 keVμm^-1.Significance.These findings show thaty_Fandy_Dreflect nanoscale energy-deposition patterns governing initial DNA strand-break induction. This microdosimetry-damage relationship extends to low-energy AEs as well as proton and alpha particles.