Curve fitting of combined comet intensity profiles : a new global concept to quantify DNA damage by the comet assay

Abstract The comet assay has become a widely used technique to detect a broad spectrum of DNA damage with the particularity of being performed at cell level. Usual stress quantification methods include individual comet visual examination (“visual scoring”) and computer-assisted image analysis. However, a certain subjectivity, loss of information or dispersion of data associated with these methods do not always allow to ascertain low-level genotoxicity nor to exactly quantify damage magnitude. This paper validates on two cell lines (murine lymphoma P388D1 and human melanoma HBL), treated with increasing doses of ethyl methanesulfonate, a new concept developed within the Matlab® environment for DNA damage quantification by comet assay. Instead of collecting data at cell-level, we propose to build a mathematical model from the combination of the sampled comet intensity profiles. The proposed fitting model is the sum of 2 bell-shaped curves. The results show that this mathematical modelling approach represents a good tool to ascertain the presence of DNA damage as well as quantify DNA damage. In this latter case, DNA damage may be quantified either (i) directly from model parameters, or (ii) by recomputing classical morphological comet metrics such as Tail DNA on the fitted profile.