A novel resonance Rayleigh scattering aptasensor for dopamine detection based on an Exonuclease III assisted signal amplification by G - quadruplex nanowires formation

A new method was constructed for detecting dopamine based on aptamer-specific recognition and resonance Rayleigh scattering (RRS) of G - quadruplex nanowires (G - wires). The dopamine aptamer was used to recognize the target of dopamine, and the Exonuclease III was applied to cleave the hairpin DNA, and the G - wire formation was induced in the presence of K⁺ and Mg²⁺. This phenomenon was confirmed by polyacrylamide gel electrophoresis. Thus, a quantitative relationship between the RRS intensity of the G - wires and the dopamine concentration was established. The experimental conditions were optimized, such as the concentration of Mg²⁺, reaction temperature, reaction time and the concentration of Exonuclease III in the reaction system, and the interference substances were investigated, such as uric acid, ascorbic acid and serotonin. Under the optimal conditions, there was a good linear relationship between the RRS and the logarithm of dopamine concentration in the range from 5.0 × 10^-11 M to 1.0 × 10^-8 M (r = 0.995), with a detection limit of 1.2 × 10^-11 M. The novel method for dopamine detection showed excellent selectivity and high sensitivity, and could be used to detect dopamine in mice brain tissues.