Cs-131 as an experimental tool for the investigation and quantification of the radiotoxicity of intracellular Auger decays in vitro

Purpose In this work, we set out to provide an experimental setup, using Cs-131, with associated dosimetry for studying relative biological effectiveness (RBE) of Auger emitters. Material and methods Cs-131 decays by 100% electron capture producing K- (9%) and L- (80%) Auger electrons with mean energies of 26 keV and 3.5 keV, respectively, plus approximate to 9.4 very low energy electrons (<0.5 keV) per decay. Cs-131 accumulates in the cells through the Na+/K+-ATPase. By this uptake mechanism and the alkali chemistry of Cs+, we argue for its intracellular homogeneous distribution. Cs-131 was added to the cell culture medium of HeLa and V79 Cells. The bio-kinetics of Cs-131 (uptake, release, intracellular distribution) was examined by measuring its intracellular activity concentration over time. Taking advantage of the 100% confluent cellular monolayer, we developed a new and robust dosimetry that is entrusted to a quantity calledS(C)-value. Results TheS(C)-values evaluated in the cell nucleus are almost independent of the nuclear size and geometry. We obtained dose-rate controlled RBE-values for intracellular Cs-131 decay. Using the gamma H2AX assay, the RBE was 1 for HeLa cells. Using the clonogenic cell survival, it was 3.9 for HeLa cells and 3.2 for V79 cells. Conclusion This experimental setup and dosimetry provides reliable RBE-values for Auger emitters in various cell lines.

Automated summary

This study provides an experimental setup using Cs-131 and dosimetry for studying the relative biological effectiveness (RBE) of Auger emitters. The intracellular activity concentration of Cs-131 was measured over time to evaluate RBE-values. The findings are important for understanding the biological effects of Auger emitters in different cell lines.