A novel fluorescent aptasensing assay using carbon dots and Ag-Au nanoparticles for the detection of Pb2+ions

Lead (Pb) as one of the highly toxic heavy metals poses a threat to human health even at trace levels. The development of sensitive and rapid method to detect Pb2+ is important. Herein, a new biosensor was developed based on fluorescence quenching and ssDNA as a recognition tool for Pb2+ detection. A fluorimetric aptasensor was introduced using carbon dots as fluorophores conjugated to aptamers (CDs-Apt) and Ag@Au nanoparticles (Ag@AuNPs) as a quencher. The interaction between the Ag@AuNPs and CDs-Apt leads to a decrease in the fluorescence signal. By the addition of Pb2+ to the solution, specific interactions between the aptamers and Pb2+ ions cause to detach CDs-Apt from Ag@AuNPs. Consequently, the fluorescence intensity is enhanced proportionally to the Pb2+ concentration. The proposed aptasensor is able to detect Pb2+ in a linear range of 0.5 to 300 nM with 0.2 nM as a detection limit. The aptasensor is able to monitor Pb2+ levels in the real samples with satisfactory results.