Highly sensitive detection of DNA fragments by fluorescence correlation spectroscopy

DNA fragments in circulation released from apoptotic and necrotic cells were regarded as a novel prognostic or predictive biomarker for clinical diagnosis in recent years. However, DNA concentration in plasma ranged between 1 and 10 ng ml-1, which needed a single-molecule technology to analyze the base pair and concentration of DNA fragments. In this study, a series of different lengths of DNA fragments were studied, which showed that a good linear relationship between the DNA concentration and the molar concentration. The results suggested fluorescence correlation spectroscopy could access the nanomolar concentration of DNA labelled by SYBR Green I. Moreover, the relationship between the length of DNA fragment and the diffusion coefficient of DNA was scaled with the standard samples. The results demonstrates fluorescence correlation spectroscopy is a highly sensitive method for DNA detection.