Sensing electrode for dopamine detection

Abstract

A sensing electrode for dopamine detection is disclosed, which detects dopamine in a test solution. The electrode comprises a conductive substrate and a dopamine detection coating. The conductive substrate has a conductive thin film with a connection region and a sensing region defined thereon. The connection region is connected to an electrochemical analyzer, and the sensing region extends into the test solution. The dopamine detection coating is applied to the sensing region and is a mixture of an iron-based metal-organic framework (MIL-101) powder and a noble metal nanoparticle powder, wherein the noble metal nanoparticle powder is selected from gold nanoparticles, silver nanoparticles, and gold-core silver-shell nanoparticles. Accordingly, this invention is used as the working electrode of the electrochemical analyzer to detect the test solution and quickly determine the concentration of dopamine.

Description

Technical Field

[0001] This invention relates to dopamine detection, and more particularly to a sensing electrode for dopamine detection. Prior Technology

[0002] Dopamine (DA) is a biologically important catecholamine neurotransmitter that regulates the metabolism and normal function of the central nervous system, renal system, and hormonal system. It is mainly found in brain cells and body fluids, and facilitates signal exchange between dendrites. Abnormal dopamine levels in the body may indicate neurological disorders such as hypertension, schizophrenia, Parkinson's disease, Alzheimer's disease, HIV, and attention deficit hyperactivity disorder (ADHD), with Parkinson's disease being the most common neurological disorder.

[0003] Parkinson's disease is mainly caused by the gradual death of dopamine neurons in the substantia nigra of the basal ganglia of the brain, resulting in insufficient dopamine, a neurotransmitter in the brain. When the concentration of dopamine in the brain is lower than 80% of that in normal people, motor function gradually deteriorates and clinical symptoms appear.

[0004] Parkinson's disease is actually detectable, and if it is detected and treated early, the treatment outcome is usually better. In addition to using the "Parkinson's Disease Self-Assessment Scale" for people to self-test at home, it is also possible to test the concentration of dopamine in bodily fluids to help determine whether further diagnosis by a neurologist is necessary.

[0005] There are many ways to detect dopamine, such as colorimetry, ion chromatography, spectrophotometry, ultraviolet spectrophotometry, high performance liquid chromatography, etc. However, these conventional methods of detecting dopamine have problems such as long detection time, high cost and complicated process. Moreover, most of the above methods require the solution to be separated or purified in advance, which is not suitable for the general public to use for self-testing. They can only be performed in specialized institutions or laboratories. Summary of the Invention

[0006] Therefore, the main objective of this invention is to disclose a sensing electrode for dopamine detection that can meet the need for simple operation and rapid detection of dopamine concentration in human body fluids.

[0007] To achieve the above objectives, the present invention provides a sensing electrode for dopamine detection, used as the working electrode of an electrochemical analyzer to detect a solution. The electrode comprises a conductive substrate and a dopamine detection coating. The conductive substrate has a conductive thin film with a connection region and a sensing region defined on it. The connection region connects to the electrochemical analyzer, and the sensing region extends into the solution to be detected. The dopamine detection coating is applied to the sensing region and is formed by dripping a mixed solution onto the sensing region and drying it. The mixed solution comprises an iron-based metal-organic framework MIL-101 (Fe) powder, a noble metal nanoparticle powder, and a fixative solution. The noble metal nanoparticle powder is selected from gold nanoparticles, silver nanoparticles, and gold-core-silver-shell nanoparticles. The fixative solution is a perfluorinated resin solution. Simple Explanation of the Diagram

[0008] Figure 1 is a schematic diagram of the structure of the present invention. Figure 2 is a schematic diagram of the present invention used for detection. Figure 3 shows the CV regression curve of MIL-101(Fe) concentration change. Figure 4 shows the CV regression curve of Ag@MIL-101(Fe) concentration change. Figure 5 shows the CV regression curve of Au@MIL-101(Fe) concentration change. Figure 6 shows the CV regression curve of Au@Ag@MIL-101(Fe) concentration change. Figure 7 shows the linear fitting curve of the timing current of MIL-101(Fe). Figure 8 shows the linear fitting curve of the chronocurrent of Ag@MIL-101(Fe). Figure 9 shows the linear fitting curve of the timing current of Au@MIL-101(Fe). Figure 10 shows the linear fitting curve of the timing current of Au@Ag@MIL-101(Fe). Implementation

[0009] The technical content of this invention is explained below with reference to the accompanying drawings.

[0010] Please refer to Figures 1 and 2. This invention relates to a sensor S, which can be used for dopamine detection. This sensor S serves as the working electrode WE of an electrochemical analyzer 10. The sensor S is used to detect a solution 20 to be tested. The sensor S includes a conductive substrate 30 and a dopamine detection coating 40. The conductive substrate 30 has a conductive film 31. A connection area 311 and a sensing area 312 are planned on the conductive film 31. The connection area 311 is connected to the electrochemical analyzer 10. The sensing area 312 extends into the solution 20 to be tested. The dopamine detection coating 40 is coated on the sensing area 312. The dopamine detection coating 40 is formed by dripping a mixed solution onto the sensing area 312 and drying it. The mixed solution includes an iron-based metal-organic framework MIL-101 (Fe) powder, a noble metal nanoparticle powder and a fixative solution. The noble metal nanoparticle powder is any one of gold nanoparticles, silver nanoparticles and gold core silver shell nanoparticles. The fixative solution is a perfluorinated resin solution.

[0011] This iron-based metal-organic framework MIL-101(Fe) powder is derived from MIL-101(Cr). The chemical formula of the MIL framework is Cr3X(H2O)2O(BDC)3. A chromium ion (Cr) is provided as the framework center by a hydrothermal synthesis of a metal oxide, combined with the organic ligand BDC. It exhibits a high pore volume of approximately 2 cm³ / g and a high specific surface area of ​​approximately 5900 m² / g. MIL-101(Fe) can be applied in various fields, including gas adsorption, drug delivery, catalysis, and proton exchange membranes. It has nanocages of approximately 2.9-3.4 nanometers and pore sizes of approximately 1.2-1.6 nanometers, suitable for the free entry of large molecules.

[0012] In one embodiment, the conductive film 31 is bonded to a polyimide tape 50, and the exposed portion of the conductive film 31 on the polyimide tape 50 forms the connection area 311 and the sensing area 312. Preferably, the sensing area 312 has a rectangular area of ​​0.8 cm * 0.8 cm.

[0013] In one embodiment, the preparation steps of the iron-based metal-organic framework MIL-101(Fe) powder include: mixing ferric chloride hexahydrate and terephthalic acid in a molar ratio of 2:1 and adding the mixture to a beaker containing 15 mL of dimethylformamide, stirring until completely dissolved to produce a dimethylformamide mixed solution; placing the dimethylformamide mixed solution into a stainless steel reactor lined with polytetrafluoroethylene, heating it in a high-temperature furnace at 110°C for 20 hours, and then allowing it to cool naturally; removing the dimethylformamide mixed solution and performing an extraction operation at 6000 rpm for 10 minutes using a centrifuge; filtering the dimethylformamide... A precipitate was extracted from the amide-nitrogen mixture and washed with ethanol at 60°C for 3 hours to remove unreacted substances. The precipitate was then extracted using a centrifuge at 6000 rpm for 10 minutes, filtered again, and washed a second time with ethanol at 60°C for 3 hours. This extraction was repeated, followed by filtration to remove the precipitate. The precipitate was placed in a sample vial and dried in a vacuum environment at 70°C for 3 hours. Once the precipitate was confirmed to be completely dry, it was removed, thus completing the synthesis of the iron-based metal-organic framework MIL-101(Fe) powder.

[0014] In one embodiment, the preparation steps of the gold nanoparticles include: soaking a glass container and a magnet in aqua regia for 30 minutes to remove organic matter before use, rinsing several times with DIwater, and then drying for later use. 50 ml of 0.01% tetrachloroauric acid trihydrate (HAuCl 4·3H 2O) is placed in the glass container, and stirred and heated to boiling using the magnet; 3 ml of 38.3 mmol sodium citrate (Na 3C 6H 5O 7) is added to form a mixture and stirred continuously; when the mixture begins to turn a deep wine-red color, stirring and heating are continued for at least 15 minutes, then heating is turned off, and the mixture is allowed to cool to room temperature to complete the preparation of the gold nanoparticles.

[0015] In one embodiment, the preparation steps of silver nanoparticles include: first, dissolving 0.1 g of sodium citrate in 10 mL of DIwater to prepare a 1% sodium citrate aqueous solution; heating and stirring 25 mL of 1 mmol silver nitrate (AgNO3) aqueous solution to boiling; and rapidly adding 2.5 mL of sodium citrate (Na3C6H5O7) dropwise during stirring. Heating is stopped when the solution changes from colorless to yellow, thus completing the preparation of silver nanoparticles.

[0016] In one embodiment, the preparation steps of gold core silver shell nanoparticles include: first, preparing 0.1 mol of ascorbic acid and 0.01 mol of silver nitrate; taking 5 ml of gold nanoparticles and stirring, then adding 300 μL of ascorbic acid and mixing; then slowly adding 200 μL of silver nitrate, the solution will change from wine red to orange, thus completing the preparation of gold core silver shell nanoparticles.

[0017] The manufacturing method of the dopamine detection coating 40 is described below.

[0018] If the precious metal nanoparticle powder is gold nanoparticles, first take 15 ml of gold nanoparticles and add 50 mg of the iron-based metal-organic framework MIL-101(Fe) powder and stir for 8 hours. After extraction at 6000 rpm for 10 minutes, place it in a vacuum environment and dry at 40°C for 3 hours to complete the preparation of Au@MIL-101(Fe) powder. The Au@MIL-101(Fe) powder is then mixed with the fixative solution to form the mixed solution.

[0019] In one embodiment, the mixed solution contains 0.296 g of Au@MIL-101(Fe) powder and 40 g of the fixative solution, which is 1 g of Nafion D-521 (commercially available product), 19.5 g of DIwater and 19.5 g of isopropanol. The mixed solution is completely dispersed by ultrasonic agitation for more than 10 minutes, and 8 μL of the mixed solution is dropped onto the sensing area in two separate applications. After the mixed solution dries, the dopamine detection coating 40 of Au@MIL-101(Fe) is formed.

[0020] If the precious metal nanoparticle powder is silver nanoparticles, first take 15 ml of silver nanoparticles and add 50 mg of the iron-based metal-organic framework MIL-101(Fe) powder and stir for 8 hours. After extraction at 6000 rpm for 10 minutes, place it in a vacuum environment and dry at 40°C for 3 hours to complete the preparation of Ag@MIL-101(Fe) powder. Then mix the Ag@MIL-101(Fe) powder with the fixative solution to form the mixed solution.

[0021] In one embodiment, the mixed solution contains 0.162 g of Ag@MIL-101(Fe) powder and 40 g of the fixative solution, which is 1 g of Nafion D-521, 19.5 g of DIwater and 19.5 g of isopropanol. The mixed solution is completely dispersed by ultrasonic agitation for more than 10 minutes. The mixed solution is then taken out in two 8 μL portions and dropped onto the sensing area. After the mixed solution dries, the Ag@MIL-101(Fe) dopamine detection coating 40 is formed.

[0022] If the precious metal nanoparticle powder is gold core silver shell nanoparticle, first take 15 ml of gold core silver shell nanoparticle and add 50 mg of the iron-based metal-organic framework MIL-101(Fe) powder and stir for 3 hours. After extraction at 6000 rpm for 10 minutes, place it in a vacuum environment and dry at 40°C for 4 hours to complete the preparation of Au@Ag@MIL-101(Fe) powder. The Au@Ag@MIL-101(Fe) powder is then mixed with the fixative solution to form the mixed solution.

[0023] In one embodiment, the mixed solution comprises 0.1525 g of Au@Ag@MIL-101(Fe) powder and 40 g of the fixative solution, which is 1 g of Nafion D-521, 19.5 g of DIwater and 19.5 g of isopropanol. The mixed solution is completely dispersed by ultrasonic agitation for more than 10 minutes, and 8 μL of the mixed solution is dropped onto the sensing area in two separate applications.

[0024] Please refer to Figure 2 again. The sensor S of the present invention is used as the working electrode WE of the electrochemical analyzer 10. In addition to the working electrode WE, the electrochemical analyzer 10 also includes a counter electrode CE and a reference electrode RE, so that the solution to be tested 20 can be detected.

[0025] This invention uses cyclic voltammetry (CV) and chronoamperometry (CA) for measurement, wherein cyclic voltammetry is used to plot CV regression curves and chronoamperometry is used to plot linear fitting curves.

[0026] Please refer to Figures 3, 4, 5, and 6, which are CV regression curves showing the concentration changes of MIL-101(Fe) (control group), Ag@MIL-101(Fe), Au@MIL-101(Fe), and Au@Ag@MIL-101(Fe), respectively.

[0027] As shown in Figures 3, 4, 5, and 6, there is a direct proportional relationship between dopamine (DA) concentration and current magnitude, demonstrating that MIL-101(Fe) has a specific effect on dopamine in the test solution 20. Furthermore, as shown in Figures 4, 5, and 6, compared to Figure 3, the iron-based metal-organic framework MIL-101(Fe) powder of the present invention exhibits a significant increase in current after the addition of any one of gold nanoparticles, silver nanoparticles, or gold-core silver-shell nanoparticles. The effect of gold-core silver-shell nanoparticles is particularly significant. This phenomenon may be attributed to the high catalytic activity of gold, silver, and gold-core silver-shell nanoparticles, as well as the surface plasma resonance phenomenon due to nanoscale effects. This means that the current signal can be better transmitted, increasing the sensing sensitivity of the iron-based metal-organic framework MIL-101(Fe) powder, reducing the accuracy requirements of the electrochemical analyzer 10, thus lowering equipment costs and accelerating detection accuracy and speed.

[0028] Please refer to Figures 7, 8, 9, and 10, which show the chronocurrent linear fitting curves for MIL-101(Fe) (control group), Ag@MIL-101(Fe), Au@MIL-101(Fe), and Au@Ag@MIL-101(Fe), respectively.

[0029] As shown in Figures 7, 8, 9, and 10, the reaction current increases linearly, and the current also increases with the increase of dopamine concentration. The current response of sensor S after incorporating gold nanoparticles, silver nanoparticles, and gold-core silver-shell nanoparticles is significantly greater than that of the undoped sensor. Therefore, this further proves that incorporating gold nanoparticles, silver nanoparticles, and gold-core silver-shell nanoparticles can increase the sensing sensitivity of the iron-based metal-organic framework MIL-101(Fe) powder, reduce the accuracy requirements of the electrochemical analyzer 10, thereby reducing equipment costs, and accelerating the accuracy and speed of detection.

[0030] As described above, the features of the present invention include at least:

[0031] 1. Compared with traditional sensors, this invention not only simplifies the manufacturing process, but also has the advantages of low cost, easy operation and easy mass production.

[0032] 2. It can reduce the accuracy requirements of the electrochemical analyzer, thereby lowering the equipment cost and making it affordable for the general public, thus having the potential to be developed into a home self-testing device.

[0033] 3. Compared with conventional methods, electrochemical detection methods are more flexible, highly sensitive, capable of continuous monitoring, miniaturized equipment, low cost, and have a fast reaction time.

[0034] S: Sensor WE: Working electrode CE: Counter electrode RE: Reference Electrode 10: Electrochemical Analyzer 20: Solution to be tested 30: Conductive substrate 31: Conductive thin film 311: Connection Area 312: Sensing Area 40: Dopamine detection coating 50: Polyimide tape

Claims

1. A sensing electrode for dopamine detection, used as a working electrode of an electrochemical analyzer to detect a solution to be tested, comprising: a conductive substrate having a conductive thin film, wherein a connection area for connecting the electrochemical analyzer and a sensing area extending into the solution to be tested are defined on the conductive thin film; and a dopamine detection coating, wherein the dopamine detection coating is coated on the sensing area, the dopamine detection coating is formed by dripping a mixed solution onto the sensing area and drying it, and the mixed solution comprises an iron-based metal-organic framework MIL-101(Fe) powder, a noble metal nanoparticle powder and a fixative solution, wherein the noble metal nanoparticle powder is selected from any one of gold nanoparticles, silver nanoparticles and gold core silver shell nanoparticles, and the fixative solution is a perfluorinated resin solution.

2. The sensing electrode for dopamine detection as claimed in claim 1, wherein the conductive film is bonded to a polyimide tape, and a portion of the conductive film is exposed to form the connection region and the sensing region.

3. The sensing electrode for dopamine detection as described in claim 1, wherein the preparation steps of the iron-based metal-organic framework MIL-101(Fe) powder include: adding ferric chloride hexahydrate and terephthalic acid in a molar ratio of 2:1 to a beaker containing 15 mL of dimethylformamide, stirring until completely dissolved to produce a dimethylformamide mixed solution; placing the dimethylformamide mixed solution into a stainless steel reactor lined with polytetrafluoroethylene, heating it in a high-temperature furnace at 110°C for 20 hours, and then allowing it to cool naturally; removing the dimethylformamide mixed solution and performing an extraction operation at 6000 rpm for 10 minutes using a centrifuge; filtering the dimethylformamide mixed solution to obtain a precipitate, washing the precipitate with ethanol at 60°C for a first washing of 3 hours to remove unreacted substances; Extraction was performed using a centrifuge at 6000 rpm for 10 minutes. The precipitate was then filtered and washed a second time with ethanol at 60°C for 3 hours. Extraction was performed again using a centrifuge at 6000 rpm for 10 minutes. The precipitate was then filtered and collected. The precipitate was placed in a sample vial and dried in a vacuum environment at 70°C for 3 hours. After confirming that the precipitate was completely dry, it was removed, thus completing the synthesis of the iron-based metal-organic framework MIL-101(Fe) powder.

4. The sensing electrode for dopamine detection as described in claim 1, wherein the preparation steps of the gold nanoparticles include: soaking a glass dish and a magnet in aqua regia for 30 minutes to remove organic matter before use, rinsing several times with DI water, and drying for later use; placing 50 ml of 0.01% tetrachloroauric acid trihydrate (HAuCl4·3H2O) in the glass dish, stirring with the magnet, and heating to boiling; adding 3 ml of 38.3 mmol sodium citrate (Na3C6H5O7) to form a mixture and stirring continuously; and when the mixture begins to turn a deep wine red color, continuing to stir and heat for more than 15 minutes, then turning off the heating and allowing it to cool to room temperature, thus completing the preparation of the gold nanoparticles.

5. The sensing electrode for dopamine detection as described in claim 4, wherein the noble metal nanoparticle powder is gold nanoparticles, and the Au@MIL-101(Fe) powder is prepared by first adding 50 mg of the iron-based metal-organic framework MIL-101(Fe) powder to 15 mL of gold nanoparticles and stirring for 8 hours, followed by extraction at 6000 rpm for 10 minutes, and then drying in a vacuum environment at 40°C for 3 hours. The Au@MIL-101(Fe) powder is then mixed with the fixative solution to form the mixed solution. The mixed solution contains 0.296 g of Au@MIL-101(Fe) powder and 40 g of the fixative solution, which consists of 1 g of Nafion D-521, 19.5 g of DIwater and 19.5 g of isopropanol. The mixed solution is completely dispersed by ultrasonic vibration for more than 10 minutes, and 8 μL of the mixed solution is dropped onto the sensing area in two separate applications.

6. The sensing electrode for dopamine detection as described in claim 1, wherein the preparation steps of the silver nanoparticles include: first, dissolving 0.1 g of sodium citrate in 10 mL of DIwater to prepare a 1% sodium citrate aqueous solution; heating and stirring 25 mL of a 1 mM silver nitrate (AgNO3) aqueous solution to boiling; and rapidly adding 2.5 mL of sodium citrate (Na3C6H5O7) dropwise during stirring, stopping heating when the solution changes from colorless to yellow, thus completing the preparation of the silver nanoparticles.

7. The sensing electrode for dopamine detection as described in claim 6, wherein the noble metal nanoparticle powder is silver nanoparticles, and the Ag@MIL-101(Fe) powder is prepared by first adding 50 mg of the iron-based metal-organic framework MIL-101(Fe) powder to 15 mL of silver nanoparticles and stirring for 8 hours, followed by extraction at 6000 rpm for 10 minutes, and then drying in a vacuum environment at 40°C for 3 hours. The Ag@MIL-101(Fe) powder is then mixed with the fixative solution to form the mixed solution. The mixed solution contains 0.162 g of Ag@MIL-101(Fe) powder and 40 g of the fixative solution, which is 1 g of Nafion D-521, 19.5 g of DIwater and 19.5 g of isopropanol. The mixed solution is completely dispersed by ultrasonic vibration for more than 10 minutes, and 8 μL of the mixed solution is dropped onto the sensing area in two separate applications.

8. The sensing electrode for dopamine detection as described in claim 4, wherein the preparation steps of the gold core and silver shell nanoparticles include: first, preparing 0.1 mol of ascorbic acid and 0.01 mol of silver nitrate; taking 5 mL of gold nanoparticles and stirring, then adding 300 μL of ascorbic acid and mixing; and then slowly adding 200 μL of silver nitrate, the solution will change from wine red to orange, thus completing the preparation of the gold core and silver shell nanoparticles.

9. The sensing electrode for dopamine detection as described in claim 8, wherein the noble metal nanoparticle powder is gold-core silver-shell nanoparticles, prepared by first adding 50 mg of the iron-based metal-organic framework MIL-101(Fe) powder to 15 mL of gold-core silver-shell nanoparticles and stirring for 3 hours, followed by extraction at 6000 rpm for 10 minutes, and then drying in a vacuum environment at 40°C for 4 hours to complete the preparation of Au@Ag@MIL-101(Fe) powder, which is then mixed with the fixative solution to form the mixed solution; the mixed solution contains 0.1525 g of Au@Ag@MIL-101(Fe) powder and 40 g of the fixative solution, which is 1 g of Nafion D-521, 19.5 g of DIwater and 19.5 g of isopropanol, and the mixed solution is completely dispersed by ultrasonic vibration for more than 10 minutes, and the mixed solution is taken out in two 8 μL portions and dropped onto the sensing area.

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