Detections Of Mercury(Ⅱ) And Lead(Ⅱ) Ions Based On Nucleic Acid Probes

Heavy metal ions are one kind of main pollutants in the environment, which have caused great threat to human living conditions. Heavy metal ions in the environment are difficult to degrade, which can be accumulated into the human body through the food chain, leading a serious threat to people's health and life. Therefore, it is of great significance to establish a simple, fast, sensitive method to detect them as to the control of environmental pollution and the protection of human health. Probes based on nucleic acids (DNA probe) with advantages of real-time, quick, stable, selective and visual inspection make its broad space to used in pharmaceutical, environment, food and metal areas. In this research paper, we construct three DNA probes to detect mercury and lead ions, the details are described as follows:(1) A probe based on the thymine-Hg²⁺-thymine (T-Hg²⁺-T) coordination chemistry and the inclusion interaction ofγ-cyclodextrin was developed. A bis-pyrene-labeled thymine-rich DNA strand was used as the detection probe. In the presence of Hg²⁺, the stem-close-shaped DNA strand can be formed under the cooperation ofγ-cyclodextrin and predominantly emit the excimer fluorescence ideally. With the optimum conditions, the system exhibits a dynamic response range for Hg²⁺ from 0.5 to 3μM with a detection limit of 0.3μM. This strategy afforded exquisite selectivity for Hg²⁺ against other environmentally related metal ions. At the same time, pyrene excimer has a longer fluorescence lifetime, combined with lifetime-based measurements, the probe hold potential applied in complex biological samples.(2) A probe based on label-free DNAzyme colorimetric molecular switch for detection of Pb²⁺ was developed. The system including DNAzyme and guanine(G)-rich DNA strand. In the presence of Pb²⁺, the substrate strands was released to solution and formed G-quadruplex, resulting absorbance change to detect Pb²⁺. The system exhibits a dynamic response range for Pb²⁺ from 5 to 100 nM with a detection limit of 3 nM. In addition, the selectivity of the sensor for Pb²⁺ against other environmentally related metal ions is outstanding.(3) A probe based on label-free DNAzyme ?uorescing molecular switch for detection of Pb²⁺ was developed. In the presence of Pb²⁺, DNAzyme was fracture, and the obvious fluorescent change of the Sybr Green I (SG), after binding to double strand or single strand DNA was observed. The system exhibits a dynamic response range for Pb²⁺ from 1 to 8μM with a detection limit of 0.6μM. this strategy afforded exquisite selectivity for Pb²⁺ against other environmentally related metal ions.