CN111562298A - Construction and application of electrochemical aptamer sensor for high-sensitivity detection of lead ions by taking methylene blue as indicator - Google Patents
Construction and application of electrochemical aptamer sensor for high-sensitivity detection of lead ions by taking methylene blue as indicator Download PDFInfo
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Abstract
The invention discloses a method for detecting lead ions (Pb) with high sensitivity by taking Methylene Blue (MB) as an indicator2+) The construction and application method of the electrochemical aptamer sensor. The carbon ion liquid electrode is used as a substrate electrode, platinum-loaded carbon nanofiber and nanogold are used as sensitizing materials for sensing interface modification, a capture probe is self-assembled on the surface of the electrode by utilizing a gold-sulfur bond, nonspecific adsorption is eliminated by utilizing thioglycolic acid, a stable double-stranded DNA structure is further formed by combining an aptamer probe, and MB is used as a hybridization indicator to construct a probe for the detection of the hybridization of the carbon ion liquid electrode and the nanogoldIn detecting Pb2+The electrochemical aptamer sensor of (1). The working principle is Pb2+Can induce the aptamer probe rich in G base to form G-quadruplex conformation, thereby destroying double-stranded structure to form more stable G-quadruplex structure, releasing MB embedded in double strands from the surface of the electrode, and detecting the MB and Pb2+Realization of Pb by electric signal change of MB before and after reaction2+Quantitative determination, thereby establishing a rapid and effective Pb2+Analyzing the strategy and applying to the actual sample detection.
Description
Technical Field
The invention mainly provides a construction and application method of an electrochemical aptamer sensor for detecting lead ions with high sensitivity by taking methylene blue as an indicator, belonging to the field of electrochemical analysis and biosensors.
Background
Heavy metal elements can have harmful effects on human and animals, and are therefore considered to be one of the most serious sources of environmental pollution. Lead ion (Pb)2+) The heavy metal ion is a heavy metal ion which has a threat to human health and has the characteristics of nondegradability, transferability, bioaccumulation and the like in an ecological system. Toxicological experiments show that Pb2+Can be enriched in the human body by the food chain, causing severe damage to the blood and nervous system. Therefore, establishing a method with high sensitivity and high selectivity for quantitatively analyzing the content of heavy metal lead ions is of great significance.
Electrochemical analysis is receiving increasing attention due to its fast response speed, high sensitivity and strong operability. Compared with many existing lead ion detection technologies such as surface plasma resonance spectroscopy, quartz crystal microbalance, fluorescence spectroscopy and the like, electrochemical analysis has the advantages of simplicity and convenience in operation, good selectivity, low cost, capability of analyzing multiple targets simultaneously and the like. However, electrochemical detection on a limited electrode surface usually limits the detection sensitivity due to few surface electroactive sites, poor adsorption capacity of ions, and the like. In order to realize electrochemical analysis with high sensitivity, many nanomaterials have been used for electrode modification, which generally have large specific surface area, good mechanical strength and excellent physicochemical properties. As one of important members of carbon materials, Carbon Nanofibers (CNF) have advantages of a fast electron transfer rate, a large active surface area, high physicochemical stability, and the like, and thus have received wide attention in various fields.
The invention combines the methods of electrostatic spinning, hydrothermal synthesis, electrochemical deposition and the like to prepare a platinum-loaded carbon nanofiber (Pt @ CNF) composite material, and the composite material is used for constructing an electrochemical aptamer sensor to realize the quantitative detection of heavy metal lead ions. Methylene blue is used as an electrochemical indicator and is embedded into an aptamer DNA double chain, lead ions can induce an aptamer probe to form G-quadruplex conformation so as to destroy the DNA double chain structure, quantitative release of MB on the surface of an electrode is realized by means of high-specificity combination between the aptamer probe and the lead ions, the aim of quantitatively determining the content of the lead ions is achieved by recording MB electrochemical signals, and a novel sensing strategy with high efficiency, convenience, sensitivity and accuracy is provided for quantitative analysis of heavy metal lead ions.
Disclosure of Invention
The invention aims to provide a construction and application method of an electrochemical aptamer sensor for detecting lead ions with high sensitivity by taking methylene blue as an indicator. The method realizes the quantitative analysis of the lead ions by introducing the DNA double chains for specifically recognizing the lead ions to carry out hybridization, embedding methylene blue into the double-chain DNA as a hybridization indicator, and utilizing a high-sensitivity differential pulse voltammetry as a detection means according to the electrochemical signal change corresponding to the methylene blue concentration change on the surface of the electrode caused before and after the aptamer probe is combined with the lead ions. The electrochemical aptamer sensor has the advantages of high response speed, high sensitivity, good selectivity, wide detection range, good reproducibility and stability and the like.
The technical means adopted by the invention are as follows:
(1) 2.75 g Polyacrylonitrile (PAN) was dissolved in 35.0 mL N' N-Dimethylformamide (DMF) solvent and subjected to ultrasonic oscillation to obtain a 7.85% polymer solution (PAN)DMF), spinning under an electrostatic field to obtain precursor polyacrylonitrile fiber (PANF), wherein the spinning voltage is 17.27 kV, the rotating speed of a receiving roller is 1450 rpm, and the flow rate of an injection pump is 20.00 mu L/min; further carbonizing the PANF at high temperature in a vacuum tube furnace to obtain Carbon Nanofiber (CNF), wherein the carbonization temperature is 800 ℃, the time is 2 hours, and the carbonization process is carried out in a nitrogen atmosphere; further loading platinum nanoparticles (PtNPs) on the surface of the CNF by a hydrothermal synthesis method, and placing the prepared CNF in a container containing 0.5mg/mL of H2PtCl6And heating the solution in a high-pressure reaction kettle at 180 ℃ for 12h, cooling, taking out, washing and drying to obtain the platinum loaded carbon nanofiber (Pt @ CNF) composite material.
(2) And (3) uniformly coating 8.0 mu L of 1.5 mg/mL Pt @ CNF dispersion liquid on the surface of a Carbon Ion Liquid Electrode (CILE) serving as a substrate electrode, and airing at room temperature to obtain Pt @ CNF/CILE.
(3) Further Pt @ CNF/CILE was placed in 2.0 mmol/L HAuCl4And 0.1 mol/L NaNO3And carrying out constant potential deposition in the mixed solution, wherein the deposition potential is-0.3V, the deposition time is 100 s, taking out the electrode, washing, and naturally drying to obtain Au/Pt @ CNF/CILE.
(4) Further immersing Au/Pt @ CNF/CILE into a 1.0 mu mol/L Capture Probe (CP), self-assembling for 12h at 4 ℃, taking out, washing and drying to obtain the CP/Au/Pt @ CNF/CILE.
(5) Further coated with 30.0 μ L1.0 mmol/L TGA on CP/Au/Pt @ CNF/CILE surface, combined at room temperature 25 ℃ for 30 min, rinsed with ultra-pure water and dried.
(6) And further immersing the CP/Au/Pt @ CNF/CILE into a 1.0 mu mol/L Aptamer Probe (AP) for hybridization at room temperature of 25 ℃ for 1 h, taking out, washing and drying to obtain the electrochemical aptamer sensor (AP/CP/Au/Pt @ CNF/CILE).
(7) The electrochemical aptamer sensor was further placed in 0.2 mol/L MB solution, bound for 15 min at room temperature at 25 ℃, rinsed with ultra-pure water and air dried.
(8) Further placing the aptamer sensor embedded with methylene blue in lead ion solutions with different concentrations, incubating at 25 ℃ for 40 min, washing with ultrapure water, and drying.
(9) In the electrochemical experiment, methylene blue is used as an electric signal probe, a working curve is formulated by recording the change value of methylene blue electric signals caused before and after the aptamer sensor reacts with lead ions by adopting a differential pulse voltammetry method, and the sample solution containing the lead ions is quantitatively analyzed.
Compared with the prior art, the invention has the advantages that:
(1) the invention uses a ternary nano composite material (Au/Pt @ CNF) as an electrode interface sensitizer, after the Au/Pt @ CNF composite material is gradually modified on the CILE surface, the specific surface area and the electron transmission capability of the sensor are greatly improved, the good biocompatibility and the large specific surface area of the sensor are more beneficial to the fixation of a biological recognition element aptamer sequence, and the response speed and the sensitivity of the sensor are improved.
(2) The DNA double strand used in the invention is a complementary strand capable of hybridizing, and the aptamer probe in the invention can specifically recognize lead ions and is induced to form a G-quadruplex structure, so that the DNA double strand structure is damaged, and the electric signal of the electrochemical indicator on the surface of the electrode is changed, therefore, the prepared aptamer sensor has good specific recognition capability and selectivity.
(3) The method takes methylene blue as an electric signal indicator, adopts differential pulse voltammetry to carry out quantitative analysis on lead ions, and obtains a detection range of 1.0 × 10-16To 1.0 × 10-11mol/L, detection limit of 3.33 × 10-17mol/L (3 sigma), can meet the daily analysis requirement.
Drawings
FIG. 1 scanning electron micrograph of Pt @ CNF composite at different magnifications.
FIG. 2 (A) XRD characterization of Pt @ CNF composites; (B) XPS characterization of Pt @ CNF composites, where (C) C1s, (D) N1 s, (E) O1 s, (F) Pt 4F.
FIG. 3(A) different modified electrodes at 1.0 mmol/L K3[Fe(CN)6]And cyclic voltammograms in 0.5 mol/L KCl mixed electrolyte at a sweep rate of 100 mV/s, where (a) Au/Pt @ CNF/CILE, (b)CP/Au/Pt @ CNF/CILE, (c) AP/CP/Au/Pt @ CNF/CILE, (d) Pt @ CNF/CILE, (e) CILE; (B) the different modified electrodes are 10.0 mmol/L K3[Fe(CN)6]And the alternating current impedance spectrum in 0.1 mol/L KCl mixed electrolyte, and the scanning frequency range is 0.1-105Hz, wherein (a) Au/Pt @ CNF/CILE, (b) CP/Au/Pt @ CNF/CILE, (c) AP/CP/Au/Pt @ CNF/CILE, (d) Pt @ CNF/CILE, and (e) CILE.
FIG. 4 (A) current response values caused by MB intercalating DNA double strand at different binding times; (B) aptamer probe and Pb2+The change in the MB electrical signal caused at different binding times.
FIG. 5 (A) electrochemical aptamer sensors with varying concentrations of Pb2+Differential pulse voltammogram after binding in Tris-HCl buffer pH = 7.8, with Pb from a to j2+The concentrations are 0, 1.0 × 10-16，5.0×10-16，1.0×10-15，5.0×10-15，1.0×10-14，5.0×10-14，1.0×10-13，1.0×10-12，1.0×10-11mol/L; (B) change value (Delta I) of MB electrical signal and Pb caused before and after combination with lead ion2+Linear relationship between the logarithm of the concentration (lgC).
FIG. 6 the selectivity of electrochemical aptamer sensors in the presence of different interfering metal ions.
TABLE 1 electrochemical aptamer sensor for the determination of Pb in nail polish samples2+(n = 3).
Detailed Description
The principles and features of this invention are described below in conjunction with examples which are set forth to illustrate, but are not to be construed to limit the scope of the invention.
Example 1
The preparation method of AP/CP/Au/Pt @ CNF/CILE comprises the following steps:
taking 1.6 g of graphite powder and 0.8 g N-hexyl pyridine Hexafluorophosphate (HPPF)6) Fully grinding the mixture into paste in a mortar, filling the paste into a glass electrode tube, and inserting a copper wire as a lead to obtain CILE;
dripping 8.0 mu L of 1.5 mg/mL Pt @ CNF dispersion liquid on the surface of CILE, and naturally airing at room temperature to obtain Pt @ CNF/CILE;
place Pt @ CNF/CILE in 2.0 mmol/L HAuCl4And 0.1 mol/L NaNO3Carrying out an electrodeposition experiment in the mixed solution, wherein the deposition potential is-0.3V, the deposition time is 100 s, and taking out, washing and airing to obtain Au/Pt @ CNF/CILE;
the method comprises the steps of immersing Au/Pt @ CNF/CILE into a 1.0 mu mol/L capture probe, carrying out self-assembly for 12h at 4 ℃, taking out, washing and airing, further coating 30.0 mu L1.0 mmol/L TGA, combining for 30 min at room temperature of 25 ℃, washing and airing to obtain CP/Au/Pt @ CNF/CILE;
and (3) immersing the CP/Au/Pt @ CNF/CILE into a 1.0 mu mol/L aptamer probe, hybridizing at 25 ℃ for 1 h at room temperature, taking out, washing and drying to obtain the AP/CP/Au/Pt @ CNF/CILE.
Comparative example 1
The preparation of CILE comprises the following steps:
taking 1.6 g of graphite powder and 0.8 g of HPPF6And fully grinding the mixture into paste in a mortar, introducing the paste into a glass electrode tube, and inserting a copper wire as a lead to obtain the CILE.
Comparative example 2
The preparation method of Pt @ CNF/CILE comprises the following steps:
taking 1.6 g of graphite powder and 0.8 g N-hexyl pyridine Hexafluorophosphate (HPPF)6) Fully grinding the mixture into paste in a mortar, filling the paste into a glass electrode tube, and inserting a copper wire as a lead to obtain CILE;
and (3) dripping 8.0 mu L of 1.5 mg/mL Pt @ CNF dispersion liquid on the surface of CILE, and naturally airing at room temperature to obtain Pt @ CNF/CILE.
Comparative example 3
The preparation method of Au/Pt @ CNF/CILE comprises the following steps:
taking 1.6 g of graphite powder and 0.8 g N-hexyl pyridine Hexafluorophosphate (HPPF)6) Fully grinding the mixture into paste in a mortar, filling the paste into a glass electrode tube, and inserting a copper wire as a lead to obtain CILE;
dripping 8.0 mu L of 1.5 mg/mL Pt @ CNF dispersion liquid on the surface of CILE, and naturally airing at room temperature to obtain Pt @ CNF/CILE;
place Pt @ CNF/CILE at 2.0 mmol/L HAuCl4And 0.1 mol/L NaNO3And performing an electrodeposition experiment in the mixed solution, wherein the deposition potential is-0.3V, the deposition time is 100 s, and taking out, washing and drying to obtain Au/Pt @ CNF/CILE.
Comparative example 4
The preparation of CP/Au/Pt @ CNF/CILE comprises the following steps:
taking 1.6 g of graphite powder and 0.8 g N-hexyl pyridine Hexafluorophosphate (HPPF)6) Fully grinding the mixture into paste in a mortar, filling the paste into a glass electrode tube, and inserting a copper wire as a lead to obtain CILE;
dripping 8.0 mu L of 1.5 mg/mL Pt @ CNF dispersion liquid on the surface of CILE, and naturally airing at room temperature to obtain Pt @ CNF/CILE;
place Pt @ CNF/CILE in 2.0 mmol/L HAuCl4And 0.1 mol/L NaNO3Carrying out an electrodeposition experiment in the mixed solution, wherein the deposition potential is-0.3V, the deposition time is 100 s, and taking out, washing and airing to obtain Au/Pt @ CNF/CILE;
and placing the Au/Pt @ CNF/CILE into a 1.0 mu mol/L capture probe, performing self-assembly for 12h at 4 ℃, taking out, washing and drying, further coating 30.0 mu L1.0 mmol/L TGA, combining for 30 min at room temperature of 25 ℃, washing and drying to obtain the CP/Au/Pt @ CNF/CILE.
Firstly, material preparation
2.75 g PAN was dissolved in 35.0 mL DMF solvent and subjected to ultrasonic oscillation for 1 h to give a 7.85% polymer solution (PAN/DMF), and spinning was carried out in an electrostatic field at a voltage of 17.27 kV, a receiving roller rotation speed of 1450 rpm, a gap between a spinneret and a receiver of 18 cm, a flow rate of a syringe pump of 20.00. mu.L/min, and a moving distance between the left and right of the spinneret of 30 cm. After continuous spinning for 4 h, the precursor polyacrylonitrile fiber (PANF) can be collected on the tin foil paper.
And carbonizing the PANF in a vacuum tube furnace by adopting a temperature programming method to obtain the CNF. The method comprises the following specific steps: the first step is to raise the temperature to 300C at a rate of 5C/min. And (3) raising the temperature to 800 ℃ at a rate of 10 ℃ per min in the second step. The third step was to maintain the temperature at 800 ℃ for 2h to complete carbonization. The whole process is carried out in nitrogen atmosphere, and finally, the CNF is obtained after cooling to room temperature.
PtNPs are loaded on the surface of CNF by a hydrothermal synthesis method. The specific steps are that the CNF prepared above is put in H of 0.5mg/mL2PtCl6And transferring the solution into a high-pressure reaction kettle, heating the solution at 180 ℃ for 12 hours, cooling the solution to room temperature, taking the solution out, washing the solution with ultrapure water, and drying the solution to obtain the Pt @ CNF composite material.
Second, characterization of materials
The characterization result of a scanning electron microscope of the Pt @ CNF composite material under different magnification factors is shown in figure 1, the Pt @ CNF composite material presents a good net-shaped communication structure in space, and the fiber diameter is about 350 nm. In addition, it was found that PtNPs were uniformly and stably attached to the surface of CNF, and had a particle size of about 60 nm.
XRD characterization results are shown in fig. 2 (a), where Pt @ CNF composite shows very high crystallinity, and its characteristic diffraction peak at 25.6 ° can correspond to (002) plane of CNF, indicating formation of graphite structure. While the 4 strong peaks at 40.1 °, 46.2 °, 67.5 ° and 81.6 ° correspond to the (111), (200), (220) and (311) faces of PtNPs, indicating that Pt has been successfully reduced to the metallic state.
The XPS results are shown in fig. 2 (B), and the presence of four elements, C, N, O, and Pt, was observed, and the content of each element was 88.3%, 6.17%, 5.10%, and 0.37%, respectively. It can be observed from FIG. 2 (C) that one distinct peak at about 284 eV is attributable to C1s, which can be further divided into 284.7 eV, 286.5 eV and 289.5 eV peaks, corresponding to C-C (sp) respectively2C) C-O or C-N and C ¼ O bonds. FIG. 2 (D) is a spectrum of N1 s, with two peaks corresponding to C.ident.N (398 eV) and graphitic nitrogen (400 eV), respectively. FIG. 2 (E) shows the peak for O1 s, mainly around 532 eV. The Pt 4F spectrum of FIG. 2 (F) shows two peaks, respectively 72 eV (Pt 4F)7/2) And 75 eV (Pt 4 f)5/2) Indicating H during the heat treatment2PtCl6Has been completely reduced.
Third, electrochemical characterization
The electrochemical response of different modified electrodes was investigated by cyclic voltammetry. As shown in fig. 3(a), a pair of redox peaks are shown on CILE (curve e). After modification of the Pt @ CNF composite, the redox peak current on the Pt @ CNF/CILE (curve d) was enhanced. After further electrodeposition of nanogold, the redox peak current value on Au/Pt @ CNF/CILE (curve a) continued to rise to a maximum value. The current signal on CP/Au/Pt @ CNF/CILE (curve b) decreases by self-assembling the capture probe CP and using TGA as the active site blocker, and after further hybridization with the aptamer probe AP, the current response continues to decrease on AP/CP/Au/Pt @ CNF/CILE (curve c), because the DNA chain has no conductivity with TGA and thus blocks the electron transfer process.
The change in the interface resistance during electrode modification was examined by the ac impedance method, and the result is shown in fig. 3 (B). The resistance value on CILE (curve e) is 163.59 Ω. After Pt @ CNF and Au are gradually modified, the resistance values of Pt @ CNF/CILE (curve d, 131.61 omega) and Au/Pt @ CNF/CILE (curve a, 29.20 omega) are gradually reduced, which shows that the Au/Pt @ CNF ternary material has excellent conductivity and reduces the interface resistance of the modified electrode. After the CP, TGA and AP are gradually modified, the resistance value is gradually increased on CP/Au/Pt @ CNF/CILE (curve b) and AP/CP/Au/Pt @ CNF/CILE (curve c), which indicates that the DNA is successfully fixed on the surface of the electrode, and the result is consistent with the cyclic voltammetry characterization result.
Fourth, optimizing experimental conditions
The time of action of the DNA double strand with the indicator MB was optimized in Tris-HCl buffer at pH 7.8, and the results are shown in FIG. 4 (A). The highest current response was shown when the aptamer sensor was soaked in the MB solution for 15 min, indicating that the concentration of MB intercalated on the double-stranded DNA was the greatest at this time, and thus the binding time of DNA double-strand to MB was selected to be 15 min. The binding time of the aptamer probe to the lead ion as the target was further examined, and the result is shown in fig. 4 (B). When the combination time of the aptamer probe and the lead ions reaches 40 min, a plateau value appears in current response, which indicates that the formation of the G-quadruplex structure by the aptamer probe induced by the lead ions is basically completed. Therefore, the time for the aptamer probe to react with the lead ions is selected to be 40 min.
Fifth, the working curve
Methylene blue is used as electrochemical indicator by changing Pb2+The analytical performance of the constructed electrochemical aptamer sensor is researched by using differential pulse voltammetry. The results are shown in FIG. 5 (A), at Pb2+The concentration is 1.0 × 10-16To 1.0 × 10-11In the detection range of mol/L, the peak current gradually decreases with the increase of the concentration of the target. Aptamer probe binding to Pb2+The change value of Δ I and Pb of the front and rear peak currents2+The logarithm of concentration (lgC) is in a better linear relationship, as shown in FIG. 5 (B), the linear regression equation is Δ I (μ A) = 0.52 × lgC (mol/L) +12.35 (n = 11, γ = 0.993), the detection limit is 3.33 × 10-17mol/L（3σ）。
Sixth, interference measurement
Investigating the electrochemical aptamer sensor pair Pb2+The effect of several common interfering metal ions, such as 1.0 × 10 concentration, was tested by differential pulse voltammetry-11mol/L of Ag+、Ni2+、Hg2+、Ca2+、Mn2+、Cd2+、K+、Al3+Etc., the results are shown in fig. 6. Removing Pb2+All ions outside showed small current changes, indicating that the designed electrochemical aptamer sensor is sensitive to Pb2+Has good selectivity.
Seventhly, sample detection
The practical application effect of the aptamer sensor is considered, and a red nail polish (purchased from miniso, Japan) is selected as a sample. Nail polish was diluted 1000 times in pH = 7.8 Tris-HCl buffer and stirred rapidly to homogeneity, using the prepared aptamer sensor for Pb in nail polish2+The concentration is measured, and Pb in the sample is solved by adopting a standard curve method2+The recovery rate was obtained by the standard addition method, and the results are shown in table 1, and the obtained recovery rate was 100.57% to 103.77%, and the RSD value was 1.58%, indicating that the aptamer sensor can be used for detection and analysis of actual samples.
TABLE 1 electrochemical aptamer sensor for the determination of Pb in nail polish samples2+Content of (n = 3)
In summary, the present invention uses MB as the electrochemical indicator, and uses the aptamer probe and Pb2+The high specificity combination realizes the quantitative falling of MB on the surface of the electrode, and simultaneously, the Pt @ CNF and AuNPs ternary nano composite material is introduced on the surface of the electrode to play a synergistic effect to realize the signal amplification, thus constructing the electrochemical aptamer sensor (AP/CP/Au/Pt @ CNF/CILE) which has high sensitivity and specific identification and can quantitatively detect lead ions and is used for Pb2+The linear range of detection is 1.0 × 10-11To 1.0 × 10-16mol/L, detection limit of 3.33 × 10-17mol/L (3. sigma.). Thereby realizing the Pb-free electrode by monitoring the electric signal change of the electrode interface2+The quantitative analysis provides a new method for detecting the lead ions efficiently, conveniently, sensitively and accurately.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (8)
1. A construction and application method of an electrochemical Aptamer sensor for high-sensitively detecting lead ions by taking methylene blue as an indicator is characterized in that a layer of platinum-loaded carbon nanofiber composite material (Pt @ CNF) is modified on the surface of a substrate electrode (CILE) by a coating method, gold nanoparticles (AuNPs) are modified by an electrodeposition method, a Capture Probe (Capture Probe) is self-assembled on the surface of the electrode by utilizing an Au-S bond, thioglycolic acid (TGA) is used as a sealant which is not combined with an active site, the Aptamer Probe (Aptamer Probe) is further fixed in a DNA double-strand hybridization form, the Methylene Blue (MB) is used as the electrochemical indicator to prepare the electrochemical Aptamer sensor (AP/CP/Au/Pt @ CNF/CILE) for high-sensitively detecting the lead ions, and a working curve is formulated by detecting the change condition of an MB electrical signal caused before and after the Aptamer sensor is incubated in lead ion solutions with different concentrations, and realizing the quantitative analysis of the lead ion sample.
2. The method for constructing and using the electrochemical aptamer sensor for detecting lead ions with high sensitivity by using methylene blue as an indicator according to claim 1, wherein the capture probe sequence used is 5' -CAC CCA CCC AC-C6SH-3' with the concentration of 1.0 mu mol/L, the self-assembly time of 12h and the temperature condition of 4 ℃.
3. The method for constructing and applying the electrochemical aptamer sensor for detecting the lead ions with high sensitivity by taking methylene blue as the indicator according to claim 1, wherein the concentration of the thioglycolic acid used is 1.0 mmol/L, the reaction time is 30 min, and the temperature condition is 25 ℃ at room temperature.
4. The method for constructing and applying the electrochemical aptamer sensor for detecting the lead ions with high sensitivity by using the methylene blue as the indicator according to claim 1, wherein the sequence of the aptamer probe used is 5'-GGG TGG GTG GGTGGG T-3', the concentration is 1.0 μmol/L, the hybridization time is 1 h, and the temperature condition is 25 ℃ at room temperature.
5. The method for constructing and applying the electrochemical aptamer sensor for highly sensitively detecting lead ions by using methylene blue as the indicator according to claim 1, wherein the concentration of the selected methylene blue is 0.2 mmol/L, the soaking time is 15 min, and the temperature condition is 25 ℃ at room temperature.
6. The method for constructing and applying the electrochemical aptamer sensor for detecting the lead ions with high sensitivity by taking methylene blue as the indicator according to claim 1, wherein the incubation time of the electrochemical aptamer sensor in lead ion solutions with different concentrations is 40 min, and the temperature condition is 25 ℃ at room temperature.
7. The method for constructing and applying the electrochemical aptamer sensor for detecting the lead ions with high sensitivity by taking methylene blue as the indicator according to claim 1, wherein the selected buffer solution is Tris-HCl, the pH condition is 7.8, and the concentration is 0.1 mol/L.
8. The method for constructing and applying the electrochemical aptamer sensor for detecting the lead ions with high sensitivity by taking methylene blue as the indicator according to claim 1, wherein the lead ions are quantitatively detected by taking the methylene blue as the electrochemical indicator through differential pulse voltammetry.
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