Label free DNA detection based on gold nanoparticles quenching fluorescence of Rhodamine B

A novel and sensitive label free DNA detection method using gold nanoparticles (GNPs) and Rhodamine B (RB) has been developed. The assay is based on the following two properties. One is the different adsorption properties of single-stranded and double-stranded DNA on GNPs in colloidal solution. The other is the different quenching ability of aggregated GNPs and dispersed GNPs on RB. Un-aggregated GNPs could effectively quench the fluorescence of RB. However, the quenching ability greatly decreases after GNPs aggregated. The hybridization of probe DNA and target DNA is monitored by the fluorescence detection after the RB is added to the solution. Under the optimal experimental conditions, the detection limit of this assay is 2.9 x 10(-13) mol L-1. (C) 2011 Elsevier B.V. All rights reserved.