Reference electrode of dynamic blood glucose monitor capable of being implanted subcutaneously and preparation method of reference electrode

Abstract

The invention discloses a reference electrode of a dynamic blood glucose monitor capable of being implanted subcutaneously and a preparation method of the reference electrode, relates to the technical field of dynamic blood glucose monitoring sensors, and aims to solve the problems that a reference electrode used by a dynamic blood glucose monitor capable of being implanted subcutaneously in the prior art is easy to corrode and the like. The method comprises: plating gold on the surface of a substrate needle to obtain a gold-plated substrate needle; modifying a silver / silver chloride layer on the gold-plated substrate needle to obtain a modified gold-plated substrate needle; and coating the surface of the modified gold-plated substrate needle with a biocompatible film solution, and forming a thin film from the biocompatible film solution to obtain the reference electrode. The prepared reference electrode is compact and smooth in surface, improved in conductivity and good in corrosion resistance, and the working stability of a dynamic blood glucose monitoring sensor composed of the reference electrode and a working electrode is improved to a great extent.

Description

Technical Field

[0001] The present invention relates to a reference electrode for an implantable subcutaneous continuous glucose monitor and a preparation method thereof, belonging to the technical field of continuous glucose monitoring sensors. Background Art

[0002] Diabetes has become the chronic disease with the largest number of patients globally. Real-time, safe, and effective blood glucose detection is an important means to achieve good control of diabetes. However, due to fear of invasive detection and the need for test strip consumables, etc., it is still quite difficult to perform regular blood glucose monitoring. Long-term continuous blood glucose monitoring can obtain more blood glucose fluctuation information, which is better used for treatment plan adjustment and risk prediction.

[0003] The reaction principle of glucose detection is as follows: ; ; When a continuous glucose monitor works, it needs to have a working electrode and a reference electrode at the same time. Currently, most continuous glucose monitors on the market use metal or alloy materials as the reference electrode for sensor operation. The following problems will occur when this kind of electrochemical glucose sensor works in the body: 1. The electrochemical reaction with glucose oxidase as a catalyst will generate hydrogen ions. After long-term use, the hydrogen ion aggregation effect is obvious, and an acidic environment will be formed around the entire electrode.

[0004] 2. The existing sensors are implanted within the range of 4 - 5 mm under the skin. The sensors detect the glucose concentration in the interstitial fluid. Due to differences in human constitutions, a considerable number of people have weakly acidic interstitial fluid itself.

[0005] 3. Whether a sensor has one needle, two needles, three needles or more, at least one needle is connected to the external electronic circuit, and electrons generated in the electrochemical equation will be conducted out through this electrode.

[0006] Under the combined action of the above three situations, the electrode made of metal or alloy material will produce slow corrosion. In severe cases, the electrode needle will break in the body. In addition, the corrosion of the reference electrode will cause the sensor sensitivity to decrease, the detected blood glucose value to be inaccurate and deviated, and the performance of the entire sensor will gradually decrease. Summary of the Invention

[0007] The purpose of the present invention is to overcome the deficiencies in the prior art, and provide a reference electrode for an implantable subcutaneous continuous glucose monitor and a preparation method thereof. The prepared reference electrode has a dense and smooth surface, improved conductivity, and good corrosion resistance, which greatly improves the working stability of the continuous glucose monitoring sensor composed of the working electrode.

[0008] To achieve the above object, the present invention is implemented by the following technical solutions: In a first aspect, the present invention provides a method for preparing a reference electrode of a dynamic blood glucose monitor that can be implanted subcutaneously for a long time, comprising the following steps: Gold-plate the surface of the base needle to obtain a gold-plated base needle; Modify a silver / silver chloride layer on the gold-plated base needle to obtain a modified gold-plated base needle; Coat a biocompatible film solution on the surface of the modified gold-plated base needle, and a reference electrode is obtained after the biocompatible film solution forms a thin film.

[0009] Further, the gold-plating of the surface of the base needle to obtain a gold-plated base needle includes: Use a platinum mesh electrode as the anode and the base needle as the cathode for pre-gold plating to obtain a pre-gold-plated base needle; Stir and wash the pre-gold-plated base needle with ultrapure water, then gold-plate it, and take it out again and stir and wash it with ultrapure water to obtain a gold-plated base needle.

[0010] Further, the plating time of the pre-gold plating does not exceed 5 min, and the plating time range of the gold plating is 25-35 min.

[0011] Further, after obtaining the gold-plated base needle, the denseness of the coating of the gold-plated base needle needs to be tested, and the testing method includes the following steps: Use a micrometer to measure the coating thickness of the gold-plated base needle; Install the gold-plated base needle on the coating film unit board, and put them together into ultrapure water for ultrasonic cleaning to obtain a gold-plated base needle after ultrasonic cleaning; Place the tip of the gold-plated base needle after ultrasonic cleaning upward and dry it at 80-100 °C for 3-5 min to obtain a dried gold-plated base needle; Conduct an electrochemical test on the dried gold-plated base needle. The electrochemical test includes: using the gold-plated base needle as the anode, in a phosphate buffer solution, testing the change of current with time under a constant voltage, and the testing time is 10-20 min; If the coating thickness of the gold-plated base needle meets the range of 20-30 μm and the current in the electrochemical test is lower than 100 nA, then the denseness of the coating of the gold-plated base needle meets the requirements; otherwise, use the next base needle to re-perform the gold-plating operation until the denseness of the coating of the gold-plated base needle meets the requirements.

[0012] Further, the components of the biocompatible film solution include polyurethane and tetrahydrofuran.

[0013] Further, the thickness of the biocompatible thin film is 20-30 μm.

[0014] Second aspect, the present invention also provides a reference electrode for a long-term implantable subcutaneous continuous glucose monitor, which is prepared by the preparation method of the reference electrode for a long-term implantable subcutaneous continuous glucose monitor described in any one of the above.

[0015] Third aspect, the present invention also provides a long-term implantable subcutaneous continuous glucose monitor, which includes a reference electrode, and the reference electrode is the reference electrode prepared by the preparation method of the reference electrode for a long-term implantable subcutaneous continuous glucose monitor described in any one of the above or the reference electrode for a long-term implantable subcutaneous continuous glucose monitor described above.

[0016] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: The reference electrode prepared by the present invention provides a stable and corrosion-resistant basis by modifying a layer of metal that is more stable and corrosion-resistant than silver, namely a gold plating layer, on the base needle, making it not easily oxidized as a reference electrode subsequently, effectively extending the service life of the reference electrode; silver / silver chloride modification is used to enhance conductivity. Since the potential difference of silver / silver chloride is small, it has high consistency, and the standard potential of silver / silver chloride is known, which is suitable as a reference electrode modification layer. Finally, a biocompatible film is coated, which can improve the biocompatibility of the reference electrode, reduce the rejection reaction of the reference electrode in the biological environment, reduce inflammation and immune reactions, and improve the compatibility with organisms; it can also prevent bacterial growth, reduce the interference risk, enhance the mechanical properties of the reference electrode, improve the wear resistance and strength of the material, and further extend the service life of the reference electrode. The surface of the reference electrode prepared by the present invention is dense, smooth, has improved conductivity and good corrosion resistance, greatly improving the working stability of the continuous glucose monitoring sensor composed of the working electrode. Description of the Drawings

[0017] Figure 1 Schematic diagram of the current change curve over time in the first 14 days during the process of implanting the reference electrode prepared in Example 1 of the present invention into a subcutaneous continuous glucose sensor for continuous glucose monitoring; Figure 2 Schematic diagram of the current change curve over time in the first 12 days during the process of implanting the reference electrode prepared in the comparative example of the present invention into a subcutaneous continuous glucose sensor for continuous glucose monitoring; Figure 3 Schematic diagram of the current change curve over time in the first 30 days during the process of implanting the reference electrode prepared in Example 1 of the present invention into a subcutaneous continuous glucose sensor for continuous glucose monitoring. Detailed Embodiments

[0018] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention. Embodiment 1

[0019] As Figure 1 shown, the embodiment of the present invention provides a preparation method for a reference electrode of a dynamic blood glucose detector that can be implanted subcutaneously for a long time, including the following steps: The first step: Gold-plate the surface of the base needle to obtain a gold-plated base needle. Specifically: Preparation work: Fix the platinum mesh electrode on both sides of the pre-gold plating tank and the gold plating tank respectively with gold-plated copper wires, and fix the positive poles of the pre-gold plating and gold plating constant current power supplies on the two groups of electrode plates respectively. Connect the power supply of the circulation, filtration, and heating and stabilization control system of the gold plating constant temperature circulation tank.

[0020] Turn on the constant current power supply switch, adjust the current to zero, and then slightly callback to make a small current. Clamp the conductive end of the base needle (any needle body that is medically allowed to enter the human body, and its materials include but are not limited to stainless steel, carbon, titanium and its alloys, platinum iridium, platinum, etc.) with the clip connecting the negative pole of the output terminal of the pre-gold plating constant current power supply.

[0021] Put the base needle into the pre-gold plating solution, adjust the current to 5 mA, and the plating time is 5 min. Take out the base needle from the pre-gold plating solution, and the pre-gold plating is completed.

[0022] Turn on the stirrer for pre-gold plating, put the base needle after pre-gold plating into ultrapure water for stirring and cleaning, and after cleaning, change to another ultrapure water for stirring and cleaning again to obtain a cleaned base needle.

[0023] Turn on the constant current power supply for gold plating, adjust the current to zero, and then slightly callback to make a small current. Clamp the conductive end of the base needle cleaned with ultrapure water with the clip connecting the negative pole of the output terminal of the gold plating constant current power supply.

[0024] Put the base needle with a small amount of electricity into the gold plating solution, adjust the current to 5 mA, turn on the cathode moving power supply and the pump power supply, and under the condition of cathode movement and plating solution filtration, plate for 30 min, and the gold plating is completed.

[0025] Put the gold-plated base needle into ultrapure water for stirring and cleaning, and after cleaning, change to another ultrapure water for stirring and cleaning again to obtain a cleaned base needle, and the gold plating is ended.

[0026] The second step: Test the gold-plated base needle. The test method includes the following steps: Use a micrometer to measure whether the coating thickness of the gold-plated base needle is between 20 and 30 μm. In this embodiment, the measured coating thickness is 30 μm.

[0027] After measuring the coating thickness of the gold-plated substrate needles, the gold-plated substrate needles are mounted on the coating unit board, and they are put into ultrapure water together for ultrasonic cleaning, and then put into another ultrapure water for stirring cleaning, with the temperature being 90 °C.

[0028] The tips of the gold-plated substrate needles after cleaning are placed upward on an electric furnace with an asbestos net, and dried at 90 °C for 4 min.

[0029] The dried gold-plated substrate needles are subjected to electrochemical testing. Using the gold-plated substrate needles as the anode, in PBS solution, at a constant voltage of 0.60 V, the change of the test current with time is measured. The test time is 15 min. When the current is lower than 100 nA, the coating compactness of the gold-plated substrate needles in this embodiment meets the requirements and the test is qualified.

[0030] The qualified gold-plated substrate needles after testing are cleaned with ultrapure water and then dried in the air.

[0031] Second step: Modify a silver / silver chloride layer on the gold-plated substrate needles to obtain the modified gold-plated substrate needles. Specifically: Prepare silver / silver chloride paste and dilute it with the supporting diluent. The concentration ratio of the diluent is 6%. Modify the silver / silver chloride layer on the surface of the gold-plated substrate needles by the film pulling method, and then place it in a blast drying oven at 120 °C for curing for 25 min.

[0032] Third step: Coat a biocompatible film solution on the surface of the modified gold-plated substrate needles Prepare a biocompatible solution: Add polyurethane to tetrahydrofuran, and control the concentration of polyurethane to be 25 mg / mL.

[0033] Place the biocompatible solution on a magnetic stirrer and stir it in advance for 18 minutes.

[0034] Mount the modified gold-plated substrate needles on the coating unit board of the coater, put the coating unit board into the coater seat, and close the coater cabin door. Press the start button on the coater control panel, set the coating process to run automatically, and it will stop automatically after completion to obtain a reference electrode. In this embodiment, the thickness of the biocompatible film is 25 μm. Example 2

[0035] The embodiment of the present invention provides a preparation method for a reference electrode of a dynamic blood glucose detector that can be implanted subcutaneously for a long time, including the following steps: First step: Gold-plate the surface of the substrate needles to obtain gold-plated substrate needles. Specifically: Preparation work: Fix the platinum mesh electrode on both sides of the pre-gold-plating tank and the gold-plating tank with gold-plated copper wires respectively, and fix the positive electrodes of the pre-gold-plating and gold-plating constant current power supplies on the two groups of electrode plates respectively, and turn on the power supply of the circulation, filtration, heating and stabilization control system of the gold-plating constant temperature circulation tank.

[0036] Turn on the constant current power supply switch, adjust the current to zero, and then slightly turn it back to allow a small current. Use the clip connected to the negative terminal of the output of the constant current power supply for pre-gilding to clamp the conductive end of the substrate needle after weak acid etching.

[0037] Put the substrate needle into the pre-gilding solution, adjust the current to 5 mA, and the plating time is 3 min. Take out the substrate needle from the pre-gilding solution, and the pre-gilding is completed.

[0038] Turn on the stirrer for pre-gilding, put the substrate needle after pre-gilding into ultrapure water for stirring and cleaning, and after cleaning, change to another ultrapure water for stirring and cleaning again to obtain the cleaned substrate needle.

[0039] Turn on the constant current power supply for gilding, adjust the current to zero, and then slightly turn it back to allow a small current. Use the clip connected to the negative terminal of the output of the gilding constant current power supply to clamp the conductive end of the substrate needle after cleaning with ultrapure water.

[0040] Put the substrate needle with a small amount of electricity into the gilding solution, adjust the current to 5 mA, turn on the cathode moving power supply and the pump power supply. Under the conditions of cathode movement and plating solution filtration, plate for 25 min, and the gilding is completed.

[0041] Put the substrate needle after gilding into ultrapure water for stirring and cleaning, and after cleaning, change to another ultrapure water for stirring and cleaning again to obtain the cleaned substrate needle, and the gilding is ended.

[0042] Step 2: Test the gilded substrate needle. The test method includes the following steps: Use a micrometer to measure whether the coating thickness of the gilded substrate needle is between 20 and 30 μm. In this embodiment, the measured coating thickness is 27 μm.

[0043] Install the gilded substrate needle after measuring the coating thickness on the coating unit board, put it into ultrapure water for ultrasonic cleaning together, and then put it into another ultrapure water for stirring and cleaning, and the temperature is 90 °C.

[0044] Place the cleaned gilded substrate needle with the tip facing up on an electric furnace with an asbestos net and dry it at 90 °C for 4 min.

[0045] Conduct an electrochemical test on the dried gilded substrate needle. Use the gilded substrate needle as the anode, in PBS solution, at a constant voltage of 0.60 V, test the change of current with time, and the test time is 15 min. When the current is lower than 100 nA, so the coating density of the gilded substrate needle in this embodiment meets the requirements and the test is qualified.

[0046] Clean the gilded substrate needle that has passed the test with ultrapure water and then air-dry it.

[0047] Step 2: Modify a gold-plated base needle with a silver / silver chloride layer to obtain a modified gold-plated base needle. Specifically: Prepare a silver / silver chloride paste and dilute it with a supporting diluent. The concentration ratio of the diluent is 7%. Modify the silver / silver chloride layer on the surface of the gold-plated base needle by the film pulling method, and then place it in a blast drying oven at 120 °C for curing for 20 min.

[0048] Step 3: Coat a biocompatible film solution on the surface of the modified gold-plated base needle Prepare a biocompatible solution: Add polyurethane to tetrahydrofuran and control the concentration of polyurethane to be 25 mg / mL.

[0049] Place the biocompatible solution on a magnetic stirrer and stir it in advance for 18 minutes.

[0050] Install the modified gold-plated base needle on the film coating unit plate of the film coater, place the film coating unit plate into the film coater seat, and close the film coater cabin door. Press the start button on the film coater control panel, set to automatically run the film coating process, and it will automatically stop after completion to obtain a reference electrode. In this embodiment, the thickness of the biocompatible film is 23 μm.

[0051] Comparative example: This comparative example provides a method for preparing a common reference electrode, including the following steps: Step 1: Modify a base needle with a silver / silver chloride layer to obtain a modified silver / silver chloride base needle. Specifically: Prepare a silver / silver chloride paste and dilute it with a supporting diluent. The concentration ratio of the diluent is 6%. Modify the silver / silver chloride layer on the surface of the base needle by the film pulling method, and then place it in a blast drying oven at 120 °C for curing for 25 min.

[0052] Step 2: Coat a biocompatible film solution on the surface of the modified silver / silver chloride base needle Prepare a biocompatible solution: Add polyurethane to tetrahydrofuran and control the concentration of polyurethane to be 25 mg / mL.

[0053] Place the biocompatible solution on a magnetic stirrer and stir it in advance for 18 minutes.

[0054] Install the modified silver / silver chloride base needle on the film coating unit plate of the film coater, place the film coating unit plate into the film coater seat, and close the film coater cabin door. Press the start button on the film coater control panel, set to automatically run the film coating process, and it will automatically stop after completion. In this embodiment, the thickness of the biocompatible film is 25 μm.

[0055] Analyze the reference electrodes prepared in Example 1 and the comparative example as follows: The current-time curves during the dynamic blood glucose monitoring process were obtained by assembling the reference electrodes prepared in Example 1 and the comparative example into a dynamic glucose sensor and implanting it subcutaneously. The results are shown in Figure 1 and Figure 2 respectively. Among them, Figure 1 is the current-time curve during the dynamic blood glucose monitoring process obtained by assembling the reference electrode prepared in Example 1 into a dynamic glucose sensor and implanting it subcutaneously, Figure 2 is the current-time curve during the dynamic blood glucose monitoring process obtained by assembling the reference electrode prepared in the comparative example into a dynamic glucose sensor and implanting it subcutaneously.

[0056] It can be seen from the figure that when the sensor composed of the ordinary reference electrode works, the current value shows a gradually decreasing trend. It decreases by 50% on the 12th day, and the performance of the sensor gradually deteriorates. While the sensor composed of the reference electrode in Example 1 only decreases by 12% in 14 days, and a total of 16% after 30 days. This shows that the reference electrode in Example 1 can greatly improve the accuracy and stability of the dynamic glucose sensor.

[0057] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and deformations can still be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a reference electrode for a long-term implantable subcutaneous continuous glucose monitor, characterized in that, It includes the following steps: Gold-plate the surface of the base needle to obtain a gold-plated base needle; Modify a silver / silver chloride layer on the gold-plated base needle to obtain a modified gold-plated base needle; Coat a biocompatible membrane solution on the surface of the modified gold-plated base needle, and a reference electrode is obtained after the biocompatible membrane solution forms a thin film.

2. The preparation method of the reference electrode of the long-term implantable subcutaneous dynamic blood glucose detector according to claim 1, characterized in that, The gold-plating of the surface of the base needle to obtain a gold-plated base needle includes: Use a platinum mesh electrode as the anode and the base needle as the cathode for pre-gold plating to obtain a pre-gold-plated base needle; Stir and wash the pre-gold-plated base needle with ultrapure water and then gold-plate it, and take it out again and stir and wash it with ultrapure water to obtain a gold-plated base needle.

3. The preparation method of the reference electrode of the long-term implantable subcutaneous dynamic blood glucose detector according to claim 2, characterized in that, The plating time of the pre-gold plating does not exceed 5 min, and the plating time range of the gold plating is 25 - 35 min.

4. The preparation method of the reference electrode of the long-term implantable subcutaneous dynamic blood glucose detector according to claim 1, characterized in that, After obtaining the gold-plated base needle, the compactness of the coating of the gold-plated base needle needs to be tested. The testing method includes the following steps: Measure the coating thickness of the gold-plated base needle with a micrometer; Install the gold-plated base needle on the coating unit board and put them together into ultrapure water for ultrasonic cleaning to obtain an ultrasonically cleaned gold-plated base needle; Dry the ultrasonically cleaned gold-plated base needle with the tip facing up at 80 - 100 °C for 3 - 5 min to obtain a dried gold-plated base needle; Conduct an electrochemical test on the dried gold-plated base needle. The electrochemical test includes: using the gold-plated base needle as the anode, in a phosphate buffer solution, test the change of current with time under a constant voltage, and the test time is 10 - 20 min; If the coating thickness of the gold-plated base needle meets the range of 20 - 30 μm and the current in the electrochemical test is lower than 100 nA, then the compactness of the coating of the gold-plated base needle meets the requirements, otherwise use the next base needle to conduct the gold-plating operation again until the compactness of the coating of the gold-plated base needle meets the requirements.

5. The preparation method of the reference electrode of the long-term implantable subcutaneous dynamic blood glucose detector according to claim 1, characterized in that, The components of the biocompatible membrane solution include polyurethane and tetrahydrofuran.

6. The preparation method of the reference electrode of the long-term implantable subcutaneous dynamic blood glucose detector according to claim 1, characterized in that, The thickness of the biocompatible thin film is 20 - 30 μm.

7. A reference electrode for a long-term implantable subcutaneous continuous glucose monitor, characterized in that, It is prepared by the preparation method of the reference electrode of the long-term implantable subcutaneous dynamic blood glucose detector described in any one of claims 1 - 6.

8. A dynamic blood glucose monitor that can be implanted subcutaneously for a long time, characterized in that, It includes a reference electrode, and the reference electrode is the reference electrode prepared by the preparation method of the reference electrode of the long-term implantable subcutaneous dynamic blood glucose detector described in any one of claims 1 - 6 or the reference electrode of the long-term implantable subcutaneous dynamic blood glucose detector described in claim 7.

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