Flexible microelectrode modified by composite conductive material as well as preparation method and application of flexible microelectrode

Abstract

The invention discloses a composite conductive material modified flexible microelectrode and a preparation method and application thereof, and relates to the technical field of flexible microelectrodes, the flexible microelectrode comprises a Parylene substrate, a gold electrode, a Parylene packaging layer and a serine / PEDOT: PSS composite organic conductive material which are sequentially stacked from bottom to top, wherein the Parylene substrate is used for structural support and electrical isolation of the flexible microelectrode; the serine / PEDOT: PSS composite organic conductive material is used for modifying the gold electrode and is in direct electric contact with the gold electrode; and the Parylene packaging layer is used for packaging the microelectrode array wire led out from the gold electrode. According to the prepared flexible microelectrode modified by the composite conductive material, the biocompatibility of the flexible microelectrode is improved, the impedance of the flexible microelectrode and the PEDOT: PSS toxicity are reduced, and safe and accurate bioelectrophysiological signal testing can be achieved.

Description

Technical Field

[0001] This invention relates to the field of flexible microelectrode technology, and in particular to a flexible microelectrode modified with a composite conductive material, its preparation method, and its application. Background Technology

[0002] Microelectrode arrays are important instruments for measuring biological signals. Using microelectrodes to analyze neural activity provides a research tool for the biomedical field, revealing the main developmental mechanisms of life processes. They have been widely used to measure the action potentials of cardiomyocytes and nerve cells, as well as signal propagation in heart and brain tissue slices.

[0003] Poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS), with its excellent mixed ionic-electronic conductivity, large specific surface area, and high interfacial capacitance, can effectively transform the high-impedance gold microelectrode / electrolyte interface into a low-impedance interface, and is often used to modify metal microelectrodes. However, PEDOT:PSS is slightly toxic, affecting the long-term biosignal testing of invasive microelectrodes. Furthermore, metal microelectrodes modified with PEDOT:PSS have high impedance, making it difficult to capture weaker bioelectrophysiological signals.

[0004] To address the aforementioned issues, there is an urgent need for a flexible microelectrode modified with a composite conductive material to improve its biocompatibility and reduce its impedance and PEDOT:PSS toxicity. Summary of the Invention

[0005] The purpose of this invention is to provide a flexible microelectrode modified with a composite conductive material, its preparation method, and its application, so as to improve the biocompatibility of the flexible microelectrode, reduce the impedance and PEDOT:PSS toxicity of the flexible microelectrode, and achieve safe and accurate testing of bioelectrophysiological signals.

[0006] To achieve the above objectives, the present invention provides a flexible microelectrode modified with a composite conductive material, comprising: a Parylene substrate, a gold electrode, a Parylene encapsulation layer, and a sericin / PEDOT:PSS composite organic conductive material stacked sequentially from bottom to top; The Parylene substrate is used for structural support and electrical isolation of the flexible microelectrode; The sericin / PEDOT:PSS composite organic conductive material is used to modify the gold electrode and is in direct electrical contact with the gold electrode. The Parylene encapsulation layer is used to encapsulate the microelectrode array wires leading from the gold electrode.

[0007] Preferably, the mass ratio of sericin to PEDOT:PSS in the sericin / PEDOT:PSS composite organic conductive material is 1:2.

[0008] Preferably, the sericin is prepared by carboxylation modification of silk fibroin with succinic anhydride.

[0009] This invention also provides a method for preparing a flexible microelectrode modified with a composite conductive material, which includes the following steps: S1. Fabricate gold electrodes on a Parylene substrate; S2. Deposit a Parylene encapsulation layer at the microelectrode array wires led out from the gold electrode; S3. Prepare a sericin solution and mix the sericin solution with a PEDOT:PSS solution at a mass ratio of 1:2 to obtain a composite conductive paste; S4. The composite conductive paste is coated on the surface of the gold electrode and annealed to obtain a sericin / PEDOT:PSS composite organic conductive material, thus obtaining a flexible microelectrode modified with the composite conductive material.

[0010] Preferably, the preparation method of the sericin solution in S3 is to dissolve the regenerated silk fibroin in anhydrous DMSO / LiCl solution, and then add succinic anhydride to carry out a carboxylation reaction to obtain the sericin solution.

[0011] Preferably, the mass ratio of the regenerated silk fibroin to the succinic anhydride is 1:5.

[0012] Preferably, the annealing temperature in S4 is 80 ℃~100 ℃, and the annealing time is 0.5 h~1.5 h.

[0013] Preferably, the method for preparing the gold electrode in S1 includes vacuum sputtering and thermal evaporation.

[0014] Preferably, the method for coating the composite conductive paste onto the surface of the gold electrode in S4 includes spin coating and inkjet printing.

[0015] The present invention also provides an application of a flexible microelectrode modified with a composite conductive material, which is used for bioelectrophysiological signal testing.

[0016] In summary, the flexible microelectrode modified with a composite conductive material, its preparation method, and its application provided by this invention offer the following advantages compared to traditional technologies: The flexible microelectrode modified with sericin / PEDOT:PSS composite organic conductive material not only improves the biocompatibility of the flexible microelectrode and reduces the toxicity of PEDOT:PSS, thus reducing biological immune rejection or inflammatory responses, but also lowers the impedance of the flexible microelectrode, facilitating the recording and analysis of weak biological signals and further enabling safe and accurate testing of bioelectrophysiological signals. Simultaneously, this flexible microelectrode features a high signal-to-noise ratio, reliability, and safety, contributing to its widespread application in medical fields such as brain-computer interfaces and invasive microelectrodes.

[0017] The technical method of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a flexible microelectrode modified with a composite conductive material according to the present invention. Figure 2 This is a flowchart of a method for preparing a flexible microelectrode modified with a composite conductive material according to the present invention; Figure 3 This is a process flow diagram of a method for preparing a flexible microelectrode modified with a composite conductive material according to the present invention. Figure 4 The impedance comparison diagram shows the flexible microelectrode modified with sericin / PEDOT:PSS composite organic conductive material and the flexible microelectrode modified with pure PEDOT:PSS. Figure 5 The figures show the cytotoxicity test results of a flexible microelectrode modified with sericin / PEDOT:PSS composite organic conductive material and a flexible microelectrode modified with pure PEDOT:PSS. Figure 5 (a) shows the activity of cells cultured after 2 days after being immersed in cell culture medium using sericin / PEDOT:PSS composite organic conductive material. Figure 5 (b) shows the activity of cells cultured after 2 days after being immersed in pure PEDOT:PSS in cell culture medium; Figure 5 (c) in the figure is a comparison of cell death / survival.

[0019] Figure Labels 1-Parylene substrate; 2-Gold electrode; 3-Parylene encapsulation layer; 4-Seric acid / PEDOT:PSS composite organic conductive material. Detailed Implementation

[0020] The technical method of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0022] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0023] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0024] This invention provides a flexible microelectrode modified with a composite conductive material, such as... Figure 1 As shown, it includes: a poly-para-xylylene (Parylene) substrate 1, a gold electrode 2, a Parylene encapsulation layer 3, and a seric acid / PEDOT:PSS composite organic conductive material 4, which are stacked sequentially from bottom to top.

[0025] Parylene substrate 1 is used for structural support and electrical isolation of the flexible microelectrode.

[0026] Seric acid / PEDOT:PSS composite organic conductive material 4 is used to modify gold electrode 2 and is in direct electrical contact with gold electrode 2. It has mixed ionic-electronic conductivity, large specific surface area and high interfacial capacitance, which can significantly reduce the impedance of gold electrode, increase the signal-to-noise ratio of the test, improve the biocompatibility of microelectrode, and reduce the damage of gold electrode to biological organs or cells.

[0027] In the sericin / PEDOT:PSS composite organic conductive material 4, the mass ratio of sericin to PEDOT:PSS is 1:2. The sericin is prepared by carboxylation modification of silk fibroin with succinic anhydride.

[0028] Parylene encapsulation layer 3 is used to encapsulate the microelectrode array wires led out from the gold electrode 2, which can avoid signal interference between electrodes. Parylene encapsulation layer 3 covers and insulates the electrode array wires led out from the gold electrode 2, leaving only the electrode area modified by sericin / PEDOT:PSS composite organic conductive material 4 as the working window.

[0029] like Figure 2 As shown, this invention also provides a method for preparing flexible microelectrodes modified with composite conductive materials, the process flow diagram of which is shown below. Figure 3 As shown, it includes the following steps: S1. Fabricate a gold electrode 2 on a Parylene substrate 1. The gold electrode 2 is fabricated using vacuum sputtering and thermal evaporation methods. The Parylene substrate 1 is obtained by depositing Parylene on a silicon (Si) substrate.

[0030] S2. A Parylene encapsulation layer 4 is deposited at the microelectrode array wires led out from the gold electrode 2. Further, after depositing the Parylene encapsulation layer 4, plasma etching is performed to expose the working electrode region, in preparation for the preparation of sericin / PEDOT:PSS composite organic conductive material 4.

[0031] S3. Prepare a sericin solution and mix the sericin solution with a PEDOT:PSS solution at a mass ratio of 1:2 to obtain a composite conductive paste.

[0032] Furthermore, the preparation method of the sericin solution in S3 is specifically to extract regenerated silk fibroin (RSF) from silkworm cocoons, dissolve the regenerated silk fibroin in anhydrous dimethyl sulfoxide (DMSO) / lithium chloride (LiCl) solution, and then add succinic anhydride at a mass ratio of 1:5 between the regenerated silk fibroin and succinic anhydride. The succinic anhydride reacts with the hydroxyl and amino groups in the silk fibroin, causing the silk fibroin to carboxylate and form sericin, thus obtaining the sericin solution.

[0033] In an exemplary embodiment of the present invention, the method for preparing the sericin solution is as follows: 1.0 g of regenerated silk fibroin is dissolved in 50 mL of 1.0 M anhydrous DMSO / LiCl solution, and then 5.0 g of succinic anhydride is added to synthesize sericin. The mixture is stirred at 50 °C for 6 hours. After the carboxylation reaction is completed, 80 mL of 1.0 M NaOH aqueous solution is added to neutralize the solution to a pH value greater than 7. Then, the solution is dialyzed with deionized water for 72 hours (the water is changed every 12 hours). Finally, the solution is purified by centrifugation at 9000 rpm to obtain a purified sericin solution.

[0034] S4. The composite conductive paste is coated onto the surface of the gold electrode 2, and then annealed to obtain a sericin (SA) / PEDOT:PSS (PEDOT:PSS / SA) composite organic conductive material 4, ultimately yielding a flexible microelectrode modified with the composite conductive material. The methods for coating the composite conductive paste onto the gold electrode surface include spin coating and inkjet printing. The annealing temperature is 80 ℃~100 ℃, and the annealing time is 0.5 h~1.5 h.

[0035] In an exemplary embodiment of the present invention, a composite conductive paste is spin-coated onto the surface of a gold electrode at 1000 rpm for 40 seconds, and then annealed at 80 °C for 1 hour to obtain a sericin / PEDOT:PSS composite organic conductive material.

[0036] The impedance and cytotoxicity of the flexible microelectrode modified with sericin / PEDOT:PSS composite organic conductive material 4 and the flexible microelectrode modified with pure PEDOT:PSS were tested in this invention.

[0037] Impedance comparison of flexible microelectrodes modified with sericin / PEDOT:PSS composite organic conductive material 4 and flexible microelectrodes modified with pure PEDOT:PSS, such as... Figure 4 As shown, PEDOT:PSS / SA is sericin (SA) / PEDOT:PSS. According to... Figure 4 It can be seen that the impedance of the flexible microelectrode modified with sericin / PEDOT:PSS composite organic conductive material 3 is significantly lower than that of the flexible microelectrode modified with pure PEDOT:PSS.

[0038] The cytotoxicity testing of flexible microelectrodes modified with sericin / PEDOT:PSS composite organic conductive material and flexible microelectrodes based on pure PEDOT:PSS modification, such as... Figure 5 As shown, PEDOT:PSS / SA is sericin (SA) / PEDOT:PSS. According to... Figure 5 As shown in (a), cells cultured in cell culture medium soaked in serine / PEDOT:PSS exhibited a very low cell death rate of approximately 3% after 2 days. According to... Figure 5 As shown in (b), pure PEDOT:PSS has a significant impact on cell viability, with a mortality rate reaching up to approximately 40%. According to... Figure 5 As can be seen from (c) in this paper, the flexible microelectrode modified with sericin / PEDOT:PSS composite organic conductive material 4 of this invention has significantly lower cytotoxicity than the flexible microelectrode modified with pure PEDOT:PSS.

[0039] In summary, the flexible microelectrode modified with composite conductive material prepared in this invention can be used for bioelectrophysiological signal testing.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical methods of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical methods of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical methods to deviate from the spirit and scope of the technical methods of the present invention.

Claims

1. A flexible microelectrode modified with a composite conductive material, characterized in that, The flexible microelectrode modified by the composite conductive material comprises, from bottom to top, a Parylene substrate, a gold electrode, a Parylene encapsulation layer and a silk acid / PEDOT:PSS composite organic conductive material arranged in sequence. The Parylene substrate is used for structural support and electrical isolation of the flexible microelectrode. The silk acid / PEDOT:PSS composite organic conductive material is used for modifying the gold electrode and directly electrically contacting the gold electrode. The Parylene encapsulation layer is used for encapsulating microelectrode array wire leads drawn from the gold electrode.

2. The flexible microelectrode modified by the composite conductive material according to claim 1, wherein, The mass ratio of silk acid to PEDOT:PSS in the silk acid / PEDOT:PSS composite organic conductive material is 1:

2.

3. The flexible microelectrode modified with a composite conductive material according to claim 2, wherein, The silk acid is prepared by carboxylation modification of silk fibroin with succinic anhydride.

4. A method for preparing a flexible microelectrode modified with a composite conductive material, characterized in that, The method for preparing the flexible microelectrode modified by the composite conductive material according to any one of claims 1-3 comprises the following steps: S1, preparing a gold electrode on a Parylene substrate; S2, depositing a Parylene encapsulation layer at microelectrode array wire leads drawn from the gold electrode; S3, preparing a silk acid solution, and mixing the silk acid solution with a PEDOT:PSS solution at a mass ratio of 1:2 to obtain a composite conductive slurry; S4, coating the composite conductive slurry on the surface of the gold electrode, and obtaining a silk acid / PEDOT:PSS composite organic conductive material through annealing to obtain the flexible microelectrode modified by the composite conductive material.

5. The method for preparing a flexible microelectrode modified with a composite conductive material according to claim 4, characterized in that, The preparation method of the silk acid solution in S3 specifically comprises dissolving regenerated silk fibroin in a dehydrated DMSO / LiCl solution, and then adding succinic anhydride to perform carboxylation reaction to obtain the silk acid solution.

6. The method for preparing a flexible microelectrode modified with a composite conductive material according to claim 5, characterized in that, The mass ratio of the regenerated silk fibroin to the succinic anhydride is 1:

5.

7. The method for preparing a flexible microelectrode modified with a composite conductive material according to claim 4, characterized in that, The annealing temperature in S4 is 80 ℃-100 ℃, and the annealing time is 0.5 h-1.5 h.

8. The method of claim 4, wherein the flexible microelectrode is prepared by coating a flexible substrate with a composite conductive material. The method for preparing the gold electrode in S1 comprises a vacuum sputtering method and a thermal evaporation method.

9. The method for preparing a flexible microelectrode modified with a composite conductive material according to claim 4, characterized in that, The method for coating the composite conductive slurry on the surface of the gold electrode in S4 comprises a spin coating method and an inkjet printing method.

10. A flexible microelectrode application modified with a composite conductive material, characterized in that, The flexible microelectrode modified by the composite conductive material according to any one of claims 1-3 is used for bioelectrophysiological signal testing.

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