Selection of DNA aptamers for the development of light-up biosensor to detect Pb(II)

In order to develop a simple, facile, and cost-effective light-up biosensor with high specificity for Pb(II), a modified affinity chromatography SELEX (Systematic Evolution of Ligands by Exponential Enrichment) method based on target-induced release of strands was used to isolate aptamers of Pb(II). After 14 rounds positive selection and 4 rounds negative selection, two aptamers with high binding affinity and good specificity were obtained, which have the dissociation constant Kd values of 1.60 +/- 0.16 mu M and 0.76 +/- 0.18 mu M, respectively. Then we designed a biosensor for Pb(II), which is based on the Pb(II)-induced release of fluorescence-labeled aptamer from complex with a quencher-labeled short complementary sequence. The biosensor showed a Pb(II) concentration-dependent increase of fluorescence intensity in the low micromolar range and a detecting linear range from 100 to 1000 nM, and great specificity even in the existence of various interfering metal ions. Moreover, this simple and reliable biosensor obtained satisfying results for the detection of Pb(II) in lake water and serum samples. (C) 2017 Elsevier B.V. All rights reserved.