•Pb2 +-specific DNAzyme and G-quadruplex DNAzyme sensors for the detection of Pb2 + are reviewed.•Development and applications of fluorescent, colorimetric and electrochemical sensors are discussed in this paper.•Advantages and disadvantages of different kinds of DNAzyme sensors are compared, giving prospects of the future development.Lead ion (Pb2 +) is a kind of toxic metal pollutant that widely spread in the environment, which is of serious concern to human health. So it is of great significance to develop simple, fast method for the detection of Pb2 +. Up to now, a number of DNA sensors have been designed to recognize Pb2 +, especially DNAzyme-based sensors have attracted much attention due to its advantages, such as high selectivity and sensitivity. In this review, we summarize the recent progress of two types of DNAzyme-based sensors for the detection of toxic Pb2 +, including Pb2 +-specific DNAzyme and G-quadruplex DNAzyme sensors. On the basis of the sensor transducers and their signal types, development and applications of fluorescent DNAzyme sensors, colorimetric DNAzyme sensors and electrochemical DNAzyme sensors are to be discussed in this paper. These DNAzyme-based sensors are highly sensitive and selective toward Pb2 +, and has proved to be a useful tool in the potential application for on-site and real-time real sample (such as environmental and biological samples) monitoring in the future.

•Occurrence and multi-phase distribution of antibiotics were monitored seasonally.•Colloids can play an important role to remove antibiotics from aquatic environments.•Partition coefficient log Kcol. was mainly negatively correlated with binding Ca and Mg.•Competitive adsorption was insignificant in the colloidal sorption behaviors of antibiotics.•Colloid-bounding is important in the environmental behaviors of organic pollutants.Understanding antibiotic adsorption on natural colloids is crucial for prediction of the behavior, bioavailability and toxicity of antibiotics in natural waters. In the present study, the filtered water (dissolved phase, < 0.7 μm) was further separated into colloidal phase (1 kDa-0.7 μm) and soluble phase (< 1 kDa) by cross-flow ultrafiltration (CFUF), and the spatial-temporal variation and distribution of six antibiotics in multi-phases were investigated in Baiyangdian Lake. Results indicated that antibiotic concentrations differed significantly with sampling location and time. The mean concentrations of antibiotics ranged between 13.65 and 320.44 ng L− 1 in the dissolved phase, and the colloidal phase accounted for 4.7–49.8% of all antibiotics, suggesting that natural colloids play an important role as carriers of antibiotics in aquatic environments. Because of the influence of colloids, the partition coefficients of antibiotics between suspended particulate matter (SPM) and soluble phase (intrinsic partition coefficients, Kpint) were found to be 6.18–109.60% higher than corresponding observed partition coefficients (Kpobs, between SPM and dissolved phase). The mean partition coefficients between colloidal and soluble phase (Kcol.) ranged between 6218 and 117,374 L kg− 1, which were 1–2 orders of magnitude greater than Kpint values. In order to explore the adsorption mechanism of antibiotics on colloids, Pearson's correlations were performed. The results showed that log Kcol. were negatively correlated with cations in natural colloids; especially with Mg (r, − 0.643, P < 0.01) for oxytetracycline (OTC), and with both Ca (− 0.595, P < 0.01) and Mg (− 0.593, P < 0.01) in the case of ofloxacin (OFL). This result revealed that the competitive effect between cations and antibiotics was the main factor influencing the adsorption behavior of antibiotics on natural colloids in the lake.Download high-res image (267KB)Download full-size image

The distribution, sources, and ecological risk of polycyclic aromatic hydrocarbons (PAHs) were investigated in surface sediments from the Haihe River. Total PAH concentrations varied from 171.4 to 9511.2 ng g−1 with an average of 2125.4 ng g−1, suggesting serious pollution of the Haihe River in comparison with other reported rivers worldwide. PAH contaminants differed significantly among 17 sampling locations with high values occurring in industrial areas and densely populated areas. The composition of PAHs was characterized by high abundance of 4-ring and 5-ring PAHs, and benzo[a]anthracene, chrysene, and benzo[a]pyrene were the predominant components. Molecular diagnostic ratios have confirmed that PAHs in Haihe River sediments resulted from mixed sources, primarily including various combustion processes. Ecological risk assessment using the Sediments Quality Guidelines indicated that PAHs in sediments could cause certain negative effects on aquatic organisms in most survey regions.

Cadmium (Cd) toxicity in agricultural soil has received significant attention because of its higher transformation in the food chain and toxicity to humans. The aim of the present study was to develop sensitive and specific biomarkers for Cd stress. Therefore, transcriptional analyses were performed to investigate concentration-response characteristics of Cd responsive genes identified from a Solanum lycopersicum microarray. The results showed that the lowest observable adverse effect concentrations (LOAECs) of Cd to S. lycopersicum were 1 mg/kg for seed germination, 8 mg/kg for root dry weight, 8 mg/kg for root elongation, and 8 mg/kg for root morphology. Furthermore, the genes were differentially expressed even at the lowest Cd concentrations (0.5 mg/kg), indicating that the detection of Cd in soil at the molecular level is a highly sensitive method. Cd in soil was positively correlated with the expression of the F-box protein PP2-B15 (r = 0.809, p < 0.01) and zinc transporter 4 (r = 0.643, p < 0.01), indicating that these two genes could be selected as indicators of soil Cd contamination.

The size of soil particles strongly affects the accumulation and adsorption of heavy metals which partly controls the co-transport of heavy metals by soil colloids. However, the effect of the size of soil particles on the accumulation and adsorption of heavy metals in the colloidal dimension has seldom been studied. In this study, variable charge soils were selected and separated into five size fractions to elucidate the effect of the size of soil particles on Cd accumulation and adsorption.Five soil particle size fractions (>10, 10–1, 1–0.45, 0.45–0.2 and <0.2 μm) were obtained from Cd-contaminated soil by natural sedimentation and fractional centrifugation. The concentrations and species of Cd were measured in various sized soil particles. Batch adsorption experiments of Cd on the obtained soil particles were conducted under different pH values and concentrations of NaCl.Generally, the concentration of Cd increased with decreasing soil particle sizes, and the Cd proportion of exchangeable and carbonate fraction decreased from 43.84 to 17.75% with decreasing particle size. The soil particles with a size of 10–1 and <0.2 μm possessed a stronger adsorption ability than the other fractions in most cases. Moreover, the Cd adsorption capacities of the soil particles increased with increasing pH values and decreasing concentrations of NaCl, especially for soil particles containing more organic matter (OM) and variable charge minerals.Smaller soil particles are more capable of accumulating Cd and make Cd more stable. The adsorption capability of Cd is negatively related to the particle size and NaCl concentration and is positively related to the pH. The effects of the size of variable charge soil particles on Cd accumulation and adsorption are attributed to the differences in the physicochemical properties among various soil particle size fractions. This study contributes to the understanding of the co-transport of heavy metals in soil by soil colloids.

•Label-free aptamer DNA sensor is developed for EA detection.•Aptamer switches to G-quadruplex on the electrode, offering the binding site of EA.•CD and EIS confirm the sensing mechanism.•The sensor exhibits excellent selectivity and high sensitivity.•The sensor is successfully challenged in serum and tap water samples.A label-free sensing assay for ethanolamine (EA) detection based on G-quadruplex-EA binding interaction is presented by using G-rich aptamer DNA (Ap-DNA) and electrochemical impedance spectroscopy (EIS). The presence of K+ induces the Ap-DNA to form a K+-stabilized G-quadruplex structure which provides binding sites for EA. The sensing mechanism was further confirmed by circular dichroism (CD) spectroscopy and EIS measurement. As a result, the charge transfer resistance (RCT) is strongly increased as demonstrated by using the ferro/ferricyanide ([Fe(CN)6]3−/4−) as a redox probe. Under the optimized conditions, a linear relationship between ΔRCT and EA concentration was obtained over the range of 0.16 nM and 16 nM EA, with a detection limit of 0.08 nM. Interference by other selected chemicals with similar structure was negligible. Analytical results of EA spiked into tap water and serum by the sensor suggested the assay could be successfully applied to real sample analysis. With the advantages of high sensitivity, selectivity and simple sensor construction, this method is potentially suitable for the on-site monitoring of EA contamination.

In this study, the temporal and spatial trends of ten antibiotics belong to four different groups in aqueous and sediment matrices were investigated in the intertidal zone of Bohai Bay as a single object. The total concentrations of those antibiotics ranged from 41.53 to 222.43 ng L−1 and 7.71 to 130.36 ng g−1 in the surface water and sediment, respectively, and they contained higher levels and detected rates than those in the coastal and offshore areas. Seasonal variation might be impacted by the seasonal river discharge and aquaculture activities. As exhibit, the regions with river discharge or human aquaculture activities exhibited high concentrations of antibiotics in the water and sediments. The pseudo-partitioning values of targeted compounds ranged from 10 to 591 L kg−1, but they were relatively smaller in the intertidal zone of the Bohai Bay than in the fresh water.

The effects of heavy metals in agricultural soils have received special attention due to their potential for accumulation in crops, which can affect species at all trophic levels. Therefore, there is a critical need for reliable bioassays for assessing risk levels due to heavy metals in agricultural soil. In the present study, we used microarrays to investigate changes in gene expression of Lycopersicon esculentum in response to Cd-, Cr-, Hg-, or Pb-spiked soil. Exposure to 1/10 median lethal concentrations (LC50) of Cd, Cr, Hg, or Pb for 7 days resulted in expression changes in 29 Cd-specific, 58 Cr-specific, 192 Hg-specific and 864 Pb-specific genes as determined by microarray analysis, whereas conventional morphological and physiological bioassays did not reveal any toxicant stresses. Hierarchical clustering analysis showed that the characteristic gene expression profiles induced by Cd, Cr, Hg, and Pb were distinct from not only the control but also one another. Furthermore, a total of three genes related to “ion transport” for Cd, 14 genes related to “external encapsulating structure organization”, “reproductive developmental process”, “lipid metabolic process” and “response to stimulus” for Cr, 11 genes related to “cellular metabolic process” and “cellular response to stimulus” for Hg, 78 genes related to 20 biological processes (e.g., DNA metabolic process, monosaccharide catabolic process, cell division) for Pb were identified and selected as their potential biomarkers. These findings demonstrated that microarray-based analysis of Lycopersicon esculentum was a sensitive tool for the early detection of potential toxicity of heavy metals in agricultural soil, as well as an effective tool for identifying the heavy metal-specific genes, which should be useful for assessing risk levels due to heavy metals in agricultural soil.

We describe a sensitive and selective biosensor for the environmental metabolite 2-hydroxyfluorene (2-HOFlu). It is based on electrochemical impedance spectroscopy and was obtained by assembling a thiolated single-stranded DNA on a gold electrode via S-Au covalent bonding. It is then transformed to a K+-stabilized G-quadruplex-hemin complex which exhibits peroxidase-like activity to catalyze the oxidation of 2-HOFlu by H2O2. This results in the formation of insoluble products that are precipitated on the gold electrode. As a result, the charge transfer resistance (RCT) between the solution and the electrode surface is strongly increased within 10 min as demonstrated by using the ferro/ferricyanide system as a redox probe. The difference in the charge transfer resistances (ΔRCT) before and after incubation of the DNA film with 2-HOFlu and H2O2 serves as the signal for the quantitation of 2-HOFlu with a 1.2. nM detection limit in water of pH 7.4. The assay is highly selective over other selected fluorene derivatives. It was exploited to determine 2-HOFlu in spiked lake water samples where it displayed a detection limit of 3.6 nM. Conceivably, this method has a wide scope in that it may be applied to other analytes for which respective G-quadruplexes are available.

We investigated the adsorption behaviour of ten potentially toxic metals (Ni, Co, Cd, Fe, Ba, Sr, Cr, Hg, Ag and Zn) on negatively charged liposome vesicles composed of phosphatidyl choline (PC), phosphatidyl glycerol (PG) and cholesterol. The adsorption data for selected metal ions closely fit the Freundlich isotherm. Most metal ions (except Cr3+ and Cd2+) were strongly adsorbed by liposomes (n > 1) and the ionic covalent index significantly affected the Freundlich adsorption intensity. We used multivariate statistical methods, including principal components analysis regression and partial least squares regression, to elucidate the adsorption relationships between 18 physical and chemical properties and their respective Freundlich isotherm constants (KF). The cross-validated correlation efficient (Qcum2) and correlation coefficient (RY2) of the model were 0.76 and 0.91, respectively. High Qcum2 and RY2 values indicated that the predictive model was both precise and robust. According to the VIP value, parameters like ionic polarisation, ion charge and ionisation potential played crucial roles in predicting KF.

The direct interaction of hairpin DNA with 9-hydroxyfluorene (9-OHFLU) through hydrogen bonds was investigated by electrochemical impedance spectroscopy (EIS), UV-Vis spectroscopy and 1H NMR spectra. Based on these results, an electrochemical hairpin DNA sensor was developed for the detection of 9-OHFLU by EIS. Upon 9-OHFLU interacting with hairpin DNA film on the gold electrodes, the charge transfer resistance (RCT) of the hairpin DNA film was significantly increased and remained constant after 30 min. Depending on the difference in charge transfer resistance (ΔRCT) before and after 9-OHFLU interaction with the hairpin DNA, 9-OHFLU could be detected with a concentration as low as 1 nM. However, only a much smaller ΔRCT appeared when eight selected hydroxyl polycyclic aromatic hydrocarbons (HO-PAHs) interacted with the hairpin DNA for 30 min, which demonstrated that 9-OHFLU could be discriminated from other HO-PAHs by EIS. The performance of the sensor in real lake water sample was further explored for the detection of 9-OHFLU with the detection limit of 4 nM.

A large-scale sampling program was conducted to simultaneously collect surface water, overlying water, pore water and sediment samples at monthly intervals from March to December 2010 from the Baiyangdian Lake, North China to assess the distribution of hexachlorocyclohexanes (HCHs) and determine the net direction of sediment–water exchange. Total HCHs concentrations ranged from 6.30–53.90 ng L−1, 16.59–148.48 ng L−1, 247.93–459.07 ng L−1 and 3.60–12.50 ng g−1 in surface water, overlying water, pore water and sediments, respectively, which was at the intermediate level compared to those of other areas in China. Seasonal variations of HCHs were featured by lower concentrations in April, July and November due to the dilution of HCHs caused by a great deal of fresh water being allocated to the Baiyangdian Lake in these months. Sediment–water fugacity ratios of the HCH isomers were used to predict the direction of the sediment–water exchange of these isomers. The sediment–surface water and sediment–overlying water fugacity ratios of HCH isomers averaged 11.4 and 3.0, which is significantly greater than the equilibrium status (1.0), suggesting that the net flux directions were from the sediment to water and the sediment acted as a secondary source to the water. Sediment–pore water fugacity ratios indicated near equilibrium or escape from pore water to sediment, depending on the isomer and sampling time. The difference of HCH concentrations between sediment and water samples were found to be an important factor affecting the diffusion of HCH from the sediment to water.

A highly sensitive, reusable G-rich DNA sensor was reported for the detection of α-naphthol by electrochemical impedance spectroscopy (EIS). Specifically, a single-stranded G-rich DNA was self-assembled on the electrode and transformed into K+-stabilized G-quadruplex, which could catalyze H2O2-mediated oxidation of α-naphthol (with hemin as a cofactor) to 1, 4-naphthoquinone precipitated on the DNA films. Due to the insolubility of 1, 4-naphthoquinone, the charge transfer resistance (RCT) was increased to maximum within 15 min. Depending on the difference in charge transfer resistance change (ΔRCT), the α-naphthol could be detected with the detection limit of 0.1 nM in Tris–ClO4 buffer solution (20 mM, pH=7.4). Moreover, the sensor demonstrated a high selectivity over other selected phenolic compounds. The performance of the sensor in the real lake water was also explored with the detection limit of 0.8 nM. Finally, the regeneration of the sensor was investigated, which allowed for reuse more than 4 cycles with a mean recovery of 94% of the original signal.Highlights► We provide a new strategy of G-DNA modified gold electrode to detect α-naphthol. ► UV–vis spectroscopy, fluorescence spectra, SEM and DPV confirm the mechanism. ► The sensor exhibits better selectivity, sensitivity and regenerability. ► The detection limit is 0.1 nM in buffer solution, or 0.8 nM in natural lake water.

•Hairpin DNA sensor was developed to study the amino-substituted naphthalene compounds.•Fluorescence spectra, Raman spectroscopy, DPV and EIS confirm the mechanism.•The ΔRCT is confirmed to be correlative to the binding constants (R2=0.99).•The sensor exhibits excellent selectivity and high sensitivity, nano-mole detection limit.•The sensor is successfully performed in natural water sample with a recovery of 96–102%.The amino-substituted naphthalene compounds, such as 1,8-diaminonaphthalene (1,8-DANAP), 2,3-diaminonaphthalene (2,3-DANAP), 1,5-diaminonaphthalene (1,5-DANAP), 1-naphthylamine (1-NAP) and 2-naphthylamine (2-NAP), were investigated by electrochemical impedance spectroscopy (EIS), which was based on the interaction with hairpin DNA immobilized on the gold electrodes. Upon hairpin DNA interacting with the target chemicals, the charge transfer resistance (RCT) of the hairpin DNA films was significantly decreased and the charge transfer resistance change (ΔRCT) decreased in a sequence of ΔRCT 1,8-DANAP>ΔRCT 2,3-DANAP>ΔRCT 1,5-DANAP>ΔRCT 1-NAP>ΔRCT 2-NAP. The ΔRCT changes were due to the difference in the binding constant (KSV) of the target chemicals to DNA. In addition, the interaction mechanism was further explored using 1,8-DANAP as a model analyte by fluorescence spectra, Raman spectroscopy, differential pulse voltammetry (DPV) and EIS, correspondingly. The results demonstrated that the amino-substituted naphthalene compounds intercalated into “stem” appearing in the hairpin DNA. Moreover, the hairpin DNA sensor exhibited high sensitivity to the amino-substituted naphthalene compounds with the detection limit of nano-mole, and maintained high selectivity over other selected environmental pollutants. Finally, the DNA sensor was challenged in natural water sample with a recovery of 96–102%, which offered a platform for prospective future development of a simple, rapid, sensitive and low-cost assay for the detection of target aromatic amine pollutants.

An electrochemical DNA sensor based on DNA conformational changes for simultaneous detection of Hg2+ and Pb2+ was reported. The sensor was consisted of a probe strand (DNA), a Pb2+-specific DNAzyme, and a substrate strand contains mercury-specific oligonucleotide (MSO). When Hg2+ and Pb2+ interacted with DNA, the induced conformational changes were tracked by electrochemical impedance spectroscopy (EIS), which led to a decreased RCT. The RCT difference (ΔRCT) was applied to selectively detect Hg2+ and Pb2+ with detection limit of 1 pM and 0.1 pM, respectively. Through using masking agents, such as cysteine (masking Hg2+) and G-DNA (CTG-GGA-GGG-AGG-GAG-GGA) (masking Pb2+), Hg2+ and Pb2+ were simultaneously detected in buffer solution, human serum and river water, respectively.

Organochlorine contaminants (OCs) in fish were determined to evaluate the potential risk to humans consuming fish originating in Baiyangdian Lake, North China. Relatively low levels of PCBs, HCHs and DDTs were observed, with mean concentrations ranging from 0.28 to 3.28 ng/g, wet weight. Among various fish species tested, the highest burden of OCs was recorded in northern snakehead (7.39 ng/g, wet weight) and the lowest was in grass carp (2.04 ng/g, wet weight). The hazard ratios (HRs), based on noncancer risk were all less than 1.0, while the HRs based on cancer risk exceeded 1.0 only for PCBs based on the 90th percentile concentration.

Brassica Campestis L. was cultivated in the soil at the laboratory. The red edge, the visual spectrum and the near-infrared spectrum of Brassica Campestis L. leaf were used to explore the spectral response of Brassica Campestis L. leaf to the copper stress. As the Cu content in the soil gets increased, the copper level in Brassica Campestris L. leaf would be increased, and the chlorophyll level in Brassica Campestris L. leaf would be decreased. As a result, the visual spectral reflectance (A1) of Brassica Campestris L. leaf is increased, and the blue-shift (moving towards the shorter waveband) degree (S) of the red edge (the ascending region of the reflectivity at 680–740 nm) gets increased. However, the near-infrared spectral reflectance (A2) decreases. With the correlation coefficient R2 more than 0.95, these parameters of A1, A2 and S can be perfectly used to simulate and predict the copper level in Brassica Campestris L. leaf.

•Cd and Cu are the main pollutants in agricultural soils along the polluted river.•Cd, Cu, Pb and Zn are derived from mining activities and metal smelting.•Cd indicated the highest risk in most soils according to fraction analysis.•The agricultural soils near the mines or smelters were severely polluted.As a tributary of Le'an River in Jiangxi Province of China, Jishui River has been seriously polluted by non-ferrous heavy metal mining activities, and long-term irrigation using Jishui River water has caused severe heavy metal pollution of soil. We collected samples of agricultural soils along the river and determined the contents of As, Cd, Cr, Cu, Mn, Ni, Pb and Zn. The results showed that Cd and Cu were two primary pollutants in the soils with concentrations of 0.52–2.55 mg·kg− 1 and 27.87–426.15 mg·kg− 1, respectively. The mean concentrations of As, Mn, Pb and Zn in the soils were 33.99 mg·kg− 1, 468.70 mg·kg− 1, 125.32 mg·kg− 1 and 171.48 mg·kg− 1, respectively. Moreover, higher heavy metal concentrations were found in the agricultural soils closer to mines and metal smelters. The metal speciation analysis showed that Cd was mainly in the exchangeable and carbonate fraction, and the reducible fraction of Mn and Pb was a significant proportion in most soils. However, Cu and Zn were mainly in the residual fraction in all samples. Assessments of pollution levels revealed that (1) heavy metals that were mainly from anthropogenic sources, such as Cd, Cu, Pb and Zn, were much higher than their background value, (2) heavy metal pollution in the agricultural soils closer to the mines and smelters was often more severe, and (3) the environmental risk of Cd was highest and should be of special concern.

•Ten intertidal sediment samples were collected for investigation of PAHs.•Ace could be used as a suitable indicator to estimate total PAH concentrations.•PAHs originated from mixed sources, and the major was local combustion.•Adverse effects related to Acy would occur occasionally in partial study regions.Polycyclic aromatic hydrocarbons (PAHs) can enter intertidal zones by various pathways and pose potential threats to intertidal ecosystem. We investigated distribution, composition, sources and risk assessment of PAHs in intertidal surface sediments of Bohai Bay. Total PAH concentrations ranged from 37.2 ng·g− 1 to 206.6 ng·g− 1, among which high values occurred near Nanpaishuihe River Estuary and Haihe River Estuary. The composition patterns of PAHs were characterized by the predominance of 3-ring and 4-ring PAHs, and acenaphthylene was the most dominant component. Diagnostic ratios and principal component analysis have confirmed that PAH contaminants originated from mixed sources, and the major was local combustion. The mean benzo(a)pyrene equivalent concentration of total PAHs in intertidal sediments was 15.67 ng·g− 1, which was mostly contributed by seven carcinogenic PAHs. According to ecological risk assessment, negative effects related to acenaphthylene would occur occasionally in partial survey regions of the study.Download high-res image (124KB)Download full-size image

A large-scale sampling program was conducted to simultaneously collect surface water, overlying water, pore water and sediment samples at monthly intervals from March to December 2010 from the Baiyangdian Lake, North China to assess the distribution of hexachlorocyclohexanes (HCHs) and determine the net direction of sediment–water exchange. Total HCHs concentrations ranged from 6.30–53.90 ng L−1, 16.59–148.48 ng L−1, 247.93–459.07 ng L−1 and 3.60–12.50 ng g−1 in surface water, overlying water, pore water and sediments, respectively, which was at the intermediate level compared to those of other areas in China. Seasonal variations of HCHs were featured by lower concentrations in April, July and November due to the dilution of HCHs caused by a great deal of fresh water being allocated to the Baiyangdian Lake in these months. Sediment–water fugacity ratios of the HCH isomers were used to predict the direction of the sediment–water exchange of these isomers. The sediment–surface water and sediment–overlying water fugacity ratios of HCH isomers averaged 11.4 and 3.0, which is significantly greater than the equilibrium status (1.0), suggesting that the net flux directions were from the sediment to water and the sediment acted as a secondary source to the water. Sediment–pore water fugacity ratios indicated near equilibrium or escape from pore water to sediment, depending on the isomer and sampling time. The difference of HCH concentrations between sediment and water samples were found to be an important factor affecting the diffusion of HCH from the sediment to water.

An electrochemical DNA sensor based on DNA conformational changes for simultaneous detection of Hg2+ and Pb2+ was reported. The sensor was consisted of a probe strand (DNA), a Pb2+-specific DNAzyme, and a substrate strand contains mercury-specific oligonucleotide (MSO). When Hg2+ and Pb2+ interacted with DNA, the induced conformational changes were tracked by electrochemical impedance spectroscopy (EIS), which led to a decreased RCT. The RCT difference (ΔRCT) was applied to selectively detect Hg2+ and Pb2+ with detection limit of 1 pM and 0.1 pM, respectively. Through using masking agents, such as cysteine (masking Hg2+) and G-DNA (CTG-GGA-GGG-AGG-GAG-GGA) (masking Pb2+), Hg2+ and Pb2+ were simultaneously detected in buffer solution, human serum and river water, respectively.