Abstract
In this work, we report on the development of an electrochemical biosensor for high selectivity and rapid detection of Hg2+ and Pb2+ ions using DNA-based specific aptamer probes labeled with ferrocene (or methylene blue) and thiol groups at their 5′ and 3′ termini, respectively. Aptamers were immobilized onto the surface of screen-printed gold electrodes via the SH (thiol) groups, and then cyclic voltammetry and impedance spectra measurements were performed in buffer solutions with the addition of HgCl2 and PbCl2 salts at different concentrations. Changes in 3D conformation of aptamers, caused by binding their respective targets, e.g., Hg2+ and Pb2+ ions, were accompanied by an increase in the electron transfer between the redox label and the electrode. Accordingly, the presence of the above ions can be detected electrochemically. The detection of Hg2+ and Pb2+ ions in a wide range of concentrations as low as 0.1 ng/mL (or 0.1 ppb) was achieved. The study of the kinetics of aptamer/heavy metal ions binding gave the values of the affinity constants of approximately 9.10−7 mol, which proved the high specificity of the aptamers used.
Highlights
The detection of toxic metal ions in aquatic environment is an important global issue because these contaminants may have severe effects on plants, animals, and humans as well as on ecosystem [1].Among the most toxic metallic water pollutants in aquatic environments are mercury and lead [2].Lead can cause renal malfunction and can inhibit brain development in humans [3]; mercury can cause damage of the brain, heart, and kidneys [4]
The detection of heavy metals in low concentrations is a difficult task; it can be achieved with existing advanced analytical methods, such as atomic absorption or atomic emission spectroscopies (AAS, AES), inductively coupled plasma mass spectroscopy (ICP-MS), cold vapor atomic fluorescence spectroscopy (CVAFS), and high-performance liquid chromatography (HPLC) [5]
7, 27 reference curves were recorded in pure Hepes binding buffer (HBB) without heavy metal salts added
Summary
The detection of toxic metal ions in aquatic environment is an important global issue because these contaminants may have severe effects on plants, animals, and humans as well as on ecosystem [1].Among the most toxic metallic water pollutants in aquatic environments are mercury and lead [2].Lead can cause renal malfunction and can inhibit brain development in humans [3]; mercury can cause damage of the brain, heart, and kidneys [4]. Among the most toxic metallic water pollutants in aquatic environments are mercury and lead [2]. The detection of heavy metals in low concentrations is a difficult task; it can be achieved with existing advanced analytical methods, such as atomic absorption or atomic emission spectroscopies (AAS, AES), inductively coupled plasma mass spectroscopy (ICP-MS), cold vapor atomic fluorescence spectroscopy (CVAFS), and high-performance liquid chromatography (HPLC) [5]. These methods are extremely sensitive but expensive and require specialized laboratory conditions and highly trained personnel. Both the time and cost of the analysis are very high
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