Oxygen supply carbon paste and electrochemical test strip containing same

Abstract

The invention discloses oxygen supply carbon paste which comprises the following components in parts by mass (wt%): 26-52 parts of a solvent, 1-5 parts of graphite powder, 1-5 parts of conductive carbon black, 0.5-3 parts of a surfactant, 5-20 parts of polyester resin and 10-30 parts of an oxygen supply agent, the invention also discloses an electrochemical test strip containing the oxygen supply carbon paste. The method can effectively solve the problem of oxygen deficit in the reaction process, and widens the types of blood samples detected by an oxidase method.

Description

Technical Field

[0001] The invention relates to the technical field of oxidase detection, in particular to an oxygen supplying carbon slurry and an electrochemical test strip containing the same. Background Art

[0002] In recent years, disposable electrochemical test strips prepared by screen printing technology have been widely used in the field of instant detection. For example, an electrochemical sensor for measuring blood sugar levels is manufactured by the following method: a conductive carbon paste is screen-printed on a PET substrate, a reagent including an enzyme, an electron mediator, various stabilizers and a dispersant is added to a working electrode, and the working electrode to which the reagent is added is dried. According to this method, biosensors for total cholesterol, triglycerides, creatinine, etc. can be manufactured. In the production of the above-mentioned sensors, enzymes need to be used as catalysts, especially the use of oxidative enzymes to catalyze the analyte to produce hydrogen peroxide, and then peroxidase is used to catalyze the hydrogen peroxide reaction to produce electrons, and the electrons generated by the reaction are transferred through an electron mediator. When an oxidase is used as a catalyst, oxygen is required in the reaction process. When the analyte content is high, the amount of oxygen in the reaction is insufficient, resulting in attenuation of the current signal at high analyte concentrations, affecting the linear gradient, and thus affecting the measurement range and accuracy of the product. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides oxygen supply carbon slurry and electrochemical test strip containing the same, which can effectively solve the problem of hypoxia in the reaction process and broaden the types of blood samples detected by oxidase method.

[0004] The technical solution provided by the present invention is as follows: An oxygen-supplying carbon slurry comprises the following components: a solvent, graphite powder, conductive carbon black, a surfactant, a polyester resin and an oxygen-supplying agent.

[0005] Preferably, the content of each component by mass fraction (wt%) is as follows: 26-52 parts of solvent, 1-5 parts of graphite powder, 1-5 parts of conductive carbon black, 0.5-3 parts of surfactant, 5-20 parts of polyester resin, and 10-30 parts of oxygen supply agent.

[0006] Preferably, the oxygen supplying agent comprises a compound that can generate hydrogen peroxide or oxygen when in contact with water.

[0007] Preferably, the oxygen supply agent includes one or a combination of sodium persulfate, sodium percarbonate, sodium peroxide, calcium peroxide, zinc peroxide or potassium peroxide.

[0008] Preferably, the solvent includes a ketone solvent and an ester solvent.

[0009] Preferably, the polyester resin includes one or a combination of chloroacetic acid resin, epoxy resin, polyimide resin or phenolic resin.

[0010] An electrochemical test strip comprises a plurality of electrodes, wherein the preparation material of at least one electrode comprises the oxygen-supplying carbon slurry mentioned above.

[0011] Preferably, the plurality of electrodes at least include a working electrode and a reference electrode, and the preparation material of the working electrode includes conductive carbon paste and oxygen-supplying carbon paste.

[0012] Preferably, the working electrode comprises a conductive carbon paste layer and an oxygen supplying carbon paste layer stacked up and down; the conductive carbon paste layer is formed by printing a conductive carbon paste, and the oxygen supplying carbon paste layer is formed by printing an oxygen supplying carbon paste.

[0013] Preferably, the working electrode comprises a conductive carbon paste layer and an oxygen supplying carbon paste layer arranged side by side, the oxygen supplying carbon paste layer is adjacent to at least one side of the conductive carbon paste layer; the conductive carbon paste layer is printed by conductive carbon paste, and the oxygen supplying carbon paste layer is printed by oxygen supplying carbon paste.

[0014] The realization principle of the method for reducing the influence of oxygen partial pressure by the oxygen supply carbon slurry of the present invention is as follows: When the electrochemical method is used to detect physiological indicators in blood, the corresponding oxidase is generally used to produce a redox reaction with the test object, and sufficient oxygen is required to participate in the reaction process of the oxidase. Taking the detection of total cholesterol as an example, the reaction process is as follows: cholesterol ester is hydrolyzed to generate cholesterol under the action of cholesterol esterase, free cholesterol and cholesterol generated by hydrolysis react with oxygen to generate △ 4-cholestenone and hydrogen peroxide under the action of cholesterol oxidase, and hydrogen peroxide reacts with the redox electron mediator to form a current signal under the excitation voltage. The instrument realizes the quantification of cholesterol concentration by detecting the electrical signal. It can be seen from the reaction process that in a channel with a fixed sample volume, when there is an excess of oxygen in the sample blood, cholesterol can fully react, but when the concentration of fixed cholesterol remains unchanged, if the concentration of oxygen in the sample changes, the generated current signal will also change. The following example can be used to illustrate: when fresh venous blood is used to test total cholesterol, the current signal is 100nA, and when the fingertip blood of the same person is collected and tested at the same time, the current signal is 150nA, and the current increases. It can be seen from the literature that the oxygen partial pressure of fresh venous blood is 20-40 mmHg, and the oxygen partial pressure of fingertip blood is 60-70 mmHg. When the oxygen partial pressure of the above fresh venous blood is increased to 60-70 mmHg, the current signal immediately reaches 150 nA, which can explain that the increase in oxygen partial pressure and the increase in dissolved oxygen content in the blood directly lead to changes in the current signal. Ideally, we hope that the current signals under different oxygen partial pressures are consistent, so that the sensor can be used for more types of whole blood samples. However, in this reaction system, the existing technology cannot meet the requirements. In this scheme, the oxygen supply agent is added to the electrode by printing and is separated from the working electrode. When the sample enters the reaction area, the oxygen supply electrode and the working electrode both start to react, and the oxygen produced by the reaction on the oxygen supply electrode will diffuse into the blood. Since the amount of oxygen is sufficient, that is, the oxygen is excessive, and the diffusion time is long enough, there will be sufficient oxygen on the working electrode for cholesterol oxidation reaction, thereby achieving accurate measurement of total cholesterol.

[0015] The present invention has the following advantages over the prior art: The present invention provides oxygen-supplying carbon slurry and manufactures electrochemical test strips from the oxygen-supplying carbon slurry, thereby realizing accurate and rapid measurement of electrochemical test strips involving oxidase, effectively solving the oxygen deficiency problem of oxidase during the electrochemical reaction process, and broadening the types of blood samples detected by the oxidase method. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A schematic diagram of the structure of the electrode structure in an embodiment of the present invention; Figure 2 This is a calibration curve diagram before improvement in an embodiment of the present invention; Figure 3 This is a calibration curve diagram after improvement in an embodiment of the present invention; Figure 4 This is a linear graph of current under different oxygen partial pressures before improvement in an embodiment of the present invention; Figure 5 This is a linear graph of current under different oxygen partial pressures after improvement in an embodiment of the present invention.

[0018] Reference numerals: 1. Injection channel; 2. Conductive carbon slurry layer; 3. Oxygen supply carbon slurry layer; 4. Reference electrode; 5. PET substrate. DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention.

[0020] The embodiment of the present invention provides an oxygen supply carbon slurry, which includes the following components by mass fraction (wt %): 26 to 52 parts of solvent, 1 to 5 parts of graphite powder, 1 to 5 parts of conductive carbon black, 0.5 to 3 parts of surfactant, 5 to 20 parts of polyester resin, and 10 to 30 parts of oxygen supply agent.

[0021] In this embodiment, the oxygen supply agent includes a compound that can generate hydrogen peroxide or oxygen when in contact with water. Specifically, the oxygen supply agent includes one or a combination of sodium persulfate, sodium percarbonate, sodium peroxide, calcium peroxide, zinc peroxide or potassium peroxide.

[0022] In this embodiment, the solvent includes a ketone solvent and an ester solvent.

[0023] In this embodiment, the polyester resin includes one or a combination of chloroacetic acid resin, epoxy resin, polyimide resin or phenolic resin.

[0024] An electrochemical test strip comprises a plurality of electrodes, wherein the preparation material of at least one electrode contains the above-mentioned oxygen-supplying carbon slurry.

[0025] In this embodiment, Figure 1As shown, the multiple electrodes at least include a working electrode and a reference electrode 4, and the preparation material of the working electrode includes a conductive carbon paste and an oxygen supply carbon paste. The working electrode includes a conductive carbon paste layer 2 and an oxygen supply carbon paste layer 3 stacked up and down; the conductive carbon paste layer 2 is printed by conductive carbon paste, and the oxygen supply carbon paste layer 3 is printed by oxygen supply carbon paste; specifically, the oxygen supply carbon paste layer 3 is laid at the bottom, and the conductive carbon paste layer 2 is laid on the upper surface of the oxygen supply carbon paste layer 3, forming a stacked structure, and the laying area of ​​the oxygen supply carbon paste layer 3 is larger than the laying area of ​​the conductive carbon paste layer 2. In other embodiments, the working electrode may also include a conductive carbon paste layer 2 and an oxygen-supplying carbon paste layer 3 arranged side by side, and the oxygen-supplying carbon paste layer 3 is adjacent to at least one side of the conductive carbon paste layer 2; the conductive carbon paste layer 2 is printed by conductive carbon paste, and the oxygen-supplying carbon paste layer is printed by oxygen-supplying carbon paste; specifically, the conductive carbon paste layer 2 is first laid, and then the oxygen-supplying carbon paste layer 3 is laid side by side on at least one side of the conductive carbon paste layer 2, for example, the oxygen-supplying carbon paste layer 3 is laid at one position of the upper side and the lower side of the conductive carbon paste layer 2, or the oxygen-supplying carbon paste layer 3 is laid on both the upper side and the lower side of the conductive carbon paste layer 2, and further, the oxygen-supplying carbon paste layer 3 can be laid on the four upper, lower, left and right sides of the conductive carbon paste layer 2.

[0026] The preparation process of the electrochemical test strip is as follows: S1. Preparation of oxygen supply carbon slurry: Solvent, graphite powder, conductive carbon black, surfactant, polyester resin and oxygen supply agent are fully mixed in a certain proportion, and repeatedly rolled to obtain oxygen supply carbon slurry with uniformity meeting the requirements; S2. Provide a substrate, the substrate material can be PET; S3, screen printing oxygen supply carbon paste and conductive carbon paste on the substrate respectively; S4, screen printing silver / silver oxide paste on the conductive carbon paste screen printed in step S3; S5, screen printing a conductive carbon paste on the oxygen supply carbon paste screen printed in step S3; S6, screen printing insulation ink; S7, dripping enzyme solution on the working electrode in the limited area of ​​insulating ink and drying, the enzyme solution includes buffer, stabilizer, protective agent, oxidase and electron mediator, and the enzyme components are adjusted, increased or decreased according to the test items; S8. Use packaging materials to fit the test strips to form the final electrochemical test strips. The packaging materials include a three-layer structure consisting of a hydrophilic film, a double-sided tape, and a cover film. The cut double-sided tape is pasted on top of the insulating ink according to the shape of the area limited by the insulating ink, so that a three-dimensional channel is formed in the area where the electrode is located. The hydrophilic film is then covered on top of the double-sided tape. The front end of the hydrophilic film is aligned with the PET substrate, and the rear end slightly exceeds the last electrode. The cover film is then pasted on the double-sided tape, and a narrow exhaust gap is formed with the rear end of the hydrophilic film to facilitate the injection of fluid samples from the front end of the hydrophilic film. A complete electrochemical test strip is made in this way, which can be used for different test items according to the different reaction solutions dripped on the working electrode, such as blood glucose, uric acid, cholesterol, triglycerides, blood ketones, lactic acid, creatinine, and ethanol tests.

[0027] The effect verification test of the electrochemical test strip of this embodiment is as follows: (1) The comparison of oxygen content in the test strip before and after adding oxygen supply agent to a specific working electrode is shown in Table 1.

[0028] Table 1 Comparison of oxygen content in the test strip before and after adding oxygen supply agent to a specific working electrode

[0029] From Table 1, we can see that: 1) For the printed working electrode, the electrode area size is designed to be 0.3 cm in length, 0.2 cm in width, and 0.0015 cm in thickness. The calculated volume of the printed carbon paste is 0.00009 cm 3 Generally, the density of conductive carbon paste is between 1.3 and 1.6 g / cm 3 Here, the density of carbon slurry is 1.5 g / cm 3 Calculation: When the content of oxygen supply agent in carbon slurry reaches 10% (the content of active oxygen in oxygen supply agent is 10%), the oxygen content in oxygen supply electrode can be calculated to be 0.00000117g, i.e. 0.00003656mmol; 2) Calculation of oxygen content in blood on working electrode: The design length of working electrode is 0.15cm, width is 0.2cm, and height of injection channel is 0.015cm. At this time, the volume of blood on working electrode is 0.00045 cm 3 , the concentration of oxygen in venous blood is generally around 0.054mmol / L, and the concentration of oxygen in arterial blood is generally around 0.214mmol / L (existing literature is cited here). Based on this, if the sample is venous blood, the amount of oxygen on the working electrode is 0.000000024mmol, and the oxygen content in the oxygen supply agent is 1505 times the oxygen content in the blood at this time; if the sample is arterial blood, the amount of oxygen on the working electrode is 0.000000096mmol, and the oxygen content in the oxygen supply agent is 380 times the oxygen content in the blood at this time. The above theoretical analysis shows that the oxygen supply electrode can provide enough oxygen to participate in the reaction.

[0030] (2) Taking the electrochemical detection of total cholesterol as an example, take one blood sample each of low, medium and high total cholesterol concentrations, and control the oxygen partial pressure of the sample at each concentration at 40 mmHg, 80 mmHg and 200 mmHg respectively for testing. According to the chronoamperometry, collect the current once every 0.1 second, collect the original current signal value continuously for 10 seconds, take the current value at 5 seconds for analysis, take the concentration value tested by the biochemical analyzer as the Y axis, and take the current value of the sample at an oxygen partial pressure of 200 mmHg as the X axis, establish a regression equation, Y=Ax+B, calculate the concentration value of the sample at each oxygen partial pressure based on this regression equation, and calculate the relative deviation of the test value of the sample at each oxygen partial pressure with the biochemical test value as a reference. For details, see the attached Figure 2-5 . By attaching Figure 2-5 From the comparison, it can be seen that the deviation between the test value and the biochemical value at different oxygen partial pressures is significantly reduced after the addition of oxygen supply agent to improve the test results of the test strips, and reaches the deviation level required by the industry.

[0031] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An oxygen supply carbon slurry, characterized in that: The invention comprises the following components: solvent, graphite powder, conductive carbon black, surfactant, polyester resin and oxygen supply agent.

2. The oxygen supply carbon slurry according to claim 1, characterized in that: The content of each component by mass fraction (wt%) is as follows: 26-52 parts of solvent, 1-5 parts of graphite powder, 1-5 parts of conductive carbon black, 0.5-3 parts of surfactant, 5-20 parts of polyester resin, and 10-30 parts of oxygen supply agent.

3. The oxygen supply carbon slurry according to claim 1 or 2, characterized in that: The oxygen supplying agent includes a compound that can generate hydrogen peroxide or oxygen when in contact with water.

4. The oxygen supply carbon slurry according to claim 3, characterized in that: The oxygen supply agent includes one or a combination of sodium persulfate, sodium percarbonate, sodium peroxide, calcium peroxide, zinc peroxide or potassium peroxide.

5. The oxygen supply carbon slurry according to claim 3, characterized in that: The solvent includes ketone solvents and ester solvents.

6. The oxygen supply carbon slurry according to claim 3, characterized in that: The polyester resin includes one or a combination of chloroacetic acid resin, epoxy resin, polyimide resin or phenolic resin.

7. An electrochemical test strip, characterized in that The invention comprises a plurality of electrodes, wherein the preparation material of at least one electrode comprises the oxygen-supplying carbon slurry as claimed in any one of claims 1 to 6.

8. The electrochemical test strip according to claim 7, characterized in that The plurality of electrodes at least include a working electrode and a reference electrode, and the preparation material of the working electrode includes conductive carbon paste and oxygen-supplying carbon paste.

9. The electrochemical test strip according to claim 8, characterized in that The working electrode comprises a conductive carbon paste layer and an oxygen supply carbon paste layer stacked up and down; the conductive carbon paste layer is formed by printing conductive carbon paste, and the oxygen supply carbon paste layer is formed by printing oxygen supply carbon paste.

10. The electrochemical test strip according to claim 8, characterized in that The working electrode comprises a conductive carbon paste layer and an oxygen supply carbon paste layer arranged side by side, wherein the oxygen supply carbon paste layer is adjacent to at least one side of the conductive carbon paste layer; the conductive carbon paste layer is printed by conductive carbon paste, and the oxygen supply carbon paste layer is printed by the oxygen supply carbon paste.

Images