Simultaneous detection of lead (II) and mercury (II) ions using nucleic acid aptamer molecular beacons

ABSTRACT

We have developed a fluorescence quantitative analysis method for the simultaneous detection of Hg²⁺ and Pb²⁺ based on nucleic acid aptamer molecular beacon (MB) probes. In this analytical method, two MB probes for Hg²⁺ (P_Hg) and Pb²⁺ (P_Pb) were designed. The carboxyl fluorescein (FAM) and tetramethyl-6-carboxyrhodamine (TAMRA) were selected as fluorophores of P_Hg and P_Pb, Black Hole Quencher 1 (BHQ-1) and Black Hole Quencher 2 (BHQ-2) were selected as organic quenchers, and several continuous nucleotides with guanine (G base) were connected to organic quenchers. The aptamers are put in as a part of stem and loop. In general, the fluorescence of fluorophores was dually quenched by BHQ and G bases, so the fluorescence signals were weak. In the presence of Hg²⁺ and Pb²⁺, P_Hg and P_Pb bonded with them, and the stem-loop structure of MB was destroyed and the fluorescence recovered. Under the optimal conditions, the fluorescence intensity of FAM had a good linear relationship with the concentration of Hg²⁺ in the range from 0.7 nmol/L to 84 nmol/L, and that of TAMRA and Pb²⁺ in the range from 0.2 nmol/L to 24 nmol/L. The detection limit of Hg²⁺ is 0.36 nmol/L and that of Pb²⁺ is 0.16 nmol/L (3σ, n = 11). The relative standard deviations (RSD) for determination of Hg²⁺ and Pb²⁺ were both lower than 5%, the average recoveries of this method in real samples were 96.55–102.78%, which indicated that the method had a high accuracy.

KEYWORDS:

• Fluorescence
• simultaneous detection
• aptamer
• Lead (II)
• Mercury (II)

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Science Foundation of China (21465010), the Open Foundation of Key Laboratory of Biologic Resources Protection and Utilization of Hubei Province (PKLHB1918, PKLHB1730), the Scientific and Technological Research Program of the Chongqing Municipal Education Commission (KJ1401021), Hubei Provincial Natural Science Foundation of China (2018CFB247) and Special Funds for “Double First-Class” Construction in Hubei Province.