Construction method and use of photoelectrochemical aptamer sensor based on z-type nickel titanate-polyaniline heterojunction

Abstract

The application belongs to the technical field of photoelectrochemical sensing, and particularly relates to a construction method of a photoelectrochemical aptamer sensor based on a Z-type nickel titanate-polyaniline heterojunction and application thereof. The application specifically prepares a direct Z-type NiTiO3-PANI heterojunction with high light utilization efficiency, functionalizes the inert surface of NiTiO3 by using the high conductivity and hydrophilicity of PANI, improves the dispersibility in an aqueous solution, further improves the separation efficiency of electron-hole pairs, and generates a strong base signal. In combination with the specificity of an aptamer, a signal-on photoelectrochemical aptamer sensor is constructed, sensitive analysis of OTA is realized, and in the detection of a sample in a complex matrix, the sensor can realize high-sensitivity and high-selectivity detection of OTA, and a good recovery rate (88.4-106.6%) is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photoelectrochemical sensing, and particularly relates to construction of a photoelectrochemical aptamer sensor based on a Z-type nickel titanate-polyaniline (NiTiO3-PANI) heterojunction and use thereof for ochratoxin A detection. BACKGROUND

[0002] Ochratoxin A (OTA) is a secondary metabolite produced by Aspergillus and Penicillium, widely exists in nature, has strong toxicity, and is classified as a class IIB carcinogen by the state. Growing crops are susceptible to fungal toxin infection, affecting crop yield; if the external environment of the crops during storage, transportation, processing and preservation meets the growth conditions of fungi, the fungi will continue to grow; further, if humans or animals mistakenly eat crops infected with OTA, it will cause a decline in immunity and even harm health. At present, most research focuses on detecting OTA in crops, but ignores an important source of OTA, soil. After the crops are harvested, the OTA remaining in the soil will be absorbed and enriched by the crops planted later, causing more serious infection problems. The state stipulates that the limit of OTA in cereals and their products is 5.0 μg / kg. Therefore, it is of great significance to realize sensitive and accurate detection of OTA in crops and soil for improving crop yield and monitoring soil quality.

[0003] Photoelectrochemical method has attracted extensive attention due to its low background signal, high sensitivity and easy miniaturization of equipment, and is one of the most promising methods for OTA detection. NiTiO3 has attracted its application in photoelectrochemical sensing due to its large specific surface area, strong light absorption capacity and chemical stability in the visible light range. However, NiTiO3 has low light utilization efficiency and poor photocatalytic activity due to its narrow band gap and fast recombination of photo-generated electron-hole pairs. At present, the method for improving the photocatalytic performance of NiTiO3 mainly improves the separation efficiency of photo-generated electron-hole pairs, and the construction of heterojunction is considered as one of the most effective methods. Compared with traditional type-II heterojunction, Z-type heterojunction has better light trapping capacity and spatially separated oxidation and reduction active sites. Based on this, the application constructs a photoelectrochemical aptamer sensor based on NiTiO3-PANI heterojunction, which can realize accurate and sensitive analysis of OTA in complex matrix. SUMMARY

[0004] In view of the problems of easy recombination of electron-hole of NiTiO3 and large interference of complex matrix sample, the application designs and prepares an efficient direct Z-type NiTiO3-PANI heterojunction by compounding nickel titanate (NiTiO3) and polyaniline (PANI), and realizes high-sensitivity and accurate detection of OTA in soil and corn.

[0005] The application designs and prepares a direct Z-type NiTiO3-PANI heterojunction by an electrostatic adsorption method, which is used as a substrate to generate a strong photocurrent. The dual-function PANI complements the light absorption advantage of NiTiO3 in the visible light range, widens the light absorption range, and improves the separation efficiency of electron-hole pairs after forming a Z-type heterojunction with NiTiO3. On the other hand, the PANI with high conductivity and hydrophilicity can functionalize the surface of NiTiO3, improve the dispersibility of the composite material in an aqueous solution, and further improve the electron transfer rate. At present, there is no report on the research of the photoelectrochemical aptamer sensor for detecting OTA in soil. Based on this, the application constructs a photoelectrochemical aptamer sensor based on a direct Z-type NiTiO3-PANI heterojunction by a layer-by-layer modification method, which has the advantages of simple production, low detection limit, strong selectivity, good stability and the like. In addition, by analyzing corn and soil samples in farmland, the applicability of the aptamer sensor is verified.

[0006] The application provides a construction method of a photoelectrochemical aptamer sensor based on a direct Z-type NiTiO3-PANI heterojunction, and specifically includes the following steps.

[0007] (1) Preparation of NiTiO3 nanomaterials:

[0008] Firstly, nickel acetate tetrahydrate is added to ethylene glycol to form a uniform solution by ultrasonic dispersion, then tetrabutyl titanate is added to the solution under stirring, a blue precursor precipitate is generated during stirring, after continuing the stirring reaction, the precipitate is collected by centrifugation and washed with ethanol, and the washed precipitate is dried to obtain a nickel titanate precursor; finally, the nickel titanate precursor is calcined, and the powder obtained after grinding is the NiTiO3 nanomaterial;

[0009] Preferably, the amount ratio of nickel acetate tetrahydrate, ethylene glycol and tetrabutyl titanate in step (1) is 2.067g:50mL:2.833mL; the time for continuing the stirring reaction is 1h; the drying temperature is 60-80℃, and the time is 6h; the calcination temperature is 600℃, the heating rate is 2℃ / min, and the calcination time is 2h.

[0010] (2) Preparation of NiTiO3-PANI heterojunction composite material:

[0011] Firstly, the NiTiO3 nanomaterial prepared in step (1) and PANI are dispersed in a mixed solution of N,N-dimethylacetamide (DMAC) and water, and after stirring at room temperature, the precipitate is collected by centrifugation and washed with ethanol, and the washed product is dried to obtain the NiTiO3-PANI heterojunction composite material;

[0012] Preferably, the amount of NiTiO3 nanomaterial, PANI and mixed solution in step (2) is 6 mg: 1.2-30 mg: 4 mL; the volume ratio of N, N-dimethylacetamide (DMAC) and water in the mixed solution is 9:1; the stirring speed at room temperature is 650 rpm, and the stirring time is 24 h.

[0013] (3) The indium tin oxide glass (ITO) electrode is sequentially subjected to ultrasonic treatment in ethanol and water, then boiled in a sodium hydroxide solution for a period of time, and finally subjected to ultrasonic treatment in ethanol and ultrapure water to obtain a pretreated ITO electrode;

[0014] Preferably, the diameter of the ITO electrode in step (3) is 6 mm, the sodium hydroxide solution used is 0.3 M, the boiling time is 30 min, and the ultrasonic treatment time is 15 min.

[0015] (4) The NiTiO3-PANI heterojunction composite material prepared in step (2) is dispersed in ultrapure water to obtain a NiTiO3-PANI dispersion liquid; then the NiTiO3-PANI dispersion liquid is modified to the surface of the pretreated ITO electrode in step (3), and after incubation, the product obtained is denoted as NiTiO3-PANI / ITO;

[0016] Preferably, the concentration of the NiTiO3-PANI dispersion liquid in step (4) is 4 mg / mL, and the modification amount is 20 μL; the incubation temperature is 37°C, and the incubation time is 1 h.

[0017] (5) First, an acetic acid solution is prepared, then chitosan is dissolved in the acetic acid solution to obtain a chitosan solution, and then the obtained chitosan solution is modified to the surface of the NiTiO3-PANI / ITO obtained in step (4), and after incubation, the product obtained is denoted as CS / NiTiO3-PANI / ITO;

[0018] Preferably, the mass fraction of the acetic acid solution in step (5) is 2%, the mass fraction of the chitosan solution is 0.01%, the modification amount of the chitosan solution is 10 μL, the incubation temperature is 37°C, and the incubation time is 30 min.

[0019] (6) The OTA aptamer solution is modified to the surface of the CS / NiTiO3-PANI / ITO obtained in step (5), and after incubation, it is rinsed with a phosphate buffer solution (PBS), and after rinsing and air-drying, a photoelectrochemical aptamer sensor based on a direct Z-type NiTiO3-PANI heterojunction is obtained, denoted as Apt / CS / NiTiO3-PANI / ITO;

[0020] Preferably, the sequence of the OTA aptamer in step (6) is as follows:

[0021] 5'-GAT CGG GTG TGG GTG GCG TAA AGG GAG CAT CGG ACA-3'

[0022] Wherein, the concentration of the OTA aptamer solution is 0.5-3.0 μM, the modification amount is 20 μL, the incubation temperature is 4℃, and the incubation time is 12-15 h; the concentration of the elution solution phosphate buffer (PBS) is 0.01 M.

[0023] The use of the photoelectrochemical aptamer sensor based on the direct Z-type NiTiO3-PANI heterojunction for OTA detection, the steps are as follows:

[0024] (1) First, prepare OTA standard solutions of different concentrations, then modify V1 volume of the OTA standard solution on the surface of the photoelectrochemical aptamer sensor (Apt / CS / NiTiO3-PANI / ITO) based on the direct Z-type NiTiO3-PANI heterojunction prepared in the above step, incubate at a certain temperature for a period of time, then use ultrapure water to elute and remove the unbound OTA, and the obtained sensor is recorded as OTA / Apt / CS / NiTiO3-PANI / ITO; (wherein the photoelectric current of the sensor OTA / Apt / CS / NiTiO3-PANI / ITO is in one-to-one correspondence with the concentration of the OTA standard solution, that is, the different photoelectric responses of the sensor correspond to the OTA standard solutions of different concentrations in turn; thereby obtaining the photoelectrochemical aptamer sensor based on the direct Z-type NiTiO3-PANI heterojunction;

[0025] (2) Take the OTA / Apt / CS / NiTiO3-PANI / ITO obtained in step (1) as the working electrode, take the Ag / AgCl electrode as the reference electrode, and take the platinum wire electrode as the counter electrode to perform photoelectrochemical detection, record the photoelectric current signal, take the concentration of the OTA standard solution as the abscissa, and take the photoelectric current generated by the OTA of different concentrations as the ordinate, and establish a standard curve;

[0026] (3) Detection of OTA in actual samples: first, prepare a sample solution, then modify V1 volume of the sample solution on the Apt / CS / NiTiO3-PANI / ITO sensing interface, incubate at a certain temperature for a period of time, then clean the counter electrode with ultrapure water, and then perform photoelectrochemical detection to obtain the corresponding photoelectric current signal; then substitute the generated photoelectric current signal into the standard curve constructed in step (2), and the concentration of the OTA in the actual sample can be obtained, and the detection of the OTA in the actual sample can be realized.

[0027] Preferably, the concentration of the OTA standard solution in step (1) is 1 pg / mL-2 ng / mL.

[0028] Preferably, in steps (1) and (3), the incubation temperature is room temperature, and the incubation time is 20-120 min; and the V1 is 20 μL.

[0029] Preferably, in steps (2) and (3), the instrument for photoelectrochemical detection is an electrochemical workstation of CHI660E (Shanghai Chenhua), the excitation light source is a BBZM-III xenon lamp cold light source, and the bias voltage range during detection is 0 V, and the interval between the on and off light is 10 s.

[0030] (1) The present application is based on the matched energy level band gap of NiTiO3 and PANI, and a high-efficiency direct Z-type NiTiO3-PANI heterojunction is designed and prepared, and the selectivity of the sensor is improved by combining with a specific aptamer, so that high-sensitivity and high-selectivity detection of OTA is realized.

[0031] (2) In the present application, the inert NiTiO3 surface is functionalized by using the high conductivity and hydrophilicity of PANI, so that the dispersibility of the composite material in the solution is improved, the electron transfer efficiency is improved, and the analysis performance is improved.

[0032] (3) The photoelectrochemical aptamer sensor based on the direct Z-type NiTiO3-PANI heterojunction is used for the detection of OTA, and has a wide linear range (1 pg / mL-2 ng / mL) and a low detection limit of 0.33 pg / mL.

[0033] (4) The photoelectrochemical aptamer sensor constructed in the present application has been successfully used for the detection of OTA in farmland corn and soil, and has good reliability and selectivity. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 Figure 1 is a schematic diagram of the construction process of the photoelectrochemical aptamer sensor of the present application; Figure (A) is a schematic diagram of the preparation process of the NiTiO3-PANI heterojunction composite material, Figure (B) is a flow chart of the construction of the sensor, and Figure (C) is a schematic diagram of the photocurrent response of the sensor before and after the addition of OTA.

[0035] Figure 2 Figure (A) is a SEM image of the NiTiO3 nanomaterial; and Figure (B) is a SEM image of the NiTiO3-PANI heterojunction composite material.

[0036] Figure 3 Figure (A) is an aptamer concentration optimization diagram; and Figure (B) is an aptamer-OTA binding time optimization diagram.

[0037] Figure 4 Figure (A) is a linear relationship diagram between different concentrations of OTA standard solution and photocurrent; and Figure (B) is the selectivity of the photoelectrochemical aptamer sensor.

[0038] Figure 5 (A) is the reproducibility of the photoelectrochemical aptamer sensor; (B) is the 7-day stability of the photoelectrochemical aptamer sensor. DETAILED DESCRIPTION

[0039] Various exemplary embodiments of the present application will now be described in detail, which should be considered to be illustrative of certain aspects, features and embodiments of the present application, but not a limitation of the scope of the present application.

[0040] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application.

[0041] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in full the methods and / or materials which are described therein. In case of conflict, the content of the present specification will control.

[0042] Various modifications and changes can be made to the specific embodiments of the present application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples presented herein. The description and examples are illustrative of certain aspects, features and embodiments of the present application and are not intended to limit the scope of the application in any way.

[0043] The OTA aptamer used in the present application is purchased from Shengwo Bioengineering (Shanghai) Co., Ltd.

[0044] Condition optimization:

[0045] (1) First, 2.067 g of nickel acetate tetrahydrate was added to 50 mL of ethylene glycol, ultrasonically dispersed to form a uniform solution, stirred at room temperature, then 2.833 mL of tetrabutyl titanate was added while stirring, and blue precursor precipitates were generated during stirring. Continue stirring for 1 h until the reaction is complete; centrifuge to collect the precipitate, wash with ethanol three times, dry the obtained precipitate, and obtain the nickel titanate (NiTiO3) precursor; finally, the precursor is calcined at 600°C at a rate of 2°C / min in a tube furnace, and the NiTiO3 nanomaterial is obtained after calcination at high temperature for 2 h, and is ground and stored in the dark.

[0046] (2) 6 mg NiTiO3 nanomaterials and 12 mg PANI were dispersed in 4 mL of a mixed solution of N, N-dimethylacetamide (DMAC) and water (v:v = 9:1), and stirred at room temperature at a speed of 650 rpm for 24 h, then the mixture was centrifuged to collect the precipitate and washed with ethanol; finally, the NiTiO3-PANI heterojunction composite material was obtained by drying in a drying oven;

[0047] (3) The indium tin oxide glass (ITO) electrode was sequentially treated with ethanol and water for 15 min, then boiled in 0.3 M sodium hydroxide solution for 30 min, and finally treated with ethanol and ultrapure water for 15 min, and dried to obtain a pretreated ITO electrode;

[0048] (4) The powdered NiTiO3-PANI heterojunction composite material prepared in step (2) was dissolved in ultrapure water to obtain a 4 mg / mL NiTiO3-PANI dispersion; 20 μL of the NiTiO3-PANI dispersion was modified onto the surface of the ITO electrode treated in step (3) and incubated in a 37°C incubator for 1 h, and the resulting product was labeled as NiTiO3-PANI / ITO;

[0049] (5) First, prepare a 2% acetic acid solution, then dissolve chitosan in the acetic acid solution to obtain a chitosan solution, wherein the mass fraction of the chitosan solution is 0.01%; then modify 10 μL of the chitosan solution onto the surface of the NiTiO3-PANI / ITO obtained in step (4) and incubate in a 37°C incubator for 30 min, and the resulting product is labeled as CS / NiTiO3-PANI / ITO;

[0050] (6) 20 μL of OTA aptamer solution (Apt) with a concentration of 0.5-3.0 μM (specifically 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 μM) was modified onto the surface of the CS / NiTiO3-PANI / ITO obtained in step (5), and was labeled as Apt / CS / NiTiO3-PANI / ITO; the effect of Apt concentration on the photocurrent response was investigated, and the results are shown in Figure 3 (A),

[0051] Figure 3 Figure A in (A) is a graph showing the relationship between Apt concentration and photocurrent response. When the Apt concentration increases from 0.5 to 2.0 μM, the photocurrent gradually decreases and tends to be stable at 2.5 μM, so 2.5 μM is selected as the optimal aptamer concentration.

[0052] (7) Based on the modification of the Apt / CS / NiTiO3-PANI / ITO solution with a concentration of 2.5 μM OTA aptamer in step (6), 20 μL of OTA solution with a concentration of 100 pg / mL was modified on the surface of Apt / CS / NiTiO3-PANI / ITO, and incubated in an incubator (20, 40, 60, 80, 100, 120 min) to explore the effect of incubation time on the photocurrent response. The results are shown in FIG. 8. Figure 3 (B) as shown in FIG. 8, Figure 3 (B) is a graph showing the effect of the binding time of OTA and Apt on the photocurrent response. When the binding time increases from 20 min to 80 min, the photocurrent gradually increases and tends to be stable at 100 min. Therefore, 100 min is selected as the optimal binding time.

[0053] Example 1:

[0054] (1) First, 2.067 g of nickel acetate tetrahydrate was added to 50 mL of ethylene glycol and ultrasonically dispersed to form a uniform solution, which was stirred at room temperature. Then, 2.833 mL of tetrabutyl titanate was added while stirring, and blue precursor precipitates were generated during the stirring process. The stirring was continued for 1 h until the reaction was complete. The precipitate was collected by centrifugation and washed with ethanol three times. The obtained precipitate was dried to obtain a nickel titanate (NiTiO3) precursor. Finally, the precursor was calcined in a tube furnace at 2 ℃ / min to 600 ℃ for 2 h to obtain NiTiO3 nanomaterials, which were ground and stored in the dark.

[0055] (2) 6 mg of NiTiO3 nanomaterials and 12 mg of PANI were dispersed in 4 mL of a mixed solution of N, N-dimethylacetamide (DMAC) and water (v:v = 9:1) and stirred at room temperature at a speed of 650 rpm for 24 h to form a NiTiO3-PANI composite material. The precipitate was collected by centrifugation and washed with ethanol. Finally, the NiTiO3-PANI heterojunction composite material was dried in a drying oven.

[0056] Figure 2 FIG. 8(A) is a SEM image of NiTiO3, which has a regular rod-like structure. The rod-like structure is composed of many nanoparticles, with an average length of about 1.2 μm and a diameter of about 300 nm. FIG. 8(B) is a SEM image of the NiTiO3-PANI heterojunction, in which two-dimensional sheet-like PANI is attached to the surface of the nanorods, and the rod-like structure does not change significantly.

[0057] (3) The indium tin oxide glass (ITO) electrode was ultrasonically treated in ethanol and water, respectively, and then boiled in a 0.3 M sodium hydroxide solution for 30 min. Finally, the ITO electrode was ultrasonically treated in ethanol and ultrapure water, respectively, and dried to obtain the ITO electrode.

[0058] (4) The powder-like NiTiO3-PANI prepared in step (2) was dissolved in ultrapure water to obtain a NiTiO3-PANI dispersion of 4 mg / mL; 20 μL of the NiTiO3-PANI dispersion was modified to the surface of the ITO electrode in step (3) and incubated in an incubator to obtain a product marked as NiTiO3-PANI / ITO;

[0059] (5) First, an acetic acid solution with a mass fraction of 2% was prepared, and then chitosan was dissolved in the acetic acid solution to obtain a chitosan solution, wherein the mass fraction of the chitosan solution was 0.01%; the chitosan solution was then modified to the surface of the NiTiO3-PANI / ITO obtained in step (3) and incubated in an incubator to obtain a product marked as CS / NiTiO3-PANI / ITO;

[0060] (6) 20 μL of an OTA aptamer solution (Apt) with a concentration of 2.5 μM was modified to the surface of the CS / NiTiO3-PANI / ITO obtained in step (5) and incubated in an incubator for 100 min, and then eluted with 0.01 M PBS to obtain a photoelectrochemical aptamer sensor based on a direct Z-type NiTiO3-PANI heterojunction, marked as Apt / CS / NiTiO3-PANI / ITO;

[0061] Example 2:

[0062] The surface of the Apt / CS / NiTiO3-PANI / ITO sensor provided in Example 1 was modified with different concentrations of OTA standard solutions, and the combination of the aptamer and the OTA was saturated at room temperature for 100 min, and then the sensor was washed with ultrapure water to remove the unbound OTA and the combined complex to obtain a product marked as OTA / Apt / CS / NiTiO3-PANI / ITO; the OTA standard solutions were 1.0, 2.0, 5.0, 10.0, 20.0, 50.0, 100.0, 200.0, 500.0, 1000.0, and 2000.0 pg / mL, respectively.

[0063] The above product (OTA / Apt / CS / NiTiO3-PANI / ITO) was used as a working electrode, an Ag / AgCl (saturated KCl) electrode was used as a reference electrode, and a platinum wire electrode was used as a counter electrode, and an electrochemical workstation with a model number of CHI660E (Shanghai Chenhua) was used to detect and record the photocurrent signal. The photocurrent signal was collected by chronoamperometry, the bias voltage was set to 0 V, and the switch light interval was 10 s. The logarithm of the concentration of the OTA standard solution was used as the abscissa, and the photocurrent signal corresponding to different concentrations of the OTA standard solution was used as the ordinate, and a corresponding standard curve was established for the detection of the OTA concentration in an actual sample.

[0064] From Figure 4 (A) It can be seen that the photocurrent gradually increases with the increase of OTA concentration, and shows a good linear relationship in the concentration range of 1 pg / mL ~ 2 ng / mL, and the calibration curve is I = 51.86lgC OTA + 205.4, (R 2 = 0.998), and the detection limit is 0.33 pg / mL.

[0065] Example 3:

[0066] Performance analysis of photoelectrochemical aptamer sensor:

[0067] Figure 4 (B) Taking the photoelectrochemical aptamer sensor as an example, the selectivity of the sensor was investigated: where ΔI is the difference between the photocurrent in the presence of interferents or target and the photocurrent in the absence of modified interferents or target; AFB1, FB1, NAP, ZEN, and OTB were used as interferents, and the corresponding concentrations were all 1 ng / mL; Mix was a mixture of the above interferents, and the concentration of each interferent in the mixture was 1 ng / mL; OTA was the target, and the corresponding concentration was 1 ng / mL; Mix + OTA was a mixture of interferents and OTA, and the concentration of Mix and OTA in the mixture was both 1 ng / mL.

[0068] The interferents AFB1, FB1, NAP, ZEN, OTB, and the above interferent mixture (Mix) were incubated with the sensor, and the obtained photocurrent response results were basically the same as the blank test results. After 1 ng / mL OTA was incubated with the sensor, the photocurrent response result was significantly higher than the blank. When the biosensor was incubated with Mix + OTA solution, its response was basically consistent with that of pure OTA. The results showed that the changes in photocurrent signal caused by other interferents and the mixture of interferents were negligible, thereby proving that the photoelectrochemical aptamer sensor had good selectivity.

[0069] Figure 5 (B) Taking the aptamer sensor as an example, the reproducibility of the sensor was investigated: seven aptamer sensors of the same batch were tested, and the changes in photocurrent response were observed, with an RSD of 1.9%, showing good reproducibility.

[0070] Figure 5 The stability test was performed for 7 consecutive days in (B), and the RSD value of the photocurrent response within 7 days was 2.4%, indicating that the OTA / Apt / CS / NiTiO3-PANI / ITO sensor had excellent stability.

[0071] Example 4:

[0072] The constructed photoelectrochemical aptamer sensor based on the direct Z-type NiTiO3-PANI heterojunction is used for analyzing actual samples, and the steps are as follows:

[0073] (1) Corn and soil samples are collected in a corn field in Fuyang City, Anhui Province, crushed by a crusher, then extracted by an extraction solution, and the supernatant is filtered by a 0.22 μm organic filter membrane to obtain the actual sample extract.

[0074] (2) Solutions containing OTA at concentrations of 100 pg / mL and 1000 pg / mL are prepared, and the actual sample is analyzed, and it is detected by testing that the original concentrations of OTA in corn and soil are 11 pg / mL and 4 pg / mL respectively, and the recoveries after spiking are 88.4-94.6% and 92.6-106.6% respectively, and the relative standard deviations (RSD) are less than 4.2% and 3.0% respectively, indicating that the sensor can be used for actual sample detection.

[0075] (3) The reliability of the constructed sensor is further verified by the high performance liquid chromatography-mass spectrometry (HPLC-MS / MS) standard method, and the detection results of HPLC-MS / MS method are consistent with the actual spiking amount, and are basically consistent with the detection results of the constructed sensor, indicating that the constructed sensor has good reliability.

[0076] The related test results are shown in Table 1.

[0077] Table 1:

[0078]

[0079]

[0080] It should be noted that the above examples are only used to illustrate the present application and are not intended to limit the technical solutions described in the present application; therefore, although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that the present application can still be modified or replaced by equivalents; and all technical solutions and improvements that do not deviate from the spirit and scope of the present application should be covered within the scope of the claims of the present application.

Claims

1. A method for constructing a photoelectrochemical aptamer sensor based on Z-type nickel titanate-polyaniline heterojunction, characterized in that, The steps comprise: (1) Preparation of NiTiO3 nanomaterials: First, add nickel acetate tetrahydrate to ethylene glycol, ultrasonically disperse to form a uniform solution, then add tetrabutyl titanate to the solution under stirring, blue precursor precipitates during stirring, continue stirring, centrifuge to collect the precipitate, wash with ethanol, dry the washed precipitate, and obtain the product, which is a nickel titanate precursor; finally, calcine the nickel titanate precursor, grind the calcined product to obtain a powder, which is the NiTiO3 nanomaterial; (2) Preparation of NiTiO3-PANI heterojunction composite material: First, disperse the NiTiO3 nanomaterial prepared in step (1) and PANI in a mixed solution of N,N-dimethylacetamide and water, stir at room temperature, centrifuge to collect the precipitate and wash with ethanol, and dry the washed product to obtain the NiTiO3-PANI heterojunction composite material; (3) First, ultrasonically treat the indium tin oxide glass electrode in ethanol and water, respectively, then boil the treated electrode in a sodium hydroxide solution for a period of time, and finally ultrasonically treat the electrode in ethanol and ultrapure water, respectively, to obtain a pretreated ITO electrode; (4) Disperse the NiTiO3-PANI heterojunction composite material prepared in step (2) in ultrapure water to obtain a NiTiO3-PANI dispersion; then modify the NiTiO3-PANI dispersion to the surface of the pretreated ITO electrode in step (3), and incubate to obtain a product, which is denoted as NiTiO3-PANI / ITO; (5) First, prepare an acetic acid solution, then dissolve chitosan in the acetic acid solution to obtain a chitosan solution, then modify the chitosan solution to the surface of the NiTiO3-PANI / ITO obtained in step (4), and incubate to obtain a product, which is denoted as CS / NiTiO3-PANI / ITO; (6) Modify an OTA aptamer solution to the surface of the CS / NiTiO3-PANI / ITO obtained in step (5), incubate, rinse with a phosphate buffer, and dry after rinsing to obtain a photoelectrochemical aptamer sensor based on a direct Z-type NiTiO3-PANI heterojunction, which is denoted as Apt / CS / NiTiO3-PANI / ITO.

2. The method for constructing a photoelectrochemical aptamer sensor based on Z-type nickel titanate-polyaniline heterojunction according to claim 1, characterized in that, The amount ratio of nickel acetate tetrahydrate, ethylene glycol and tetrabutyl titanate in step (1) is 2.067g: 50mL: 2.833mL; the time for continuing stirring is 1h; the drying temperature is 60-80℃, and the time is 6h; the calcination temperature is 600℃, the heating rate is 2℃ / min, and the calcination time is 2h.

3. The method for constructing a photoelectrochemical aptamer sensor based on Z-type nickel titanate-polyaniline heterojunction according to claim 1, characterized in that, The amount relationship of the NiTiO3 nanomaterial, PANI and the mixed solution in step (2) is 6mg: 1.2-30mg: 4mL; the volume ratio of N,N-dimethylacetamide and water in the mixed solution is 9:1; the stirring speed at room temperature is 650rpm, and the stirring time is 24h.

4. The method for constructing a photoelectrochemical aptamer sensor based on Z-type nickel titanate-polyaniline heterojunction according to claim 1, characterized in that, The diameter of the ITO electrode in step (3) is 6 mm, the sodium hydroxide solution used is 0.3 M, and the boiling time is 30 min; the ultrasonic treatment time is 15 min.

5. The method for constructing a Z-type nickel titanate-polyaniline heterojunction based photoelectrochemical aptasensor according to claim 1, wherein, The concentration of the NiTiO3-PANI dispersion liquid in step (4) is 4 mg / mL, and the modification amount is 20 μL; the incubation temperature is 37℃, and the incubation time is 1 h.

6. The method for constructing a Z-type nickel titanate-polyaniline heterojunction based photoelectrochemical aptasensor according to claim 1, wherein, The mass fraction of the acetic acid solution in step (5) is 2%, the mass fraction of the chitosan solution is 0.01%, the modification amount of the chitosan solution is 10 μL, the incubation temperature is 37℃, and the incubation time is 30 min.

7. The method for constructing a Z-type nickel titanate-polyaniline heterojunction based photoelectrochemical aptasensor according to claim 1, wherein, The OTA aptamer sequence in step (6) is as follows: 5'-GAT CGG GTG TGG GTG GCG TAA AGG GAG CAT CGG ACA-3' The OTA aptamer solution concentration is 0.5-3.0 μM, the modification amount is 20 μL, the incubation temperature is 4℃, and the incubation time is 12-15 h; the phosphate buffer concentration is 0.01 M.

8. Use of the photoelectrochemical aptamer sensor of direct Z-type NiTiO3-PANI heterojunction prepared according to the method of any one of claims 1-7 for the detection of OTA, characterized in that, The steps are as follows: (1) First, prepare an OTA standard solution with different concentrations, then modify V1 volume of the OTA standard solution on the surface of the photoelectrochemical aptamer sensor based on the direct Z-type NiTiO3-PANI heterojunction, incubate at a certain temperature for a period of time, then rinse with ultrapure water to remove the unbound OTA, and obtain the sensor, which is recorded as OTA / Apt / CS / NiTiO3-PANI / ITO; (2) Take the OTA / Apt / CS / NiTiO3-PANI / ITO obtained in step (1) as the working electrode, the Ag / AgCl electrode as the reference electrode, and the platinum wire electrode as the counter electrode for photoelectrochemical detection, record the photocurrent signal, take the log of the OTA standard solution concentration as the horizontal coordinate, and take the photocurrent generated by the OTA with different concentrations as the vertical coordinate, and establish a standard curve; (3) Detection of OTA in the actual sample: first, prepare a sample solution, then modify V1 volume of the sample solution on the Apt / CS / NiTiO3-PANI / ITO sensing interface, incubate at a certain temperature for a period of time, then clean the electrode with ultrapure water, and then perform photoelectrochemical detection to obtain the corresponding photocurrent signal; then, the generated photocurrent signal is substituted into the standard curve constructed in step (2), and the concentration of OTA in the actual sample can be obtained, thereby realizing the detection of OTA in the actual sample.

9. The use according to claim 8, wherein the concentration of the OTA standard solution in step (1) is 1 pg / mL-2 ng / mL.

10. Use according to claim 8, characterized in that, The incubation temperature in steps (1) and (3) is room temperature, and the incubation time is 20-120 min; V1 is 20 μL; The photoelectrochemical detection instrument in steps (2) and (3) is a CHI660E electrochemical workstation, the excitation light source is a BBZM-III xenon lamp cold light source, the bias voltage range during detection is 0 V, and the on-off light interval is 10 s.

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