A fluorescent aptasensor for Pb2+ detection based on gold nanoflowers and RecJf exonuclease-induced signal amplification

A fluorescent aptasensor was constructed to detect lead ion (Pb2+). Complementary DNA with sulfhydryl group (SH-cDNA) were loaded on gold nanoflowers materials (Au NFs) through Au-S bonds. Then, based on complementary base pairing between FAM modified Pb2+ aptamer (FAM-Apt) and Au NFs/SH-cDNA system, an Au NFs/SH-cDNA/FAM-Apt aptasensor was constructed. The fluorescence of FAM was quenched by Au NFs due to the fluorescence resonance energy transfer (FRET). Upon addition of Pb2+ and RecJf exonuclease (RecJf Exo) for 1.5 h, the Apt changed to a G-quadruplex structure due to the high affinity between Pb2+ and its aptamer, which lead to a large recovery in the fluorescence intensity. Under the optimized conditions, the presented aptasensor revealed high selectivity toward Pb2+ in the concentration range of 0.5 nM-1 μM, with a limit of detection (LOD) of 0.285 nM. Besides, the designed aptasensor was successfully used to recognize Pb2+ with excellent selectivity, reproducibility and stability in tap water and tea, providing a potential platform for Pb2+ detection in actual samples.