1. A preparation method of a modified electrode for detecting ochratoxin A is characterized by comprising the following steps:

(1) mixing egg shell powder with HAuCl₄Mixing the solutions together to make the eggshell powder fully absorb gold ions;

(2) the eggshell powder after absorbing the gold ions is dried and roasted to obtain Au/CaCO₃A nanoparticle;

(3) mixing Au/CaCO₃Dispersing the nano particles into Nafion solution to obtain suspension, oscillating, centrifuging and washing the suspension to obtain Au/CaCO₃Nafion nanoparticles;

(4) mixing Au/CaCO₃Dispersing Nafion nano particles in water, dripping the obtained suspension on the surface of an electrode, and drying to obtain Au/CaCO₃A Nafion modified electrode;

(5) mixing Au/CaCO₃/Nafion modified electrode immersion Ru (bpy)₃ ²⁺In the solution, after incubation, the solution is taken out, washed and dried to obtain Ru (bpy)₃ ²⁺/Au/CaCO₃A Nafion modified electrode;

(6) in Ru (bpy)₃ ²⁺/Au/CaCO₃Dripping ochratoxin A nano antibody Nb28 solution on the surface of the Nafion modified electrode, incubating, washing after incubation, then incubating the modified electrode with 1-1.5 wt% of BSA solution, washing after incubation, and drying to obtain the modified electrode for detecting ochratoxin A.

2. The method of claim 1, wherein: in step (1), HAuCl₄The concentration of the solution is 5-15mmol/L, and the egg shell powder and HAuCl are added₄The dosage relationship of the solution is as follows: 1 g: 5-10 ml; in the step (3), the concentration of the Nafion solution is 2-5wt%, Au/CaCO₃The dosage relationship of the nano particles and the Nafion solution is 1 mg: 1-2 mL.

3. The method of claim 1, wherein: in the step (1), the eggshell powder and HAuCl are mixed₄Mixing the solution for 10-12h under stirring to make the eggshell powder fully absorb gold ions; in the step (2), the eggshell powder which absorbs the gold ions is calcined for 1-2 h at the temperature of 500-550 ℃.

4. The method of claim 1, wherein: in step (4), Au/CaCO₃The concentration of Nafion nano particles in water is 1-2 mg/mL, and 5-10 mu L of suspension is dripped on the surface of an electrode; in step (5), Ru (bpy)₃ ²⁺The concentration of the solution is 15-25 mmol/L, Au/CaCO₃/Nafion modified electrode immersion Ru (bpy)₃ ²⁺Incubate in solution for 1-1.5 h at room temperature.

5. The method of claim 1, wherein: in the step (6), the nucleotide sequence of the ochratoxin A nano antibody Nb28 is shown as SEQ ID NO: 1 is shown.

6. The method according to claim 1 or 5, wherein: in step (6), in Ru (bpy)₃ ²⁺/Au/CaCO₃Nafion modified electrode surface is dripped with 4-5 muL ochratoxin A nano antibody with concentration of 20-25 mug/mLNb28 solution, incubating at 37 ℃ for 4-5 h, washing after incubation, and then incubating the modified electrode with 1-1.5 wt% BSA solution for 0.5-1 h at room temperature.

7. The method of claim 1, wherein: the electrode is a glassy carbon electrode.

8. The modified electrode for detecting ochratoxin A, prepared by the preparation method of the modified electrode for detecting ochratoxin A according to any one of claims 1 to 7, and application of the modified electrode in detection of ochratoxin A.

9. An electrochemiluminescence immunosensor for detecting ochratoxin A is characterized in that: comprising a working electrode, which is the modified electrode for detecting ochratoxin A of claim 8.

10. A method for detecting ochratoxin A is characterized by comprising the following steps: the method comprises the steps of jointly detecting the content of ochratoxin A by using a modified electrode for detecting ochratoxin A as a working electrode, a platinum electrode as an auxiliary electrode, a calomel electrode as a reference electrode and a co-reactant tri-n-propylamine solution as a detection solution according to claim 8 through a cyclic voltammetry method and an electrochemiluminescence method; preferably, the scanning potential is 0.2V-1.35V, the scanning speed is 0.1V/s, and the concentration of the tri-n-propylamine solution is 0.03-0.06 mmol/L.

Background

Ochratoxin a (ota) is a secondary metabolite produced by fungi such as aspergillus ochraceus and aspergillus flavus and is widely found in cereals, feeds, nuts, grapes and wine, coffee and products thereof. OTA has stable property, is not easy to decompose, can be accumulated in human bodies and animal bodies for a long time, has great damage to kidney, liver and nervous system, and also has teratogenicity and carcinogenicity. Therefore, the sensitive detection of the expression level of OTA in food is very important for human health. In 1993, the international cancer center identified OTA as a class 2B carcinogen, and then, standards were established in european union, united states, etc. for the limit of OTA in food, and standard detection methods and strict OTA limit standards were also established in our country for grains, beans, wine, peppers, etc. GB 5009.96-2016 specifies standard detection methods for OTA in food products and limits for different detection methods.

At present, OTA detection methods are continuously developed, and detection technologies such as thin-layer chromatography, high-performance liquid chromatography, enzyme-linked immunosorbent assay, time-resolved fluorescence immunoassay, colloidal gold immunochromatography, chemiluminescence enzyme immunoassay and the like are gradually mature. Wherein, the thin-layer chromatography and the colloidal gold immunochromatography are simple in technical method and low in detection cost, but the sensitivity is relatively low; the high performance liquid chromatography has high sensitivity and good reproducibility, but has high cost and complex operation process; the enzyme-linked immunosorbent assay is simple to operate, but has low sensitivity.

The electrochemiluminescence detection technology (ECL) is simple to operate, high in sensitivity, high in detection speed and wide in detection range, and becomes a new development direction for OTA qualitative and quantitative rapid detection. In recent years, researchers have developed a large number of novel OTA electrochemiluminescence sensors, and the sensors are applied to detection of actual samples such as wheat, corn, wine and the like, but most of the OTA aptamers are used as recognition molecules. For example, CN 101936940a discloses a method for detecting ochratoxin a by using an electrochemiluminescence aptamer sensor, wherein the method uses OTA aptamer as a recognition element, isoluminol as a luminescent reagent, the detection range is 0-3 ng/mL, the detection limit is 0.007 ng/mL, and the detection range is narrow. In order to construct an ECL sensor with higher sensitivity, better specificity and wider detection range, researchers use OTA antibodies as recognition molecules to construct an ECL immunosensor and use the ECL immunosensor for detection of orange juice samples, but the OTA antibodies are harsh in storage conditions and low in organic tolerance, so that the method is limited in wide application.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a preparation method of a modified electrode for detecting ochratoxin A, the method tries to construct the modified electrode by using OTA nano-antibody as a recognition molecule for the first time, and when the modified electrode is used as a working electrode of an ECL immunosensor, the modified electrode has the characteristics of high specificity, high sensitivity and wide detection range, and is good in stability, high in organic tolerance capacity of the OTA nano-antibody and wider in application range.

OTA is a polar small molecular substance, needs to be extracted by methanol, is difficult to avoid methanol residue, has a complex structure of a traditional antibody (a monoclonal antibody or a polyclonal antibody) and low tolerance to an organic solvent, and some researchers develop a nano antibody in order to overcome the defects of the traditional OTA antibody. The nanobody is the smallest antibody fragment with complete antigen recognition capability, and the molecular weight of the nanobody is about 15 kDa. Compared with the traditional antibody, the nano antibody has the advantages of small molecular weight, higher water solubility and stability, strong affinity, strong methanol tolerance and strong matrix interference resistance.

The invention adopts OTA nano antibody Nb28 as an identification element to construct an electrochemiluminescence immunosensor, and provides reference for the development of the nano antibody in the technical field of electrochemiluminescence. The specific technical scheme of the invention is as follows:

a preparation method of a modified electrode for detecting ochratoxin A comprises the following steps:

(1) mixing egg shell powder with HAuCl₄Mixing the solutions together to make the eggshell powder fully absorb gold ions;

(2) the eggshell powder after absorbing the gold ions is dried and roasted to obtain Au/CaCO₃A nanoparticle;

(3) mixing Au/CaCO₃Dispersing the nano particles into Nafion solution to obtain suspension, oscillating, centrifuging and washing the suspension to obtain Au/CaCO₃Nafion nanoparticles;

(4) mixing Au/CaCO₃Dispersing Nafion nano particles in water, dripping the obtained suspension on the surface of an electrode, and drying to obtain Au/CaCO₃A Nafion modified electrode;

(5) mixing Au/CaCO₃/Nafion modified electrode immersion Ru (bpy)₃ ²⁺In the solution, after incubation, the solution is taken out, washed and dried to obtain Ru (bpy)₃ ²⁺/Au/CaCO₃A Nafion modified electrode;

(6) in Ru (bpy)₃ ²⁺/Au/CaCO₃Dripping ochratoxin A nano antibody Nb28 solution on the surface of the Nafion modified electrode, incubating, washing after incubation, then incubating the modified electrode with 1-1.5 wt% of BSA solution, washing after incubation, and drying to obtain the modified electrode for detecting ochratoxin A.

Further, the electrode may be any working electrode reported in the art that can be used in an electrochemiluminescence immunosensor, such as a Glassy Carbon Electrode (GCE).

Further, in step (1), HAuCl₄The concentration of the solution is 5-15mmol/L, and the egg shell powder and HAuCl are added₄The dosage relationship of the solution is as follows: 1 g: 5-10 mL.

Further, in the step (1), the eggshell powder and HAuCl are mixed₄The solution is mixed for 10-12h under stirring, so that the eggshell powder fully absorbs gold ions.

Further, in the step (2), the eggshell powder which absorbs the gold ions is calcined for 1-2 h at the temperature of 500-550 ℃.

Further, the method comprisesIn the step (3), the concentration of the Nafion solution is 2 to 5wt%, and each 1 mgAu/CaCO₃The nanoparticles are added into 1-2 ml of the liquid to prepare a suspension. Au/CaCO₃The nanoparticles are shaken in a Nafion solution for 2-3 h, and then centrifuged and washed with water. The rotation speed of the centrifugation is generally 8000-12000 r/min, and the centrifugation time is 10-15 min.

Further, in step (4), Au/CaCO₃The concentration of Nafion nanoparticles in water is 1-2 mg/mL, and 5-10. mu.L of the suspension is dropped onto the electrode surface.

Further, in the step (5), Ru (bpy)₃ ²⁺The concentration of the solution is 15-25 mmol/L, Au/CaCO₃/Nafion modified electrode immersion Ru (bpy)₃ ²⁺Incubate in solution for 1-1.5 h at room temperature.

Furthermore, in the step (6), the ochratoxin A nano antibody Nb28 is a single-domain antibody consisting of only one heavy chain variable region, has small molecular mass, stable structure and high antigen affinity, and has great application prospect in the fields of disease, cancer diagnosis, small-molecule harmful substance and toxin detection and the like. The nucleotide sequence of the ochratoxin A nano antibody Nb28 is shown as SEQ ID NO: 1, the nano antibody can be obtained by expression in a mode of constructing recombinant engineering bacteria containing the nucleotide sequence.

Further, in step (6), in Ru (bpy)₃ ²⁺/Au/CaCO₃Dripping 4-5 mu L of ochratoxin A nano antibody Nb28 solution with the concentration of 20-25 mu g/mL on the surface of the Nafion modified electrode, and incubating for 4-5 h at 37 ℃.

Further, in step (6), the modified electrode is incubated with the BSA solution at room temperature for 0.5-1 h.

Further, the modified electrode for detecting ochratoxin A prepared by the method is also within the protection scope of the invention. The modified electrode of the invention carries Au/CaCO on the surface of the electrode₃The nano-particles can increase the surface adsorption area of the electrode, and are the invention reagent Ru (bpy)₃ ²⁺More adsorption sites are provided, and more Nb28 can be covalently bound at the same time, so that the effect of improving the sensitivity of the ECL sensor is achieved. The invention gradually repairs the surface of the electrodeDecoration Ru (bpy)₃ ²⁺And Nb28, the nonspecific binding site is blocked by BSA, when the substance to be detected OTA is incubated on the modified electrode, the electron transfer on the surface of the electrode can be blocked by the specific binding action of the antigen-antibody, so that the transfer efficiency is reduced, and the ECL signal is reduced, thereby achieving the purpose of detecting the sample with unknown concentration.

The invention also provides application of the modified electrode for detecting ochratoxin A in detection of ochratoxin A. The modified electrode can be used as a working electrode of an electrochemiluminescence immunosensor, and is matched with a three-electrode system of an auxiliary electrode and a reference electrode, so that the aim of detecting ochratoxin A with high sensitivity and high specificity is fulfilled.

Furthermore, the invention also provides an electrochemiluminescence immunosensor for detecting ochratoxin A, which comprises a working electrode, wherein the working electrode is the modified electrode for detecting ochratoxin A.

Furthermore, the electrochemical luminescence immunosensor also comprises an auxiliary electrode and a reference electrode, wherein the auxiliary electrode is a platinum electrode, and the reference electrode is a calomel electrode.

The electrochemical luminescence immunosensor can excite a luminescent substance on the surface of an electrode to react with a co-reactant thereof through an electric signal, and performs specificity detection on OTA by taking the luminous intensity as a detection signal and a specific nano antibody Nb28 as an identification element. Using Ru (bpy)₃ ²⁺As a luminescent reagent, ECL signals are detected in a tri-n-propylamine (TPrA) solution, and Au/CaCO with large specific surface area and high stability is utilized₃The immobilized luminescent reagent greatly increases the immobilization amount of the luminescent reagent, so that the sensitivity and the stability of the sensor are improved, and the specificity of the sensor is improved by taking the OTA nano antibody (Nb 28) as a specificity identification element.

The method uses the modified electrode for detecting ochratoxin A as a working electrode, a platinum electrode as an auxiliary electrode, a calomel electrode as a reference electrode, a co-reactant tri-n-propylamine (TPrA) solution as a detection solution, and jointly detects the content of the ochratoxin A by a cyclic voltammetry method and an electrochemiluminescence method.

Furthermore, in the electrochemical luminescence method, the measurement type is an intensity mode, the scanning potential is 0.2V-1.35V, the scanning rate is 0.1V/s, the amplification stage number is 4, and the high voltage of the photomultiplier is 600V.

Further, in the above electrochemical luminescence method, the concentration of the solution of tri-n-propylamine (TPrA) is 0.03 to 0.06 mmol/L.

Further, the method for detecting ochratoxin A comprises the following steps:

(1) preparing standard ochratoxin A solutions with different concentrations for later use;

(2) respectively incubating the prepared modified electrode for detecting ochratoxin A with the standard solutions of ochratoxin A with different concentrations for 4h at 37 ℃;

(3) taking out the modified electrode, matching with an auxiliary electrode and a reference electrode, and detecting an electrochemiluminescence intensity signal by taking a tri-n-propylamine solution as a detection solution;

(4) drawing a standard curve by taking the logarithm of the OTA concentration as an abscissa and the difference value of the electrochemiluminescence intensity signals as an ordinate;

(5) incubating a modified electrode for detecting ochratoxin A and a sample solution to be detected for 4h at 37 ℃, matching with an auxiliary electrode and a reference electrode, detecting an electrochemiluminescence intensity signal by taking a tri-n-propylamine solution as a detection solution to obtain a difference value of the electrochemiluminescence intensity signal, and bringing the difference value into a standard curve to obtain the concentration of OTA in the sample to be detected.

The invention relates to a multi-pore-passage Au/CaCO synthesized by taking waste egg shells as templates₃Adsorbing luminescent reagent Ru (bpy)₃ ²⁺An electrochemical luminescence sensor for detecting ochratoxin A (OTA) with high specificity, high sensitivity and wide detection range is constructed by taking an OTA nano antibody Nb28 as a targeting molecule and taking tri-n-propylamine (TPrA) as a co-reactant. Compared with the prior art, the invention has the following advantages:

1. Au/CaCO used in the invention₃The nano material is prepared by taking the waste eggshells as templates, thereby realizing the purpose of discarding the eggshellsRecycling and providing a practical and low-cost method for the comprehensive utilization of the eggshell as a valuable functional material. At the same time, the porous Au/CaCO with large specific surface area is utilized₃The nano material provides more adsorption and covalent binding sites for the luminescent reagent and the OTA nano antibody, and greatly improves the sensitivity of the immunosensor.

2. According to the invention, the OTA nano antibody Nb28 is used as a specific recognition element for the first time to construct the electrochemical luminescence immunosensor, and a reference is provided for the development of the nano antibody in the technical field of electrochemical luminescence. Proved by verification, Nb28 is adopted as a specificity recognition element, Ru (bpy) is selected₃ ²⁺As a luminescent reagent, the OTA is quantitatively analyzed by detecting an electrochemiluminescence signal, the detection range is 0.01-100 ng/mL, the detection limit can be as low as 5.7 pg/mL, and the kit has the advantages of low detection limit and wide detection range.

3. The electrochemical luminescence immunosensor can realize high-specificity and high-sensitivity detection of OTA, can be used for detection application of actual samples such as complex matrix coffee, grains and the like, can be used for detection without complex processing procedures, is high in detection speed, and solves the problems that sample pretreatment is complex and a large number of samples cannot be detected simultaneously and rapidly in the traditional method.

Drawings

FIG. 1: a schematic construction process diagram of an electrochemiluminescence immunosensor for detecting ochratoxin A based on nanometer antibody specificity;

FIG. 2: an electrochemiluminescence curve graph (A) of OTA (0.01-100 ng/mL) with different concentrations and a linear calibration curve (B) of ECL signal intensity difference of the electrochemiluminescence immunosensor and logarithm of OTA concentration.

FIG. 3: specific experimental result chart of ECL electrochemiluminescence immunosensor.

Detailed Description

The present invention is further illustrated by the following specific examples, which are intended to be exemplary only and are not intended to be limiting. Unless otherwise specified, the following terms or methods are not detailed and are prior art.

In the following examples, the OTA Nanobody Nb28 is obtained by the method described in Nanobody-based fluorescence response for Nanobody and simultaneous fluorescence detection of ochromatic a and ochromatic B (Tang Z, Liu X, Wang Y, et al, Nanobody-based fluorescence response for Nanobody and simultaneous fluorescence B [ J ] Environmental Pollution, 2019, 251 (AUG.238;: 245).

Example 1

(1) Au/CaCO using waste egg shell as template₃Preparation of nanoparticles

Cleaning eggshell, air drying, grinding into eggshell powder, collecting 0.5 g eggshell powder and 5 mL HAuCl₄The solutions (10 mM) were mixed, and the mixed solution was continuously stirred at room temperature for 12 hours to allow the eggshell powder to completely absorb gold ions. The egg shell powder is precipitated, the suspension is left to stand for about 1h, and then the supernatant is removed. Drying the obtained product in a constant-temperature oven at 60 ℃ for 1h, finally adding the dried product into a tube furnace, raising the temperature to 500 ℃ at the heating rate of 2 ℃/min, and calcining the product at the temperature for 2 h. Calcining eggshell powder gold nanoparticles (defined as Au/CaCO)₃) Stored at room temperature for later use.

（2）BSA/Nb28/Ru(bpy)₃ ²⁺/Au/CaCO₃Construction of/Nafion/GCE modified electrode

Before the Glassy Carbon Electrode (GCE) is modified, 0.3 mu m and 0.05 mu m alumina powder is used for polishing, then absolute ethyl alcohol and deionized water are respectively used for carrying out ultrasonic treatment for 2 min to obtain a mirror-shaped surface, and nitrogen is used for drying.

2 mg of Au/CaCO as described above₃The nanoparticles were dispersed in 2.6 mL of Nafion solution (concentration of Nafion solution was 2.5 wt%), shaken for 3 h, then centrifuged to remove excess Nafion solution, washed 3 times with deionized water, and 2 mg of Au/CaCO₃Dispersing the/Nafion nano composite material in 1 mL of deionized water to obtain Au/CaCO₃Nafion nanocomposite suspensions.

Taking 5 mu L of Au/CaCO₃Dripping the Nafion nano composite material suspension on the surface of the pretreated glassy carbon electrode, and drying at room temperatureDrying to obtain Au/CaCO₃the/Nafion/GCE modified electrode.

Then, Au/CaCO₃the/Nafion/GCE modified electrode was immersed in 20 mM Ru (bpy)₃ ²⁺In the solution, the solution is incubated for 1h at room temperature in the dark, and after taking out the electrode, the excess Ru (bpy) is washed gently with deionized water₃ ²⁺And drying at room temperature.

Then, 5. mu.L of Nb28 solution (20. mu.g/mL) was dropped onto Ru (bpy)₃ ²⁺/Au/CaCO₃Modifying the electrode surface with/Nafion/GCE, incubating for 4h at 37 ℃, then gently washing the electrode surface with deionized water to remove unbound Nb28 molecules, thus obtaining Nb28/Ru (bpy)₃ ²⁺/Au/CaCO₃the/Nafion/GCE modified electrode. In the process, the mercapto group of Nb28 is bonded with Au/CaCO through Au-S bond₃The gold nanoparticles of (3) are bound.

Subsequently, the modified electrode was incubated with 5. mu.L of a 1% by mass BSA solution at room temperature for 0.5 h to block non-specific binding sites, followed by gentle rinsing with deionized water to remove unbound BSA and drying at room temperature to obtain BSA/Nb28/Ru (bpy)₃ ²⁺/Au/CaCO₃the/Nafion/GCE modified electrode was stored at 4 ℃.

(3) Determination of Standard Curve and detection Limit

OTA standard solutions with the concentrations of 0.01 ng/mL, 0.1 ng/mL, 1 ng/mL, 10 ng/mL and 100 ng/mL are prepared for later use.

With BSA/Nb28/Ru (bpy)₃ ²⁺/Au/CaCO₃the/Nafion/GCE modified electrode is a working electrode, and the working electrode is firstly respectively incubated with OTA standard solutions with different concentrations for 4 hours at 37 ℃ to form OTA/BSA/Nb28/Ru (bpy)₃ ²⁺/Au/CaCO₃And then the working electrode is matched with a platinum electrode (auxiliary electrode) and a saturated calomel electrode (reference electrode) to construct a three-electrode system, and 0.05 mM TPrA solution is used as a co-reactant and a detection solution to construct an ECL (electron cyclotron resonance) immunosensor.

And (3) immersing the working electrode, the auxiliary electrode and the reference electrode into a TPrA detection solution, and detecting by using an electrochemical luminescence method, wherein the scanning potential is 0.2V-1.35V, the scanning speed is 0.1V/s, the photomultiplier tube high pressure is 600V, and the amplification level is 4 to obtain an electrochemical luminescence intensity (ECL) signal.

The reaction principle of the working electrode and the detection solution is as follows:

working electrode OTA/BSA/Nb28/Ru (bpy)₃ ²⁺/Au/CaCO₃in/Nafion/GCE, Ru (bpy)₃ ²⁺The above reaction with co-reactant TPrA at high pressure of 600V to generate ECL signal, Ru (bpy)₃ ²⁺/ Au/CaCO₃When Nb28 and BSA are respectively incubated on a/Nafion/GCE modified electrode, the electron transfer efficiency is reduced by protein inhibition, and thus ECL signal is reduced when BSA/Nb28/Ru (bpy)₃ ²⁺/Au/CaCO₃After the/Nafion/GCE modified electrode is incubated with OTA, the specific binding of the antigen-antibody strengthens the blocking effect on the electron transfer, so that the ECL signal is further reduced, and the reduced ECL signal intensity is in direct proportion to the concentration of the OTA.

At 37 ℃, ECL sensors are used for detecting OTA with different concentrations (0.01, 0.1, 1, 10, 100 ng/mL) to obtain ECL signals. With BSA/Nb28/Ru (bpy)₃ ²⁺/Au/CaCO₃The ECL signal value of the/Nafion/GCE modified electrode is a blank value, and OTA/BSA/Nb28/Ru (bpy)₃ ²⁺/Au/CaCO₃The ECL signal value of the/Nafion/GCE modified electrode is the detection value, the difference (Δ ECL) between the blank value and the detection value is calculated, the logarithm of the OTA concentration is used as the abscissa, the ECL difference value is used as the ordinate, and a standard curve is obtained by plotting (see figure 2).

As can be seen from the standard curve, the difference of the ECL signals is proportional to the logarithm of the OTA concentration, and the linear relationship is Δ ECL =2762.9 log C_OTA+10748（R²=0.9977）。

And (3) measuring blank values for multiple times, calculating the relative standard deviation of the blank values, and according to the formula: limit of detection =3 × standard deviation of blank/slope of standard curve, calculated to be 5.7 pg/mL of limit of detection for the ECL sensor.

(4) Determination of specificity

OTB, OTC, AFB1, ZEN and DON standard solutions with the concentration of 100 ng/mL are prepared respectively for later use.

BSA/Nb28/Ru (bpy) prepared in step (2) was added at 37 deg.C₃ ²⁺/Au/CaCO₃Respectively incubating the/Nafion/GCE modified electrode with standard solutions of different toxins for 4h at 37 ℃ to prepare modified electrodes containing different toxins. And (3) constructing the ECL immunosensor by using the modified electrode as a working electrode, a platinum electrode as an auxiliary electrode, a saturated calomel electrode as a reference electrode and a 0.05 mM TPrA solution as a coreactant and a detection solution.

And (3) immersing the working electrode, the auxiliary electrode and the reference electrode into a TPrA detection solution, and detecting by using an electrochemical luminescence method, wherein the scanning potential is 0.2V-1.35V, the scanning speed is 0.1V/s, the photomultiplier tube high pressure is 600V, and the amplification level is 4 to obtain an electrochemical luminescence intensity (ECL) signal.

ECL signals were obtained as detection values by detecting working electrodes containing 100 ng/mL of different toxins at 37 ℃ using an ECL sensor. With BSA/Nb28/Ru (bpy)₃ ²⁺/Au/CaCO₃The ECL signal value of the/Nafion/GCE modified electrode is a blank value, the difference between the blank value and the detection value (Δ ECL) is calculated, different toxins are used as abscissa, the ECL difference is used as ordinate, and a bar chart is drawn (see figure 3). As can be seen from the figure, only OTA had a significant decrease in ECL signal and no significant change in signal for the other toxins, indicating that the sensor of the present invention exhibits excellent selectivity for OTA.

Example 2

Preparation of sample test solutions: grinding coffee beans into powder, dissolving 4 mg of coffee powder in 1 mL of deionized water, treating the coffee powder suspension with ultrasonic waves for 30 min, and centrifuging to obtain a supernatant. Different concentrations of OTA were added to the supernatant to give final concentrations of OTA in the coffee solution of 0.05 ng/mL, 2 ng/mL and 80 ng/mL, respectively, to give actual sample test solutions.

BSA/Nb28/Ru (bpy) prepared in step (2) of example 1₃ ²⁺/Au/CaCO₃Respectively incubating the/Nafion/GCE modified electrode with coffee samples containing OTAs with different concentrations for 4h at 37 ℃, taking out the modified electrode, taking the modified electrode as a working electrode, and matching the modified electrode with a platinum electrode and a saturated calomel electrode to construct an ECL immunosensor.

Immersing the working electrode, the platinum electrode and the saturated calomel electrode into 0.05 mM TPrA detection solution, detecting by an electrochemical luminescence method with a scanning potential of 0.2V-1.35V, a scanning speed of 0.1V/s, a photomultiplier high pressure of 600V and an amplification level of 4 to obtain an electrochemical luminescence intensity (ECL) signal, and taking BSA/Nb28/Ru (bpy) as a detection value₃ ²⁺/Au/CaCO₃The ECL signal value of the/Nafion/GCE modified electrode is a blank value, the difference (Δ ECL) between the blank value and the detection value is calculated, the standard curve of the embodiment 1 is substituted to obtain the detection concentration of the OTA, and the recovery rate is calculated by the following formula. Each sample was tested in triplicate and the recovery, the mean and standard deviation of the recovery were calculated.

。

Relative Standard Deviation (RSD) = standard deviation of recovery/average of recovery × 100%.

The results are shown in table 1 below:

as can be seen from the results in the table above, the method of the invention has the advantages of high recovery rate and wide detection range, and can meet the use requirements.

Sequence listing

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