An electrochemical biosensor based on fluorine-doped tin oxide and its construction method and application

Abstract

The present invention provides an electrochemical biosensor based on fluorine-doped tin oxide, as well as its construction method and application. The electrochemical biosensor comprises a working electrode, a reference electrode, and a counter electrode. The working electrode is formed by modifying a conductive substrate with fluorine-doped tin oxide and is also loaded with an oxidase and a cross-linking agent. Hydrogen peroxide, a product of the oxidase-catalyzed reaction, is detected by electroreduction of the fluorine-doped tin oxide. Electrochemical sensors for glucose, uric acid, lactate, sarcosine, and other substances are further constructed. Interference from interfering substances is avoided during detection, resulting in strong detection specificity and high sensitivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical sensors, and in particular relates to an electrochemical biosensor based on fluorine-doped tin oxide, and a construction method and application thereof. Background Art

[0002] Hydrogen peroxide is an important reactive oxygen species. Abnormal concentrations of hydrogen peroxide in cells can indicate a variety of diseases, such as oxidative stress, cancer, and degenerative diseases. In addition, hydrogen peroxide is a product of the reaction between various biochemical markers in organisms and corresponding oxidases. By measuring the concentration of hydrogen peroxide, the concentration of biochemical markers such as glucose, uric acid, lactic acid, and cholesterol can be indirectly indicated, thereby providing effective information for disease diagnosis. Therefore, accurate detection of hydrogen peroxide is of great significance. The measurement of hydrogen peroxide and various biochemical markers using electrochemical sensors has broad application prospects and has become a current research hotspot. Generally, in order to avoid the generation of interfering signals during the detection process by various easily oxidized electroactive substances in the test solution, such as ascorbic acid, dopamine, and acetaminophen, the construction of sensors using the electroreduction reaction of hydrogen peroxide instead of the electrooxidation reaction of hydrogen peroxide has attracted people's attention.

[0003] However, there are several problems with this type of sensor that cannot be ignored. First, currently developed sensors often use precious metals such as platinum and gold as hydrogen peroxide electroreduction catalysts. However, precious metals are also efficient oxygen electroreduction catalysts, and the reduction potential ranges of the two almost overlap. This causes fluctuations in the oxygen concentration in the test liquid to cause fluctuations in the detection signal, affecting the accuracy of hydrogen peroxide detection. Second, precious metals such as platinum and gold have low reserves on Earth and are expensive, which increases the manufacturing cost of sensors. Third, in order to solve the problem of simultaneous reduction of hydrogen peroxide and oxygen, researchers have developed a Prussian blue catalyst. This catalyst does not reduce oxygen at the hydrogen peroxide reduction potential, but its stability is poor, especially when the pH of the test liquid is greater than 6.4, a large amount of hydroxide ions causes the Prussian blue structure to degrade.

[0004] To address these issues, metal oxides have been increasingly designed and developed as electroreduction catalysts. While metal oxides offer the advantages of stability and low cost, their inherent physicochemical properties result in poor electrical conductivity and slow charge transfer during the reaction. To enhance the catalytic activity of metal oxides, researchers typically create a large number of oxygen vacancies within them to improve their conductivity and charge transfer rate. However, metal oxides containing a large number of defects can reduce not only hydrogen peroxide but also oxygen, resulting in poor catalytic selectivity. In CN115266868A, the oxygen vacancies in the metal oxide are regulated to maintain a low concentration of approximately 5%, thereby reducing oxygen adsorption on the metal oxide surface and thereby reducing only hydrogen peroxide but not oxygen. However, this reduced defect concentration in the metal oxide not only reduces its oxygen reduction capacity but also its hydrogen peroxide reduction capacity. Furthermore, regulating the oxygen vacancies in the metal oxide requires either altering the calcination atmosphere or performing secondary modification and modification on the synthesized metal oxide, a complex process with poor controllability. Therefore, developing a catalyst that is simple to synthesize, inexpensive, and reacts only with hydrogen peroxide is of great significance. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides an electrochemical biosensor based on fluorine-doped tin oxide, a construction method and application thereof, and constructs an electrochemical biosensor that can not only avoid the interference of electroactive substances during the electro-oxidation process, but also avoid the interference of oxygen during the electro-reduction process.

[0006] The first object of the present invention is to provide an electrochemical biosensor based on fluorine-doped tin oxide, comprising a working electrode, a reference electrode and a counter electrode; the working electrode is obtained by modifying a conductive substrate with fluorine-doped tin oxide.

[0007] In one embodiment of the present invention, the doping concentration of fluorine atoms in the fluorine-doped tin oxide is 0.01at%-30at%, which may be 0.01at%-15at%, 1at%-15at%, 2at%-15at%, 3at%-15at%, 4at%-15at%, 5at%-15at%, 6at%-15at%, 7at%-15at%, 8at%-15at%, 9at%-15at%, 10at%-15at%, 11at%-15at%, 12at%-15at%, 13at%-15at%, 14at%-15at%, 15at%-30at%, and 0.01at%-10at%. Specifically: 0.01at%, 0.05at%, 1at%, 1.5at%, 2at%, 2.5at%, 3at%, 3.5at%, 4at%, 4.5at%, 5at%, 5.5at%, 6at%, 6.5at%, 7at%, 7.5at%, 8at% , 8.5at%, 9at%, 9.5at%, 10at%, 10.5at%, 11at%, 11.5at%, 12at%, 12.5at%, 13at%, 13.5at%, 14at%, 14.5at%, 15at%, 15.5at%, 16at %, 16at%, 17at%, 17.5at%, 18at%, 18.5at%, 19at%, 19.5at%, 20at%, 20.5at%, 21at%, 21.5at%, 22at%, 22.5at%, 23at%, 23.5at%, 24at%, 24.5at%, 25at%, 25.5at%, 26at%, 26.5at%, 27at%, 27.5at%, 28at%, 28.5at%, 29at%, 29.5at%, 30at% or any concentration value between any two of the values.

[0008] In one embodiment of the present invention, the fluorine-doped tin oxide is prepared by the following method:

[0009] Method 1:

[0010] 1) Add alkaline solution dropwise to the mixed solution of tin source, fluorine source and combustion improver until the solution becomes alkaline, and separate the solid and liquid to obtain fluorine-containing stannous hydroxide after the reaction is completed;

[0011] 2) drying the fluorine-containing stannous hydroxide in step 1);

[0012] 3) grinding the fluorine-containing stannous hydroxide in step 2) and calcining to obtain the fluorine-doped tin oxide;

[0013] In one embodiment of the present invention, in step 1), the alkaline pH is 8-14.

[0014] In one embodiment of the present invention, in step 1), the concentration of the tin source in the mixed solution is 0.01 mol / L-0.2 mol / L.

[0015] In one embodiment of the present invention, in step 1), the concentration of the fluorine source in the mixed solution is 0.001 mol / L-0.06 mol / L.

[0016] In one embodiment of the present invention, in step 1), the fluorine source is selected from one or more of ammonium fluoride, tin fluoride, sodium fluoride and potassium fluoride; the combustion aid is selected from soluble starch and / or cellulose; the alkaline solution is a conventional alkaline solution in the art, and can be selected from one or more of ammonia water, potassium hydroxide, sodium hydroxide, sodium carbonate and potassium carbonate.

[0017] In one embodiment of the present invention, in step 1), the tin source is selected from one or more of stannous fluoride, stannous chloride, stannous pyrophosphate, stannous benzoate, stannous sulfate and stannous oxalate.

[0018] In one embodiment of the present invention, in step 2), the drying temperature is 60° C.-120° C., and the drying time is 12 h-48 h.

[0019] In one embodiment of the present invention, in step 3), the calcination atmosphere is air, the calcination temperature is 400° C.-600° C., and the calcination time is 2 h-12 h.

[0020] Method 2:

[0021] 1) dissolving the tin source in anhydrous ethanol to obtain a clear solution;

[0022] II), adding a fluorine source aqueous solution to the clarified solution in step I), and mixing to obtain a clarified solution;

[0023] III), loading the clarified solution in step II) on a conductive substrate, drying and calcining to obtain the fluorine-doped tin oxide;

[0024] In one embodiment of the present invention, in step I), the concentration of the tin source is 0.05 mol / L-1.0 mol / L.

[0025] In one embodiment of the present invention, in step I), the tin source is selected from one or more of stannous fluoride, stannous chloride, stannous pyrophosphate, stannous benzoate, stannous sulfate and stannous oxalate.

[0026] In one embodiment of the present invention, in step 1), the fluorine source is selected from one or more of ammonium fluoride, tin fluoride, sodium fluoride and potassium fluoride.

[0027] In one embodiment of the present invention, in step II), the concentration of the fluorine source aqueous solution is 0.1 g / mL-1 g / mL.

[0028] In one embodiment of the present invention, in step III), the drying temperature is 40° C.-120° C., the calcination temperature is 300° C.-600° C., and the calcination time is 2 h-12 h.

[0029] In one embodiment of the present invention, the working electrode is further loaded with an oxidase and an enzyme cross-linking agent.

[0030] In one embodiment of the present invention, the oxidase is selected from one or more of glucose oxidase, choline oxidase, sarcosine oxidase, α-glycerophosphate oxidase, cholesterol oxidase, lactate oxidase, bilirubin oxidase, ascorbic acid oxidase, uricase, collagenase, urinary tractase, protease and proteinase.

[0031] In one embodiment of the present invention, the conductive substrate is selected from one or more of glassy carbon electrodes, carbon cloth, carbon paper, graphite, silicon wafers, conductive glass, metals, metal alloys, conductive ceramics and conductive polymers.

[0032] The second object of the present invention is to provide a method for constructing the electrochemical biosensor, comprising the following steps: loading fluorine-doped tin oxide on the surface of a conductive substrate to obtain a working electrode, and assembling the working electrode with a reference electrode and a counter electrode to obtain the electrochemical biosensor.

[0033] In one embodiment of the present invention, the electrochemical biosensor is obtained by modifying the surface of the working electrode with an oxidase and a cross-linking agent, and assembling the working electrode with a reference electrode and a counter electrode.

[0034] In one embodiment of the present invention, the concentration of the oxidase is 2 mg / mL-500 mg / mL.

[0035] In one embodiment of the present invention, the cross-linking agent is one or more of glutaraldehyde, N,N-thiocarbonyldiimidazole, genipin, acetic anhydride, diglycidyl ethyl ether, and methyl suberimidate.

[0036] In one embodiment of the present invention, the mass ratio of the cross-linking agent to water is (1-100): (100:10000).

[0037] In one embodiment of the present invention, the fluorine-doped tin oxide solution further comprises perfluorosulfonic acid resin (Nafion); wherein the mass ratio of the fluorine-doped tin oxide to Nafion is (0.1-2): (100-5000).

[0038] The third object of the present invention is to provide the use of the electrochemical sensor in detecting hydrogen peroxide, glucose, sucrose, lactose, uric acid, creatinine, urea, lactic acid, acetylcholine, ethanol, sarcosine, ascorbic acid, triglycerides or cholesterol.

[0039] The present invention dopes fluorine atoms into tin oxide, making the theoretical overpotential of the rate-determining step of the hydrogen peroxide electroreduction reaction (2*OH→*OH) lower than the rate-determining step of the oxygen electroreduction reaction (*O2→*OOH), thereby making the occurrence of hydrogen peroxide reduction take precedence over oxygen reduction. At the same time, the introduction of fluorine atoms improves the conductivity of tin oxide and reduces the transmission impedance of electrons from hydrogen peroxide to the metal oxide surface. In addition, fluorine atom doping reduces the oxygen vacancy concentration in tin oxide, thereby reducing the adsorption capacity of fluorine-doped tin oxide for oxygen. This enables the fluorine-doped tin oxide to have the reaction selectivity of electroreducing hydrogen peroxide but not reducing oxygen, and is not affected by other interfering substances during the electrooxidation process.

[0040] Based on this, an interference-resistant hydrogen peroxide sensor was constructed. By using the fluorine-doped tin oxide to electroreducibly detect hydrogen peroxide, a product of oxidase-catalyzed reactions, electrochemical sensors for glucose, uric acid, lactate, and sarcosine were further constructed, eliminating interference from interfering substances during the detection process. Furthermore, the preparation method of fluorine-doped tin oxide is simple, and the raw material price is lower than that of currently used precious metals, which helps reduce the production cost of the sensor.

[0041] The above technical solution of the present invention has the following advantages over the prior art:

[0042] 1. The present invention regulates the concentration of fluorine doping in tin oxide so that fluorine-doped tin oxide can electro-reduce hydrogen peroxide without reducing oxygen and interfering substances in the electro-oxidation process, thereby preparing anti-interference sensors for hydrogen peroxide, glucose, lactic acid, uric acid, creatine, etc.

[0043] 2. The raw materials used in the present invention are cheap and the synthesis steps are simple, which reduces the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0045] Figure 1The current-potential curves of the tin oxide in control group 1 and control group 2 and 5at% and 10at% fluorine-doped tin oxide prepared by precipitation method loaded on glassy carbon electrode in different PBS buffer solutions.

[0046] Figure 2 The current-potential curves of the titanium sheet loaded with fluorine-doped tin oxide in different PBS buffer solutions.

[0047] Figure 3 1 is the current-oxygen concentration curve of the hydrogen peroxide sensor described in Example 1 of the present invention in PBS buffer solutions containing different concentrations of oxygen and hydrogen peroxide.

[0048] Figure 4 (a) is the current-concentration curve of the hydrogen peroxide sensor described in Example 1 of the present invention in PBS buffer solutions containing different concentrations of hydrogen peroxide. Figure 4 (b) is a graph showing the anti-interference performance of the hydrogen peroxide sensor described in Example 1 of the present invention in a PBS buffer solution containing hydrogen peroxide.

[0049] Figure 5 (a) is the current-oxygen concentration curve of the hydrogen peroxide sensor described in Example 2 of the present invention in PBS buffer solutions containing different concentrations of oxygen and hydrogen peroxide. Figure 5 (b) is a graph showing the anti-interference performance of the hydrogen peroxide sensor described in Example 2 of the present invention in a PBS buffer solution containing hydrogen peroxide.

[0050] Figure 6 (a) is the current-concentration curve of the glucose sensor in Example 3 of the present invention in PBS buffer solutions containing different concentrations of glucose. Figure 6 Middle (b) is a test diagram of the anti-interference performance of the glucose sensor.

[0051] Figure 7 This is a test diagram of the anti-interference performance of the lactate sensor described in Example 4 of the present invention.

[0052] Figure 8 (a) is the current-concentration curve of the uric acid sensor described in Example 5 of the present invention in PBS buffer solutions containing different concentrations of uric acid, Figure 8 (b) is a test diagram of the anti-interference performance of the uric acid sensor described in Example 5 of the present invention. DETAILED DESCRIPTION

[0053] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0054] Preparation method of fluorine-doped tin oxide used in the present invention:

[0055] 1. The fluorine-doped tin oxide of the present invention is prepared according to the following precipitation method, and the specific steps are as follows:

[0056] 1) Dissolve 0.2 mol / L stannous chloride, 0.05 mol / L ammonium fluoride, and 0.001 mol / L soluble starch in water, and add 15 mL of ammonia water dropwise while stirring the solution until the pH reaches 9.

[0057] 2) After the reaction is completed, centrifuge to obtain fluorine-containing stannous hydroxide solid, and dry the solid product at 80° C. for 12 hours.

[0058] 3) Grinding the product and calcining it to obtain fluorine-doped tin oxide; wherein the calcination atmosphere is air, the calcination temperature is 550° C., and the calcination time is 2 hours.

[0059] 4) By adjusting the concentration of ammonium fluoride in step 1, the fluorine doping concentration in the tin oxide can be controlled. When the concentration of ammonium fluoride is 0.04 mol / L, the fluorine doping amount in the resulting tin oxide is 5 at%; when the concentration of ammonium fluoride is 0.05 mol / L, the fluorine doping amount in the resulting tin oxide is 10 at%.

[0060] 5) The fluorine-doped tin oxides with doping concentrations of 5 at% and 10 at% and the tin oxides of control group 1 and control group 2 were loaded on glassy carbon electrodes using Nafion, respectively. The electrodes were placed in argon-saturated PBS electrolyte, normal PBS electrolyte, and argon-saturated PBS electrolyte containing 1 mM hydrogen peroxide. Cyclic voltammetry tests were performed. The experimental results are shown in Figure 5. Figure 1As shown. The two curves of the tin oxide containing oxygen defects synthesized in control group 1 measured in normal PBS electrolyte and in PBS electrolyte saturated with argon and containing 1mM hydrogen peroxide both show an increase in current compared to the curve measured in PBS electrolyte saturated with argon, indicating that the tin oxide containing a large number of oxygen defects reduces both oxygen and hydrogen peroxide. The curves of the tin dioxide synthesized in control group 2 without oxygen defects measured in normal PBS electrolyte and PBS electrolyte saturated with argon almost overlap, indicating that reducing oxygen defects can effectively reduce the activity of the oxygen reduction reaction. However, the curve measured in PBS electrolyte saturated with argon and containing 1mM hydrogen peroxide has a lower decrease than the curve measured in PBS electrolyte saturated with argon, indicating that the reduction of oxygen defects also significantly reduces the activity of the hydrogen peroxide reduction reaction. Fluorine-doped tin oxide was obtained by doping tin oxide with 5at% and 10at% fluorine atoms. The curve measured in normal PBS electrolyte almost coincided with the curve measured in argon-saturated PBS electrolyte, while the current difference between the curve measured in argon-saturated PBS electrolyte and the curve measured in argon-saturated PBS electrolyte was large, indicating that the ability of fluorine-doped tin oxide to reduce oxygen weakened with increasing fluorine concentration, while the ability to reduce hydrogen peroxide increased.

[0061] Figure 1 The above results show that the introduction of fluorine atoms in fluorine-doped tin oxide can change the reduction performance of oxygen and hydrogen peroxide. Fluorine atom doping affects the theoretical overpotential of the reaction of tin oxide with hydrogen peroxide and oxygen, the charge transfer performance and the adsorption performance of oxygen on the surface of tin oxide, which can achieve specific reaction with hydrogen peroxide and avoid oxygen reaction.

[0062] 2. The fluorine-doped tin oxide used in the present invention is prepared according to the following immersion and pulling method, and the specific steps are as follows:

[0063] 1) Dissolve 0.5 mol / L stannous chloride in anhydrous ethanol to obtain a clear solution;

[0064] 2) Add 20 μL of 1 g / mL ammonium fluoride aqueous solution to the above 5 mL clear solution and mix to obtain a clear solution;

[0065] 3) The clarified solution in step 2) is loaded onto a conductive substrate by an immersion puller and dried in an oven at 100° C. for 10 minutes;

[0066] 4) calcining the conductive substrate loaded with the solution to obtain a conductive substrate loaded with fluorine-doped tin oxide; wherein the calcination atmosphere is air, the calcination temperature is 400° C., and the calcination time is 4 hours;

[0067] 5) By adjusting the amount of ammonium fluoride aqueous solution added in step 2), the fluorine atom doping concentration in the tin oxide can be controlled. When the concentration of the ammonium fluoride aqueous solution is 1 g / mL and the volume is 20 μL, the resulting fluorine-doped tin oxide has an appropriate concentration of fluorine atoms.

[0068] 6) The conductive substrate loaded with fluorine-doped tin oxide was used as a working electrode and placed in argon-saturated PBS electrolyte, normal PBS electrolyte, and argon-saturated PBS electrolyte containing 1 mM hydrogen peroxide, and cyclic voltammetry was performed. The experimental results are as follows: Figure 2 The curves measured in argon-saturated PBS electrolyte and normal PBS electrolyte overlap, while the current of the curve measured in argon-saturated PBS electrolyte containing 1 mM hydrogen peroxide increases, indicating that the iron oxide does not reduce oxygen but reduces hydrogen peroxide.

[0069] Control group 1:

[0070] 1) Add ammonia alkaline solution dropwise to a mixed solution of 0.2 mol / L stannous chloride and 0.001 mol / L soluble starch combustion aid until the pH is 9. After the reaction is completed, solid-liquid separation is performed to obtain stannous hydroxide;

[0071] 2) Drying the stannous hydroxide in step 1) at 80° C. for 12 h;

[0072] 3) grinding the stannous hydroxide in step 2) and calcining it at 450° C. for 2 h in an argon atmosphere to obtain the tin oxide containing oxygen vacancies;

[0073] Control group 2:

[0074] 1) Add an alkaline ammonia solution dropwise to a mixed solution of 0.2 mol / L tin chloride and 0.001 mol / L soluble starch combustion aid until the pH reaches 9. After the reaction is completed, solid-liquid separation is performed to obtain tin hydroxide;

[0075] 2) Drying the tin hydroxide in step 1) at 80° C. for 12 hours;

[0076] 3) Grinding step 2) calcining the tin hydroxide at 600° C. in an oxygen atmosphere for 2 hours to obtain the tin dioxide free of oxygen vacancies.

[0077] Example 1

[0078] This embodiment provides a hydrogen peroxide sensor and a construction method thereof, as follows:

[0079] 1) Dispersing 10 at% fluorine-doped tin oxide in a perfluorosulfonic acid resin (Nafion) aqueous solution, dropping the solution onto the surface of a glassy carbon electrode, and leaving it to dry at 25°C for 1 hour to obtain a 10 at% fluorine-doped tin oxide-modified glassy carbon electrode; wherein the mass ratio of 10 at% fluorine-doped tin oxide to the Nafion aqueous solution is 2.5:1000, and the volume ratio of the solution to water is 1:99.

[0080] 2) The dried glassy carbon electrode is used as a working electrode and assembled with a reference electrode and a counter electrode to obtain a hydrogen peroxide sensor.

[0081] 3) The hydrogen peroxide sensor was placed in PBS electrolyte, PBS electrolyte containing 0.1 mM hydrogen peroxide, and PBS electrolyte containing 1.0 mM hydrogen peroxide, respectively. The dissolved oxygen concentration in the electrolyte was changed (by passing argon gas into the solution to reduce the oxygen concentration in the solution, and passing oxygen gas into the solution to increase the oxygen concentration in the solution). Constant potential electrochemical testing was performed at a potential of -0.25 V. The experimental results are shown in FIG. Figure 3 As shown, the sensor detection current does not change, indicating that the sensor has the performance of resisting oxygen interference and can accurately detect hydrogen peroxide when the oxygen concentration fluctuates.

[0082] 4) The hydrogen peroxide sensor described in step 2) was placed in PBS electrolyte containing 0mM, 1mM, 3mM, 5mM, 7mM, 10mM, 15mM, 20mM, 25mM, 30mM, 40mM, and 50mM hydrogen peroxide, respectively, and a constant potential electrochemical test was performed at a potential of -0.25V. The experimental results are shown in FIG. Figure 4 As shown in (a), the current gradually increases with the increase of hydrogen peroxide concentration. The linear range of hydrogen peroxide detection is 0-10mM.

[0083] 5) Place the hydrogen peroxide sensor described in step 2) in PBS electrolyte, and add 0.5mM hydrogen peroxide and 0.5mM common electroactive interfering substances, including lactic acid, choline, ascorbic acid, urea, dopamine, acetaminophen, L-cysteine, salicylic acid, ethanol and glucose in sequence. The experimental results are as follows Figure 4 As shown in (b), current was generated after the addition of hydrogen peroxide, but no current was generated after the addition of interfering substances, indicating that the sensor has the ability to resist interference from interfering substances during the electro-oxidation process.

[0084] Example 2

[0085] This embodiment provides a hydrogen peroxide sensor and a construction method thereof, as follows:

[0086] 1) Dissolve 0.5 mol / L stannous fluoride in anhydrous ethanol, add 1 g / mL, 20 μL of ammonium fluoride aqueous solution to obtain a clear solution, and use an immersion puller to load the above solution on the surface of the titanium sheet, and dry it in an oven at 100°C for 10 minutes;

[0087] 2) calcining the titanium sheet loaded with the solution to obtain a titanium sheet loaded with fluorine-doped oxide; wherein the calcination atmosphere is air, the calcination temperature is 400° C., and the calcination time is 4 hours;

[0088] 3) Using a titanium sheet loaded with fluorine-doped oxide as a working electrode, and assembling it with a reference electrode and a counter electrode to obtain a hydrogen peroxide sensor;

[0089] 4) The hydrogen peroxide sensor described in step 3) was placed in PBS electrolyte and PBS electrolyte containing 1.0 mM hydrogen peroxide, respectively, and the concentration of dissolved oxygen in the electrolyte was changed, and a constant potential electrochemical test was performed at a potential of -0.25 V. The experimental results are shown in FIG. Figure 5 As shown in (a), the detection current remains constant with the increase of oxygen concentration, indicating that the hydrogen peroxide sensor is not disturbed by fluctuations in oxygen concentration.

[0090] 5) Place the hydrogen peroxide sensor described in step 3) in PBS electrolyte, and add 0.5mM hydrogen peroxide and 0.5mM common electroactive interfering substances, including methanol, ethanol, galactose, ascorbic acid, sucrose, acetaminophen, citric acid, lactic acid, dopamine and urea. The experimental results are as follows Figure 5 As shown in (b), current was generated after the addition of hydrogen peroxide, but no current was generated after the addition of interfering substances, indicating that the sensor has the ability to resist interference from interfering substances during the electro-oxidation process.

[0091] Example 3

[0092] This embodiment provides a glucose sensor and a method for constructing the same, as follows:

[0093] 1) Dissolve 0.2 mol / L stannous chloride in anhydrous ethanol, add 1 g / mL, 20 μL of ammonium fluoride aqueous solution to obtain a clear solution, and use an immersion puller to load the above solution on the surface of the titanium sheet, and dry it in an oven at 100°C for 10 minutes;

[0094] 2) calcining the titanium sheet loaded with the solution to obtain a titanium sheet loaded with fluorine-doped oxide; wherein the calcination atmosphere is air, the calcination temperature is 400° C., and the calcination time is 4 hours;

[0095] 3) Mixing the glucose oxidase solution with the chitosan solution and the glutaraldehyde solution, adding the mixture dropwise to the surface of the titanium sheet modified with fluorine-doped tin oxide in step 2), leaving the mixture to dry at 25° C. for 1 hour, and then assembling the mixture with the reference electrode and the counter electrode to obtain a glucose sensor; wherein the concentration of glucose oxidase is 20 mg / ml, the concentration of chitosan is 5 mg / ml, and the volume ratio of the glutaraldehyde solution to the aqueous solution is 1:100.

[0096] 4) The glucose sensor described in step 3) was placed in PBS electrolyte containing 0mM, 0.1mM, 0.2mM, 0.3mM, 0.5mM, 0.7mM, and 1.0mM glucose, respectively, and a constant potential electrochemical test was performed at a potential of -0.25V. The experimental results are shown in FIG. Figure 6 As shown in (a), the current gradually increases with the increase of glucose concentration. The linear range of glucose detection is 0-0.5mM.

[0097] 5) Place the glucose sensor described in step 3) in PBS electrolyte, and add 0.2mM glucose and 0.2mM common electroactive interfering substances, including galactose, acetaminophen, ethanol, ascorbic acid, methanol, sucrose, dopamine, lactic acid, and urea. The experimental results are as follows: Figure 6 As shown in (b), current was generated after the addition of glucose, but no current was generated after the addition of interfering substances, indicating that the sensor has the ability to resist interference from interfering substances during the electro-oxidation process.

[0098] Example 4

[0099] This embodiment provides a lactate sensor and a method for constructing the same, as follows:

[0100] 1) Dispersing 10 at% fluorine-doped tin oxide in a perfluorosulfonic acid resin (Nafion) aqueous solution, dropping the solution onto the surface of a glassy carbon electrode, and leaving it to dry at 25°C for 1 hour to obtain a fluorine-doped tin oxide-modified glassy carbon electrode; wherein the mass ratio of fluorine-doped tin oxide to perfluorosulfonic acid resin aqueous solution is 2.5:1000, and the volume ratio of Nafion solution to water is 1:100.

[0101] 2) Mixing the lactate oxidase solution with the chitosan solution and the glutaraldehyde solution, adding the solution dropwise to the surface of the fluorine-doped tin oxide-modified glassy carbon electrode described in step 1), leaving it at 25° C. for 1 hour to dry, and then assembling it with the reference electrode and the counter electrode to obtain a lactate sensor; wherein the concentration of lactate oxidase is 10 mg / ml, the concentration of chitosan is 5 mg / ml, and the volume ratio of the glutaraldehyde solution to the aqueous solution is 1:100.

[0102] 3) Place the lactate sensor described in step 2) in PBS electrolyte, and add 0.5mM lactic acid and 0.5mM common electroactive interfering substances, including methanol, ethanol, mannose, urea, ascorbic acid, uric acid, sucrose, acetaminophen, xylose, citric acid, dopamine and glucose in sequence. The experimental results are as follows Figure 7 As shown in the figure, current was generated after adding lactic acid, but no current was generated after adding interfering substances, indicating that the sensor has the ability to resist interference from interfering substances during the electro-oxidation process.

[0103] Example 5

[0104] This embodiment provides a uric acid sensor and a construction method thereof, as follows:

[0105] 1) Dispersing 10 at% fluorine-doped tin oxide in a Nafion aqueous solution, dropping it onto the surface of a glassy carbon electrode, and leaving it to dry at 25°C for 1 hour to obtain a fluorine-doped tin oxide-modified glassy carbon electrode; wherein the mass ratio of fluorine-doped tin oxide to perfluorosulfonic acid resin aqueous solution is 2.5:1000, and the volume ratio of Nafion solution to water is 1:100.

[0106] 2) Mixing a uricase solution with a bovine serum albumin solution and a glutaraldehyde solution, adding the mixture dropwise to the surface of the fluorine-doped tin oxide-modified glassy carbon electrode described in step 1), leaving the mixture at 25° C. for 1 hour to dry, and then assembling the mixture with a reference electrode and a counter electrode to obtain a uric acid sensor; wherein the concentration of uricase is 10 mg / ml, the mass ratio of bovine serum albumin to water is 1:9, and the volume ratio of the glutaraldehyde solution to the aqueous solution is 1:20.

[0107] 3) Place the uric acid sensor described in step 2) in PBS electrolyte and perform a constant potential electrochemical test at a potential of -0.25 V. Then, add uric acid solution to the electrolyte to make the uric acid concentration in the electrolyte 0.1mM, 0.2mM, 0.4mM, 0.6mM, and 0.8mM. The experimental results are as follows Figure 8 As shown in (a), the current gradually increases with the increase of uric acid concentration. The linear range of uric acid detection is 0-0.6mM.

[0108] 4) Place the uric acid sensor described in step 2) in PBS electrolyte, and add 0.3mM uric acid and 0.3mM common electroactive interfering substances, including ascorbic acid, urea, ethanol, acetic acid, potassium oxalate, lactic acid, sucrose, mannose, acetaminophen, dopamine, citric acid, sarcosine, glucose and choline in sequence. The experimental results are as follows Figure 8 As shown in (b), current was generated after the addition of uric acid, but no current was generated after the addition of interfering substances, indicating that the sensor has the ability to resist interference from interfering substances during the electro-oxidation process.

[0109] Example 6

[0110] This embodiment provides a sarcosine sensor and a construction method thereof, as follows:

[0111] 1) Dispersing 10 at% fluorine-doped tin oxide in a Nafion aqueous solution, dropping it onto the surface of a glassy carbon electrode, and leaving it to dry at 25°C for 1 hour to obtain a fluorine-doped tin oxide-modified glassy carbon electrode; wherein the mass ratio of fluorine-doped tin oxide to perfluorosulfonic acid resin aqueous solution is 2.5:1000, and the volume ratio of Nafion solution to water is 1:100.

[0112] 2) Mixing the sarcosine oxidase solution and the glutaraldehyde solution, adding the mixture dropwise to the surface of the fluorine-doped tin oxide-modified glassy carbon electrode described in step 1), leaving the mixture at 25° C. for 1 hour to dry, and then assembling the mixture with a reference electrode and a counter electrode to obtain a sarcosine sensor; wherein the concentration of the sarcosine oxidase is 10 mg / ml, and the volume ratio of the glutaraldehyde solution to the aqueous solution is 1:99.

[0113] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. An electrochemical biosensor based on fluorine-doped tin oxide, characterized in that: The invention comprises a working electrode, a reference electrode and a counter electrode; the working electrode is obtained by modifying a conductive substrate with fluorine-doped tin oxide; the doping concentration of fluorine atoms in the fluorine-doped tin oxide is 0.01at%-30at%.

2. The electrochemical biosensor according to claim 1, wherein The working electrode is also loaded with an oxidase and a cross-linking agent.

3. The electrochemical biosensor according to claim 2, characterized in that The oxidase is selected from one or more of glucose oxidase, ascorbic acid oxidase, choline oxidase, sarcosine oxidase, α-glycerophosphate oxidase, cholesterol oxidase, lactate oxidase, bilirubin oxidase, ascorbic acid oxidase, uricase, collagenase, urinary tractase, protease and proteinase.

4. The electrochemical biosensor according to claim 1, wherein The conductive substrate is selected from one or more of glassy carbon electrodes, carbon cloth, carbon paper, graphite, silicon wafers, conductive glass, metals, metal alloys, conductive ceramics and conductive high polymers.

5. The method for constructing the electrochemical biosensor according to any one of claims 1 to 4, characterized in that: The following steps are involved: Fluorine-doped tin oxide is loaded on the surface of a conductive substrate to obtain a working electrode, which is assembled with a reference electrode and a counter electrode to obtain the electrochemical sensor.

6. The construction method according to claim 5, characterized in that: The method also includes modifying the surface of the working electrode with an oxidase and a cross-linking agent, and assembling the surface of the working electrode with a reference electrode and a counter electrode to obtain the electrochemical sensor.

7. Use of the electrochemical biosensor according to any one of claims 1 to 4 in detecting hydrogen peroxide, glucose, sucrose, lactose, uric acid, creatinine, urea, lactic acid, acetylcholine, ethanol, sarcosine, ascorbic acid, triglyceride or cholesterol.

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