Speaker
Description
While nanopore techniques have transformed genomics, their potential for single-molecule biodosimetry remains untapped. We demonstrate a nanopore-based method to quantify DNA fragmentation in 2500 BP(base pairs) samples in solution, exposed to doses ranging from 1 Gy to 20 Gy of radiation from Co-60 gammas, 150 MeV protons, and Cf-252 neutrons. Using a fabricated nanopipette resistive pulse sensor, we monitored the concentration of intact DNA versus dose to evaluate radiation effectiveness.
By monitoring the concentration of intact DNA vs. dose for the different types of radiation, we were able to compare the effectiveness of these incident radiations according to a biological endpoint based on DNA damage. A simple model of underlying kinetics based on hydroxyl attack of DNA was used to analyze experimental data. Results show a marked decrease of intact DNA with aggregate dose in all radiations studied. Notably, there was a transition from linear to nonlinear dependence of DNA damage occurring at approximately 7 Gy, which we interpret through a kinetics-based model of hydroxyl radical attack. At fixed dose, DNA damage from protons and from neutrons exceeded damage from gammas, indicative of an elevated biological effectiveness of the massive-particle radiation as compared to gammas that varies with aggregate dose. The kinetics-based model yields a dose-response curve for gammas in good agreement with experimental data, with G-values for hydroxyl production that corroborate previous experimental determinations.
Adaptation of the dose-response model for incident protons and neutrons is in progress, but experimental evidence nevertheless points to enhanced biological effect for these high-LET types of radiation and the variation of this effect with aggregate dose. These findings support the development of a new metrological framework for radiation potency based on direct DNA lesion quantification rather than macroscopic energy deposition.