Minimally invasive implant fiber electrode of sheath-core structure and method for preparing same

Abstract

The present disclosure relates to the field of electrophysiological detection and monitoring technology, and in particular, to a minimally invasive implant fiber electrode of a sheath-core structure and a method for preparing same. The method comprises: 1, preparation of printing pastes: separately preparing a conductive paste and an encapsulation paste; 2, loading of pastes: loading the prepared conductive paste into an inner channel, and loading the encapsulation paste into an outer channel; 3, determination of printing track and implant printing: determining a track of printing with the assistance of a magnetic resonance image, drilling using a surgical instrument or directly inserting a coaxial injection needle at a target position, and printing the electrode; and 4, interface design: inserting, after the printing is finished, a lead wire into an end of the uncured coaxial fiber electrode, and allowing the conductive paste and the encapsulation paste to cure in a natural state. The present disclosure significantly reduces the manufacture complexity and cost, greatly reduces surgical traumas, and improves the biocompatibility and long-term stability of the electrode.

Description

A minimally invasive implantable skin-core fiber electrode and its preparation method Technical Field

[0001] The present invention belongs to the technical field of electrophysiological detection and monitoring, and in particular relates to a minimally invasive implantable skin-core fiber electrode and a preparation method thereof. Background Art

[0002] With the development of science and technology, the monitoring of neuroelectrophysiological signals has become an important means of diagnosing various neurological diseases and one of the key ways to reveal the pathogenesis of diseases. It is widely used in fields such as epilepsy monitoring and neural repair. Although surface electrodes have the advantage of being non-invasive, implantable electrodes can obtain bioelectric signals with higher precision, which is crucial for a deeper understanding of physiological mechanisms and disease changes. In addition, implantable electrodes can achieve long-term detection, which is of great significance for the long-term tracking of diseases and the evaluation of treatment effects. Therefore, implantable electrodes have demonstrated irreplaceable advantages in the field of neuroelectrophysiological signal detection and have broad application prospects.

[0003] However, the shape and size of traditional rigid or two-dimensional thin-film implantable electrodes are difficult to adapt to individual differences and the specific conditions of the implantation site. Traditional electrode implantation requires highly invasive surgery, which causes great pain to the patient and may cause tissue damage and infection during the implantation process. The production process of traditional rigid implantable electrodes is complex and lengthy, unable to adapt to individual and site differences, making personalized customization difficult and costly, and preventing rapid customization and immediate use. Some existing electrodes use conductive fillers such as metal particles, which have potential toxicity issues. At the same time, the electrodes lack an encapsulation layer, posing safety risks and affecting the functional stability and long-term reliability of the electrodes. Existing minimally invasive electrode implantation technologies, such as those relying on catheter-assisted implantation, carry the risk of positioning deviation, while methods that use degradable materials to temporarily improve mechanical properties have long degradation times, poor tissue adaptability and comfort, and can easily lead to acute damage during the implantation process.

[0004] An injectable electrode reported in the prior art literature (Advanced healthcare materials, 2019, 8(23): 1900892). The electrode uses prepolymer and silver microparticle materials. After being injected into the target position by syringe, the material solidifies to form an electrode. This method can reduce surgical trauma and infection risks, but this solution cannot form a fibrous structure, and it is difficult to effectively encapsulate and protect the conductor in one step, making it difficult to truly achieve on-demand preparation and stable use in specific locations. In addition, the silver filler used in this paper is potentially toxic and easily oxidized, which will affect the functional stability, safety and long-term reliability of the electrode. Therefore, the development of new implantable electrodes using safe materials and less trauma is the current technical demand and development direction.

[0005] After continuous exploration and optimization, the applicants successfully implemented a minimally invasive implantation method, achieving efficient and accurate in-situ curing electrode preparation. In terms of material selection, this solution uses carbon fiber as the skeleton material, a biocompatible conductive polymer as the active layer, and a non-toxic silicone coating substrate to ensure the electrode's excellent biostability.

[0006] Before injection, the components are thoroughly mixed to create a fluid prepolymer suitable for injection. The prepolymers are then placed in separate syringes, separated by coaxial flexible tubing. Each component is then individually molded and cured in situ at the distal end to form a skin-core structure. The needle tip of the injection printing device directly penetrates the specific tissue site, where it continuously prints fiber electrodes at the target monitoring location. After the polymer solidifies naturally, the skin-core electrode is obtained.

[0007] Summary of the Invention

[0008] To address the shortcomings of the aforementioned prior art and to address the problems of poor conformability, difficulty in customizing electrodes, complex implantation procedures, significant implant trauma, and high infection risk associated with conventional implantable electrodes, the present invention provides a novel method for fabricating coaxial fiber electrodes that are minimally invasively implanted and in situ formed. By using biocompatible materials to create the printing slurry and employing a minimally invasive implantation method, the present invention significantly reduces manufacturing complexity and cost, significantly minimizes surgical trauma, and improves the biocompatibility and long-term stability of the electrodes.

[0009] The present invention adopts materials with good biocompatibility to prepare a slurry with rheological properties suitable for printing. Through a coaxial channel, a syringe is used to minimally invasively implant the slurry into the biological tissue of the target site and rapidly solidify it, thereby printing a coaxial electrode in situ. Thanks to the characteristics of rapid in situ solidification, the electrode can be tightly integrated with the biological tissue, and can be rapidly prepared at a fixed point in the body. At the same time, there is no need for large-area incisions and exposures, which has the advantages of minimally invasive implantation with small wounds, thus realizing in situ printing and minimally invasive implantation of fiber electrodes. In situ solidification can accurately position the electrode at a specific monitoring point according to the anatomical structure and needs of the organism. This precise positioning helps to obtain more accurate and individualized monitoring results. The fiber electrode skin-core structure has the characteristics of self-encapsulation, which can effectively protect the electrode material from the influence of the external environment, help to extend the service life of the electrode, and avoid the instability of the electrode performance during use. The present invention provides a new strategy for minimally invasive implantation and in situ preparation of electrophysiological monitoring electrodes.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] In one aspect, the present invention provides a method for preparing a skin-core fiber electrode for minimally invasive implantation, comprising the following steps:

[0012] (1) Making printing paste: Prepare conductive paste and encapsulation paste separately;

[0013] The conductive paste comprises the following components in percentage by mass: 0-85% conductive filler, 15-90% polymer matrix material, and 0-10% additives;

[0014] The encapsulation paste comprises a rapidly prototyping polymer and nano-silicon dioxide with a mass concentration of 0-20%;

[0015] The addition of PEG to the conductive paste helps improve its dispersibility, allowing CNF to be evenly dispersed within the conductive polymer, thereby improving the paste's rheological properties. Silicone, as a primary component, combines with CNF, the conductive polymer, and PEG to impart semi-cured properties and formability to the conductive paste. Meanwhile, the encapsulation paste, typically composed of non-toxic materials such as silicone, is used to protect the electrodes and provide biocompatibility. The primary function of the encapsulation paste is to coat the conductive paste, forming a protective layer for the electrodes, thereby improving their stability and biocompatibility.

[0016] The electrode slurry uses an injectable rheological precursor, which remains in a plastic flow state when injected into the body. It can autonomously conform to the surface morphology of the target tissue and "lock" the optimal highly fitting interface after subsequent in-situ curing, thereby ensuring accurate conformity between the electrode and the biological tissue and improving stability after implantation.

[0017] (2) Loading the slurry: The conductive slurry and encapsulation slurry prepared in step (1) are loaded into two syringes respectively and connected to the inner and outer tubes of the coaxial needle respectively; in this way, the different components can be kept separate so as to be combined at the end to form a coaxial fiber, forming a skin-core structure.

[0018] (3) Determine the printing trajectory and implant the print: Magnetic resonance imaging (MRI) is used to assist in determining the printing trajectory, and surgical instruments are used to drill holes at the target location, or a coaxial needle is directly inserted to start printing the electrode;

[0019] During the printing process, the conductive layer slurry of the inner channel is first printed with a length of 0.01-20 mm to form an exposed monitoring point, and then the inner and outer layers are printed simultaneously to form a coaxial fiber electrode;

[0020] Minimally invasive implantation using a medical syringe allows for direct injection and curing of the electrode conductive slurry into the target biological body to construct an implantable electrode. This avoids the need for large-area open surgical exposure in traditional hard electrode implantation methods and significantly reduces surgical trauma.

[0021] One-step molding of skin-core implantable electrodes: Using a coaxial needle, this integrated molding process allows for the integrated molding of skin-core implantable electrodes. During this process, the encapsulation layer slurry is injected into the outer channel, and the conductive layer slurry is injected into the inner channel. After the conductive layer slurry is extruded for a certain distance to serve as the signal detection point, the encapsulation layer slurry and the conductive layer slurry are extruded simultaneously, allowing the encapsulation and conductive layers to be molded simultaneously, simplifying the electrode preparation process.

[0022] (4) Interface design: After the printing in step (3) above is completed, take the wire and insert it into the end of the uncured coaxial fiber electrode to allow the conductive paste and the encapsulation paste to cure and form in a natural state.

[0023] In the preparation method, the conductive filler in step (1) is selected from a mixture of one or more of carbon materials, conductive polymers, and metal conductive materials;

[0024] The polymer matrix material is platinum two-component silica gel;

[0025] The additive is selected from a mixture of one or more of polyethylene glycol (PEG) and glycerol.

[0026] In the preparation method, the carbon material is selected from a mixture of one or more of carbon nanofibers (CNF), carbon nanotubes, graphene, and carbon black.

[0027] In the preparation method, the conductive polymer is selected from a mixture of one or more of poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonic acid) (PEDOT:PSS), polypyrrole, and polyaniline.

[0028] In the preparation method, the metal conductive material is selected from a mixture of one or more of gold nanowires / sheets / particles, silver nanowires / sheets / particles, and copper nanowires / sheets / particles.

[0029] In the preparation method, the encapsulation slurry in step (1) is silica gel.

[0030] In the preparation method, the particle size of the nano-silicon dioxide in step (1) is 1-100 nm.

[0031] In the preparation method, the conductive paste and the encapsulation paste are both injectable rheological materials.

[0032] In the preparation method, the curing time in step (4) is 5-30 minutes.

[0033] In a second aspect, the present invention provides a skin-core structure fiber electrode for minimally invasive implantation, which is prepared by any of the preparation methods described above.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. Minimally invasive implantation technology: Compared with traditional hard implant electrodes that require highly invasive open surgery, the present invention adopts a minimally invasive injection implantation method, which can significantly reduce the surgical wound surface, reduce the risk of trauma caused by anesthesia and incision, and make the electrode implantation process safer and more reliable.

[0036] 2. Flexible preparation: The present invention uses an injectable flowable polymer, which avoids the tedious step of designing electrodes according to application requirements before surgery. Different amounts of electrode slurry can be prepared according to specific application requirements, and the length of the fiber electrode can be adjusted, realizing flexible and convenient electrode preparation without the need for complicated prefabricated mold design.

[0037] 3. Selection of biocompatible materials: The present invention uses carbon fiber as the skeleton material, a conductive polymer with good biocompatibility as the active layer, and non-toxic silica gel as the coating substrate. These materials have good biostability and compatibility, making the electrode more stable and reliable in the body.

[0038] 4. Realize self-packaging of electrodes: The present invention adopts coaxial needle high-precision printing technology. The inner core is a conductive functional layer and the outer shell is a packaging layer. This enables the electrode to have long-term and stable self-packaging performance after implantation. Direct contact between the functional layer and the tissue and effective isolation from the outside can be achieved without additional operation.

[0039] 5. Good conformability: The slurry of the present invention is still in a plastic flow state when printing and injecting into the target site. It can conform to the tissue surface morphology independently and lock the optimal highly fitting interface during the subsequent in-situ curing process, thereby ensuring the accurate conformal fit between the electrode and the biological tissue and improving the implant stability.

[0040] 6. Simple process and low production cost: The present invention adopts safe materials and injection in situ curing preparation method, which makes the electrode preparation process simpler and faster, reduces the production complexity and cost, and provides a better solution for the preparation of implantable neuroelectrophysiological signal monitoring electrodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG1 is a schematic diagram of the minimally invasive implantation of a coaxial fiber electrode according to the present invention, wherein: ① encapsulation layer slurry; ② conductive layer slurry; ③ coaxial structure; ④ exposure monitoring point: conductive layer;

[0042] FIG2 is a top view of a coaxial fiber electrode;

[0043] FIG3 is a cross-sectional view of a coaxial fiber electrode. DETAILED DESCRIPTION

[0044] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0045] Example 1:

[0046] First, carbon nanofibers, PEDOT:PSS, PEG, and silica gel were weighed in proportions of 10%, 25%, 5%, and 60% by weight, respectively, and stirred in a deaerator for 2 minutes to ensure a uniform conductive layer slurry. Next, the encapsulation layer slurry was prepared by mixing the platinum-based two-component silica gel in the appropriate proportions. Finally, 5% nanosilica was added and stirred in a deaerator for 2 minutes to eliminate bubbles and ensure uniform mixing.

[0047] Set the machine's operating program and the appropriate air pressure (the conductive layer is 2.5kg / cm 3 , the packaging layer is selected as 3.5kg / cm 3 ), inject the prepared conductive layer slurry and encapsulation layer slurry into two syringes respectively, and place the pistons in the syringes respectively. The two syringes are connected to the two ends of the coaxial needle respectively, where the conductive layer slurry is connected to the inner channel and the encapsulation layer slurry is connected to the outer channel (as shown in Figure 1). Then, after connecting the syringe-air pump connector, printing begins to prepare the electrode. During the printing process, the conductive layer slurry of the inner channel is first printed for 2 mm in length to form an exposed monitoring point, and then the inner and outer layers are printed simultaneously to form a coaxial fiber electrode.

[0048] After printing is completed, take the wire and insert it into the end of the uncured coaxial fiber electrode, allowing the conductive paste and encapsulation paste to cure and form in a natural state for 10 minutes.

[0049] Through microscopic observation (as shown in Figures 2 and 3), it can be clearly seen that the encapsulation layer completely wraps the conductive layer, and a fiber electrode with a skin-core structure is successfully prepared, proving that the invention can achieve the desired goal.

[0050] Example 2:

[0051] First, carbon nanofibers, PEDOT:PSS, PEG, and silica gel were weighed in ratios of 10%, 25%, 7.5%, and 57.5%, respectively, and stirred in a deaerator for two minutes to ensure a uniform conductive layer slurry. Next, the encapsulation layer slurry was prepared by mixing the platinum-based two-component silica gel in the appropriate proportions. Finally, 10% nanosilica was added and stirred in a deaerator for two minutes to eliminate bubbles and ensure uniform mixing.

[0052] Set the machine running program and the appropriate air pressure (the conductive layer is 2kg / cm 3, the packaging layer is selected as 3kg / cm 3 ), the prepared conductive layer slurry and encapsulation layer slurry are injected into two syringes respectively, and the pistons are placed in the syringes respectively. The two syringes are connected to the two ends of the coaxial needle respectively, where the conductive layer slurry is connected to the inner channel, and the encapsulation layer slurry is connected to the outer channel. Then, after connecting the syringe-air pump connector, printing begins to prepare the electrode, and a fiber electrode with a skin-core structure is successfully prepared. During the printing process, the conductive layer slurry of the inner channel is first printed for 5mm in length to form an exposure monitoring point, and then the inner and outer layers are printed simultaneously to form a coaxial fiber electrode.

[0053] After printing is completed, the wire is taken and inserted into the end of the uncured coaxial fiber electrode, allowing the conductive paste and encapsulation paste to cure and form in a natural state for 13 minutes.

Claims

1. A preparation method of a core - shell structure fiber electrode for minimally invasive implantation, characterized in that, it comprises the following steps: (1) Prepare printing slurries: Prepare conductive slurry and encapsulation slurry respectively; Among them, the conductive slurry contains the following components by mass percentage: 0 - 85% conductive filler, 15 - 90% polymer matrix material, 0 - 10% additive; The encapsulation slurry contains a polymer for rapid prototyping and 0 - 20% mass concentration of nano - silica; (2) Load the slurries: Load the conductive slurry and encapsulation slurry prepared in step (1) into two syringes respectively, and connect them to the inner pipe and outer pipe of a coaxial needle respectively; (3) Determine the printing trajectory and implant and print: Use magnetic resonance imaging (MRI) to assist in determining the printing trajectory, drill holes at the target position with surgical instruments, or directly insert the coaxial needle, and start printing the electrode; During the printing process, the conductive layer slurry in the inner layer channel is first printed for 0.01 - 20 mm in length to form an exposed monitoring point, and then the inner layer and the outer layer start printing synchronously to form a coaxial fiber electrode; (4) Interface design: After the printing in step (3) is completed, take a wire and insert it into the end of the uncured coaxial fiber electrode, so that the conductive slurry and encapsulation slurry are cured and formed in a natural state.

2. The preparation method according to claim 1, characterized in that, in step (1), the conductive filler is selected from one or a mixture of carbon materials, conductive polymers, and metal conductive materials; the polymer matrix material is platinum - based two - component silica gel; the additive is selected from one or a mixture of polyethylene glycol and glycerol.

3. The preparation method according to claim 2, characterized in that, the carbon material is selected from one or a mixture of carbon nanofibers, carbon nanotubes, graphene, and carbon black.

4. The preparation method according to claim 2, characterized in that, the conductive polymer is selected from one or a mixture of poly(3,4 - ethylenedioxythiophene) - poly(styrenesulfonic acid), polypyrrole, and polyaniline.

5. The preparation method according to claim 2, characterized in that, the metal conductive material is selected from one or a mixture of gold nanowires / sheets / particles, silver nanowires / sheets / particles, and copper nanowires / sheets / particles.

6. The preparation method according to claim 1, characterized in that, in step (1), the encapsulation slurry is silica gel.

7. The preparation method according to claim 1, characterized in that, in step (1), the particle size of the nano - silica is 1 - 100 nm.

8. The preparation method according to claim 1, characterized in that, both the conductive slurry and the encapsulation slurry are injectable rheological fluids.

9. The preparation method according to claim 1, characterized in that, in step (4), the curing and forming time is 5 - 30 minutes.

10. A core - shell structure fiber electrode for minimally invasive implantation, characterized in that, it is prepared by the preparation method according to any one of claims 1 - 9.

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