Sensitive aptamer-based fluorescence polarization assay for mercury(II) ions and cysteine using silver nanoparticles as a signal amplifier

We report here a signal amplifying strategy to construct polarization aptamer probes for small molecules. The method is based on the use of silver nanoparticles acting as a fluorescence polarization signal amplifier. It was applied to the sensitive and selective detection of the two model analytes mercury (II) and cysteine. The aptamer probes were conjugated to CdTe-CdS quantum dots and are shown to work well for both analytes. The analytical range for Hg(II) is from 10 nM to 0.4 mu M, and the limit of detection is 6.6 nM. The respective range for cysteine is from 20 nM to 0.7 mu M, and the LOD is 11 nM.