Ultrasensitive fluorescence polarization aptasensors based on exonuclease signal amplification and polystyrene...

Here, we combine T7 exonuclease (T7 Exo) signal amplification and polystyrene nanoparticle (PS NP) amplification to develop novel fluorescence polarization (FP) aptasensors. The binding of a target/open aptamer hairpin complex or a target/single-stranded aptamer complex to dye-labeled DNA bound to PS NPs, or the self-assembly of two aptamer subunits (one of them labeled with a dye) into a target/aptamer complex on PS NPs leads to the cyclic T7 Exo-catalyzed digestion of the dye-labeled DNA or the dye-labeled aptamer subunit. This results in a substantial decrease in the FP value for the amplified sensing process. Our newly developed aptasensors exhibit a sensitivity five orders of magnitude higher than that of traditional homogeneous aptasensors and a high specificity for the target molecules. These distinct advantages of our proposed assay protocol make it a generic platform for the design of amplified aptasensors for ultrasensitive detection of various target molecules.