Enzyme-free detection of DNA based on hybridization chain reaction amplification and fluorescence resonance energy transfer

A versatile enzyme-free deoxyribonucleic acid (DNA) detection method based on hybridization chain reaction (HCR) and fluorescence resonance energy transfer (FRET) was developed. Hairpin H1 and H2 are labelled with carboxyfluorescein (FAM) as the donor and tetramethylrhodamine (TAMRA) as the acceptor, respectively. In the presence of target DNA, long nicked dsDNA nanowires are self-assembled through HCR process. The donor and the acceptor are brought in close proximity, resulting in a FRET process between them. The ratio of fluorescent intensities of the acceptor and donor can be used to quantitatively detect the target DNA with a limit of detection 0.7 nmol L−1. This proposed method was applied to detect DNA in biologic samples with satisfactory results.