An electrochemical sensing electrode with detection and anti-biofouling functions, and a preparation method and application thereof

Abstract

The application belongs to the technical field of electrochemical sensing, and particularly relates to an electrochemical sensing electrode with detection and anti-biofouling functions, a preparation method and application thereof. The electrochemical sensing electrode comprises a conductive substrate and a MOF-919 material loaded on the conductive substrate, and function mode switching is realized through external potential regulation. In the detection mode, a first working voltage is applied for nitrite oxidation detection; and a second working voltage is applied to release nitric oxide in situ by reducing nitrite to inhibit microbial adhesion on the electrode surface. The application does not need to additionally set an independent antibacterial layer or add an antibacterial agent, realizes the interface anti-microbial adhesion function while maintaining good electrochemical response performance of the electrode, and significantly improves the stability of long-term use in complex samples. The application provides a new technical path for anti-pollution design of an electrochemical sensing interface.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical sensing technology, and relates to an electrochemical sensing electrode that has both detection and anti-biocontamination functions, its preparation method, and its application. Background Technology

[0002] Nitrite is a key intermediate in the nitrogen cycle and is widely present in the natural environment and organisms. Due to its chemical reactivity and the dual nature of its functionality and potential hazards in various scenarios, nitrite has significant research value and practical implications in multiple fields, including environmental monitoring, food safety, and physiological medicine. Electrochemical sensing, with its advantages of ease of operation, rapid response, high sensitivity, miniaturization, and online monitoring, has become one of the important technical means for nitrite detection. This technology achieves quantitative analysis of nitrite concentration by detecting the electrical signals generated when a target substance undergoes a redox reaction on an electrode surface. The electrode material and its surface interface properties are key factors determining the sensor's detection performance. Functional modification of the electrode surface can effectively improve electron transfer rates, enhance electrocatalytic activity, and improve detection selectivity and sensitivity.

[0003] Compared to existing electrochemical sensing systems based on MOF-derived materials, such as metal / carbon composites prepared by pyrolysis of MOF materials (e.g., Cu@C@ZIF-8), the original MOF structure is destroyed during the preparation process. The activity mainly comes from the metal nanoparticles or carbon-based conductive framework formed after pyrolysis, resulting in relatively limited functionality, primarily used for electrochemical detection. Nitrite electrochemical sensors based on natural biological enzymes (e.g., nitrate reductase) have attracted widespread attention. These sensors utilize the high specificity of enzymes for substrate catalysis, exhibiting good selectivity. However, natural biological enzymes generally suffer from poor stability, sensitivity to temperature and pH, complex immobilization processes, and high costs. They are particularly prone to inactivation in complex non-physiological systems such as wastewater and high-salt samples, making them unsuitable for long-term, on-site detection applications.

[0004] To overcome the limitations of natural enzymes, nanomaterials with enzyme-like catalytic activity have been widely used to construct non-enzymatic nitrite electrochemical sensing electrodes. Although noble metal-based nanomaterials exhibit high catalytic activity, their high cost and limited resources restrict their large-scale application. Therefore, developing low-cost, highly active, and long-term suitable non-noble metal electrochemical sensing materials remains an important research direction in this field.

[0005] However, existing nitrite electrochemical sensing electrodes still face a prominent problem in practical applications: when used for extended periods in complex media such as wastewater, groundwater, food extracts, and biological fluids, microbial adhesion and biofilm formation easily occur on the electrode surface. This biofilm not only hinders the diffusion of nitrite to the electrode surface but also increases charge transfer impedance, leading to signal attenuation, decreased sensitivity, and even sensor malfunction. Existing anti-biocontamination strategies, such as constructing physical barrier coatings or adding antibacterial agents, often struggle to simultaneously address both the electrode surface's anti-contamination capabilities and electrochemical sensing performance: the former may impede electron transfer and target diffusion, while the latter may cause problems such as biotoxicity, uncontrolled release, or secondary pollution. Summary of the Invention

[0006] This invention provides an electrochemical sensing electrode that combines detection and anti-biocontamination functions, along with its preparation method and application, to solve the problems of poor stability of natural enzymes and the susceptibility of non-enzymatic electrodes to microbial contamination during long-term use, which leads to performance degradation.

[0007] Based on the above technical problems, the present invention provides the following technical solution: In a first aspect, the present invention provides an electrochemical sensing electrode that combines detection and anti-biocontamination functions, comprising a conductive substrate and a MOF-919 material loaded on the conductive substrate; The electrochemical sensing electrode has a switchable dual-function operating mode under the control of an applied potential: in the detection mode, a first operating voltage is applied to catalyze the electrochemical oxidation reaction of nitrite through the MOF-919 material to generate a current response signal related to the nitrite concentration; in the antibacterial mode, a second operating voltage is applied to catalyze the electrochemical reduction reaction of nitrite through the MOF-919 material to generate nitric oxide in situ and inhibit the adhesion of microorganisms on the electrode surface.

[0008] In some specific embodiments of the present invention, the conductive substrate is selected from one of glassy carbon electrode, carbon cloth electrode and screen-printed electrode; the MOF-919 material is loaded by one of drop coating, spray coating and electrodeposition.

[0009] Secondly, the present invention provides a method for preparing an electrochemical sensing electrode, comprising the following steps: dispersing MOF-919 material in a solvent containing a conductive polymer to form a dispersion; loading the dispersion onto a conductive substrate and drying it to obtain the electrochemical sensing electrode.

[0010] Thirdly, the present invention provides an electrochemical sensor, including the electrochemical sensing electrode, a counter electrode and a reference electrode; wherein the electrochemical sensing electrode is a working electrode.

[0011] Fourthly, the present invention provides the application of the electrochemical sensor prepared by the above method in the electrochemical detection of nitrite in samples, realizing the quantitative detection of nitrite in complex samples under the first working voltage, and maintaining a stable electrochemical response during long-term use.

[0012] Fifthly, the present invention provides the application of the electrochemical sensor prepared by the above method in inhibiting the adhesion of microorganisms on the electrode surface, wherein nitric oxide is generated in situ under the second working voltage to inhibit bacterial adhesion and biofilm formation.

[0013] In a sixth aspect, the present invention provides a method for detecting nitrite in a sample, comprising the following steps: placing the electrochemical sensor in the sample to be tested; applying a first operating voltage to the electrochemical sensing electrode in the detection mode; detecting the current response signal generated by the electrochemical sensing electrode; and determining the concentration of nitrite in the sample to be tested based on the current response signal.

[0014] In some specific embodiments of the present invention, the first working voltage ranges from 0.8V to 1.3V, and the sample to be tested is selected from wastewater, groundwater, food extract, or biological fluid.

[0015] In a seventh aspect, the present invention provides a method for inhibiting the adhesion of microorganisms on the electrode surface, wherein the electrochemical sensor is placed in a sample to be tested, and in the antibacterial mode, a second operating voltage is applied to the electrochemical sensing electrode to inhibit the adhesion of microorganisms on the electrode surface.

[0016] In some specific embodiments of the present invention, the range of the second operating voltage is -0.9V to -1.4V; the microorganisms include one or more of Escherichia coli, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus.

[0017] Compared with the prior art, the beneficial effects of the present invention include at least the following: This invention constructs an electrochemical sensing electrode that combines nitrite detection and antimicrobial adhesion capabilities by loading MOF-919 material onto a conductive substrate. This electrode can detect nitrite and generate nitric oxide in situ through electrocatalytic nitrite reduction, thereby inhibiting microbial adhesion to the electrode surface and improving the electrode's anticontamination ability and long-term detection stability in complex samples. Compared with existing natural enzyme-based nitrite sensing systems, this invention eliminates the need to introduce natural enzymes, avoiding problems such as poor stability, easy inactivation, and complex immobilization processes associated with natural enzymes. Compared with existing physical coatings or external antimicrobial agents, this invention eliminates the need for an additional independent antimicrobial layer or additional antimicrobial agents, transforming the nitric oxide product of electrocatalytic nitrite reduction from a traditional exogenous antimicrobial factor into a potential-regulated, in-situ generated signal molecule at the interface, thus achieving controllable and integrated anticontamination function. It achieves synergistic unity of detection and anticontamination functions on the same electrode interface, maintaining good electrochemical response performance while realizing interfacial antimicrobial adhesion. The electrochemical sensor constructed based on this electrode is simple to prepare and suitable for the detection of nitrite in samples such as wastewater, groundwater, food extracts, and biological fluids, showing promising application prospects. This invention provides a new approach to electrochemical sensing interface design by achieving functional switching based on potential modulation. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a SEM image of the MOF-919 material of this invention; Figure 2 Experimental and simulated XRD patterns of the MOF-919 material of this invention; Figure 3 This is the N2 adsorption isotherm of the MOF-919 material of this invention at 77K; Figure 4 Different metal clusters and NO2 in the MOF-919 material of this invention Adsorption energy between them; Figure 5 This invention relates to MOF-919 / GCE at different NO2 concentrations. CV curve in the image; Figure 6 To illustrate this invention, different concentrations of NO2 were injected at 1.0V. Current-time response of MOF-919 / GCE; Figure 7 The steady-state current value of MOF-919 / GCE in this invention and NO2 Linear curve fitting of concentration; Figure 8 The present invention is MOF-919 / GCE containing 0~50 mM NO2. Concentration-dependent CV curves in PBS; Figure 9 This invention relates to the fluorescence spectra of electrolytes after different treatments; Figure 10 The present invention relates to MOF-919 / GCE, which involves adding 100 µL of saliva sample and NO2 to 10 mL of PBS solution. The it curve; Figure 11 This invention measures NO2 in real saliva samples from human volunteers. The content; Figure 12 These are digital photographs of the bacteria remaining on agar plates after different treatments according to the present invention. Figure 13 This is a statistical histogram of the remaining bacteria on agar plates after different treatments according to the present invention; Figure 14 The present invention is MOF-919 / GCE containing 50 mM NO2. PBS 3D CLSM images of stained biofilms treated with 1.2V. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] Metal-organic frameworks (MOFs) are porous crystalline organic-inorganic hybrid materials formed by the self-assembly of metal ions or metal clusters with organic ligands through coordination interactions. MOFs possess advantages such as high specific surface area, regular pore structure, tunable pore size, and abundant active sites. By rationally selecting metal nodes and organic ligands, precise control over the catalytic active centers, electronic structure, and microreaction environment of the material can be achieved, thereby constructing enzyme-mimicking active structures and endowing the material with excellent electrocatalytic performance. In complex media, microorganisms easily adhere to the electrode surface and form biofilms, which can block active sites on the electrode surface, affect the diffusion of target substances to the electrode interface, increase interfacial impedance, and lead to sensor signal attenuation, decreased sensitivity, and even functional failure. Therefore, constructing an electrochemical sensing interface that combines detection function and antimicrobial adhesion capability is of great significance for improving the long-term stability of electrodes in complex samples.

[0022] In this invention, the term MOF-919 / GCE represents an electrochemical sensing electrode obtained by loading MOF-919 onto a glassy carbon electrode; glassy carbon electrode (GCE); PEDOT:PSS is an aqueous dispersion composed of conductive PEDOT (poly(3,4-ethylenedioxythiophene)) and soluble PSS (poly(styrene sulfonate)). The PEDOT molecular chains themselves possess a conjugated structure, allowing charge (holes) to jump and transfer along the molecular chains and between different chains, thus serving as a conductive aid and binder component to improve the film-forming properties and conductivity of materials on conductive substrates.

[0023] Electrochemical sensing electrode with both detection and anti-biocontamination functions The electrochemical sensing electrode includes a conductive substrate and MOF-919 material loaded on the conductive substrate.

[0024] The electrochemical sensing electrode has a switchable dual-function operating mode under the control of an applied potential: in the detection mode, a first working voltage is applied to detect the nitrite concentration through the MOF-919 material; in the antibacterial mode, a second working voltage is applied to reduce nitrite through the MOF-919 material to release nitric oxide and inhibit the adhesion of microorganisms on the electrode surface.

[0025] In some specific embodiments of the present invention, the conductive substrate is selected from glassy carbon electrode, carbon cloth electrode, and screen-printed electrode. More specifically, when the conductive substrate is a glassy carbon electrode, a certain volume of the dispersion can be drop-coated onto the GCE surface to form MOF-919 / GCE. The same method is also applicable to carbon cloth electrode and screen-printed electrode.

[0026] In some specific embodiments of the present invention, the MOF-919 material is loaded onto the surface of the conductive substrate by one of the following methods: drop coating, spray coating, or electrodeposition.

[0027] Preparation method of MOF-919 material MOF-919 material can be prepared using the following methods: S1: Iron chloride (FeCl3·6H2O), copper nitrate [Cu(NO3)2·3H2O] and 1H-pyrazole-4-carboxylic acid (H2PyC) are dissolved in N,N-dimethylformamide (DMF) and then ultrasonically mixed to ensure homogeneity. S2: The resulting mixture was subjected to a solvothermal reaction to synthesize MOF-919 material, and after cooling to room temperature, a green solid was obtained; S3: The green solid is dried to obtain MOF-919 material.

[0028] Further, in step S1, the amount of FeCl3·6H2O is 30~55 mg, the amount of Cu(NO3)2·3H2O is 100~170 mg, the amount of H2PyC is 50~75 mg, and the volume of DMF is 15~40 mL.

[0029] Further, in step S2, the reaction temperature is 100~150℃, the reaction time is 12~18 h, and the reaction vessel is a Pyrex flask.

[0030] Further, in step S3, the drying temperature is 130~180℃ and the drying time is 12~24 h.

[0031] Preparation method of electrochemical sensing electrode with both detection and anti-biocontamination functions The method for preparing an electrochemical sensing electrode includes the following steps: The above MOF-919 material was dispersed in a solvent containing a conductive polymer to form a dispersion. The dispersion was loaded onto the surface of a conductive substrate and dried to obtain the electrochemical sensing electrode.

[0032] In some specific embodiments of the present invention, the conductive polymer is PEDOT:PSS added at a low concentration of 0.11%, which acts as a conductive binder to form a composite film with MOF-919, significantly improving the conductivity and stability of the electrode, thereby optimizing the electrochemical detection performance of nitrite.

[0033] In some specific embodiments of the present invention, the dispersion can be loaded onto a conductive substrate by drop coating, spraying or electrodeposition.

[0034] Electrochemical sensors The electrochemical sensor includes the aforementioned electrochemical sensing electrode, counter electrode, and reference electrode. The electrochemical sensing electrode serves as the working electrode; the counter electrode is a carbon cloth electrode or a platinum wire electrode; and the reference electrode is obtained by depositing Ag and AgCl on the surface of the carbon cloth electrode or platinum wire electrode.

[0035] In some specific embodiments of the present invention, the electrochemical sensor is configured as a three-electrode system for detecting nitrite in a sample, and the electrode surface is protected against microbial adhesion by generating nitric oxide in situ.

[0036] Application of electrochemical sensors in the electrochemical detection of nitrite in samples Electrochemical sensors can be used for the detection of nitrite in samples. The electrochemical sensing electrode of this invention is effective for nitrite (NO2) ions. It showed 132.8 μAcm -2 mM -1 It exhibits high sensitivity and maintains excellent linearity over a wide concentration range from 0.1 μM to 84.4 mM. In practical applications, its detection results on human saliva samples are highly consistent with commercial kits, and it maintains a response stability of over 93.4% after 30 days, demonstrating its reliable quantitative detection capability. When an operating voltage (-1.2 V) is applied, this electrochemical detection electrode can utilize NO2... In-situ electrocatalytic generation of nitric oxide (NO). The generated NO exhibits antibacterial effects, with a bacterial sterilization rate of nearly 100%, and can effectively eradicate existing bacterial biofilms.

[0037] In some specific embodiments of the present invention, the electrochemical sensing electrode of the present invention exhibits high sensitivity and a wide linear detection range for nitrite. In actual sample detection, it shows high consistency with commercial kits and maintains good response stability even after long-term storage, indicating its excellent quantitative detection capability and application potential.

[0038] Application of electrochemical sensors in inhibiting microbial adhesion on electrode surfaces Electrochemical sensors can be used to inhibit the adhesion of microorganisms to the electrode surface. The generated NO exhibits antibacterial effects, with a bacterial sterilization rate of nearly 100%, and can effectively eradicate existing bacterial biofilms.

[0039] In some specific embodiments of the present invention, the microorganisms include one or more of Escherichia coli, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus.

[0040] Methods for detecting nitrite in samples The method for detecting nitrite in a sample includes the following steps: Place the electrochemical sensor in the sample to be tested; In the detection mode, a first operating voltage is applied to the electrochemical sensing electrode, and the current response signal generated by the electrochemical sensing electrode is detected. The concentration of nitrite in the sample to be tested is determined based on the current response signal.

[0041] More specifically, the first operating voltage ranges from 0.8V to 1.3V, and the sample to be tested is selected from wastewater, groundwater, food extract, or biological fluid.

[0042] In some specific embodiments of the present invention, the sample is selected from wastewater, groundwater, food extract, or biological fluid.

[0043] In some specific embodiments of the present invention, the biological fluid includes blood, serum, plasma, saliva, or urine.

[0044] Preferably, the biological fluid is saliva.

[0045] In some specific embodiments of the present invention, when the sample to be tested is a biological fluid, the detection method is an in vitro detection method.

[0046] In some specific embodiments of the present invention, the electrochemical sensor is placed in a test solution containing different concentrations of nitrite, its current response signal is recorded by an electrochemical method, and quantitative analysis of nitrite concentration is achieved based on the signal.

[0047] In some specific embodiments of the present invention, the detection voltage ranges from 0.8 V to 1.3 V.

[0048] Methods to inhibit microbial adhesion on electrode surfaces A method for inhibiting microbial adhesion on the electrode surface using an electrochemical sensor includes the following steps: The electrochemical sensor is placed in the sample to be tested. In the antibacterial mode, a second operating voltage is applied to the electrochemical sensing electrode to inhibit the adhesion of microorganisms to the electrode surface.

[0049] In some specific embodiments of the present invention, in order to achieve nitrite reduction and in-situ generation of nitric oxide to inhibit the adhesion of microorganisms on the electrode surface, the range of the second working voltage is -0.9 V to -1.4 V.

[0050] Preferably, the second operating voltage is -1.2 V.

[0051] In some specific embodiments of the present invention, the application of the working voltage can be continuous or intermittent. During long-term detection, the in-situ generated nitric oxide can reduce the adhesion of microorganisms to the electrode surface and inhibit biofilm formation, thereby improving the stability of long-term electrode detection.

[0052] Example 1: Preparation of MOF-919 material and construction of electrochemical sensing electrode (1) Preparation of MOF-919 FeCl3·6H2O (35.5 mg), Cu(NO3)2·3H2O (114.5 mg), and H2PyC (54.0 mg) were completely dissolved in 10 mL of LDM and placed in a 20 mL Pyrex flask for sonication. The mixture was heated to 100 °C and reacted for 12 h, then cooled to room temperature to obtain a green solid. The green solid was then dried under vacuum at 150 °C for 12 h to obtain MOF-919 material.

[0053] Figure 1 This is a scanning electron microscope image of the MOF-919 material prepared in this embodiment. From... Figure 1 As can be seen, the prepared material has a regular morphology with an average diameter of about 200 nm.

[0054] Figure 2 The X-ray diffraction (XRD) curves of the prepared MOF-919 material are shown. The diffraction peaks are basically matched with the simulated pattern, indicating that the obtained material has good crystallinity.

[0055] Figure 3 The N2 adsorption-desorption curves of the prepared MOF-919 material show typical type IV adsorption characteristics, indicating that the material possesses mesoporous properties. BET calculations indicate a specific surface area of ​​1498.15 m². 2 ·g -1 .

[0056] Figure 4 The effect of MOF-919 material on NO2 calculated based on density functional theory. The adsorption energy results are as follows, where the adsorption energies of Cu sites and Fe sites are respectively... 0.21 eV and 0.79 eV indicates that this material is effective against NO2. It has good adsorption capacity.

[0057] (2) Preparation of electrochemical sensing electrodes MOF-919 material was dispersed in DMF and ultrasonically treated to obtain a homogeneous MOF-919 dispersion (10 mg·mL⁻¹). 1), and 0.11% of PEDOT:PSS conductive polymer was added to the dispersion, the glassy carbon electrode was polished until smooth, and then 5µL of MOF-919 dispersion was dropped onto the polished glassy carbon electrode surface and dried at 25℃ to constant weight to obtain MOF-919 / GCE electrochemical sensing electrode.

[0058] (3) Construction of electrochemical sensors The MOF-919 / GCE (working electrode), Ag / AgCl electrode (reference electrode) and platinum electrode (counter electrode) prepared in step (2) are used to construct a three-electrode system for subsequent detection of nitrite in the sample. Under appropriate voltage conditions, the electrode surface is protected against microbial adhesion by in-situ generation of nitric oxide.

[0059] Example 2: Performance Test of Nitrite Detection A series of sodium nitrite standard solutions were prepared using pure water as the solvent. The MOF-919 / GCE prepared in Example 1 was then immersed in NO2 solutions of different concentrations. Cyclic voltammetry (CV) and chronoamperometry (it) were performed in PBS solution using an electrochemical workstation with a three-electrode system (Ag / AgCl electrode as reference electrode and platinum wire electrode as counter electrode).

[0060] Figure 5 To add different concentrations of NO2 The cyclic voltammetry curves were then obtained. The results showed that the reduction current at approximately 0.8 V increased significantly after the addition of sodium nitrite.

[0061] Figure 6 and Figure 7 Different concentrations of NO2 were added respectively The subsequent chronoampere curve and steady-state current value and NO2 Linear fitting curves between concentrations were obtained. The results showed that MOF-919 / GCE exhibited good linearity in the concentration range of 0.1 μM to 84.4 mM, with a sensitivity of 132.8 μA cm⁻¹. -2 mM -1 The calibration curve equation is i p (mA)=0.00938c (mM)–0.0009.

[0062] Example 3: Study on the electrocatalytic release of nitric oxide from nitrite by MOF-919 / GCE The prepared MOF-919 / GCE was immersed in a sodium nitrite PBS solution, and its electrocatalytic performance was studied using an electrochemical workstation with a three-electrode electrochemical sensor (Ag / AgCl electrode as reference electrode and platinum wire electrode as counter electrode).

[0063] Figure 8 CV curves for detecting different concentrations of sodium nitrite using MOF-919 / GCE were obtained. These curves were obtained in PBS solutions containing 0, 10, 20, 30, 40, and 50 mM sodium nitrite, with increasing NO2 concentration. As the concentration gradually increases, the Faraday current at -1.2V increases accordingly, indicating that the MOF-919 material exhibits good performance in NO2 concentration. It exhibits good catalytic activity in electrochemical reduction reactions.

[0064] Figure 9 NO2 was determined by electrolysis in a three-electrode system containing 50 mM sodium nitrite in PBS. The products of the electrochemical reduction process were analyzed using the known NO-capturing reagent 4-amino-5-methylamino-2′,7′-difluorofluorescein (DAF-FM). The amount of NO produced was measured using this reagent, which exhibits a highly characteristic shift in the visible absorption band (λmax = 520 nm) upon binding with NO, forming a fluorescent benzotriazole derivative. The results indicate that only when NO2... A significant fluorescence signal was only observed when both the MOF-919 material and the applied voltage were present, indicating that the MOF-919 material can catalyze NO2 under the influence of the applied voltage. NO is generated.

[0065] Example 4: Actual Sample Testing The MOF-919 / GCE prepared in Example 1 was used to detect nitrite in real saliva samples and compared with commercial NO2. The test kits were compared. Five saliva samples from human volunteers were added to 10 mL of PBS solution and tested using a chronoamperometric method.

[0066] Figure 10 The image shows the it response curve obtained after adding 100 μL of saliva sample. The results indicate that the current changes rapidly and then stabilizes after sample addition, suggesting that this electrode can be used for NO2 in real saliva samples. The detection.

[0067] Figure 11 For MOF-919 / GCE and commercial NO2 Comparison of test results for saliva samples using the kit. The results show that the detection results of MOF-919 / GCE are highly consistent with those of commercial kits, indicating that the electrode has good quantitative detection capabilities.

[0068] Example 5: Antibacterial Detection of Electrochemical Sensing Electrode Single colonies of Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, and Escherichia coli were picked from LB agar plates and incubated in LB liquid medium at 37°C and 200 rpm for 16 h. After centrifugation and washing, the bacterial suspensions were resuspended in PBS and the OD was adjusted. 600 Up to 1.0, as an experimental bacterial suspension.

[0069] The antibacterial experiment was divided into 4 groups: (i) P: PBS; (ii) MGN: MOF-919 / GCE + 50 mM NO2 Solution; (iii) MG: MOF-919 / GCE (applied voltage: 1.2V vs. Ag / AgCl); (iv) MGNV: MOF-919 / GCE + 50 mM NO2 Solution (applied voltage: 1.2V vs. Ag / AgCl).

[0070] The bacterial suspensions were treated as described above and incubated at 37 °C and 200 rpm for 30 min. The bacterial suspensions were then diluted and spread onto LB agar plates, incubated at 37 °C for 20 h, and colony counts were performed. Survival rate and inhibition rate were calculated based on the colony count of group P.

[0071] like Figure 12 , 13 As shown, almost no visible colonies grew on the MGNV group plates, with an inhibition rate approaching 100%, significantly higher than other control groups, demonstrating that the NO generated in situ under electrocatalytic conditions has extremely strong bactericidal efficacy. Bacterial biofilms (BBFs) were prepared by treating the biofilms according to the above groupings. The bacteria and biofilms were stained with SYTO-9 / PI staining agent for 15 min, and the results were obtained by z-axis scanning using a confocal laser scanning microscope. Figure 14 The thickness of the stained biofilm was visualized using 3D CLSM images. SYTO-9 staining was green, representing all bacteria, and PI staining was red, representing dead bacteria. The Merge plot was a superposition of the two fluorescence types. At 1.2V, MOF-919 + 50mM NO2 A distinct red fluorescent signal was observed in the treated group, indicating that the MGNV group effectively induced bacterial death and eradicated BBF by disrupting the bacterial membrane and releasing intracellular components.

[0072] The MOF-919 material used in this invention maintains its complete structure at the electrode interface. Its active sites, formed by the synergistic interaction of metal nodes and organic ligands, are similar to those of natural copper-type nitrite reductase, allowing it to directly participate in electrochemical reactions and achieve highly efficient and selective catalysis of nitrite. Simultaneously, through external potential modulation, MOF-919 can not only catalyze the oxidation of nitrite for detection but also catalyze its reduction in situ to generate nitric oxide in another potential range, thereby endowing the electrode with antimicrobial adhesion properties. Therefore, this invention extends the application of MOFs and their derivatives to single detection methods to a multifunctional interfacial reaction system involving enzyme-mimicking MOF structures, achieving a coupling of detection and anti-fouling functions and significantly improving the long-term stability of the electrode in complex systems.

[0073] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0074] It should be noted that in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly specified.

[0075] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those 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 invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. An electrochemical sensing electrode that combines detection and anti-biocontamination functions, characterized in that, Includes a conductive substrate and a MOF-919 material loaded on the conductive substrate; The electrochemical sensing electrode has a switchable dual-function operating mode under the control of an applied potential: in the detection mode, a first operating voltage is applied to catalyze the electrochemical oxidation reaction of nitrite through the MOF-919 material to generate a current response signal related to the nitrite concentration; in the antibacterial mode, a second operating voltage is applied to catalyze the electrochemical reduction reaction of nitrite through the MOF-919 material to generate nitric oxide in situ and inhibit the adhesion of microorganisms on the electrode surface.

2. The electrochemical sensing electrode according to claim 1, characterized in that, The conductive substrate is selected from one of glassy carbon electrode, carbon cloth electrode and screen-printed electrode; the MOF-919 material is loaded by one of drop coating, spray coating and electrodeposition.

3. A method for preparing an electrochemical sensing electrode that combines detection and anti-biocontamination functions, characterized in that, The process includes the following steps: dispersing MOF-919 material in a solvent containing a conductive polymer to form a dispersion; loading the dispersion onto a conductive substrate and drying it to obtain the electrochemical sensing electrode.

4. An electrochemical sensor, characterized in that, It includes the electrochemical sensing electrode, the counter electrode, and the reference electrode; wherein the electrochemical sensing electrode is the working electrode.

5. The application of the electrochemical sensor according to claim 4 in the electrochemical detection of nitrite in samples, characterized in that, The first working voltage enables quantitative detection of nitrite in complex samples and maintains a stable electrochemical response during long-term use.

6. The application of the electrochemical sensor according to claim 4 in inhibiting microbial adhesion on the electrode surface, characterized in that, Nitric oxide is generated in situ under the second working voltage, thereby inhibiting bacterial attachment and biofilm formation.

7. A method for detecting nitrite in a sample, characterized in that, Includes the following steps: The electrochemical sensor is placed in the sample to be tested. In the detection mode, a first working voltage is applied to the electrochemical sensing electrode, and the current response signal generated by the electrochemical sensing electrode is detected. The concentration of nitrite in the sample to be tested is determined based on the current response signal.

8. The method for detecting nitrite in a sample according to claim 7, characterized in that, The first operating voltage ranges from 0.8V to 1.3V, and the sample to be tested is selected from wastewater, groundwater, food extract, or biological fluid.

9. A method for inhibiting microbial adhesion on an electrode surface, characterized in that, The electrochemical sensor is placed in the sample to be tested. In the antibacterial mode, a second operating voltage is applied to the electrochemical sensing electrode to inhibit the adhesion of microorganisms to the electrode surface.

10. The method for inhibiting microbial adhesion on the electrode surface according to claim 9, characterized in that, The second operating voltage ranges from -0.9V to -1.4V; the microorganisms include one or more of Escherichia coli, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus.

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