A resonance Rayleigh scattering sensor for detection of Pb 2+ ions via cleavage-induced G-wire formation.

A resonance Rayleigh scattering (RRS) aptasensor was fabricated for detection of Pb2+ via hairpin-like label-free substrate and G-wire for signal amplification. A hairpin-like DNA substrate contains a sequence in the loop labeled with ribonucleobase A and c-myc sequence in the stem. When hybridized with 8-17 DNAzyme in the presence of Pb2+ , the sequence in the loop was activated and cleaved. Hundreds of c-myc sequences departing from the 8-17 DNAzyme yield nanowires superstructure called G-wire in the presence of Mg2+ . The polymer G-wire was demonstrated by the RRS spectrum, polyacrylamide gel electrophoresis, and AFM. The RRS intensity was enhanced by the product G-wires, and the RRS signal at 370nm was linear with the logarithm of Pb2+ concentration in the range of 2.0nM to 5.0μM. This method was selective for Pb2+ even coexisting with other metal ions at high concentrations and was successfully applied to the determination of Pb2+ in real samples. The aptasensor holds a great promise for universal RRS sensing platform for sensitive detection of various metal ions just by changing the sequence of the probe in the loop and DNAzyme.