Label-free DNA detection based on a DNA-silver nanocluster pair

We present a simple, selective and label-free sensor for detecting DNA based on the fluorescence of DNA-silver nanoclusters (DNA-Ag NCs). Two kinds of DNA-Ag NCs with different oligonucleotide sequences can bind together as a DNA-Ag NC pair by hybridization and show strong fluorescence emission at a wavelength of 624 nm. In the presence of the target DNA, the competing reaction of DNA hybridization occurs, and the formed DNA-Ag NC pairs decrease, exhibiting weak fluorescence emission. The fluorescence intensity decreases linearly with the increase of the target DNA concentration in the range of 0.20-10.00 mu M with a limit of detection of 0.13 mu M. The relative standard deviation (RSD) values obtained from the same batch of H1N1 target DNA were 1.80%, 0.30% and 2.90% at 2.0 x 10(-7), 4.0 x 10(-7) and 6.0 x 10(-7) mol L-1, respectively. The coexisting random DNAs do not interfere with the detection at a concentration of 5.0 x 10(-6) mol L-1. With this sensor, we successfully detected H1N1 target DNA and the results indicated that our method is reliable and has the potential for real sample application.