A hydrogel, a sensor and a preparation method and application thereof

Abstract

The application discloses a hydrogel, a sensor and a preparation method and application thereof. The hydrogel is PEDOT:PSS / EMIM-Cl / Fc + PF6 ‑ The hydrogel comprises a poly 3,4-ethylenedioxythiophene: polystyrene sulfonate conductive polymer, 1-ethyl-3-methyl imidazole chloride and ferrocene hexafluorophosphate. The application can accurately control the inherent potential of the gel interface by doping 1-ethyl-3-methyl imidazole chloride and ferrocene hexafluorophosphate in the hydrogel, and realizes potential type analysis of various neurochemical molecules in the brain.

Description

Technical Field

[0001] This invention relates to the field of electrochemical analysis and detection, and more specifically, to a hydrogel, a sensor, a method for preparing the same, and its applications. Background Technology

[0002] The brain is one of the most intricate and complex organs in the human body. A variety of neurochemicals participate in the complex dynamic processes of the brain's nervous system, playing a crucial role in various physiological and pathological events. Therefore, achieving in-situ detection of neurochemicals within the brain at the in vivo level is of great significance for research in neuroscience and other fields. Currently, most sensors require an external voltage to polarize the working electrode to generate an electrical signal, and the electrical influence on the nervous system during measurement is unavoidable. However, potentiometric sensors can achieve electrochemical analysis of species simply by outputting an open-circuit potential. The entire circuit current is almost zero, exhibiting excellent biocompatibility and showing broader application prospects in the field of in vivo analysis.

[0003] Currently, potential sensors constructed using the bipolar principle typically employ a high concentration of molecules with good electrochemical activity (such as K3Fe(CN)6 / K4Fe(CN)6) as the cathode filling solution. However, the internal filling solution of this method is limited by the glass tube encapsulation, which greatly restricts the miniaturization, integration, and high-throughput development of the sensor, and also restricts its further application in in vivo electroanalysis. Summary of the Invention

[0004] This invention is based on the inventors' discovery and understanding of the following facts and problems: Most sensors require an external voltage to polarize the working electrode to generate an electrical signal, and the electrical effects on the nervous system during the measurement process are unavoidable. Furthermore, the internal filling fluid of current potentiometric sensors is limited by the glass tube encapsulation, restricting their application in in vivo electroanalysis.

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a hydrogel, a sensor, a method for preparing the same, and its applications. By doping the hydrogel with 1-ethyl-3-methylimidazole chloride and ferrocene hexafluorophosphate, the intrinsic potential of the gel interface can be precisely controlled, enabling potentiometric analysis of various neurochemical molecules in the brain.

[0006] This invention provides a hydrogel, wherein the hydrogel is PEDOT:PSS / EMIM-Cl / Fc. + PF6 - The hydrogel comprises: a conductive polymer of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), 1-ethyl-3-methylimidazole chloride (EMIM-Cl), and ferrocene hexafluorophosphate (Fc).+ PF6 - ).

[0007] Advantages and technical effects of the hydrogel in this invention embodiment: PEDOT:PSS / EMIM-Cl / Fc + PF6 - The hydrogel is a doped 1-ethyl-3-methylimidazolium chloride (EMIM-Cl) and ferrocene hexafluorophosphate (Fc). + PF6 - A conductive polymer hydrogel of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). PEDOT:PSS / EMIM-Cl / Fc + PF6 - Hydrogels possess stable and reversible redox activity, making them highly suitable for designing electrode active interfaces. Furthermore, the hydrogel of this invention exhibits strong universality for test components. By doping with ferrocene hexafluorophosphate containing a redox couple and 1-ethyl-3-methylimidazole chloride, which provides chloride ions and enhances conductivity, the intrinsic potential of the gel interface can be precisely controlled, enabling potentiometric analysis and in-situ detection of various neurochemical molecules in the brain. By using the functionalized hydrogel material of this invention to replace the traditional liquid-filled system, a fully solid-state spontaneously bipolarized molecular potential sensor is developed, providing an ideal platform for in-situ, low-interference detection of neurochemical signals and laying a solid foundation for the development of high-throughput electrode arrays. It has broad application prospects in fields such as in vivo electrochemical analysis.

[0008] In some embodiments, the PEDOT:PSS / EMIM-Cl / Fc + PF6 - In the hydrogel, the mass ratio of the poly(3,4-ethylenedioxythiophene):polystyrene sulfonate conductive polymer, 1-ethyl-3-methylimidazolium chloride, and ferrocene hexafluorophosphate is 4~5:13:3~9.

[0009] This invention provides a method for preparing a hydrogel, comprising: mixing poly(3,4-ethylenedioxythiophene):polystyrene sulfonate conductive polymer, 1-ethyl-3-methylimidazole chloride, ferrocene hexafluorophosphate, and a solvent to obtain PEDOT:PSS / EMIM-Cl / Fc + PF6 - The pregel solution was dried to obtain PEDOT:PSS / EMIM-Cl / Fc + PF6 - Hydrogel.

[0010] This invention provides an all-solid-state spontaneously polarized electrode, comprising:

[0011] A glass capillary tube, wherein one end of the glass capillary tube is a pointed tip; Carbon fiber, wherein the carbon fiber is disposed inside the glass capillary, and one end of the carbon fiber is located outside the tip; An internal reference electrode is disposed inside the glass capillary. A hydrogel, wherein the hydrogel is disposed within the glass capillary, and at least a portion of the carbon fiber and at least a portion of the internal reference electrode are located within the hydrogel.

[0012] The hydrogel is PEDOT:PSS / EMIM-Cl / Fc, as described in this embodiment of the invention. + PF6 - PEDOT:PSS / EMIM-Cl / Fc hydrogel or prepared by the method of the embodiments of the present invention + PF6 - Hydrogel.

[0013] In this embodiment of the invention, the all-solid-state spontaneously polarized electrode exhibits long-term stability in in-situ electrochemical detection. Electrochemical analysis of species can be achieved by outputting an open-circuit potential. The electrochemical process can proceed spontaneously, the current in the entire circuit is almost zero, the electrode interface reaction is in a dynamic equilibrium state, and the consumption of reactants and the amount of product formation are extremely low, demonstrating superior stability and achieving stable detection over long periods.

[0014] In some embodiments, the internal reference electrode includes an Ag / AgCl reference electrode.

[0015] This invention provides a method for preparing an all-solid-state spontaneously bipolarized electrode, comprising the following steps: (1) Carbon fiber passes through the inside of the glass capillary; one end of the glass capillary is pulled into a tip, and carbon fiber passes through the inside of the glass capillary and extends to the outside of the tip; the opening of the tip of the glass capillary is sealed. (2) Insert PEDOT:PSS / EMIM-Cl / Fc into one end of the glass capillary. + PF6 - A pregel solution is prepared, and an internal reference electrode is inserted into the glass capillary, such that at least a portion of the carbon fiber inside the glass capillary and at least a portion of the internal reference electrode are immersed in the pregel solution; then, the pregel solution is dried to form the hydrogel described in the embodiments of the present invention, thereby obtaining an all-solid-state spontaneously bipolarized electrode.

[0016] This invention provides an all-solid-state spontaneously bipolarized molecular potential sensor, comprising: a working electrode and an external reference electrode; the working electrode comprises the all-solid-state spontaneously bipolarized electrode described in this invention, or the all-solid-state spontaneously bipolarized electrode prepared by the preparation method described in this invention.

[0017] In this embodiment of the invention, PEDOT:PSS / EMIM-Cl / Fc is used. + PF6 - Functionalized hydrogel materials can replace traditional liquid-filled systems for the fabrication and application of all-solid-state spontaneous bipolar molecular potential sensors. These sensors exhibit long-term stability in in-situ electrochemical detection. Electrochemical analysis of species can be achieved simply by outputting the open-circuit potential. The electrochemical process is spontaneous, with almost zero current in the entire circuit. The electrode interface reaction is in dynamic equilibrium, with extremely low reactant consumption and product formation, demonstrating superior stability and enabling stable detection over long periods. These all-solid-state spontaneous bipolar molecular potential sensors can effectively reduce damage to brain tissue and are used for the detection of neurochemical molecules in the brain. They also exhibit strong universality for test components. By doping ferrocene hexafluorophosphate containing a redox couple with 1-ethyl-3-methylimidazolium chloride, which provides chloride ions and enhances conductivity, into the pregel matrix, the intrinsic potential of the gel interface can be precisely controlled, enabling potentiometric analysis and in-situ detection of various neurochemical molecules in the brain. Furthermore, they solve the problems of poor biocompatibility and integration difficulties of traditional electrochemical sensors.

[0018] In some embodiments, the external reference electrode comprises an Ag / AgCl electrode constructed from glass capillaries.

[0019] In some embodiments, the Ag / AgCl electrode constructed from glass capillaries includes: A glass capillary tube, wherein one end of the glass capillary tube is a pointed tip; The Ag / AgCl electrode is disposed inside the glass capillary tube; Artificial cerebrospinal fluid, wherein the artificial cerebrospinal fluid is disposed within the glass capillary, and at least a portion of the Ag / AgCl electrode is located within the artificial cerebrospinal fluid; Solid agar containing artificial cerebrospinal fluid, wherein the tip of the glass capillary is provided with the solid agar containing artificial cerebrospinal fluid.

[0020] This invention provides an integrated screen-printed sensor, comprising: A base layer, an electrode layer, and an insulating layer; the electrode layer is disposed on the base layer, and the insulating layer covers the electrode layer and the base layer; The electrode layer includes a working electrode, an internal reference electrode, and an external reference electrode; The insulating layer has an opening area to expose the middle portion of the working electrode and the internal reference electrode in the electrode layer; the opening area is provided with the hydrogel according to the embodiment of the present invention, the hydrogel covering the exposed middle portion of the working electrode and the internal reference electrode to form a gel area.

[0021] The hydrogel is PEDOT:PSS / EMIM-Cl / Fc, as described in this embodiment of the invention. + PF6 - PEDOT:PSS / EMIM-Cl / Fc hydrogel or prepared by the method of the embodiments of the present invention + PF6 - Hydrogel.

[0022] In this embodiment of the invention, the integrated screen-printed sensor can achieve electrochemical analysis of species by outputting an open-circuit potential. The electrochemical process can proceed spontaneously, with almost zero current in the entire circuit. The electrode interface reaction is in a dynamic equilibrium state, with extremely low reactant consumption and product formation, exhibiting superior stability and enabling stable detection over long periods. The integrated screen-printed sensor can effectively reduce damage to brain tissue and can be used for the detection of neurochemical molecules in the brain, realizing potential-based analysis and in-situ detection of various neurochemical molecules in the brain.

[0023] In some embodiments, one end of the internal reference electrode and one end of the external reference electrode are exposed to form a wiring area; And / or, the other end of the external reference electrode and one end of the working electrode are exposed, together forming a detection area; And / or, the working electrode includes a carbon working electrode; And / or, the internal reference electrode includes an Ag / AgCl internal reference electrode; And / or, the external reference electrode includes an Ag / AgCl external reference electrode.

[0024] This invention provides a method for fabricating an integrated screen-printed sensor, comprising the following steps: (1) An electrode layer is prepared on a substrate using screen printing technology, and an insulating layer with an opening area is covered on the electrode layer and the substrate; (2) Coating the opening area with PEDOT:PSS / EMIM-Cl / Fc + PF6 - The pregel solution is dried to form the hydrogel described in the embodiments of the present invention, and then the opening area is encapsulated to obtain an integrated screen-printed sensor.

[0025] This invention provides an all-solid-state spontaneous dual-polarization molecular potential sensor, or an integrated screen-printed sensor, for the detection of neurochemical molecules, preferably for in-situ detection of neurochemical molecules in the living brain.

[0026] In this embodiment of the invention, the sensor can achieve electrochemical analysis of species by outputting an open-circuit potential. The electrochemical process can proceed spontaneously, the current in the entire circuit is almost zero, the electrode interface reaction is in a dynamic equilibrium state, the consumption of reactants and the amount of product formation are extremely low, exhibiting superior stability and achieving stable detection over long periods of time. It can effectively reduce the damage to brain tissue and can be used for in-situ detection of neurochemical molecules in the brain. Moreover, it has strong universality for the test components and can precisely control the inherent potential of the gel interface to achieve potential-type analysis and in-situ detection of various neurochemical molecules in the brain.

[0027] In some embodiments, the neurochemical molecules include at least one of ascorbic acid (AA), dopamine, and H2S; And / or, during the detection process of the all-solid-state spontaneous bipolar molecular potential sensor, the sensor is placed in the sample to be tested, the open circuit potential value is tested, and then the content of the analyte in the sample to be tested is determined based on the open circuit potential value; And / or, during the detection process of the integrated screen printing sensor, the sensor is placed in the sample to be tested, the open circuit potential value is tested, and then the content of the analyte in the sample to be tested is determined based on the open circuit potential value. Attached Figure Description

[0028] Figure 1 It is PEDOT:PSS / EMIM-Cl / Fc in Example 1 + PF6 - Cyclic voltammograms of hydrogel-modified glassy carbon electrode in 1×PBS solution: (a) is a long-term cyclic voltammogram at a scan rate of 100 mV / s; (b) is a cyclic voltammogram at a scan rate of 1 mV / s.

[0029] Figure 2 The image shows an all-solid-state spontaneously bipolarized molecular potential sensor constructed with an all-solid-state spontaneously bipolarized electrode in Example 2 for detecting ascorbic acid. (a) is the open-circuit potential response diagram for ascorbic acid; (b) is the logarithmic relationship diagram between the obtained open-circuit potential and the ascorbic acid concentration.

[0030] Figure 3 This is a schematic diagram of the integrated screen-printed sensor in Example 3.

[0031] Figure 4 The integrated screen printing sensor in Example 3 detects ascorbic acid. (a) is the open circuit potential response diagram of ascorbic acid; (b) is the logarithmic relationship between the obtained open circuit potential and the ascorbic acid concentration.

[0032] Figure 5The diagrams show the open-circuit potential response of the all-solid-state spontaneous dual-polarization molecular potential sensor in the comparative examples to ascorbic acid and the logarithmic relationship between the obtained open-circuit potential and the ascorbic acid concentration. (a) is the sensor in Comparative Example 1 without 1-ethyl-3-methylimidazole chloride; (b) is the sensor in Comparative Example 2 without ferrocene hexafluorophosphate. Detailed Implementation

[0033] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0034] Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (also known as poly(3,4-ethylenedioxythiophene):polystyrene sulfonate or PEDOT:PSS, CAS No. 155090-83-8) possesses excellent mechanical properties, tunable electrical conductivity, and processability, and is commonly used as an electrode coating to improve the sensitivity of electrochemical signal recording. The porous structure of PEDOT:PSS allows for efficient doping of various molecules, enabling the modulation of the redox potential of the hydrogel. Based on this characteristic, PEDOT:PSS can serve as an ideal solid-state alternative material for constructing the cathode functional region of potentiometric sensors.

[0035] An embodiment of the present invention provides a hydrogel, wherein the hydrogel is PEDOT:PSS / EMIM-Cl / Fc. + PF6 - Hydrogels comprising: poly(3,4-ethylenedioxythiophene): a conductive polymer of polystyrene sulfonate, 1-ethyl-3-methylimidazole chloride, and ferrocene hexafluorophosphate.

[0036] The hydrogel of this invention is a doped form of 1-ethyl-3-methylimidazolium chloride (EMIM-Cl) and ferrocene hexafluorophosphate (Fc). + PF6 - A conductive polymer hydrogel of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). PEDOT:PSS / EMIM-Cl / Fc + PF6 -Hydrogels possess stable and reversible redox activity, making them highly suitable for designing electrode active interfaces. Furthermore, the hydrogel of this invention exhibits strong universality for test components. By doping with ferrocene hexafluorophosphate containing a redox couple and 1-ethyl-3-methylimidazole chloride, which provides chloride ions and enhances conductivity, the intrinsic potential of the gel interface can be precisely controlled, enabling potentiometric analysis and in-situ detection of various neurochemical molecules in the brain. By using the functionalized hydrogel material of this invention to replace the traditional liquid-filled system, a fully solid-state spontaneously bipolarized molecular potential sensor is developed, providing an ideal platform for in-situ, low-interference detection of neurochemical signals and laying a solid foundation for the development of high-throughput electrode arrays. It has broad application prospects in fields such as in vivo electrochemical analysis.

[0037] In some embodiments, the PEDOT:PSS / EMIM-Cl / Fc + PF6 - In the hydrogel, the mass ratio of the poly(3,4-ethylenedioxythiophene):polystyrene sulfonate conductive polymer, 1-ethyl-3-methylimidazolium chloride and ferrocene hexafluorophosphate is 4~5:13:3~9, specifically, 4~5 (e.g., 4, 4.2, 4.5, 4.8, 5):13:3~9 (3, 4, 5, 6, 7, 8, 9).

[0038] In this embodiment of the invention, by doping with ferrocene hexafluorophosphate and 1-ethyl-3-methylimidazole chloride, potentiometric analysis and in-situ detection of various neurochemical molecules in the brain can be achieved. By optimizing the content of 1-ethyl-3-methylimidazole chloride (EMIM-Cl), the chloride ion concentration in the hydrogel can be made similar to that of artificial cerebrospinal fluid, thereby improving the stability of potential measurements. By optimizing the content of ferrocene hexafluorophosphate (Fc... + PF6 - The content of ) can effectively control the interfacial potential while ensuring smooth gel formation.

[0039] In some embodiments, the PEDOT:PSS / EMIM-Cl / Fc + PF6 - The hydrogel also includes a solvent, which includes at least one of water and dimethyl sulfoxide (DMSO); the present invention does not impose any particular limitation on the content of solvent in the hydrogel.

[0040] A method for preparing a hydrogel according to an embodiment of the present invention includes: mixing poly(3,4-ethylenedioxythiophene):polystyrene sulfonate conductive polymer, 1-ethyl-3-methylimidazole chloride, ferrocene hexafluorophosphate and solvent to obtain PEDOT:PSS / EMIM-Cl / Fc + PF6 -Pregel solution (also known as PEDOT:PSS / EMIM-Cl / Fc) + PF6 - (Mixed solution), dried to obtain PEDOT:PSS / EMIM-Cl / Fc + PF6 - Hydrogel.

[0041] In some embodiments, the solvent includes at least one of water and dimethyl sulfoxide (DMSO).

[0042] In some embodiments, a solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate conductive polymer, a solution of 1-ethyl-3-methylimidazolium chloride, and a solution of ferrocene hexafluorophosphate are mixed to obtain PEDOT:PSS / EMIM-Cl / Fc. + PF6 - Pregelation solution; Optionally, the poly(3,4-ethylenedioxythiophene):polystyrene sulfonate conductive polymer solution comprises an aqueous solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate conductive polymer. Optionally, the mass percentage concentration of the aqueous solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate conductive polymer is 1.1-1.3 wt%, that is, the mass ratio of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate conductive polymer to the mass of the aqueous solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate conductive polymer is 1.1-1.3 wt%, specifically, for example, 1.1 wt%, 1.2 wt%, and 1.3 wt%. Optionally, the mass ratio of PEDOT to PSS in PEDOT:PSS is approximately 1:2.5. Optionally, the solvent of the 1-ethyl-3-methylimidazole chloride solution includes water, i.e., an aqueous solution of 1-ethyl-3-methylimidazole chloride; optionally, the water includes ultrapure water; the concentration of the 1-ethyl-3-methylimidazole chloride solution is 65-68 mg / ml, specifically, for example, 65 mg / ml, 66 mg / ml, 67 mg / ml, 68 mg / ml; Optionally, the solvent of the ferrocene hexafluorophosphate solution includes dimethyl sulfoxide (DMSO); the concentration of the ferrocene hexafluorophosphate solution is 50-150 mg / ml, specifically, for example, 50 mg / ml, 100 mg / ml, 150 mg / ml; Optionally, relative to the volume of the poly(3,4-ethylenedioxythiophene):polystyrene sulfonate aqueous solution, the volume percentage of the 1-ethyl-3-methylimidazolium chloride solution is 45-50 vol%, specifically, for example, 45 vol%, 46 vol%, 47 vol%, 48 vol%, 49 vol%, 50 vol%; and the volume percentage of the ferrocene hexafluorophosphate solution is 10-15 vol%, specifically, for example, 10 vol%, 11 vol%, 12 vol%, 13 vol%, 14 vol%, 15 vol%. Optionally, the PEDOT:PSS solution and 1-ethyl-3-methylimidazole chloride solution are first mixed, and the mixing time is 30 min; then, the solution is mixed with ferrocene hexafluorophosphate solution, and the mixing time is 30 min.

[0043] In this embodiment of the invention, DMSO can also enhance the conductivity of the gel.

[0044] In some embodiments, the mixing is carried out under stirring; the mixing is carried out at room temperature; optionally, the mixing includes stirring at room temperature.

[0045] In some embodiments, the drying includes drying at room temperature; the present invention does not have a special limitation on the drying time, as long as a hydrogel is formed, for example, the drying time can be 45 min to 2 h, specifically, for example, 45 min, 1 h, 2 h.

[0046] An embodiment of the present invention provides a PEDOT:PSS / EMIM-Cl / Fc + PF6 - The pregel solution and its preparation method are similar to the above-mentioned PEDOT:PSS / EMIM-Cl / Fc. + PF6 - The pregel solution and its preparation method are the same in the hydrogel preparation method. Specifically, PEDOT:PSS / EMIM-Cl / Fc + PF6 - The pregel solution comprises: poly(3,4-ethylenedioxythiophene):polystyrene sulfonate conductive polymer, 1-ethyl-3-methylimidazole chloride, ferrocene hexafluorophosphate, and a solvent, said solvent comprising at least one of water and dimethyl sulfoxide (DMSO).

[0047] An all-solid-state spontaneously polarized electrode according to an embodiment of the present invention includes: A glass capillary tube, wherein one end of the glass capillary tube is a pointed tip; Carbon fiber, wherein the carbon fiber is disposed inside the glass capillary, and one end of the carbon fiber is located outside the tip; An internal reference electrode is disposed inside the glass capillary. A hydrogel, wherein the hydrogel is disposed within the glass capillary, and at least a portion of the carbon fiber and at least a portion of the internal reference electrode are located within the hydrogel.

[0048] The hydrogel is PEDOT:PSS / EMIM-Cl / Fc, as described in this embodiment of the invention. + PF6 - PEDOT:PSS / EMIM-Cl / Fc hydrogel or prepared by the method of the embodiments of the present invention + PF6 - Hydrogel.

[0049] In this embodiment of the invention, the all-solid-state spontaneously polarized electrode exhibits long-term stability in in-situ electrochemical detection. Electrochemical analysis of species can be achieved by outputting an open-circuit potential. The electrochemical process can proceed spontaneously, the current in the entire circuit is almost zero, the electrode interface reaction is in a dynamic equilibrium state, and the consumption of reactants and the amount of product formation are extremely low, demonstrating superior stability and achieving stable detection over long periods.

[0050] In some embodiments, the carbon fiber is disposed inside the glass capillary, with one end of the carbon fiber located outside the tip. In other words, the carbon fiber extends from inside the glass capillary through the glass capillary and extends to the outside of the tip.

[0051] In some embodiments, the glass capillary contains a hydrogel. Optionally, the tip and adjacent portion of the glass capillary contain a hydrogel, namely PEDOT:PSS / EMIM-Cl / Fc. + PF6 - Hydrogel.

[0052] In some embodiments, a sealing layer is further included, the sealing layer being disposed between the tip opening and the carbon fiber; optionally, the sealing layer is formed of insulating adhesive; the sealing layer seals the glass capillary tip and secures the carbon fiber.

[0053] In some embodiments, the present invention does not specifically limit the source, material and size of the glass capillary. For example, in a specific embodiment, the inner diameter (diameter) of the glass capillary can be 1.5 mm, the length can be 10 cm, and the tip opening is a micron-level tip opening, for example, the tip opening diameter can be 10 μm; optionally, the tip of the glass capillary is a conical glass micron opening.

[0054] In some embodiments, the internal reference electrode includes an Ag / AgCl reference electrode; optionally, the present invention does not have a special limitation on the source and size of the Ag / AgCl reference electrode, which can be purchased or prepared. For example, in a specific embodiment, the Ag wire can be obtained by soaking in a saturated FeCl3 solution, and the Ag wire has a diameter of 0.5 mm and a length of 5 cm; optionally, soaking for 30 min, and then washing with water.

[0055] In some embodiments, the present invention does not have special limitations on the source and size of the carbon fiber, which can be purchased. For example, in a specific embodiment, the carbon fiber is a single carbon fiber with a diameter of 7 μm.

[0056] In some embodiments, the present invention does not specifically limit the length of the carbon fiber outside the tip. For example, in a specific embodiment, the length of the carbon fiber outside the tip can be 300 μm.

[0057] A method for preparing an all-solid-state spontaneously bipolarized electrode according to an embodiment of the present invention includes the following steps: (1) The carbon fiber passes through the inside of the glass capillary; one end of the glass capillary is pulled into a tip, and the carbon fiber passes through the inside of the glass capillary and extends to the outside of the tip; the opening of the tip of the glass capillary is sealed. (2) Insert PEDOT:PSS / EMIM-Cl / Fc into one end of the glass capillary. + PF6 - A pregel solution is prepared, and an internal reference electrode is inserted into the glass capillary, such that at least a portion of the carbon fiber inside the glass capillary and at least a portion of the internal reference electrode are immersed in the pregel solution; then, the pregel solution is dried to form the hydrogel described in the embodiments of the present invention, thereby obtaining an all-solid-state spontaneously bipolarized electrode.

[0058] In this embodiment of the invention, a pre-gel solution is loaded into one end of a glass capillary in an all-solid-state spontaneous dual-polarization electrode, and the electrode is dried to obtain an all-solid-state spontaneous dual-polarization electrode.

[0059] In some embodiments, in step (1), a laser drawing instrument is used to draw the glass capillary into a pointed end.

[0060] In some embodiments, in step (1), the opening of the glass capillary tip is sealed, that is, the opening of the tip is sealed with the carbon fiber; optionally, a sealing layer is used for sealing; optionally, insulating adhesive is used to seal the opening of the tip with the carbon fiber, that is, the glass capillary tip is sealed and the carbon fiber is fixed to form a sealing layer; optionally, after sealing, acetone is used to clean and remove excess adhesive.

[0061] In some embodiments, in step (1), the exposed carbon fiber extending to the outside of the glass capillary tip is cut to a fixed length; alternatively, a positioning device is used for cutting.

[0062] In some embodiments, the drying in step (2) includes room temperature drying; alternatively, the glass capillary is placed at room temperature to allow the pregel solution to dry and form a hydrogel.

[0063] In some embodiments, the activation process of the all-solid-state spontaneous dual-polarization electrode includes: applying a constant potential of 1.5 V in a 1 mol / L NaOH solution, oxidizing for 90 s for electrochemical activation, and performing cyclic voltammetry scans in the voltage range of 0.0 to +1.0 V at a scan rate of 0.05 V / s. Once the voltammetry curve stabilizes, the activation of the all-solid-state spontaneous dual-polarization electrode is complete.

[0064] An all-solid-state spontaneously bipolarized molecular potential sensor according to an embodiment of the present invention includes: a working electrode and an external reference electrode; the working electrode includes the all-solid-state spontaneously bipolarized electrode described in the embodiment of the present invention, or the all-solid-state spontaneously bipolarized electrode prepared by the preparation method described in the embodiment of the present invention.

[0065] In this embodiment of the invention, PEDOT:PSS / EMIM-Cl / Fc is used. + PF6 - Functionalized hydrogel materials can replace traditional liquid-filled systems for the fabrication and application of all-solid-state spontaneous bipolar molecular potential sensors. These sensors exhibit long-term stability in in-situ electrochemical detection. Electrochemical analysis of species can be achieved simply by outputting the open-circuit potential. The electrochemical process is spontaneous, with almost zero current in the entire circuit. The electrode interface reaction is in dynamic equilibrium, with extremely low reactant consumption and product formation, demonstrating superior stability and enabling stable detection over long periods. These all-solid-state spontaneous bipolar molecular potential sensors can effectively reduce damage to brain tissue and are used for the detection of neurochemical molecules in the brain. They also exhibit strong universality for test components. By doping ferrocene hexafluorophosphate containing a redox couple with 1-ethyl-3-methylimidazolium chloride, which provides chloride ions and enhances conductivity, into the pregel matrix, the intrinsic potential of the gel interface can be precisely controlled, enabling potentiometric analysis and in-situ detection of various neurochemical molecules in the brain. Furthermore, they solve the problems of poor biocompatibility and integration difficulties of traditional electrochemical sensors.

[0066] In some embodiments, the external reference electrode comprises an Ag / AgCl electrode constructed from glass capillaries; Optionally, the Ag / AgCl electrode constructed from the glass capillary includes: A glass capillary tube, wherein one end of the glass capillary tube is a pointed tip; Ag / AgCl electrode (optionally, Ag / AgCl wire), wherein the Ag / AgCl electrode is disposed inside the glass capillary; Artificial cerebrospinal fluid, wherein the artificial cerebrospinal fluid is disposed within the glass capillary, and at least a portion of the Ag / AgCl electrode is located (immersed) in the artificial cerebrospinal fluid; Solid agar containing artificial cerebrospinal fluid, wherein the tip of the glass capillary is provided with the solid agar containing artificial cerebrospinal fluid.

[0067] In this embodiment of the invention, when the substance to be detected is dissolved in artificial cerebrospinal fluid, artificial cerebrospinal fluid is also used in the external reference electrode. This ensures consistency with the overall environment of the detection solution and improves the stability of the potential measurement. The tip of the glass capillary is a solid agar containing artificial cerebrospinal fluid, which can exchange with external substances while preventing the internal artificial cerebrospinal fluid from flowing out.

[0068] In some embodiments, the present invention does not specifically limit the source, material and size of the glass capillary. For example, in a specific embodiment, the inner diameter (diameter) of the glass capillary can be 1.5 mm, the length can be 10 cm, and the tip opening is a micron-level tip opening, for example, the tip opening diameter can be 10 μm; optionally, the tip of the glass capillary is a conical glass micron opening.

[0069] In some embodiments, the artificial cerebrospinal fluid comprises: NaCl (125.9 mM), KCl (2.4 mM), KH2PO4 (0.5 mM), NaHCO3 (27.5 mM), Na2SO4 (0.5 mM), MgCl2 (1.8 mM), CaCl2 (1.1 mM), pH 7.2~7.4; the balance being water.

[0070] In some embodiments, the method for preparing the solid agar containing artificial cerebrospinal fluid includes: heating and dissolving artificial cerebrospinal fluid containing agar powder, and then cooling to form solid agar containing artificial cerebrospinal fluid; optionally, it contains agar powder at 10 vol.% relative to the artificial cerebrospinal fluid.

[0071] In some embodiments, the method for preparing the Ag / AgCl electrode constructed from the glass capillary includes the following steps: (1) Pull one end of the glass capillary into a pointed tip. Optionally, a gravity pulling device can be used for pulling. (2) A solid agar containing artificial cerebrospinal fluid is loaded into the tip of a glass capillary tube; Optionally, the artificial cerebrospinal fluid containing agar powder is heated and dissolved, then drawn into the tip of a glass capillary tube by siphoning, and cooled to form solid agar containing artificial cerebrospinal fluid; Optionally, the artificial cerebrospinal fluid containing agar powder is artificial cerebrospinal fluid containing 10 vol.% agar powder relative to the artificial cerebrospinal fluid. (3) Fill the glass capillary with artificial cerebrospinal fluid and insert the Ag / AgCl electrode into the glass capillary; Optionally, artificial cerebrospinal fluid is filled into the glass capillary at the other end (open end); alternatively, the other end of the glass capillary and the Ag / AgCl electrode are sealed and fixed using 502 glue.

[0072] like Figure 3 As shown, an integrated screen-printed sensor according to an embodiment of the present invention includes: A base layer, an electrode layer, and an insulating layer; the electrode layer is disposed on the base layer, and the insulating layer covers the electrode layer and the base layer; The electrode layer includes a working electrode, an internal reference electrode, and an external reference electrode; The insulating layer has an opening area to expose the middle part of the working electrode and the internal reference electrode in the electrode layer; the opening area is provided with the hydrogel described in the embodiment of the present invention, and the hydrogel covers the middle part of the exposed working electrode and the internal reference electrode (i.e., covers the opening area) to form a gel area.

[0073] The hydrogel is PEDOT:PSS / EMIM-Cl / Fc, as described in this embodiment of the invention. + PF6 - PEDOT:PSS / EMIM-Cl / Fc hydrogel or prepared by the method of the embodiments of the present invention + PF6 - Hydrogel.

[0074] In this embodiment of the invention, the integrated screen-printed sensor utilizes the spontaneous redox reaction between hydrogel and the analyte. The hydrogel conductively connects the internal and external reference electrodes to form a circuit. Electrochemical analysis of the species can be achieved by outputting an open-circuit potential. The electrochemical process can proceed spontaneously, with almost zero current in the entire circuit. The electrode interface reaction is in a dynamic equilibrium state, with extremely low reactant consumption and product formation, exhibiting superior stability and enabling stable detection over long periods. The integrated screen-printed sensor can effectively reduce damage to brain tissue and can be used for the detection of neurochemical molecules in the brain, realizing potential-based analysis and in-situ detection of various neurochemical molecules in the brain.

[0075] In some embodiments, one end of the internal reference electrode and one end of the external reference electrode are exposed to form a wiring area; optionally, one end (top) of the internal and external reference electrodes respectively retains a wiring area of ​​0.1 cm × 0.3 cm.

[0076] In some embodiments, the other end of the external reference electrode and one end of the working electrode are exposed, together forming a detection area (or detection interface).

[0077] In some embodiments, the opening region can expose the middle of the working electrode and the internal reference electrode of the electrode layer; the present invention does not have a special limitation on the shape and size of the opening region. In a specific embodiment, for example, the opening region is rectangular, optionally, an opening region of 0.5 cm × 0.6 cm.

[0078] In some embodiments, the working electrode includes a carbon working electrode; the present invention does not specifically limit the shape and size of the working electrode. In a specific embodiment, for example, the working electrode includes a first part and a second part, the first part being elongated (rectangular), the second part being circular (circular), and the first part and the second part being connected; the second part is one end of the working electrode; optionally, the elongated shape is 0.1 cm × 1.3 cm, and the circular shape has a diameter of 0.3 cm.

[0079] In some embodiments, the internal reference electrode includes an Ag / AgCl internal reference electrode; the present invention does not have a special limitation on the shape and size of the internal reference electrode. In a specific embodiment, for example, the internal reference electrode is elongated (rectangular), and optionally, the elongated shape is 0.1 cm × 1.6 cm.

[0080] In some embodiments, the external reference electrode includes an Ag / AgCl external reference electrode. The present invention does not specifically limit the shape and size of the external reference electrode. In a specific embodiment, for example, the external reference electrode includes a third part and a fourth part. The third part is elongated (rectangular), and the fourth part is curved. Optionally, the curved part is a bent strip. The third and fourth parts are connected; specifically, one end of the third part is connected to one end of the fourth part. One end of the external reference electrode is located in the third part, and the other end of the external reference electrode is located in the fourth part. Optionally, the elongated strip has dimensions of 0.1 cm × 1.6 cm, and the curved part has an outer dimension of 0.7 cm × 0.5 cm and a width of 0.1 cm.

[0081] In some embodiments, the base layer comprises polyethylene terephthalate (PET), and the base layer is a flexible base layer.

[0082] In some embodiments, the insulating layer is an insulating ink layer.

[0083] A method for fabricating an integrated screen-printed sensor according to an embodiment of the present invention includes the following steps: (1) An electrode layer is prepared on a substrate using screen printing technology, and an insulating layer with an opening area is covered on the electrode layer and the substrate; Optionally, the electrode layer is disposed on the base layer, and the insulating layer covers the electrode layer and the base layer; the electrode layer includes a working electrode, an internal reference electrode, and an external reference electrode; the insulating layer has an opening area to expose the middle portion of the working electrode and the internal reference electrode in the electrode layer; (2) Coating the opening area with PEDOT:PSS / EMIM-Cl / Fc + PF6 - The pregel solution is dried to form the hydrogel described in the embodiments of the present invention, and then the opening area is encapsulated to obtain an integrated screen-printed sensor; Optionally, the opening region is provided with the hydrogel described in the embodiments of the present invention, and the hydrogel covers the middle of the exposed working electrode and internal reference electrode to form a gel region.

[0084] In this embodiment of the invention, a pre-gel solution is coated at the connection between the working electrode and the internal reference electrode, and after drying, an integrated screen-printed sensor is obtained.

[0085] In some embodiments, in step (2), the coating includes drop coating.

[0086] In some embodiments, the drying in step (2) includes room temperature drying.

[0087] In some embodiments, in step (2), the opening area is encapsulated; alternatively, after drying to form a hydrogel, a plastic wrap is used to complete the encapsulation, that is, the opening area (on the hydrogel) is encapsulated by covering it with a plastic wrap.

[0088] This invention relates to an all-solid-state spontaneous bipolar molecular potential sensor, or an integrated screen-printed sensor, for the detection of neurochemical molecules, preferably for in-situ detection of neurochemical molecules in the living brain.

[0089] In this embodiment of the invention, the sensor can achieve electrochemical analysis of species by outputting an open-circuit potential. The electrochemical process can proceed spontaneously, the current in the entire circuit is almost zero, the electrode interface reaction is in a dynamic equilibrium state, the consumption of reactants and the amount of product formation are extremely low, exhibiting superior stability and achieving stable detection over long periods of time. It can effectively reduce the damage to brain tissue and can be used for in-situ detection of neurochemical molecules in the brain. Moreover, it has strong universality for the test components and can precisely control the inherent potential of the gel interface to achieve potential-type analysis and in-situ detection of various neurochemical molecules in the brain.

[0090] In some embodiments, the detection of neurochemical molecules includes the detection of reducing substances or substances with electrochemical activity.

[0091] In some embodiments, the detection of neurochemical molecules includes in-situ detection of neurochemical molecules.

[0092] In some embodiments, the detection of neurochemical molecules includes electrochemical analysis of neurochemical molecules in vivo.

[0093] In some embodiments, the neurochemical molecule includes a neurochemical molecule with an oxidation potential of less than +0.2V; optionally, the neurochemical molecule includes at least one of ascorbic acid (AA), dopamine, and H2S.

[0094] In this embodiment of the invention, PEDOT:PSS / EMIM-Cl / Fc + PF6 - The hydrogel has a reduction potential of +0.2 V, the ascorbic acid has an oxidation potential of -0.1 V, and the dopamine has an oxidation potential of 0 V. The hydrogel and the analyte can form a spontaneous redox reaction. The open-circuit voltage (open-circuit potential) is linearly related to the logarithm of the concentration of the analyte, thus enabling the detection of the analyte.

[0095] In some embodiments, during the detection process, the sensor is placed (e.g., inserted, immersed, etc.) in the sample to be tested, the open circuit potential value is tested, and then the content of the analyte in the sample to be tested is determined based on the open circuit potential value. Optionally, the open-circuit potential (open-circuit voltage) has a linear relationship with the logarithm of the concentration of the analyte, and the content of the analyte in the sample is determined based on the measured open-circuit potential value and the linear relationship (or the standard curve of open-circuit potential and concentration of the analyte). Optionally, during the detection process of the all-solid-state spontaneous dual-polarization molecular potential sensor, the sensor is placed in the sample to be tested, the open-circuit potential value is tested, and then the content of the analyte in the sample to be tested is determined based on the open-circuit potential value; optionally, the open-circuit potential value between the internal reference electrode and the external reference electrode is tested. Specifically, the method for detecting electrochemical signals of a test sample using an all-solid-state spontaneously bipolarized molecular potential sensor includes: using the all-solid-state spontaneously bipolarized electrode as the working electrode, using an Ag / AgCl electrode constructed from a glass capillary as the external reference electrode, inserting the working electrode and the external reference electrode into the same test sample (test component), testing the open-circuit potential value between the internal reference electrode and the external reference electrode, and then determining the content of the analyte in the test sample based on the open-circuit potential value; Optionally, during the detection process of the integrated screen printing sensor, the sensor is placed in the sample to be tested, the open circuit potential value is tested, and then the content of the analyte in the sample to be tested is determined based on the open circuit potential value; optionally, the open circuit potential value between the internal reference electrode and the external reference electrode is tested. Specifically, the method for detecting electrochemical signals of a sample by an integrated screen-printed sensor involves inserting the sensor's detection area (i.e., the working electrode and the external reference electrode exposed at the bottom) into the same sample; testing the open-circuit potential value between the internal reference electrode and the external reference electrode; and then determining the content of the analyte in the sample based on the open-circuit potential value.

[0096] In some embodiments, the test sample is a test solution containing electrochemically active neurochemical molecules; alternatively, the test sample is artificial cerebrospinal fluid containing neurochemical molecules.

[0097] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0098] Example 1 A type of PEDOT:PSS / EMIM-Cl / Fc + PF6 - The preparation method of hydrogel includes the following steps: (1) Take 2 ml of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate aqueous solution (PEDOT:PSS, 1.1-1.3wt%) into a sample bottle, add 1 ml of 1-ethyl-3-methylimidazolium chloride aqueous solution (EMIM-Cl, 65 mg / ml), and stir vigorously at room temperature for 30 min to mix evenly; (2) Add 300 μl of ferrocene hexafluorophosphate solution (Fc) to the well-mixed PEDOT:PSS / EMIM-Cl solution. + PF6 - The solvent was dimethyl sulfoxide (DMSO), 150 mg / ml. Stirring was continued at room temperature for 30 min to form PEDOT:PSS / EMIM-Cl / Fc. + PF6 - Mixed solution (i.e., pregelation solution).

[0099] (3) Take 10 μl of PEDOT:PSS / EMIM-Cl / Fc + PF6 -The mixed solution was drop-coated onto a glassy carbon electrode and dried at room temperature for 45 min to form a hydrogel. The glassy carbon electrode was polished with alumina particles (0.3 μm and 0.05 μm) before drop-coating and then sonicated three times each in ethanol and deionized water.

[0100] With PEDOT:PSS / EMIM-Cl / Fc + PF6 - A hydrogel-modified glassy carbon electrode was used as the working electrode in 5 ml of 1×PBS solution, with an Ag / AgCl electrode as the reference electrode and a platinum electrode as the counter electrode to construct a three-electrode system. This system was used for PEDOT:PSS / EMIM-Cl / Fc. + PF6 - The redox activity of the hydrogel was electrochemically tested. Cyclic voltammetry was performed at a scan rate of 100 mV / s in the range of -0.2 V to +0.6 V for 10 cycles. The results are as follows: Figure 1 As shown in (a), PEDOT:PSS / EMIM-Cl / Fc + PF6 - The hydrogel exhibited a pair of stable redox peaks; cyclic voltammetry analysis was performed at a scan rate of 1 mV / s in the range of +0.1 V to +0.4 V, and the results are as follows. Figure 1 As shown in (b), PEDOT:PSS / EMIM-Cl / Fc + PF6 - The hydrogel exhibits a pair of reversible redox peaks, with ΔEp at 77 mV. Figure 1 This invention can illustrate the PEDOT:PSS / EMIM-Cl / Fc preparation. + PF6 - Hydrogels exhibit excellent redox activity.

[0101] Example 2 A method for preparing an all-solid-state spontaneously bipolarized electrode includes the following steps: (1) Take a carbon fiber with a diameter of 7 μm and pass it through the inside of a glass capillary tube (inner diameter: 1.5 mm, length: 10 cm); (2) Using a laser drawing instrument, one end of the glass capillary is drawn into a tip, and the carbon fiber passes through the inside of the glass capillary and extends to the outside of the tip. (3) Seal the tip of the glass capillary tube with insulating glue and fix the carbon fiber for about 300 s, then clean with acetone to remove excess glue; (4) Use a positioning instrument to cut the exposed carbon fiber at the tip of the glass capillary to a length of approximately 300 μm; (5) Insert PEDOT:PSS / EMIM-Cl / Fc into one end of the sealed glass capillary tube. + PF6 - A pregel solution was prepared, and an Ag / AgCl reference electrode was inserted, such that the carbon fiber inside the glass capillary and the Ag / AgCl reference electrode were at least partially immersed in the pregel solution. PEDOT:PSS / EMIM-Cl / Fc + PF6 - The preparation of the pregel solution included: taking 2 ml of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate aqueous solution (PEDOT:PSS, 1.1-1.3 wt%) into a sample vial, adding 1 ml of 1-ethyl-3-methylimidazole chloride aqueous solution (EMIM-Cl, 65 mg / ml), and stirring vigorously at room temperature for 30 min to mix thoroughly; adding 300 μl of ferrocene hexafluorophosphate solution (Fc) to the well-mixed PEDOT:PSS / EMIM-Cl solution. + PF6 - The solvent was dimethyl sulfoxide (DMSO), 50 mg / ml. Stirring was continued at room temperature for 30 min to form PEDOT:PSS / EMIM-Cl / Fc. + PF6 - Pregelation solution.

[0102] (6) Place the glass capillary tube at room temperature and allow the pre-gel solution inside the closed end to dry to form a hydrogel, thus obtaining an all-solid-state spontaneous bipolar electrode.

[0103] The electrode activation process is as follows: a constant potential of 1.5 V is applied in a 1 mol / L NaOH solution, and electrochemical activation is performed by oxidation for 90 s. Cyclic voltammetry is then performed in the voltage range of 0.0 to +1.0 V at a scan rate of 0.05 V / s. Once the voltammetric curve stabilizes, the activation of the all-solid-state spontaneous dual-polarization electrode is complete.

[0104] The method for preparing an Ag / AgCl electrode constructed from a glass tube includes the following steps: (1) Take a glass capillary tube (inner diameter: 1.5 mm, length: 10 cm) and draw it using a gravity drawing apparatus; (2) After heating and dissolving artificial cerebrospinal fluid containing 10 vol.% agar powder in an oil bath, the solution is drawn into the tip of a glass capillary tube by siphoning and cooled to form solid agar. (3) Fill the glass capillary with artificial cerebrospinal fluid at the open end, insert an Ag / AgCl electrode (Ag / AgCl wire) into the glass capillary, and seal and fix the open end of the glass capillary and the Ag / AgCl electrode with 502.

[0105] The all-solid-state spontaneous dual-polarization molecular potential sensor mainly consists of an all-solid-state spontaneous dual-polarization electrode as the working electrode and an Ag / AgCl electrode constructed using a glass capillary as the reference electrode.

[0106] The all-solid-state spontaneously bipolarized electrode (working electrode) and the Ag / AgCl electrode (reference electrode) constructed using a glass capillary were inserted into the ascorbic acid solution, and the open-circuit potential of the system was recorded.

[0107] To test the sensing performance of the constructed all-solid-state spontaneously bipolarized molecular potential sensor, the open-circuit potential response at different ascorbic acid concentrations was detected, and a calibration curve between the open-circuit potential and the ascorbic acid concentration was plotted. Different concentrations of ascorbic acid were continuously added to artificial cerebrospinal fluid containing 10 μM ascorbic acid, resulting in detection concentrations of (50 μM, 99.0 μM, 196 μM, 385 μM, 741 μM, and 1.07 mM). The open-circuit potential signal of the system was recorded in real time, and the results are as follows: Figure 2 As shown in (a), the open-circuit potential increases with increasing ascorbic acid concentration, indicating that the sensor has a good response to ascorbic acid. The calibration curve plotted based on the open-circuit potential response and the logarithm of concentration is referenced. Figure 2 (b) indicates that the open-circuit potential response of the electrochemical sensor exhibits a good linear response relationship with the logarithm of the ascorbic acid concentration, and can realize the detection of ascorbic acid concentration.

[0108] Example 3 A method for fabricating an integrated screen-printed sensor includes the following steps: (1) Using screen printing technology, an electrode layer is prepared on a 2.2 cm × 1.0 cm polyethylene terephthalate (PET) substrate, and then an insulating layer with an opening area is covered on the electrode layer and the substrate.

[0109] The electrode layer includes a carbon working electrode composed of a 0.1 cm × 1.3 cm rectangle and a 0.3 cm diameter circle, an Ag / AgCl internal reference electrode in the shape of a 0.1 cm × 1.6 cm rectangle, and an Ag / AgCl external reference electrode composed of a 0.1 cm × 1.6 cm rectangle and a curved portion with an outer dimension of 0.7 cm × 0.5 cm and a width of 0.1 cm. The insulating layer is a 1.3 cm × 1.0 cm insulating ink layer, with a 0.5 cm × 0.6 cm opening in the middle to expose a portion (middle) of the working electrode and the internal reference electrode. Meanwhile, the electrode layer has multiple functional exposure areas: a 0.5 cm × 0.6 cm gel area is located in the middle of the working electrode and the internal reference electrode; the tops of the internal and external reference electrodes each retain a 0.1 cm × 0.3 cm wiring area; and the circular area of ​​the working electrode and the curved part of the external reference electrode form a detection interface. Its structural schematic diagram is shown below. Figure 3 As shown.

[0110] (2) At the opening area of ​​the insulating ink layer, drop-coat PEDOT:PSS / EMIM-Cl / Fc + PF6 - The pre-gelled solution is dried at room temperature to form a hydrogel, and then covered with plastic wrap to complete the encapsulation. PEDOT:PSS / EMIM-Cl / Fc + PF6 - The preparation of the pregel solution included: taking 2 ml of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate aqueous solution (PEDOT:PSS, 1.1-1.3 wt%) into a sample vial, adding 1 ml of 1-ethyl-3-methylimidazole chloride aqueous solution (EMIM-Cl, 65 mg / ml), and stirring vigorously at room temperature for 30 min to mix thoroughly; adding 300 μl of ferrocene hexafluorophosphate solution (Fc) to the well-mixed PEDOT:PSS / EMIM-Cl solution. + PF6 - The solvent was dimethyl sulfoxide (DMSO), 50 mg / ml. Stirring was continued at room temperature for 30 min to form PEDOT:PSS / EMIM-Cl / Fc. + PF6 - Pregelation solution.

[0111] The integrated screen-printed sensor was inserted into the ascorbic acid solution to record the system open-circuit potential.

[0112] To test the sensing performance of the integrated screen-printed sensor, the open-circuit potential response at different ascorbic acid concentrations was detected, and a calibration curve between the open-circuit potential and the ascorbic acid concentration was plotted. Different concentrations of ascorbic acid were continuously added to artificial cerebrospinal fluid containing 10 μM ascorbic acid, resulting in detection concentrations of (50 μM, 99.0 μM, 196 μM, 385 μM, 741 μM, and 1.07 mM). The open-circuit potential signal of the system was recorded in real time, and the results are as follows: Figure 4 As shown in (a), the open-circuit potential increases with increasing ascorbic acid concentration, indicating that the electrochemical sensor has a good response to ascorbic acid. The calibration curves plotted based on the open-circuit potential response and the logarithm of concentration are referenced. Figure 4(b) indicates that the open-circuit potential response of the electrochemical sensor exhibits a good linear response relationship with the logarithm of the ascorbic acid concentration, and can realize the detection of ascorbic acid concentration.

[0113] Comparative Example 1 The method is the same as in Example 2, except that PEDOT:PSS / EMIM-Cl / Fc is used instead. + PF6 - The pregel solution was replaced with PEDOT:PSS / H2O / Fc + PF6 - A pregel solution was prepared by replacing the EMIM-Cl aqueous solution in the pregel solution preparation process with an equal volume of water. This resulted in an all-solid-state spontaneously bipolarized electrode without 1-ethyl-3-methylimidazole chloride.

[0114] To test the sensing performance of the constructed potentiometric electrochemical sensor, the open-circuit potential response at different ascorbic acid concentrations was detected, and a calibration curve between the open-circuit potential and the ascorbic acid concentration was plotted. Different concentrations of ascorbic acid were continuously added to artificial cerebrospinal fluid containing 10 μM ascorbic acid, resulting in detection concentrations of (50 μM, 99.0 μM, 196 μM, 385 μM, 741 μM, and 1.07 mM). The open-circuit potential signal of the system was recorded in real time, and a calibration curve was plotted based on the logarithm of the open-circuit potential response and concentration. Figure 5 (a) indicates that the open-circuit potential response of the electrochemical sensor does not exhibit a linear relationship with the logarithm of the ascorbic acid concentration.

[0115] Comparative Example 2 The method is the same as in Example 2, except that PEDOT:PSS / EMIM-Cl / Fc is used instead. + PF6 - The pregel solution was replaced with a PEDOT:PSS / EMIM-Cl / DMSO pregel solution, meaning that the Fc in the pregel solution preparation process was replaced. + PF6 - The solution was replaced with an equal volume of DMSO. This yielded an all-solid-state spontaneously bipolarized electrode without ferrocene hexafluorophosphate doping.

[0116] To test the sensing performance of the constructed potentiometric electrochemical sensor, the open-circuit potential response at different ascorbic acid concentrations was detected, and a calibration curve between the open-circuit potential and the ascorbic acid concentration was plotted. Different concentrations of ascorbic acid were continuously added to artificial cerebrospinal fluid containing 10 μM ascorbic acid, resulting in detection concentrations of (50 μM, 99.0 μM, 196 μM, 385 μM, 741 μM, and 1.07 mM). The open-circuit potential signal of the system was recorded in real time, and a calibration curve was plotted based on the logarithm of the open-circuit potential response and concentration. Figure 5 (b) indicates that the open-circuit potential response of the electrochemical sensor does not exhibit a linear relationship with the logarithm of the ascorbic acid concentration.

[0117] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0118] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A hydrogel, characterized in that, The hydrogel is PEDOT:PSS / EMIM-Cl / Fc + PF6 - Hydrogels comprising: poly(3,4-ethylenedioxythiophene): a conductive polymer of polystyrene sulfonate, 1-ethyl-3-methylimidazole chloride, and ferrocene hexafluorophosphate.

2. The hydrogel according to claim 1, characterized in that, The PEDOT:PSS / EMIM-Cl / Fc + PF6 - In the hydrogel, the mass ratio of the poly(3,4-ethylenedioxythiophene):polystyrene sulfonate conductive polymer, 1-ethyl-3-methylimidazolium chloride, and ferrocene hexafluorophosphate is 4~5:13:3~9.

3. A method for preparing the hydrogel according to claim 1 or 2, characterized in that, include: Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate conductive polymer, 1-ethyl-3-methylimidazolium chloride, ferrocene hexafluorophosphate, and solvent were mixed to obtain PEDOT:PSS / EMIM-Cl / Fc + PF6 - The pregel solution was dried to obtain PEDOT:PSS / EMIM-Cl / Fc + PF6 - Hydrogel.

4. A fully solid-state spontaneously bipolarized electrode, characterized in that, include: A glass capillary tube, wherein one end of the glass capillary tube is a pointed tip; Carbon fiber, wherein the carbon fiber is disposed inside the glass capillary, and one end of the carbon fiber is located outside the tip; An internal reference electrode is disposed within the glass capillary; optionally, the internal reference electrode includes an Ag / AgCl reference electrode. The hydrogel of claim 1 or 2, wherein the hydrogel is disposed within the glass capillary, and at least a portion of the carbon fiber and at least a portion of the internal reference electrode are located within the hydrogel.

5. A method for preparing the all-solid-state spontaneously polarized electrode according to claim 4, characterized in that, Includes the following steps: (1) The carbon fiber passes through the inside of the glass capillary; one end of the glass capillary is pulled into a pointed tip, and the carbon fiber passes through the inside of the glass capillary and extends to the outside of the pointed tip; The opening at the tip of the glass capillary is sealed. (2) Insert PEDOT:PSS / EMIM-Cl / Fc into one end of the glass capillary. + PF6 - A pregel solution is prepared, and an internal reference electrode is inserted into the glass capillary, such that at least a portion of the carbon fibers inside the glass capillary and at least a portion of the internal reference electrode are immersed in the pregel solution; then the pregel solution is dried to form the hydrogel according to claim 1 or 2, thereby obtaining an all-solid-state spontaneously bipolarized electrode.

6. A fully solid-state spontaneously bipolarized molecular potential sensor, characterized in that, include: Working electrode and external reference electrode; the working electrode includes the all-solid-state spontaneous bipolar electrode as described in claim 4, or the all-solid-state spontaneous bipolar electrode prepared by the preparation method described in claim 5.

7. The all-solid-state spontaneously bipolarized molecular potential sensor according to claim 6, characterized in that, The external reference electrode includes an Ag / AgCl electrode constructed from glass capillaries; Preferably, the Ag / AgCl electrode constructed from glass capillaries comprises: A glass capillary tube, wherein one end of the glass capillary tube is a pointed tip; The Ag / AgCl electrode is disposed inside the glass capillary tube; Artificial cerebrospinal fluid, wherein the artificial cerebrospinal fluid is disposed within the glass capillary, and at least a portion of the Ag / AgCl electrode is located within the artificial cerebrospinal fluid; Solid agar containing artificial cerebrospinal fluid, wherein the tip of the glass capillary is provided with the solid agar containing artificial cerebrospinal fluid.

8. An integrated screen-printed sensor, characterized in that, include: A base layer, an electrode layer, and an insulating layer; the electrode layer is disposed on the base layer, and the insulating layer covers the electrode layer and the base layer; The electrode layer includes a working electrode, an internal reference electrode, and an external reference electrode; The insulating layer has an opening to expose the middle portion of the working electrode and the internal reference electrode in the electrode layer; the opening is provided with the hydrogel according to claim 1 or 2, the hydrogel covering the exposed middle portion of the working electrode and the internal reference electrode to form a gel region.

9. The integrated screen-printed sensor according to claim 8, characterized in that, One end of the internal reference electrode and one end of the external reference electrode are exposed to form a wiring area; And / or, the other end of the external reference electrode and one end of the working electrode are exposed, together forming a detection area; And / or, the working electrode includes a carbon working electrode; And / or, the internal reference electrode includes an Ag / AgCl internal reference electrode; And / or, the external reference electrode includes an Ag / AgCl external reference electrode.

10. A method for preparing an integrated screen-printed sensor as described in claim 8 or 9, characterized in that, Includes the following steps: (1) An electrode layer is prepared on a substrate using screen printing technology, and an insulating layer with an opening area is covered on the electrode layer and the substrate; (2) Coating the opening area with PEDOT:PSS / EMIM-Cl / Fc + PF6 - The pregel solution is dried to form the hydrogel as described in claim 1 or 2, and then the opening area is encapsulated to obtain an integrated screen-printed sensor.

11. An application of the all-solid-state spontaneously bipolarized molecular potential sensor as described in claim 6 or 7, or the integrated screen-printed sensor as described in claim 8 or 9, characterized in that, For the detection of neurochemical molecules, preferably for the in situ detection of neurochemical molecules in the living brain.

12. The application according to claim 11, characterized in that, The neurochemical molecules include at least one of ascorbic acid, dopamine, and H2S; And / or, during the detection process of the all-solid-state spontaneous bipolar molecular potential sensor, the sensor is placed in the sample to be tested, the open circuit potential value is tested, and then the content of the analyte in the sample to be tested is determined based on the open circuit potential value; And / or, during the detection process of the integrated screen printing sensor, the sensor is placed in the sample to be tested, the open circuit potential value is tested, and then the content of the analyte in the sample to be tested is determined based on the open circuit potential value.

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