CN113092554A

CN113092554A - Preparation method and application of sensing electrode for glucose detection

Info

Publication number: CN113092554A
Application number: CN202110259055.4A
Authority: CN
Inventors: 李荣毓
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-03-10
Filing date: 2021-03-10
Publication date: 2021-07-09

Abstract

The invention discloses a preparation method and application of a sensing electrode for glucose detection, and belongs to the field of glucose detection. In order to solve the problems that a sensor material for detecting glucose is low in detection sensitivity and high in detection condition requirement, the detection of the glucose is easily interfered by coexisting substances or structural analogues, and the like, a ZIF-67/CNT composite material is prepared, and then a dispersion liquid of the composite material is modified on a glassy carbon electrode to obtain a modified electrode. The modified electrode is placed in boric acid-acetic acid-phosphoric acid buffer solution containing glucose and p-phenylenediamine, cyclic voltammetry scanning is carried out in a set potential interval, the electrode is taken out, naturally placed to be dry, and eluted by liquid, so that the molecularly imprinted sensing electrode with specific response to glucose is obtained.

Description

Preparation method and application of sensing electrode for glucose detection

Technical Field

The invention belongs to the field of glucose detection, and particularly relates to a sensing electrode for glucose detection, and a preparation method and application thereof.

Background

The establishment of a sensitive and specific detection method for glucose, one of the main life-essential compounds, is of great importance in all fields of social production and life. For example, in the medical field, with the improvement of living standard, the incidence rate of diabetes is increased year by year, and reliable and sensitive blood sugar concentration monitoring is particularly important for the early warning and treatment of diabetes.

Various methods are currently used for glucose detection, such as fluorescence spectroscopy, high performance liquid chromatography, gas chromatography and colorimetry. However, these methods require complicated equipment and high cost, and thus are generally difficult to commercialize. Electrochemical glucose sensors are being widely studied due to their advantages of lower cost and rapid operation. Therefore, finding a glucose sensor with low cost and excellent performance has been a research hotspot in the field of sensor research. The common glucose sensing electrode needs to be combined with glucose oxidase through a physical adsorption or chemical fixation method to obtain a high-sensitivity glucose oxidase biosensing electrode, but the biological enzyme is limited by enzyme activity and can be denatured or inactivated due to the influence of temperature, pH value and other ions in the environment, so that the service life of the GOD sensor is directly influenced; secondly, the cost control of the biological enzyme sensor is limited, and the enzyme sensor is not easy to control in the aspects of enzyme immobilization process and dosage, so that the difference among enzyme sensor individuals is directly influenced, the stability and the repeatability are difficult to control, and the biological enzyme sensor is difficult to store and use for a long time. Therefore, in recent years, a great deal of research has been conducted on non-enzymatic glucose sensors. For the enzyme-free glucose sensor, the reaction kinetics of the enzyme-free catalyst to the glucose oxidation is slow, and the selectivity is poor, so that the sensitivity and the performance of the enzyme-free glucose sensor are poor. Thus limiting the application of enzyme-free glucose sensors. Therefore, the improvement of the sensitivity, selectivity and stability of the enzyme-free glucose sensor material becomes a research hotspot in the field.

In CN202010400976.3, a method for detecting glucose based on a cobalt-based metal organic framework enzyme-free glucose sensor is used for preparing a cobalt-based metal organic framework material Co-MOF modified electrode, an Ag/AgCl electrode is used as a reference electrode, and a platinum sheet electrode is used as a counter electrode for detection. But the electrochemical test needs to be carried out by taking NaOH solution as electrolyte, the application environment is obvious, and the influence of coexistence of similar components on glucose selectivity interference is not researched. At present, when the sensor is tested, the sensor mostly needs to be in the condition environment such as alkaline medium, and the neutral condition is not beneficial to the improvement of sensitivity, so that the practical application of the sensor is limited. In the preparation method of the CN201610674615.1 enzyme-free glucose electrochemical sensor, the metal organic framework material ZIF-67 is prepared, and the powder after heat treatment is modified on the surface of a glassy carbon electrode to be used as the electrochemical sensor. Firstly, the conductivity of the ZIF-67 material is lower than that of a bare glassy carbon electrode, the detection sensitivity of the sensor material is very low, and the influence on glucose interference when similar components coexist is not researched. The detection of glucose is easily interfered by coexisting materials or structural analogues.

Therefore, how to obtain an enzyme-free glucose electrochemical sensor with high sensitivity and specific recognition response to glucose in a neutral environment is the focus of the research of the invention.

Disclosure of Invention

In order to solve the problems in the background art, the invention provides a sensing electrode for glucose detection, a preparation method and application thereof.

The technical scheme adopted by the invention is as follows:

preparation of sensing electrode for glucose detection:

dispersing aminated Carbon Nanotubes (CNT) in N, N-Dimethylformamide (DMF) solution, adding cobalt nitrate, dissolving a certain amount of dimethylimidazole in methanol solution, and adding the solution, wherein the molar ratio of the cobalt nitrate to the dimethylimidazole is 1: 4-1: 20; the mass ratio of the aminated carbon nanotube to the cobalt nitrate is 1: 3-5. Reacting at room temperature for 20-30 h. The product was collected by centrifugation and washed with methanol. And drying in an oven at the temperature of 60-100 ℃ for 8-15 h to obtain the ZIF-67/CNT composite material.

The prepared ZIF-67/CNT composite was dispersed in N, N-Dimethylformamide (DMF) solution to form a 1mg/mL dispersion. And (3) taking a certain amount of the glass carbon electrode to be coated on the polished glass carbon electrode in a dripping mode, and naturally drying. The modified electrode prepared in the way is placed in a container containing glucose and p-phenylenediamine (the molar ratio of the glucose to the p-phenylenediamine is 1:1)) 0.1mol/L boric acid-acetic acid-phosphoric acid buffer solution (pH 2) at 0.02Vs^-1The sweep rate of (a) is in the voltage range of 0-0.8V for 20 cycles of cyclic voltammetric sweep. Taking out the electrode, and naturally standing to dry. And eluting by using a methanol/acetic acid solution with the volume ratio of 75:25 to obtain the molecularly imprinted sensor with specific response to glucose.

The application of the prepared sensing electrode in glucose detection is as follows:

the prepared molecular imprinting sensor is used as a working electrode, the reference electrode is Ag/AgCl, the counter electrode is Pt wire, the three-electrode system is placed in glucose solutions with different concentrations (the glucose solution means that glucose is configured in phosphate buffer solution with pH of 7.0 and 0.05M), an electrochemical signal is tested by a differential pulse voltammetry method, and the test conditions are as follows: the voltage range is 0.2-0.6V, the potential increment is 0.004V, the pulse amplitude is 0.05V, the pulse width is 0.05V, the standing time is 2s, the linear relation between the electrochemical response signal and the concentration of the glucose is obtained, and the corresponding linear regression equation is obtained. The lowest detection limit was 1.0. mu.M.

When the actual sample is detected, the sample needs to be diluted, a buffer solution is added to adjust the pH value to be neutral, and the measured electrochemical response signal is used for calculating the concentration of glucose in the sample to be detected through a linear regression equation.

Compared with the prior art, the invention has the beneficial effects that:

the molecularly imprinted electrochemical sensor prepared by the invention is used in a specific recognition analysis technology for glucose, and in order to solve the problems that the detection of the glucose is easily interfered by coexisting substances or structural analogues and the like, the molecularly imprinted electrochemical sensor is provided for specific recognition response to the glucose in a neutral environment. The modified electrode material is simple to prepare and low in price, the provided detection method uses a differential pulse voltammetry technology, can be used for rapidly detecting the concentration of glucose in a neutral environment, is high in detection sensitivity, has strong anti-interference capability, and is more beneficial to practical application.

Drawings

FIG. 1 is a graph showing a selective study of a sensor electrode on glucose.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

The invention is described in more detail below with reference to the following examples:

example 1

(1) Preparation of sensor electrodes

0.06g of aminated Carbon Nanotube (CNT) was dispersed in 20mL of N-Dimethylformamide (DMF) solution, 1.2mmol of cobalt nitrate was added, and 1.53g of dimethylimidazole in 50mL of methanol was added to the solution, followed by reaction at room temperature for 24 hours. The product was collected by centrifugation and washed with methanol. And drying in an oven at 80 ℃ for 12h to obtain the ZIF-67/CNT composite material.

The prepared ZIF-67/CNT composite was dispersed in N, N-Dimethylformamide (DMF) solution to form a 1mg/mL dispersion. And (3) dripping a certain amount (about 6 mu L) of the modified electrode on the polished glassy carbon electrode, and naturally airing to obtain the modified electrode.

The modified electrode prepared above was placed in 0.1mol/L boric acid-acetic acid-phosphoric acid buffer solution (pH 2) containing glucose and p-phenylenediamine (molar ratio 1:1) at 0.02V s^-1The sweep rate of (a) is in the voltage range of 0-0.8V for 20 cycles of cyclic voltammetric sweep. Taking out the electrode, and naturally standing to dry. And eluting by using a methanol/acetic acid solution to obtain the molecularly imprinted sensor with specific response to the glucose.

(2) Drawing of standard curve

The prepared sensor is used as a working electrode, the reference electrode is Ag/AgCl, the counter electrode is Pt wire, the three-electrode system is placed in glucose solution with different concentrations (the concentration range is 4.00-80.0 mu M, the glucose solution means that glucose is configured in phosphate buffer solution with pH of 7.0 and 0.05M), electrochemical signals are tested by differential pulse voltammetry, and the test conditions are as follows: the voltage range is 0.2-0.6V, the potential increment is 0.004V, the pulse amplitude is 0.05V, the pulse width is 0.05V, and the standing time is 2 s. The obtained electrochemical response signal and the concentration of the glucose form a linear relation, and the obtained corresponding linear regression equation is as follows: i-8.7488 +0.2742C, correlation coefficient (R) 0.994, and minimum detection limit 1.0 μ M.

(3) Detection of actual samples

When detecting an actual sample, the sample needs to be diluted, and a buffer solution is added to adjust the pH value to be neutral. If 1.00mL of serum sample is taken into a 10mL centrifuge tube, 1.00mL of 20 wt% trichloroacetic acid is added, the mixture is fully mixed and kept stand for 5min, after centrifugation, the supernatant is taken and diluted to the corresponding concentration by phosphate buffer solution with pH being 7.00 for determination, the test is carried out according to the same test conditions in the step (2), electrochemical response signals are recorded, and the concentration of glucose in the diluted sample to be detected is calculated according to the linear regression equation obtained in the step (2).

Selective anti-interference experiment test:

the response of the prepared sensor to coexisting substances of glucose (acetaminophen, lactose, ascorbic acid) was further examined.

The specific test experiment is as follows: the molecular imprinting sensor electrode prepared in example 1 was used as a working electrode, an Ag/AgCl electrode as a reference electrode, and a Pt wire as a counter electrode. The detection of glucose, acetaminophen, lactose and ascorbic acid at a concentration of 50 μ M was carried out at a voltage range of-0.2 to 0.6V using DPV as a detection means. The detection conditions are set as follows: potential increment is 0.004V, pulse amplitude is 0.05V, pulse width is 0.05V, and standing time is 2 s.

From the test results of fig. 1, it was revealed that the detection of acetaminophen, lactose and ascorbic acid for the same concentration of glucose showed excellent selective interference resistance to glucose.

Comparative example 1

Comparative example 1 differs from example 1 mainly in that: preparing a ZIF-67/GCE modified electrode. Then, glucose detection was performed by the same pretreatment method as in example 1, using the sensor electrode obtained by performing cyclic voltammetric scanning of the modified electrode in a 0.1mol/L boric acid-acetic acid-phosphoric acid buffer solution (pH 2) containing glucose and p-phenylenediamine (molar ratio 1:1), as a working electrode.

After research, the current of the ZIF-67 material is reduced by 1/4 compared with that of a bare glassy carbon electrode, the modified ZIF-67 material is not beneficial to improving the conductivity of a sensing electrode, the detection sensitivity is very low, and the selectivity and the anti-interference performance are not ideal.

Comparative example 2

Comparative example 2 differs from example 1 mainly in that: a CNT/GCE modified electrode was prepared as a working electrode, and glucose detection was performed by the same pretreatment method as in example 1, namely, the modified electrode was placed in a 0.1mol/L boric acid-acetic acid-phosphoric acid buffer solution (pH 2) containing glucose and p-phenylenediamine (molar ratio 1:1) to perform cyclic voltammetric scanning, and the obtained sensor electrode was used as a working electrode, and glucose detection was performed by the same method as in example 1.

After detection, the current value of the CNT/GCE modified electrode is higher than that of ZIF-67/CNT/GCE, but the detection sensitivity of the CNT/GCE to glucose is remarkably lower than that of the ZIF-67/CNT/GCE, the minimum detection limit reached by the CNT/GCE is 3 mu M, and the selectivity and the anti-interference performance are not ideal.

Compared with the single ZIF-67 or CNT, the sensor prepared from the ZIF-67/CNT composite material has higher sensitivity, stronger selectivity and stronger anti-interference capability when being used for specifically recognizing and responding to glucose in a neutral environment.

Claims

1. A preparation method of a sensing electrode for detecting glucose is characterized by comprising the following steps: the preparation method of the sensing electrode comprises the following steps:

firstly, preparing a ZIF-67/CNT composite material, then dispersing the ZIF-67/CNT composite material in an organic solvent to form a dispersion liquid, dropwise coating the dispersion liquid on a polished glassy carbon electrode, and naturally airing to obtain a ZIF-67/CNT/GCE modified electrode;

and (2) placing the ZIF-67/CNT/GCE modified electrode in boric acid-acetic acid-phosphoric acid buffer solution containing glucose and p-phenylenediamine, performing cyclic voltammetry scanning in a set potential interval, taking out the electrode, naturally placing the electrode to be dry, and eluting the electrode by using a solvent to obtain the molecularly imprinted sensing electrode with specific response to the glucose.

2. The method of manufacturing a sensing electrode for glucose detection according to claim 1, wherein: the cyclic voltammetry scanning conditions were: 0.02Vs^-1The sweep rate of (a) is in the voltage range of 0-0.8V for 20 cycles of cyclic voltammetric sweep.

3. The method of manufacturing a sensing electrode for glucose detection according to claim 1, wherein: the preparation method of the ZIF-67/CNT composite material comprises the following steps:

dispersing aminated Carbon Nanotubes (CNT) in a N, N-Dimethylformamide (DMF) solution, adding a cobalt nitrate solution, dissolving a certain amount of dimethyl imidazole in a methanol solution, adding the solution, reacting at room temperature for 20-30 h, centrifuging the obtained product, collecting the product, washing with methanol, and drying in a drying oven to obtain the ZIF-67/CNT composite material.

4. The method of claim 3, wherein the sensing electrode is prepared by: the molar ratio of the cobalt nitrate to the dimethyl imidazole is 1: 4-1: 20; the mass ratio of the aminated carbon nanotube to the cobalt nitrate is 1: 3-5.

5. The method for detecting glucose by using the sensing electrode according to any one of claims 1 to 4, wherein: the detection method comprises the following steps:

taking a molecular imprinting sensing electrode as a working electrode, a reference electrode as Ag/AgCl and a counter electrode as Pt wires to form a three-electrode system, placing the three-electrode system in glucose solutions with different concentrations, testing electrochemical signals by a differential pulse voltammetry method, wherein the electrochemical response signals and the concentrations of glucose form a linear relation to obtain a corresponding linear regression equation;

when the actual sample is detected, the sample needs to be diluted, a buffer solution is added to adjust the pH value to be neutral, an electrochemical response signal is measured, and the glucose concentration in the detected sample is calculated through a linear regression equation.

6. The method for detecting glucose according to claim 5, wherein: the glucose solution is prepared by dissolving glucose in 0.05M phosphate buffer (pH7.0).

7. The method for detecting glucose according to claim 5, wherein: the test conditions of the differential pulse voltammetry are: the voltage range is 0.2-0.6V, the potential increment is 0.004V, the pulse amplitude is 0.05V, the pulse width is 0.05V, and the standing time is 2 s.