Fluorescence switch for silver ion detection utilizing dimerization of DNA-Ag nanoclusters

A fluorescence switch that consists of DNA-templated silver nanoclusters (DNA-AgNCs) triggered by silver ion (Ag+) is developed to detect Ag+. The mechanism of the fluorescence switching of DNA-AgNCs is investigated by fluorescence spectroscopy, circular dichroism spectroscopy, DNA hybridization assay and mass spectrometry. Ag+ induces a dimeric structure of Cyt(12)-AgNCs by forming a bridge between two Cyt(12)-AgNCs, where Cyt(12) is cytosine 12-mer; this dimer formation causes the fluorescence change of Cyt(12)-AgNCs from red to green. Using this Ag+-triggered fluorescence switch, we successfully detected Ag+ at concentrations as low as 10 nM. Furthermore, we quantitatively detected the Ag+ in the Silmazin (R), which is dermatological burn ointment having silver sulfadiazine. Ag+ detection using this fluorescence switch has high selectivity and sensitivity, and short response time, and can be used successfully even in the presence of other metal ions. (C) 2015 Elsevier B.V. All rights reserved.