A resonance Rayleigh scattering sensor for detection of Pb²⁺ 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.