Glucose sensor

Abstract

The invention relates to a glucose sensor which is prepared by the following steps: (1) dispersing NiCl2. 6H2O and Na2MoO4 in water, dissolving 2-aminoterephthalic acid in water, stirring and dissolving, uniformly mixing the NiCl2. 6H2O and the Na2MoO4, transferring the mixture into a stainless steel autoclave with a Teflon lining, and reacting at 100-140 DEG C; after the reaction is finished, cooling to room temperature, respectively washing a reaction product with absolute ethyl alcohol and water, and drying to obtain NiMo-MOF; (2) firstly, putting the screen-printed electrode into a PBS (Phosphate Buffer Solution), activating the electrode for 35-45 circles by using a cyclic voltammetry method within-0.6 V to 1.6 V, and controlling the scanning rate to be 100 mV / s; and dripping a NiMo-MOF aqueous solution with the concentration of 2mg / mL on the surface of the screen-printed electrode, naturally airing, and dripping a Nafion solution with the mass concentration of 0.1% to obtain the glucose sensor NiMo-MOF / Nafion / SPE. The non-invasive non-enzymatic glucose sensor constructed by taking NiMo-MOF as a working electrode material is used for monitoring sweat of a human body in real time.

Description

Technical Field

[0001] The present invention belongs to the technical field of glucose detection devices and relates to a glucose sensor. Background Art

[0002] Diabetes has always been one of the major diseases that researchers need to strive to overcome. At present, blood glucose meters are widely used in the market to detect blood glucose levels. This invasive detection method is very unfriendly to patients. Therefore, it is very urgent to develop a non-invasive glucose sensor. Existing glucose detection methods include colorimetry, fluorescence method, chemiluminescence method, enzyme-based electrochemical sensing, non-enzyme electrochemical sensing, etc. These methods have their own advantages and disadvantages. Colorimetry is simple and easy to operate, but usually has poor sensitivity; the fluorescence method has high sensitivity and high selectivity, but the stability of the fluorescent probe is limited and it is easily interfered by other substances; chemiluminescence method has high stability and can quickly detect results, but there are many interfering factors and the detection cost is high; enzyme-based electrochemical sensing has high sensitivity and high selectivity, but natural enzymes are easily affected by the environment; non-enzyme electrochemical sensing has high sensitivity and good stability, and the selection of appropriate working electrode materials will significantly affect the performance of the glucose sensor. Therefore, it is necessary to select nanomaterials with good stability and high catalytic activity to construct a non-enzyme glucose sensor.

[0003] There are many kinds of nanomaterials required for constructing a non-enzyme glucose sensor. For example, transition metal nanomaterials, commonly used ones are Au, Ag, Pt, Fe, Co, Ni, Cu, etc.; in addition, carbon-based nanomaterials and conductive polymer nanomaterials are also widely used; in addition, in recent years, metal-organic framework nanomaterials (MOF) have received wide attention, which have a high specific surface area and porosity and can greatly improve the detection level. Summary of the Invention

[0004] The purpose of the present invention is to provide a robust high-performance liquid chromatography determination method for monitoring lamotrigine serum therapeutic drugs.

[0005] To achieve the above object and other related objects, the technical solution provided by the present invention is: a glucose sensor, comprising: (1) Synthesis of NiMo-MOF Disperse NiCl2·6H2O and Na2MoO4 in water, then dissolve 2-aminoterephthalic acid in water. After stirring and dissolving, then mix the two evenly, and then transfer the mixture to a stainless steel autoclave with a Teflon liner and react at 100-140 °C; after the reaction is completed, cool to room temperature, wash the reaction product with absolute ethanol and water respectively, and dry to obtain NiMo-MOF; (2) Construction of the glucose sensor First, place the screen-printed electrode in PBS solution and activate the electrode for 35 - 45 cycles within -0.6 V - 1.6 V using cyclic voltammetry at a scan rate of 100 mV / s. Then, take an aqueous solution of NiMo-MOF with a concentration of 2 mg / mL and drop it onto the surface of the screen-printed electrode. After natural drying, dropwise add a Nafion solution with a mass concentration of 0.1% to obtain the glucose sensor NiMo-MOF / Nafion / SPE.

[0006] The preferred technical solution is that the mass ratio between NiCl₂·6H₂O and Na₂MoO₄ is 0.4 - 0.55:1 - 1.5.

[0007] The preferred technical solution is that the ratio of 2-aminoterephthalic acid to water is: water 0.9 - 1.2 g:40 ml.

[0008] The preferred technical solution is that the ratio of Na₂MoO₄ to water is 1 - 1.5 g:20 ml.

[0009] The preferred technical solution is that the reaction time is 10 - 14 h; the drying temperature is 45 - 55 °C.

[0010] The preferred technical solution is that the pH value of the PBS solution is 7 and the concentration is 0.1 M.

[0011] Due to the application of the above technical solutions, the advantages of the present invention compared with the prior art are: The non-invasive non-enzymatic glucose sensor constructed by the present invention using NiMo-MOF as the working electrode material monitors human sweat in real time. Through the connection between sweat glucose and blood glucose, accurate detection of human glucose levels can be achieved, and non-invasive blood glucose detection can be realized. Brief Description of the Drawings

[0012] Figure 1 A of is the TEM image of NiMo-MOF; Figure 1 B of is the EDS spectrum of NiMo-MOF.

[0013] Figure 2 A of is the CV curves of NiMo-MOF / Nafion / SPE in 0.1 M PBS (pH = 7) for solutions without glucose, containing 0.1 mM glucose, and containing 1 mM glucose, with a scan rate of 100 mV s −1 , and the potential range is 0 - 0.8 V; Figure 2 B of is the CV curves of NiMo-MOF / Nafion / SPE at different scan rates; Figure 2 C of is Figure 2 The linear fitting curve of B of.

[0014] Figure 3 Optimization of NiMo-MOF / Nafion / SPE under different conditions: (A) NiMo ratio, (B) reaction time, (C) reaction temperature, (D) working potential, (E) MOF dropping amount, (F) MOF concentration.

[0015] Figure 4 A shows the i-t curve of NiMo-MOF / Nafion / SPE with continuous addition of glucose in 0.1 M PBS (pH = 7); Figure 4 B shows the linear fitting curve.

[0016] Figure 5 Selectivity study (A), repeatability study (B) and stability study (C) of NiMo-MOF / Nafion / SPE.

[0017] Figure 6 The i-t curve of NiMo-MOF / Nafion / SPE with continuous addition of glucose in artificial sweat.

[0018] Figure 7 The linear fitting curve. Detailed implementation manners

[0019] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this embodiment.

[0020] Please refer to Figure 1-7 . It should be noted that the structures, ratios, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those skilled in the art to understand and read, and are not used to limit the limiting conditions under which the present invention can be implemented. Therefore, they do not have a technical essence. Any modification of the structure, change of the proportional relationship or adjustment of the size. The following embodiments are provided to better understand the present invention, rather than to limit the present invention. The experimental materials used in the following embodiments are all obtained from regular biochemical reagent stores without special instructions.

[0021] Example 1: A glucose sensor A The present invention constructs a non-invasive non-enzymatic glucose sensor using NiMo-MOF as the working electrode material to monitor human sweat in real time. Through the relationship between sweat glucose and blood glucose, accurate detection of human glucose levels can be achieved. According to literature retrieval, there is currently no non-invasive non-enzymatic glucose sensor composed of NiMo bimetallic organic framework as the working electrode material for real-time monitoring of human sweat. Therefore, the constructed system is novel.

[0022] A1 Selection of working electrode material: Metal-organic frameworks are composite materials composed of a connected porous framework consisting of metal sites and organic ligands. Due to their advantages such as large specific surface area, adjustable pore size, rich active centers, and controllable morphology, they can provide a large number of active sites for glucose catalysis. Therefore, they are widely used in catalysis and sensing. The redox reaction of glucose catalyzed by nickel nanomaterials is generally explained as the Ni(III) / Ni(II) redox pair for the deprotonation and isomerization of glucose, which can improve the electrocatalytic performance of the material and provide rich electrochemically active sites. Therefore, nickel nanomaterials have great potential in electrochemical sensors. The valence electron orbit of metallic molybdenum is in a half-filled state ([Kr]4d 5 5s 1 ), with stable properties. Research shows that the stability of the metal itself can enhance the stability of the sensor. Due to the positive synergistic effect between different components, bimetallic nanomaterials have more excellent properties than single components, such as electrocatalytic performance, electron transfer rate, anti-interference performance, etc., which can improve the performance of electrochemical sensors. Therefore, the present invention selects NiMo-MOF as the working electrode material.

[0023] A2 Reagents and materials: Nickel chloride hexahydrate (NiCl2·6H2O), sodium molybdate anhydrous (Na2MoO4), 2-aminoterephthalic acid, potassium ferrocyanide (K4[Fe(CN)6]), potassium ferricyanide (K3[Fe(CN)6]), potassium chloride (KCl), disodium hydrogen phosphate (Na2HPO4), sodium dihydrogen phosphate (NaH2PO4), sodium chloride (NaCl), calcium chloride (CaCl2), magnesium chloride (MgCl2), ammonium chloride (NH4Cl), urea, lactic acid (LA), uric acid (UA), ascorbic acid (AA), and absolute ethanol were purchased from Shanghai Chemical Reagent Co., Ltd. of Sinopharm Group (Shanghai, China). Glucose (C6H 12 O6) and Nafion were purchased from Shanghai Macklin Biochemical Co., Ltd. (Shanghai, China). Screen-printed electrodes were purchased from Beijing Mingtai Jiaxin Technology Co., Ltd. (Beijing, China). All reagents were of analytical grade, and the experimental water was ultrapure water.

[0024] B Material synthesis: B1 Synthesis of NiMo-MOF: Dissolve 0.475 g of NiCl2·6H2O and 1.235 g of Na2MoO4 in 20 mL of ultrapure water. Then weigh 1.087 g of 2-aminoterephthalic acid and dissolve it in 40 mL of ultrapure water. After stirring to dissolve, mix the two solutions and ultrasonically mix them for 1 h. Then transfer the mixture to a 100 mL Teflon-lined stainless steel autoclave and react at 120 °C for 12 h. After cooling to room temperature, wash the mixture 3 times with absolute ethanol and ultrapure water respectively, and dry it overnight at 50 °C to obtain NiMo-MOF.

[0025] Preparation of B2 artificial sweat: The prepared artificial sweat contains 80 mM NaCl, 22 mM urea, 8 mM KCl, 5.5 mM LA, 3 mM NH4Cl, 0.4 mM CaCl2, 50 μM MgCl2, and 25 μM UA.

[0026] Construction of C sensor: First, place the screen-printed electrode in a 0.1 M PBS (pH = 7) solution and activate the electrode for 40 cycles by cyclic voltammetry within -0.6 V to 1.6 V, with a scanning rate of 100 mV / s. Then take 5 μL of a 2 mg / mL aqueous solution of NiMo-MOF and drop it on the surface of the working electrode. After natural drying, drop 5 μL of 0.1% Nafion solution to obtain NiMo-MOF / Nafion / SPE.

[0027] D Results and discussion: D1 Morphological characterization of materials: The prepared electrode materials were characterized by transmission electron microscopy (TEM). As Figure 1 shown in A, it can be observed that NiMo-MOF is stacked in a sheet-like structure. Figure 1 B in shows the EDS spectrum of NiMo-MOF. Ni and Mo are evenly distributed on the surface of the material, indicating the successful synthesis of NiMo-MOF.

[0028] D2 Electrocatalytic performance of NiMo-MOF towards glucose: The electrochemical performance of NiMo-MOF / Nafion / SPE in the presence and absence of glucose in 0.1 M PBS (pH = 7) was investigated by CV method, with a scanning rate of 100 mV s −1 , and the potential range was 0 to 0.8 V. As Figure 2 shown in A, in the absence of glucose, NiMo-MOF / Nafion / SPE has a pair of redox peaks, which may be attributed to Ni 2+ and Ni 3+Transformation; after adding low-concentration glucose, the oxidation peak current increased significantly, and the increase was more remarkable after adding high-concentration glucose, indicating that NiMo-MOF / Nafion / SPE has excellent electrocatalytic performance for glucose.

[0029] The effect of scan rate on the point catalytic performance was studied in the range of 10 - 100 mV s −1 as shown in B of, the oxidation peak current increased with the increase of scan rate, and the current was proportional to the square root of the scan rate ( Figure 2 C of), this linear relationship indicates that the oxidation of glucose on NiMo-MOF / Nafion / SPE is controlled by the diffusion process. Figure 2

[0030] Optimization of D3 material: In order to achieve the best detection effect of the sensor, the materials were optimized, including the NiMo ratio of NiMo-MOF, the reaction time for material synthesis, the reaction temperature for material synthesis, the working potential for electrochemical detection, the modification amount of NiMo-MOF material, and the concentration of NiMo-MOF. As Figure 3 shown, the optimal NiMo ratio is 1:3, the optimal reaction time for material synthesis is 12 h, the optimal reaction temperature is 120 °C, the optimal working potential for electrochemical detection is 0.55 V, the optimal modification amount of NiMo-MOF material is 5 μL, and the optimal concentration of NiMo-MOF is 2 mg / mL.

[0031] Electrochemical detection of D4 glucose: Glucose analysis of NiMo-MOF / Nafion / SPE was carried out by chronoamperometry. Under the optimal conditions, glucose solution was continuously added to 0.1 M PBS (pH = 7), and the current response was recorded. As Figure 4 shown in A of, the response current increased gradually with the addition of glucose. Figure 4 B of shows the corresponding calibration curve (y = 0.114x + 10.231, R 2 = 0.998), the calculated linear range is 49.5 μM - 614 μM, including the physiological sweat glucose level (55 - 220 μM), and the sensitivity is 1612 μA·mM -1 ·cm -2 and the detection limit is 13.4 μM (S / N = 3).

[0032] Study on selectivity, repeatability and stability: In addition to glucose, sweat also contains several other chemicals, such as sodium chloride (NaCl), lactic acid (LA), uric acid (UA), and urea. The effective anti-interference detection performance of the glucose sensor is very important. A variety of common interfering substances were added to 0.1 M PBS (pH = 7) to study their effects on the current response of the glucose sensor. As Figure 5 shown in A of Figure 5 , it can be seen that except for the addition of glucose, there is no obvious change in the current, indicating that the glucose sensor has good selectivity. In addition, the repeatability of the sensor was studied. Five different batches of glucose sensors were constructed and measured 5 times under the same experimental conditions. As Figure 5 shown in B of Figure 5 , the RSD of the five NiMo-MOF / Nafion / SPEs is about 1.63%, indicating that the sensor has good repeatability. In addition, the stability of the sensor was also studied. The electrode was stored at room temperature for 5, 10, 15, and 20 days respectively, and the response of the sensor to glucose was measured. After 20 days, 89.3% of the initial response current was still maintained, indicating that the sensor has good stability.

[0033] D6 Detection of real samples: Before measuring the glucose in real human sweat samples, for the accuracy of the measurement, the response current was recorded by continuously adding different concentrations of glucose to artificial sweat ( Figure 6 ), and linear fitting was performed ( Figure 7 ). The results show that compared with 0.1 M PBS (pH = 7), the calibration curve of the sensor in artificial sweat has no significant change, which strengthens its reliability and practicality in the actual detection of glucose in sweat.

[0034] Next, we used it to measure the glucose level in real human sweat. Sweat samples were collected from healthy volunteers and stored in a refrigerator at 5 °C. The standard addition method was used to determine the glucose level in the samples. As shown in the following table, the recovery rate was between 98.7% and 100.5%, and the RSD < 2.82%, indicating the reliability of the glucose sensor in detecting glucose in actual samples.

[0035] Sample Addition amount / μM Detected value / μM Recovery rate / % RSD / % 1 50 49.55 98.7 1.31 2 100 100.32 100.5 2.82 3 200 198.41 99.1 2.56 The above are only preferred embodiments for explaining the present invention and are not intended to limit the present invention in any form. Therefore, any modification or change to the present invention made in the same inventive spirit should still be included within the scope intended to be protected by the present invention.

Claims

1. A glucose sensor, characterized in that: include: (1) Synthesis of NiMo-MOF Disperse NiCl2·6H2O and Na2MoO4 in water, dissolve 2-aminoterephthalic acid in water, stir and dissolve, then mix the two evenly, then transfer the mixture to a stainless steel autoclave with a Teflon lining, and react at 100-140°C; after the reaction is completed, cool to room temperature, wash the reaction product with anhydrous ethanol and water respectively, and dry to obtain NiMo-MOF; (2) Construction of glucose sensor First, the screen-printed electrode was placed in a PBS solution and activated by cyclic voltammetry for 35-45 cycles in the range of -0.6V-1.6V with a scanning rate of 100mV / s. Then, a 2mg / mL NiMo-MOF aqueous solution was dripped on the surface of the screen-printed electrode. After natural air drying, a Nafion solution with a mass concentration of 0.1% was added to obtain a glucose sensor NiMo-MOF / Nafion / SPE.

2. The glucose sensor according to claim 1, characterized in that: The mass ratio between NiCl2·6H2O and Na2MoO4 is 0.4-0.55:1-1.

5.

3. The glucose sensor according to claim 1, characterized in that: The ratio of 2-aminoterephthalic acid to water is: water 0.9-1.2g:40ml.

4. The glucose sensor according to claim 1, characterized in that: The ratio of Na2MoO4 to water is 1-1.5g:20ml.

5. The glucose sensor according to claim 1, characterized in that: The reaction time is 10-14h; the drying temperature is 45-55°C.

6. The glucose sensor according to claim 1, characterized in that: The pH value of PBS solution is 7 and the concentration is 0.1M.

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