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

Abstract

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 μM with a limit of detection of 0.13 μM. 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 × 10⁻⁷, 4.0 × 10⁻⁷ and 6.0 × 10⁻⁷ mol L⁻¹, respectively. The coexisting random DNAs do not interfere with the detection at a concentration of 5.0 × 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.