A highly sensitive aptamer method for Ag+ sensing using resonance Rayleigh scattering as the detection technique and a modified nanogold probe

Abstract

An aptamer was modified using a gold nanoparticle (AuNP) to form a stable aptamer–AuNP probe that was not aggregated in the pH 7.2 2-4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) buffer solution in the presence of NaCl. The Ag⁺ reacted with the aptamer–AuNP probe to form a hairpin structure complex of Ag⁺–aptamer and released the AuNPs that were aggregated to large particles, which led to a resonance Rayleigh scattering (RRS) peak at 596 nm enhancement. The enhanced value ΔI_596 nm varies linearly with the Ag⁺ concentration in the range 6.7–133.3 × 10⁻⁸ M. The probe in the aptamer reaction solution has a strong catalytic effect on the Cu₂O particle reaction of Fehling reagent and glucose, and the particle products exhibited a strong RRS peak at 610 nm. However, catalysis of AuNP aggregation is very weak, which means it can not be removed from the aptamer reaction solution. When the concentration of Ag⁺ increased, the RRS peak intensity at 610 nm decreased. The decreased value ΔI_610 nm is linear to the Ag⁺ concentration in the range of 3.3–666.7 × 10⁻⁹ M. Thus, two new RRS methods were proposed for the detection of Ag⁺, with high sensitivity, good selectivity and simplicity. A highly sensitive resonance Rayleigh scattering method was proposed for trace Ag⁺ sensing using the aptamer-modified nanogold as a probe.