LAUSR

In this study, a simple paper-based aptasensor has been developed for the ultrasensitive detection of lead (Pb2+) ion within about 10 min. The aptasensor has been successfully designed by taking advantages of the Förster Resonance Energy Transfer (FRET) process and the super fluorescence quenching property of graphene oxide (GO) sheet. The sensing mechanism of the aptasensor is based on the conformational switch of the Pb2+-specific aptamer from a random coil to a G-quadruplex structure. An injection of Pb2+ on the paper-based platform induces the release of the specific aptamer from the GO surface that recovers the fluorescence emission. Under the optimal experimental conditions, there is a good linear relationship between the fluorescence recovery and the Pb2+concentration in the ranges of 5-70 pM and 0.07-20 nM. Moreover, the aptasensing array exhibits a high sensitivity to Pb2+ with an ultra-low detection limit of 0.5 pM. The developed aptasensor has been successfully applied to determine Pb2+ in tap water, lake water, milk, and human blood serum. The paper-based aptasensor can be efficiently utilized to detect other metal ions and biological molecules by substituting target specific aptamer.