Abstract:

The simple and rapid Pb²⁺ detection method is constructed by using a fluorescent aptasensor that is based on G-quadruplex formation in Tris-HCl buffer solution. In the absence of Pb²⁺, the Thioflavin T (ThT) dye binds to the G-rich Pb²⁺ aptamer and forms a Pb²⁺ aptamer/ThT G-quadruplex complex, which results in high fluorescence intensity. Upon addition of Pb²⁺, the Pb²⁺ aptamer/ThT complex will be replaced by the formation of a Pb²⁺ aptamer/Pb²⁺ complex and the fluorescence intensity of the solution decreases dramatically.The experimental conditions such as the buffer solution, the concentration of ThT fluorescent molecules, the concentration of Pb²⁺ aptamer, and the reaction time were optimized. When the concentrations of ThT fluorescent molecules and Pb²⁺ aptamers were 10 μmol/L and 200 nmol/L, respectively, the fluorescence intensity decreased with the increase of Pb ²⁺ concentration in 10 mmol/L Tris-HCl(pH=8.3, containing 2 mmol/L MgCl₂) buffer solution. When the concentration of Pb²⁺ was in the range of 20—1000 nmol/L, there was a good linear relationship between the fluorescence intensity and the concentration of Pb²⁺(R²=0.9941), and this fluorescence aptasensor was highly sensitive and rapid, with a detection limit of 1 nmol/L and a total reaction time of only 10 min. Furthermore, this method is cost-effective and simple, removing the requirement for labeling the detection reagents with a fluorophore-quencher pair.

Key words: Thioflavin T, G-quadruplex, Lead ion