Simple, one step and sensitive fluorescent nanoprobe for simultaneous detection of Pb2+ and Cu2+ based on pincer enzyme strand and signal amplification strategy

A simple, one step and sensitive fluorescent nanoprobe was developed for simultaneous detection of Pb2+ and Cu2+ based on pincer enzyme strand (E-DNA) and circular catalytic cleavage reaction. A pincer E-DNA can be formed by two split E-DNA. The formed pincer E-DNA can form Pb2+ and Cu2+ dependent DNAzyme by combining with the substrate strand (S-DNA) on the gold nanoparticles (AuNPs). Then, the fluorophore labeled S-DNA is cleaved and released from the surface of AuNPs with the assistance of Pb2+ and Cu2+. Meanwhile, the pincer E-DNA is also released for circular catalytic cleavage reaction, causing significant recovery of the fluorescent intensities for both Pb2+ and Cu2+. This method offers high sensitivity with detection limit of 80 pM for Pb2+ and 30 pM for Cu2+. It also shows high specificity for simultaneously detection of Pb2+ and Cu2+. This strategy has great potential to be used for simultaneous detection and imaging of metal ions in environmental and living cell samples.