A Fluorescence Sensor for Lead (II) Ions Determination Based on Label-Free Gold Nanoparticles (GNPs)-DNAzyme Using Time-Gated Mode in Aqueous Solution.

This paper describes a label-free 17E DNAzyme-based time-gated fluorescence sensor for Pb2+ detection by unmodified gold nanoparticles (GNPs) and a terbium ternary complex. The fluorophore that used in this paper is a terbium ternary complex. Its signal can be measured in a time-gated manner which could eliminate most of the unspecific fluorescent background. It is well known that unfolded single-stranded DNA (ssDNA) could be adsorbed on GNPs while double-stranded DNA could not. The cleavage of the substrate by the 17E DNAzyme in the presence of Pb2+ causes the release of ssDNA from the 17E-17S duplex to be absorbed onto GNPs, preventing the aggregation of GNPs and then leading to a fluorescence decrease of terbium ternary complex. By means of this method, the authors have successfully detected Pb2+ over a range of 10 nM to 2500 nM with a detection limit of 1.7 nM. The sensor also exhibited good selectivity. The sensor provided a simple, cost-effective, rapid and sensitive measurement tool for Pb2+ detection.