MnO2 nanosheet-assisted ligand-DNA interaction-based fluorescence polarization biosensor for the detection of Ag+ ions

Silver (Ag+) ions are highly toxic to aquatic organisms and accumulate in the human body via the food chain. Therefore, the development of sensitive and selective quantitative analytical methods for detecting trace amounts of these ions is necessary. In the present study, a MnO2 nanosheet-assisted, ligand-DNA interaction and fluorescence polarization-based method was developed, for the first time, for sensitive detection of Ag+. The addition of Ag+ to the preformed proflavine-DNA complex induced the release of proflavine, which elicited weak changes in fluorescence polarization. The subsequent addition of MnO2 nanosheets magnified the observed changes, making this a feasible method for the detection of Ag+. The calibration graphs indicated good linearity over the concentration ranges of 30-240 nM for Ag+, with a detection limit (S/N=3) of 9.1 nM. This method additionally exhibits high selectivity. The mechanism underlying the changes in fluorescence polarization caused by the addition of Ag+ in the presence of MnO2 nanosheets was further explored in this study. These findings demonstrate that the present MnO2 nanosheet-assisted fluorescence polarization biosensor may represent a promising tool for the detection of Ag+ ions. The results for practical detecting Ag+ proved that this biosensor can be applied to environmental water sample analysis.