A synergistic method for capturing silver ions and anti-sensitivity based on graphene pore regulation

Abstract

The present application relates to the technical field of electrocardio electrode, and relates to a silver ion capture and anti-sensitivity synergistic method based on graphene pore regulation, comprising: freezing and freeze-drying an oxidized graphene dispersion liquid in a directional gradient to form a substrate with an axial macropore-mesopore gradient structure; wherein the macropore aperture of the first surface is larger than that of the second surface, and the mesopore network is distributed in the thickness direction of the substrate; sequentially reducing, sulfonic acid group electropolymerizing and thiol group fixing the substrate, spin coating a chitosan-hyaluronic acid composite layer on the first surface to obtain a functional film; constructing an Ag / AgCl conductive layer on a flexible substrate and adhering the second surface to the conductive layer, and coating an ionic gel on the interface to form an electrocardio electrode; adhering the first surface to the skin, and allowing sweat to penetrate into the conductive layer to generate Ag + Reverse diffusion to the functional film is dynamically captured by the sulfonic acid group and bonded with the adjacent thiol group. The present application solves the problem of sensitization caused by silver ion penetration in the existing electrode, and improves the biological safety of long-term application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrocardio electrode, and relates to a silver ion capture and anti-allergy synergistic method based on graphene pore regulation. BACKGROUND

[0002] Long-term dynamic electrocardio monitoring plays a key role in the diagnosis of cardiac diseases such as arrhythmia, and can continuously monitor electrocardio signals for a long time to capture abnormal electrocardio changes that cannot be found by conventional electrocardiogram. As a core component of medical diagnosis, the performance of electrocardio monitoring electrodes directly affects the accuracy of the detected signals and the safety of patients.

[0003] At present, there are various electrocardio electrode technologies on the market. Traditional Ag / AgCl electrodes are widely used, often in combination with conductive gel. This type of electrode enhances the conduction of electrical signals through conductive gel. However, clinical studies have found that when used for a long time, Ag+ will be released from the surface of the electrode due to oxidation, corrosion or micro-dissolution, penetrate the skin through the conductive gel, and cause contact dermatitis or even immune reactions. This not only causes pain to the patient and affects the patient's use experience, but also may cause the patient to terminate the monitoring prematurely, affecting the accuracy of the diagnosis results and the continuity of the monitoring. Moreover, during long-term use, the gel is prone to dry out and fail, resulting in an increase in interface impedance, an increase in signal noise, an increase in signal baseline drift and motion artifacts, especially in long-term monitoring of more than 72 hours, the signal distortion rate increases significantly, which is not conducive to the development of long-term dynamic electrocardio monitoring.

[0004] As a single-atom layer two-dimensional carbon material, graphene has ultra-high electrical conductivity, which can ensure efficient transmission of electrocardio signals. Its atomic-level flat surface is more compatible with the skin than metal. These characteristics make graphene theoretically solve the problem of metal ion sensitization of traditional electrodes and consider the stability of signal transmission. However, the pore structure of the existing graphene electrode lacks precise regulation. At present, the graphene film prepared by the chemical vapor deposition method used in most studies is an unordered accumulation structure with small porosity. Although the material prepared by the oxidation-reduction method has improved porosity, the pore size distribution is wide, and there is no gradient design, which cannot intercept silver ions specifically, resulting in an increase in interface impedance. Moreover, the existing technology focuses on the optimization of electrical conductivity, but ignores the synergistic improvement of silver ion capture and anti-sensitivity performance. This makes it difficult to avoid the risk of metal ion sensitization even if the graphene electrode performs well in signal transmission. In the long-term application process, silver ions can still penetrate the skin through the disordered pore structure, causing an allergic reaction. At the same time, the unreasonable pore distribution also affects the ion exchange efficiency of the electrode-skin interface, further exacerbating the fluctuation of the interface impedance, leading to unstable electrocardio signal acquisition. In addition, due to the lack of precise design of the pore structure, the adaptability of the graphene electrode to other components such as the conductive gel layer and the conductive silver electrode buckle is poor, and the interface contact is poor, which not only reduces the signal transmission efficiency, but also may cause additional stimulation to the skin due to local current concentration, which seriously restricts the practical application value of the graphene electrode in long-term dynamic electrocardio monitoring.

[0005] The information disclosed in this Background section is only for the purpose of enhancing the understanding of the general background of the application and should not be taken as admitting that this information is prior art known to those of ordinary skill in the art. SUMMARY

[0006] The first object of the present application is to provide a silver ion capture and anti-sensitivity synergistic method based on graphene pore regulation. By directional gradient pore regulation of graphene film, precise interception of Ag+ is achieved, the problem of silver ion penetration-induced sensitization in existing electrodes is solved, and the biological safety of long-term application is improved.

[0007] The above technical object of the present application is achieved by the following technical solution:

[0008] A silver ion dynamic capture and anti-sensitivity synergistic method based on graphene pore regulation, comprising:

[0009] S1 freeze-drying graphene oxide dispersion liquid in a gradient direction to form a substrate with an axial macro-mesoporous gradient structure, wherein the macro-pore size gradually decreases from the first surface to the second surface, and the mesoporous forms a connected network throughout the thickness; sequentially reducing, sulfonate electropolymerizing and thiolating the substrate; spin-coating a chitosan-hyaluronic acid composite layer on the first surface to obtain a functional membrane;

[0010] Specifically, step S1 comprises:

[0011] S11 gradient freezing and freeze-drying of graphene oxide substrate:

[0012] A graphene oxide (GO) dispersion liquid with a concentration of 5-10 mg / mL is injected into a polytetrafluoroethylene mold, the bottom of the mold is in contact with a cold table at-30 to-20℃, and the top is exposed to room temperature air, and the ice crystal growth direction is controlled to extend along the thickness direction of the substrate at a gradient cooling rate of 0.5-2℃ / min. During this process, the ice crystals act as templates to guide the ordered arrangement of graphene oxide layers, and the interlayer spacing of the graphene oxide layers presents a "loose top and dense bottom" feature due to the pushing force generated by ice crystal growth, which not only ensures the connectivity of the macro-pore channel, but also provides a support skeleton for the mesoporous network. A porous structure with an axial gradient is formed.

[0013] After freezing, maintain at-40℃ for 4-6h to ensure complete freezing and avoid ice crystal recrystallization, then warm up to-20℃ at a rate of 0.5℃ / min and maintain for 10-12h to complete the freeze-drying process. During this process, the ice crystals sublimate to form porous channels, and finally a substrate with an axial macro-mesoporous gradient structure is obtained. The slow warming rate of 0.5℃ / min can reduce the stress impact when the ice crystals sublimate, avoiding the collapse of the mesoporous, and maintaining at-20℃ for 10-12h can completely remove the residual moisture, ensuring that the pore structure does not deform in subsequent processing.

[0014] The final formed substrate has a second surface on the side in contact with the mold bottom and a first surface facing the air, and the porosity of the first surface is higher than that of the second surface. The reason is that the mold bottom is in contact with the cold table, the ice crystal nucleation density is high and the growth space is limited, forming small-size macro-pores; the top is exposed to air, the ice crystals grow fully, forming large-size macro-pores, and there are more residual pores after the sublimation of the top ice crystals, so the porosity of the first surface is higher.

[0015] The porosity gradient matches the silver ion migration path with the pore size gradient, the macro-pore size of the first surface is larger, which contacts the skin side and dominates the sweat permeation and ion exchange; the macro-pore size of the second surface is smaller, which is in contact with the Ag / AgCl conductive layer; the mesoporous connected network: distributed in the entire thickness direction of the substrate, providing Ag +Transmission channel. The application ensures high porosity of the first surface and dense structure of the second surface by precisely regulating the pore gradient structure, improves ion conduction efficiency through mesoporous connectivity, and reduces silver ion permeability by more than 90% compared to disordered pore structure.

[0016] S12 Reduction, sulfonic acid group electropolymerization and thiolation fixation of the substrate:

[0017] The freeze-dried substrate is immersed in a 0.1-0.5 mol / L L-ascorbic acid aqueous solution to reduce the resistivity to 10 -1 ~10 -3 Ω·m. During the reduction process, ascorbic acid reduces the oxygen-containing functional groups on the surface of the graphene oxide, restores the conjugated structure of graphene, and improves the conductivity.

[0018] Specifically, the reduction reaction is carried out in a water bath at 30-50°C, the reaction time is 2-6h, and low-speed continuous stirring is required to ensure sufficient contact between the L-ascorbic acid solution and the graphene substrate. Temperature <30°C will result in too slow reduction rate, and temperature >50°C may cause ascorbic acid decomposition failure. During the process, a four-probe resistivity tester is used to test different areas of the substrate every 30 minutes, and the average value is taken as the current resistivity. When the resistivity difference of two consecutive tests is <5%, and the value is stable in the range of 10 -1 ~10 -3 Ω·m, it is determined that the reduction reaction has reached the end point.

[0019] After reduction is completed, the substrate is taken out, immersed in a 0.05 mol / L EDTA solution for purification to remove metal ion impurities, then washed with ultrapure water several times, and dried in an oven. The dried substrate after reduction is immersed in a solution containing 1-5 mmol / L sulfonic acid aniline monomer; constant potential mode is used for electropolymerization, the potential is controlled at +0.70~+0.80V, and the polymerization termination condition is charge quantity of 0.8-1.2 C / cm 2 .

[0020] As preferred, the solvent of the sulfonic acid aniline monomer solution is 0.5 mol / L H2SO4 aqueous solution. H2SO4 aqueous solution is used to provide an acidic environment to promote the protonation of aniline monomer, and high-purity nitrogen gas is introduced to remove oxygen for 15-20 min before solution preparation to avoid oxygen interference with the polymerization reaction.

[0021] As preferred, the electropolymerization is carried out using a three-electrode system (working electrode: substrate; counter electrode: platinum sheet; reference electrode: Ag / AgCl). The working potential is controlled at +0.70~+0.80V to ensure the ordered polymerization of sulfonic acid aniline monomer on the surface of graphene, and avoid disordered accumulation caused by overpotential. During the polymerization process, the charge quantity method is used for monitoring, and when the charge quantity reaches 0.8-1.2 C / cm 2The reaction is terminated to ensure a moderate loading of sulfonic acid groups. This process forms a polyaniline sulfonic acid layer on the substrate surface and mesoporous inner wall, which provides Ag + binding sites for the sulfonic acid groups (-SO3H).

[0022] After polymerization, the substrate is immersed in a 0.1 mol / L H2SO4 solution and ultrasonically cleaned at a power of 100-150 W for 5-10 min to remove the physically adsorbed monomers and oligomers on the surface; then dried in a vacuum drying oven at 40-60°C for 1-2 h to avoid degradation of the polyaniline sulfonic acid chains caused by high temperature and ensure the electrochemical activity of the sulfonic acid groups.

[0023] After drying, the acrylic acid is plasma grafted on the substrate to generate carboxyl groups, and the reaction conditions are controlled to achieve a carboxyl group density of 3.5-4.2 groups / nm 2 After the carboxyl groups are activated by an NHS / EDC activation solution and reacted with a 0.1-0.5 mol / L N-acetylcysteine solution for 4-8 h, drying is performed to achieve covalent immobilization of the sulfhydryl groups (-SH).

[0024] As a preferred, argon (Ar) plasma is used, with a gas flow rate of 20-30 sccm and a vacuum degree of 5-10 Pa; the acrylic acid is introduced into the reaction chamber in gaseous form, and the plasma treatment power is 50-100 W, with a treatment time of 2-5 min. The substrate temperature during grafting should not exceed 80°C to avoid damage to the graphene structure.

[0025] Specifically, X-ray photoelectron spectroscopy (XPS) can be used to detect the surface elemental composition, and the carboxyl group density can be calculated by the proportion of the characteristic peak area of the carboxyl carbon (-COOH) in the C1s peak. If the density is less than 3.5 groups / nm 2 , the plasma treatment time can be extended by 1-2 min or the acrylic acid evaporation temperature can be increased by 5-10°C; if the density is too high, the power can be reduced by 10-20 W or the treatment time can be shortened by 1 min to avoid steric hindrance caused by excessive carboxyl groups.

[0026] As a preferred, the activation solution uses a 0.1 mol / L MES buffer with a pH of 5.0-6.0 as the solvent, and the concentrations of NHS and EDC are both 0.05-0.1 mol / L. After the substrate is immersed in the activation solution, it is reacted at 25-30°C in the dark for 15-30 min with slight stirring to ensure that the carboxyl groups are fully activated into active esters.

[0027] As preferred, after activation, react with 0.1-0.5 mol / L N-acetyl cysteine solution, the reaction is carried out in 0.05 mol / L PBS buffer (pH 7.2-7.4) to avoid excessive acidity leading to thiol protonation; the reaction temperature is 30-37℃, and nitrogen is introduced to prevent thiol oxidation; after the reaction is completed, the substrate is cleaned with ultrapure water for 10-15 min to remove physically adsorbed N-acetyl cysteine. The cleaned substrate is dried in a vacuum drying oven at 30-40℃ for 2-3h, the vacuum degree is -0.08~-0.1MPa, and a small amount of nitrogen is introduced as a protective gas during the drying process; after drying, the subsequent assembly needs to be carried out within 24h, or it is sealed and stored in a desiccator to prevent the thiol from reacting with oxygen in the air to form disulfide bonds.

[0028] S13 Spin-coating modification of chitosan-hyaluronic acid composite layer:

[0029] Prepare a composite solution containing 1-3wt% chitosan (degree of deacetylation ≥90%) and 0.5-2wt% hyaluronic acid (molecular weight 100-300kDa), and the solvent of the composite solution is 1% acetic acid aqueous solution; specifically, first slowly add chitosan to 1% acetic acid aqueous solution, stir at 300-500rpm at 30-40℃ for 2-4h until completely dissolved, then add hyaluronic acid, continue to stir for 1-2h to form a uniform solution; the solution needs to be filtered through a 0.22μm filter membrane to remove undissolved substances, stored at 4℃ and restored to room temperature before use, and the storage time should not exceed 72h to prevent degradation of hyaluronic acid. For different molecular weight hyaluronic acid, the stirring time can be adjusted to ensure that the molecular chain is fully stretched.

[0030] Spin-coat the chitosan-hyaluronic acid composite solution on the first surface of the substrate at a speed of 1000-3000rpm to form a functional layer with a thickness of 1-2μm. The composite layer has pH responsiveness: initial dry state: pore size 5-10nm; after contacting with sweat (pH 5.5-7.0): swells to a pore size of 2-5nm. The spin-coating is carried out in two steps: first spin at a low speed of 500rpm for 5s to evenly spread the solution, then increase to the target speed and spin for 30-60s; the substrate needs to be fixed on the spin-coater chuck in advance to ensure that the first surface is horizontal and the inclination is <0.5°, to avoid uneven distribution of the solution leading to thickness deviation.

[0031] In the dry state, the molecular chains of chitosan-hyaluronic acid composite layer are tightly stacked through hydrogen bonds, forming a relatively loose porous structure; after contacting with sweat (pH 5.5-7.0), the amino groups (-NH2) in the chitosan molecular chain are protonated to form -NH3 + , which has electrostatic attraction with the carboxyl groups (-COO-) of hyaluronic acid, driving the molecular chains to approach each other. Since the total volume of the composite layer is limited by the substrate and remains unchanged, the aggregation of molecular chains leads to a decrease in the distance between the pore walls, and the pore size shrinks from 5-10nm to 2-5nm.

[0032] S2 constructing Ag / AgCl conductive layer on flexible substrate and pasting with second surface, interface coated with ionogel to form ECG electrode;

[0033] As preferred, in step S2, the Ag / AgCl conductive layer is formed by screen printing and curing at 70-90℃ from Ag / AgCl mixed paste, and the mass ratio of AgCl in the Ag / AgCl mixed paste is 30-70%. The Ag / AgCl mixed paste uses deionized water as solvent, adds 2-5wt% ethyl cellulose as binder and 1-3wt% triethanolamine as dispersant, and is ball milled by a planetary ball mill for 2-4h to ensure uniform dispersion of Ag and AgCl particles and avoid agglomeration.

[0034] The screen printing selects a 100-200 mesh stainless steel screen, the printing pressure is 30-50N, and the doctor blade angle is 45-60° to ensure uniform thickness of the conductive layer; the curing process adopts a stepwise temperature rise: first pre-baking at 50℃ for 30min to remove the solvent, then heating to 70-90℃ for 1-2h, and the heating rate is 5℃ / min to avoid cracking of the paste caused by rapid heating.

[0035] As preferred, in step S2, the ionogel includes 6-8wt% hydroxyethyl cellulose, 10wt% glycerol, and the rest electrolyte salt, wherein the hydroxyethyl cellulose provides the gel skeleton, and the concentration of 6-8wt% can balance the mechanical strength and ion conductivity; the 10wt% glycerol acts as a humectant, combines with water molecules through hydrogen bonds, so that the weight loss rate of the gel is less than 10% within 72h; the LiCl and KCl in the electrolyte salt are mixed at a molar ratio of 5:1, and the total concentration is 1-2mol / L, which can be optimized by alternating current impedance spectrum to ensure that the conductivity is stable at 0.12-0.15S / m at 25℃; the gel preparation needs to be treated in a vacuum degassing machine to remove air bubbles to avoid poor interface contact.

[0036] As preferred, in step S2: align the Ag / AgCl conductive layer coated with ionogel with the second surface, and hot-press at 0.1-0.3MPa and 40-50℃ for 30-60s, the ionogel completely fills the micro gap between the conductive layer and the second surface, and the nanopore channel forms a molecular sieve effect, selectively allowing H2O, Cl - to pass through while blocking Ag + and providing Li + / K + dominant ion conduction path.

[0037] S3 pasting the first surface to the skin, sweat permeates to the Ag / AgCl conductive layer to initiate electrochemical corrosion, and the generated Ag + diffuses reversely to the functional film to be dynamically captured by the sulfonic acid group and bonded with the adjacent thiol group.

[0038] As preferred, in step S3, Ag + diffuses in the direction opposite to the sweat permeation direction, Ag + The driving force of the reverse diffusion includes the difference in Ag+concentration gradient between the interface of the conductive layer and the mesoporous region of the functional film, and the negative potential of the sulfonic acid-modified mesoporous wall.

[0039] The electrostatic attraction between the sulfonic acid group and Ag + is a fast reversible reaction, Ag + migrates to the adjacent sulfhydryl group under the driving of the negative potential gradient, while the soft acid-soft base reaction between the sulfhydryl group and Ag + has an irreversible covalent bond with a binding constant much larger than that of the sulfonic acid group and Ag + Under the driving of the concentration gradient and thermodynamic advantage, it migrates from the sulfonic acid group site to the adjacent sulfhydryl group and is finally covalently fixed. Ag-S covalent bond is formed.

[0040] As preferred, in step S3, the chitosan-hyaluronic acid composite layer swells to form a hydrated barrier under the pH of sweat; free histamine is captured by hydrogen bonds. Free histamine is derived from the local skin stress reaction caused by the electrode skin, and Ag + can stimulate mast cells to release histamine into sweat when the mechanical pressure is > 15 kPa or the sweat pH is abnormal (pH < 5.0 or > 8.5).

[0041] Compared with the prior art, the present application has the following beneficial effects: in the present application, the axial macropore-mesoporous gradient structure formed by directional gradient freezing and freeze-drying, combined with the synergistic effect of sulfonic acid group electropolymerization and thiolation fixation, constructs a multi-level interception-stable fixation system for Ag+. The first surface macroporous structure allows sweat to permeate to maintain ion conduction, while the mesoporous network can precisely intercept Ag + through size screening, and the negative potential and concentration gradient of the sulfonic acid group form a double driving force to covalently bond and fix the reverse diffused Ag + , significantly reducing the amount of Ag + migrating to the skin. Compared with traditional Ag / AgCl electrodes and unregulated graphene electrodes, the silver ion permeability can be reduced by more than 90%, fundamentally reducing the occurrence of allergic reactions such as contact dermatitis, and greatly improving the long-term biological safety of skin.

[0042] In the present application, the graphene film with gradient pore structure maintains excellent conductivity after reduction treatment, the mesoporous network not only ensures the continuity of the electron conduction path, but also maintains efficient interface contact with the conductive gel layer and the conductive silver electrode buckle through the through structure, avoiding the impedance fluctuation caused by the traditional disordered pore structure. The sulfonic acid group modification not only enhances the silver ion capture ability, but also can reduce the interface impedance through ion conduction assistance, cooperates with the electrolyte environment of the conductive gel layer, stabilizes the electrode-skin interface impedance, reduces the signal noise, ensures the complete collection of weak electrocardio signals such as P wave and T wave, and solves the signal distortion problem caused by the release of silver ions or the increase of impedance of the existing electrode.

[0043] In the present application, the chitosan-hyaluronic acid composite layer spin-coated on the first surface has pH response characteristics, and when the pH value of the skin changes due to sweat secretion, the pore size can be shrunk to 2-5nm, further strengthening the physical barrier effect of Ag + and irritating substances; at the same time, the natural biocompatibility of chitosan and hyaluronic acid can soothe the skin and reduce the mechanical stimulation caused by the direct contact of graphene and the skin, meeting the comfort demand of long-term monitoring. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0045] Figure 1 The step flow chart of the silver ion dynamic capture and anti-sensitivity synergistic method based on graphene pore regulation; DETAILED DESCRIPTION

[0046] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the specific implementation, features and effects of the silver ion capture and anti-sensitivity synergistic method based on graphene pore regulation according to the present application are described in detail as follows. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0047] Example 1:

[0048] As Figure 1 shown, a silver ion dynamic capture and anti-sensitivity synergistic method based on graphene pore regulation comprises:

[0049] S1 freeze-drying graphene oxide dispersion liquid in a gradient direction to form a substrate with an axial macropore-mesopore gradient structure, wherein the macropore size gradually decreases from the first surface to the second surface, and the mesopores form a connected network throughout the thickness; sequentially reducing, sulfonic acid group electropolymerizing and thiol group fixing the substrate; spin-coating a chitosan-hyaluronic acid composite layer on the first surface to obtain a functional membrane;

[0050] Specifically, step S1 comprises:

[0051] S11 gradient freezing and freeze-drying of graphene oxide substrate:

[0052] Take graphene oxide dispersion liquid with a concentration of 5 mg / mL and inject it into a polytetrafluoroethylene mold.

[0053] Contact the bottom of the mold with a cold table set at a temperature of -25℃, and expose the top of the mold to room temperature air environment, and cool at a gradient cooling rate of 1℃ / min to make the ice crystal growth direction extend along the thickness direction of the substrate.

[0054] After freezing is completed, place the mold in a freeze dryer and maintain at -40℃ for 5h to ensure complete freezing of the substrate.

[0055] Subsequently, increase the temperature of the freeze dryer to -20℃ at a rate of 0.5℃ / min and maintain at this temperature for 11h to complete the freeze-drying process. At this time, the ice crystals sublimate to form porous channels, and a substrate with an axial macropore-mesopore gradient structure is obtained. The side in contact with the bottom of the mold is the second surface, and the side facing the air is the first surface, and the porosity of the first surface is higher than that of the second surface.

[0056] S12 reduction, sulfonic acid group electropolymerization and thiol group fixation of the substrate:

[0057] After freeze-drying, immerse the substrate in a 0.3 mol / L aqueous L-ascorbic acid solution for reduction treatment, and measure the resistivity of the substrate periodically during the treatment until the resistivity decreases to 10 -2 Ω·m. The oxygen-carbon ratio of graphene oxide before reduction is 0.3, and after reduction by L-ascorbic acid, the oxygen-carbon ratio decreases to 0.05-0.15, wherein the reduction rate of hydroxyl and epoxy groups is >80%, and the reduction rate of carboxyl groups is >60%. After reduction is completed, remove the substrate, immerse it in a 0.05 mol / L EDTA solution for purification to remove metal ion impurities, then rinse with ultrapure water several times, and dry in an oven.

[0058] Prepare a solution containing 3 mmol / L sulfonic acid group-containing aniline monomer, and the solvent is 0.5 mol / L H2SO4 aqueous solution. Immerse the dried substrate in the solution.

[0059] The three-electrode system (working electrode: substrate; counter electrode: platinum plate; reference electrode: Ag / AgCl) was used for electro-polymerization on an electrochemical workstation, the constant potential mode was selected, the working potential was controlled at +0.75 V, and the polymerization process was monitored by chronocoulometry. When the charge reached 1.0 C / cm 2 , the reaction was terminated.

[0060] After the electro-polymerization was completed, the substrate was taken out and dried, and then placed in a plasma treatment instrument for 3 min at a power of 75 W to graft acrylic acid on the surface of the substrate to generate carboxyl groups. The reaction conditions were controlled to make the surface carboxyl group density reach 3.8 / nm 2 .

[0061] An NHS / EDC activation solution (the molar ratio of NHS to EDC was 1:1) was prepared, and the above-processed substrate was immersed in the activation solution to activate the carboxyl groups. Then the substrate was taken out and reacted with a 0.3 mol / L N-acetyl cysteine solution for 6 h. After the reaction was completed, the substrate was dried to realize the covalent fixation of the thiol group.

[0062] S13 spin-coating modification of chitosan-hyaluronic acid composite layer:

[0063] A composite solution containing 2wt% chitosan (degree of deacetylation ≥90%) and 1wt% hyaluronic acid (molecular weight 100-300 kDa) was prepared, and the solvent of the composite solution was 1% acetic acid aqueous solution.

[0064] The above chitosan-hyaluronic acid composite solution was spin-coated on the first surface of the substrate at a speed of 2000 rpm to form a functional layer with a thickness of 1.5 μm.

[0065] S2 On the flexible substrate, the Ag / AgCl mixed paste (AgCl mass ratio 50%) was printed into an Ag / AgCl conductive layer by using a silk screen printing equipment, and then placed in an oven at 70-90°C for curing.

[0066] An ionic gel was prepared, which was composed of 7wt% hydroxyethyl cellulose, 10wt% glycerol and the rest of electrolyte salt (lithium chloride and potassium chloride were mixed in a molar ratio of 5:1), and the conductivity of the ionic gel at 25°C was 0.13 S / m.

[0067] The above ionic gel was coated between the Ag / AgCl conductive layer and the second surface of the functional film prepared in step S1 to make the ionic gel completely fill the micro gaps between them, and they were attached together. The external lead was connected to the other side of the Ag / AgCl conductive layer to form an electrocardio electrode.

[0068] S3 The first surface of the electrocardio electrode was attached to the human skin. When the sweat permeated to the Ag / AgCl conductive layer, electrochemical corrosion was triggered, and Ag +will diffuse reversely along the direction opposite to the sweat permeation direction. In the interface of the conductive layer and the mesoporous region of the functional film, Ag + Under the dual driving force of the difference of concentration gradient and the negative potential of the sulfonic acid group modified mesoporous wall, Ag + diffuses to the functional film, and is reversibly combined with the sulfonic acid group through electrostatic attraction + -SO3 - , and then Ag + is driven to migrate to the adjacent sulfhydryl group by the negative potential gradient, and forms Ag-S covalent bond through soft acid-soft base reaction.

[0069] At the same time, the chitosan-hyaluronic acid composite layer swells to form a hydration barrier under the pH of sweat, and captures free histamine released by mast cells in the local skin stress reaction caused by the electrode skin through hydrogen bonds. When the mechanical pressure is > 15 kPa or the sweat pH is abnormal (pH < 5.0 or > 8.5), it can effectively deal with the adverse effects of histamine and enhance the anti-allergic effect.

[0070] Example 2:

[0071] A silver ion dynamic capture and anti-allergic synergistic method based on graphene pore regulation, comprising:

[0072] S1, after directional gradient freezing of graphene oxide dispersion and freeze-drying, a substrate with an axial macropore-mesoporous gradient structure is formed; wherein the macropore diameter of the first surface is larger than that of the second surface, and the mesoporous network is distributed in the thickness direction of the substrate, and the substrate is sequentially reduced, sulfonic acid group electropolymerization and thiol group fixation, spin coating a chitosan-hyaluronic acid composite layer on the first surface to obtain a functional film;

[0073] Specifically, step S1 comprises:

[0074] S11, gradient freezing and freeze-drying of graphene oxide substrate:

[0075] Take the concentration of graphene oxide dispersion solution as 8 mg / mL, and inject it into a polytetrafluoroethylene mold.

[0076] Contact the bottom of the mold with a cold table with a temperature set to -20℃, and expose the top of the mold to room temperature air environment, and cool at a gradient cooling rate of 0.5℃ / min, so that the ice crystal growth direction extends along the thickness direction of the substrate.

[0077] After freezing is completed, the mold is placed in a freeze dryer, and the temperature is maintained at -40℃ for 4h to ensure that the substrate is completely frozen.

[0078] The temperature of the freeze-drier is then raised to -20°C at a rate of 0.5°C / min, and the freeze-drying process is completed at this temperature for 10 h. At this time, ice crystals sublimate to form porous channels, and a substrate with an axial macropore-mesopore gradient structure is obtained. The side in contact with the bottom of the mold is the second surface, the side facing the air is the first surface, and the porosity of the first surface is higher than that of the second surface.

[0079] S12 Reduction, electropolymerization of sulfonic acid groups, and thiolation of the substrate:

[0080] After freeze-drying, the substrate is immersed in an aqueous L-ascorbic acid solution with a concentration of 0.5 mol / L for reduction treatment. The resistivity of the substrate is measured periodically during the treatment until the resistivity decreases to 10 -1 Ω·m. Before reduction, the oxygen-carbon ratio of the graphene oxide is 0.3, and after reduction by L-ascorbic acid, the oxygen-carbon ratio decreases to 0.05-0.15. The reduction rate of hydroxyl and epoxy groups is >80%, and the reduction rate of carboxyl groups is >60%. After reduction is completed, the substrate is removed and immersed in an EDTA solution with a concentration of 0.05 mol / L for purification to remove metal ion impurities. Then, the substrate is washed multiple times with ultrapure water and dried in an oven.

[0081] A solution containing 5 mmol / L of sulfonic acid group-containing aniline monomers is prepared using 0.5 mol / L of H2SO4 aqueous solution as the solvent, and the dried substrate is immersed in the solution.

[0082] The electropolymerization is carried out on an electrochemical workstation using a three-electrode system (working electrode: substrate; counter electrode: platinum plate; reference electrode: Ag / AgCl). The constant potential mode is selected, and the working potential is controlled at +0.80 V. The polymerization process is monitored by chronocoulometry, and the reaction is terminated when the charge reaches 1.2 C / cm 2 .

[0083] After electropolymerization is completed, the substrate is removed and dried, and then placed in a plasma treatment instrument for 5 min at a power of 100 W to graft acrylic acid onto the surface of the substrate to form carboxyl groups. The reaction conditions are controlled to achieve a surface carboxyl group density of 4.2 / nm 2 .

[0084] An NHS / EDC activation solution (the molar ratio of NHS to EDC is 1:1) is prepared, and the treated substrate is immersed in the activation solution to activate the carboxyl groups. Then, the substrate is removed and reacted with a 0.5 mol / L N-acetylcysteine solution for 6 h. After the reaction is completed, the substrate is dried to achieve covalent fixation of the thiol groups.

[0085] S13 Spin coating modification of the chitosan-hyaluronic acid composite layer:

[0086] A complex solution containing 3wt% chitosan (degree of deacetylation ≥ 90%) and 2wt% hyaluronic acid (molecular weight 100-300kDa) is prepared, and the solvent of the complex solution is 1% acetic acid aqueous solution; the chitosan-hyaluronic acid complex solution is spin-coated on the first surface of the substrate at a speed of 3000 rpm to form a functional layer with a thickness of 1.5 μm.

[0087] In S2, a Ag / AgCl mixed slurry (AgCl mass ratio 70%) is printed on the flexible substrate to form a Ag / AgCl conductive layer by using a screen printing device, and then placed in an oven at 70-90℃ for curing.

[0088] An ionic gel is prepared, which is composed of 7wt% hydroxyethyl cellulose, 10wt% glycerol and the rest of electrolyte salt (lithium chloride and potassium chloride are mixed in a molar ratio of 5:1), and the conductivity of the ionic gel at 25℃ is 0.13S / m.

[0089] The ionic gel is coated between the Ag / AgCl conductive layer and the second surface of the functional film prepared in step S1, so that the ionic gel completely fills the micro gaps between them, and they are attached together, and the external lead is connected to the other side of the Ag / AgCl conductive layer to form an electrocardio electrode.

[0090] In S3, the first surface of the electrocardio electrode is attached to the human skin, and when the sweat permeates into the Ag / AgCl conductive layer, electrochemical corrosion is triggered, and Ag + diffuses in the opposite direction of the sweat permeation direction. Under the dual driving force of the Ag + concentration gradient difference between the conductive layer interface and the mesoporous region of the functional film and the negative potential of the sulfonic acid modified mesoporous wall, Ag + diffuses to the functional film and is reversibly combined with the sulfonic acid group through electrostatic attraction, and then Ag + -SO3 - is driven by the negative potential gradient to migrate to the adjacent sulfhydryl group to form an Ag-S covalent bond through soft acid-soft base reaction. +

[0091] Meanwhile, the chitosan-hyaluronic acid complex layer swells to form a hydration barrier under the pH of sweat, and captures the free histamine released by mast cells in the local skin stress reaction caused by the electrode attached to the skin through hydrogen bonds. When the mechanical pressure is > 15kPa or the pH of sweat is abnormal (pH < 5.0 or > 8.5), it can effectively cope with the adverse effects of histamine and enhance the anti-allergic effect.

[0092] Example 3:

[0093] A silver ion dynamic capture and anti-allergy synergistic method based on graphene pore regulation, comprising:

[0094] ​S1 freeze-drying the graphene oxide dispersion liquid in a gradient direction to form a substrate with an axial macropore-mesopore gradient structure; wherein the macropore diameter of the first surface is larger than that of the second surface, and the mesopore network is distributed in the thickness direction of the substrate; sequentially reducing, sulfonic acid group electropolymerizing and thiolating the substrate, spin-coating a chitosan-hyaluronic acid composite layer on the first surface to obtain a functional membrane;

[0095] Specifically, step S1 comprises:

[0096] S11 gradient freezing and freeze-drying of the graphene oxide substrate:

[0097] Take a graphene oxide dispersion liquid with a concentration of 10 mg / mL and inject it into a polytetrafluoroethylene mold.

[0098] Contact the bottom of the mold with a cold table set at -30°C, and expose the top of the mold to room temperature air environment, and cool at a gradient cooling rate of 2°C / min to make the ice crystal growth direction extend along the thickness direction of the substrate.

[0099] After freezing, place the mold in a freeze dryer and maintain at -40°C for 6h to ensure complete freezing of the substrate.

[0100] Then increase the temperature of the freeze dryer to -20°C at a rate of 0.5°C / min and maintain at this temperature for 12h to complete the freeze-drying process. At this time, the ice crystals sublimate to form porous channels, and a substrate with an axial macropore-mesopore gradient structure is obtained. The side in contact with the bottom of the mold is the second surface, and the side facing the air is the first surface, and the porosity of the first surface is higher than that of the second surface.

[0101] S12 reduction, sulfonic acid group electropolymerization and thiolation of the substrate:

[0102] After freeze-drying, immerse the substrate in a 0.1 mol / L aqueous L-ascorbic acid solution for reduction treatment, and measure the resistivity of the substrate periodically during the treatment until the resistivity decreases to 10 -3 Ω·m. The oxygen-carbon ratio of the graphene oxide before reduction is 0.3, and after reduction by L-ascorbic acid, the oxygen-carbon ratio decreases to 0.05-0.15, wherein the reduction rate of hydroxyl and epoxy groups is >80%, and the reduction rate of carboxyl groups is >60%. After reduction, the substrate is taken out, immersed in a 0.05 mol / L EDTA solution for purification to remove metal ion impurities, then washed with ultrapure water several times, and dried in an oven.

[0103] Prepare a solution containing 1 mmol / L sulfonic acid group-containing aniline monomer, and the solvent is 0.5 mol / L H2SO4 aqueous solution. Immerse the dried substrate in the solution.

[0104] The three-electrode system (working electrode: substrate; counter electrode: platinum plate; reference electrode: Ag / AgCl) was used for electro-polymerization on an electrochemical workstation, the constant potential mode was selected, the working potential was controlled at +0.70 V, and the polymerization process was monitored by chronometric charge method, and the reaction was terminated when the charge reached 0.8 C / cm 2 .

[0105] After the electro-polymerization was completed, the substrate was taken out and dried, and then was placed in a plasma treatment instrument for 2 min under the condition of a power of 50 W, so that the acrylic acid was grafted on the surface of the substrate to generate carboxyl groups, and the reaction conditions were controlled to make the surface carboxyl group density reach 3.5 / nm 2 .

[0106] The NHS / EDC activation solution (the molar ratio of NHS to EDC was 1:1) was prepared, the above-processed substrate was immersed in the activation solution to activate the carboxyl groups, then the substrate was taken out and reacted with a 0.2 mol / L N-acetyl cysteine solution for 6 h, and after the reaction was completed, the substrate was dried to realize the covalent fixation of the thiol groups.

[0107] S13 spin-coating modification of the chitosan-hyaluronic acid composite layer:

[0108] A composite solution containing 1 wt% chitosan (degree of deacetylation ≥90%) and 0.5 wt% hyaluronic acid (molecular weight 100-300 kDa) was prepared, and the solvent of the composite solution was 1% acetic acid aqueous solution; the above chitosan-hyaluronic acid composite solution was spin-coated on the first surface of the substrate at a speed of 1000 rpm to form a functional layer with a thickness of 1.5 μm.

[0109] S2 On the flexible substrate, the Ag / AgCl mixed paste (AgCl mass ratio 30%) was printed into an Ag / AgCl conductive layer by using a silk screen printing device, and then was placed in an oven at 70-90°C for curing.

[0110] An ionic gel was prepared, which was composed of 7 wt% hydroxyethyl cellulose, 10 wt% glycerol and the rest of electrolyte salt (lithium chloride and potassium chloride were mixed in a molar ratio of 5:1), and the conductivity of the ionic gel at 25°C was 0.12 S / m.

[0111] The above ionic gel was coated between the Ag / AgCl conductive layer and the second surface of the functional film prepared in step S1, so that the ionic gel completely filled the micro gaps between them, and they were attached together, and the external lead was connected to the other side of the Ag / AgCl conductive layer to form an electrocardio electrode.

[0112] S3 The first surface of the electrocardio electrode was attached to the human skin, when the sweat permeated to the Ag / AgCl conductive layer, electrochemical corrosion was induced, and Ag +will diffuse in the opposite direction of the sweat penetration direction. In the Ag + Under the dual driving force of the difference in concentration gradient and the negative potential of the sulfonic acid group modified mesoporous wall, Ag + diffuse to the functional film, and the sulfonic acid group forms Ag + -SO3 - reversible combination, and then Ag + is driven by the negative potential gradient to migrate to the adjacent sulfhydryl group and form an Ag-S covalent bond through a soft acid-soft base reaction.

[0113] At the same time, the chitosan-hyaluronic acid composite layer swells to form a hydration barrier under the pH of sweat, and captures free histamine released by mast cells in the local skin stress reaction caused by the electrode skin through hydrogen bonds. When the mechanical pressure is >15kPa or the sweat pH is abnormal (pH<5.0 or >8.5), it can effectively deal with the adverse effects of histamine and enhance the anti-allergic effect.

[0114] Comparative Example 1:

[0115] This comparative example is compared with Example 1. The graphene oxide dispersion liquid is directly freeze-dried (without directional gradient freezing), and the pores are randomly distributed. The rest of the conditions are the same as Example 1, which will not be repeated here.

[0116] Comparative Example 2:

[0117] This comparative example is compared with Example 1. The graphene substrate is only reduced, and is not subjected to sulfonic acid group electropolymerization and sulfhydryl fixation. The rest of the conditions are the same as Example 1, which will not be repeated here.

[0118] Comparative Example 3:

[0119] This comparative example is compared with Example 1. There is no graphene film, and a traditional Ag / AgCl electrode is used with a common conductive gel.

[0120] Performance verification:

[0121] The electrode samples prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to silver ion permeability, interface impedance, and continuous 72h application allergy incidence detection, and the test data are shown in Table 1 below:

[0122] Among them, 1. Silver ion permeability: determined by inductively coupled plasma mass spectrometry (ICP-MS). The specific steps are as follows:

[0123] The electrode samples of the examples and the comparative examples were immersed in simulated sweat (composition: 0.5wt% NaCl, 0.1wt% lactic acid, 0.1wt% urea, pH adjusted to 6.5), and a constant temperature environment of 37°C (simulating human body temperature) was set for 72h. The immersion liquid was periodically drawn out, and the concentration of silver ions therein was detected by ICP-MS to calculate the total amount of silver ions permeating through the electrode per unit time. The silver ion permeation rate calculation formula is: (total amount of silver ions permeating through the electrode / total amount of silver in the electrode initially) x 100%.

[0124] 2. Interfacial impedance (1 kHz): determined by electrochemical workstation using electrochemical impedance spectroscopy (EIS). Specific operation:

[0125] The electrode samples were attached to the simulated skin (simulated by pigskin or special conductive gel) to form an "electrode-simulated skin" test system. A three-electrode system (working electrode: electrode to be tested; counter electrode: platinum plate; reference electrode: Ag / AgCl) was used to test the impedance value of the system at a frequency of 1 kHz (main frequency range of electrocardiosignal). The test was repeated 3 times, and the average value was taken as the final interfacial impedance data.

[0126] 3. Allergic reaction rate after continuous 72h attachment: animal skin attachment test was carried out according to ISO 10993-10 "Skin Irritation and Sensitization Test". Specific steps:

[0127] SPF guinea pigs aged 6-8 weeks (10 in each group) were selected, and the electrode samples of the examples and the comparative examples were attached to the depilated areas on their backs, and the attachment was continued for 72h after fixation. After removing the electrodes, the skin reactions were observed at 24h, 48h and 72h, and evaluated according to the skin irritation reaction scoring standard. The allergic reaction rate calculation formula is: (number of guinea pigs with obvious erythema or edema / total number of test guinea pigs) x 100%.

[0128] Table 1: Performance test data of examples 1-3 and comparative examples 1-3

[0129]

[0130] As can be seen from the above data, comparative example 1 did not use directional gradient freezing to construct an axial macroporous-mesoporous gradient structure, and in the disordered pore structure, macropores and mesopores were randomly distributed, lacking gradient screening effect. Ag + can directly diffuse to the first surface; and the mesoporous network is easy to collapse, causing the ion conduction path to break, the interfacial impedance to rise, the silver ion permeation rate to reach 35.60%, and the allergic reaction rate to be high;

[0131] Comparative example 2 lacks sulfonic acid group electropolymerization and thiolation fixation, and cannot effectively dynamically capture and stably bind silver ions. Only physical barrier can hardly prevent silver ion permeation, and at the same time affects the adjustment of interfacial potential, resulting in poor performance.

[0132] Comparative Example 3 is a traditional Ag / AgCl electrode without a graphene functional layer, Ag + The silver ion permeability, interface impedance and allergic incidence are much higher than those of Example 1 because the conductive gel can directly diffuse to the skin and the gel is easy to dry, which increases the interface impedance.

[0133] The present application can efficiently intercept silver ions and greatly reduce their penetration to the skin by gradient pore regulation and functional modification of graphene, thereby reducing the risk of sensitization from the source. By gradient pore design and interface optimization of ionic gel, the contact impedance between the electrode and the skin is effectively reduced, ensuring that the electrocardio signal can be stably and efficiently transmitted, reducing signal attenuation and noise interference. During the continuous 72h application process, the pH response barrier effect, histamine capture function and low silver ion permeability of the chitosan-hyaluronic acid composite layer significantly reduce the risk of skin allergy, meeting the comfort and safety requirements of long-term clinical use.

[0134] Those skilled in the art should understand that the present application is not limited to the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for dynamic capture and anti-sensitivity synergy of silver ions based on graphene pore regulation, characterized in that: include: S1 involves directional gradient freezing and freeze-drying of a graphene oxide dispersion to form a substrate with an axial macropore-mesopore gradient structure, wherein the macropore diameter gradually decreases from the first surface to the second surface, and the mesopores form a connected network that runs through the entire thickness; the substrate is then subjected to reduction, sulfonic acid electropolymerization, and thiolation fixation in sequence; a chitosan-hyaluronic acid composite layer is spin-coated onto the first surface to obtain a functional film; S2 constructs an Ag / AgCl conductive layer on a flexible substrate and attaches it to the second surface, and then coats the interface with ion gel to form an electrocardiogram electrode. S3 places the first surface against the skin; sweat penetrates the Ag / AgCl conductive layer, triggering electrochemical corrosion and producing Ag... + The reverse diffusion to the functional membrane is dynamically captured by sulfonic acid groups and bonded to adjacent thiol groups.

2. The method for dynamic capture and anti-sensitivity synergy of silver ions based on graphene pore regulation according to claim 1, characterized in that, In step S1, the directional gradient freezing followed by freeze-drying includes: The graphene oxide dispersion was injected into a mold, with the bottom of the mold in contact with a cold table at -30~-20℃ and the top exposed to air. The temperature was gradually reduced at a rate of 0.5~2℃ / min, with the ice crystal growth direction parallel to the thickness direction. After directional gradient freezing, the temperature is maintained at -40℃ for 4~6 hours, and then increased to -20℃ at 0.5℃ / min and maintained for 10~12 hours to achieve freeze-drying.

3. The method for dynamic capture and anti-sensitivity synergy of silver ions based on graphene pore regulation according to claim 2, characterized in that, In the substrate with an axial macropore-mesopore gradient structure, the side in contact with the bottom of the mold is the second surface, the side facing the air is the first surface, and the porosity of the first surface is higher than that of the second surface.

4. The method for dynamic capture and anti-sensitivity synergy of silver ions based on graphene pore regulation according to claim 1, characterized in that, In step S1, the sequential reduction, sulfonic acid electropolymerization, and thiolization fixation of the substrate includes: The substrate was immersed in an L-ascorbic acid aqueous solution and reduced until the resistivity dropped to 10. -1 ~10 -3 After purification and drying by EDTA, the substrate is immersed in a solution of sulfonic acid aniline monomer for electropolymerization. After drying, acrylic acid is plasma-grafted onto the substrate to generate carboxyl groups. After activation of the carboxyl groups by an activation solution, the substrate is reacted with an N-acetylcysteine ​​solution and then dried.

5. The method for dynamic capture and anti-sensitivity synergy of silver ions based on graphene pore regulation according to claim 4, characterized in that, The electropolymerization is performed in a constant potential mode, with the potential controlled between +0.70 and +0.80V. The polymerization is terminated when the charge reaches 0.8 to 1.2 C / cm. 2 .

6. The method for dynamic capture and anti-sensitivity synergy of silver ions based on graphene pore regulation according to claim 4, characterized in that, The plasma grafting of acrylic acid to generate carboxyl groups aims to achieve a surface carboxyl group density of 3.5~4.2 groups / nm. 2 .

7. The method for dynamic capture and anti-sensitivity synergy of silver ions based on graphene pore regulation according to claim 1, characterized in that, In step S1, the chitosan-hyaluronic acid composite layer has a thickness of 1~2μm and a pore size of 5~10nm.

8. The method for dynamic capture and anti-sensitivity synergy of silver ions based on graphene pore regulation according to claim 1, characterized in that, In step S2, the Ag / AgCl conductive layer is formed by screen printing and curing of Ag / AgCl mixed slurry at 70~90°C, wherein the mass ratio of AgCl in the Ag / AgCl mixed slurry is 30~70%.

9. The method for dynamic capture and anti-sensitivity synergy of silver ions based on graphene pore regulation according to claim 1, characterized in that, In step S2, the ionogel comprises 6-8 wt% hydroxyethyl cellulose, 10 wt% glycerol, and the balance electrolyte salt, wherein the electrolyte salt comprises lithium chloride and potassium chloride mixed in a molar ratio of 5:1, and its conductivity at 25°C is 0.12-0.15 S / m.

10. The method for dynamic capture and anti-sensitivity synergy of silver ions based on graphene pore regulation according to claim 1, characterized in that, In step S3, the reverse is Ag + The diffusion direction is opposite to the sweat penetration direction, the Ag + The driving force for reverse diffusion includes Ag at the conductive layer interface and the mesoporous region of the functional film. + The concentration gradient difference, and the negative potential of the sulfonic acid group-modified mesoporous wall.

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