Quantification of DNA through a fluorescence biosensor based on click chemistry.

A simple, sensitive and selective fluorescence biosensor for determination of DNA using CuS particles based on click chemistry is reported. Biotin-modified capture DNA was modified on Streptavidin MagneSphere Paramagnetic Particles (PMPs) and hybridized with target DNA (hepatitis B virus DNA had been chosen as an example), then bound target DNA was hybridized with DNA-CuS particles and formed a sandwich like structure. CuS particles on the sandwich structures can be destroyed by acid to form Cu(II), and Cu(II) can be reduced to Cu(I) by sodium ascorbate, which in turn catalyzes the reaction between a weak-fluorescent 3-azido-7-hydroxycoumarin and propargyl alcohol to form a fluorescent 1,2,3-triazole compound. Using this method, target DNA concentration can be determined by a change in the fluorescence intensity of the system. It is found that the fluorescence increase factor has a direct linear relationship to the logarithm of target DNA concentrations in the range of 0.1 to 100 nM, and the detection limit is 0.04 nM (S/N = 3). The proposed sensor not only allows high sensitivity and good reproducibility, but also has a good selectivity to single-nucleotide mismatches.