Implantable nerve probe

Abstract

An implantable nerve probe according to the present invention includes a substrate, wiring that is formed on the substrate, an insulation layer that covers the wiring, an electrode that is provided at one end part of the wiring so as to be exposed, and an immunomodulation layer that is provided at at least an embedding region of the surface of the insulation layer that is to be embedded in a living body. The immunomodulation layer is a surface treatment film that is formed by the bonding of a functional group from an immunomodulator to the surface of the insulation layer.

Description

Implantable neural probes

[0001] The present invention relates to implantable neural probes.

[0002] An implantable neural probe measures electrical signals flowing through neural tissue in a living body and / or inputs electrical signals to the neural tissue. An implantable neural probe is used by placing electrodes in neural tissue such as the brain or spinal cord. For example, an implantable neural probe is used to stimulate nerves in patients with epilepsy or spinal cord injuries.

[0003] Implantable neural probes are a key component in brain-machine interface technologies, which connect neural tissue with machines. For example, implantable neural probes, which place electrodes inside the brain, offer the advantage of being able to measure the neural activity of individual neurons and populations of neurons with high precision compared to devices that place electrodes outside the body.

[0004] However, when measuring neural activity using implantable neural probes, there is a concern that placing electrodes inside the body may damage neural tissue, making it difficult to apply implantable neural probes to humans, and they have mainly been used for research purposes using laboratory animals.

[0005] Conventional implantable nerve probes include those described in Non-Patent Document 1 and Non-Patent Document 2. Non-Patent Document 1 describes a probe having a cross-sectional area of ​​250 μm per electrode. ２ A flexible intracortical probe is described. Non-Patent Document 1 describes the fabrication of a flexible intracortical probe using the polymer Parylene C. Non-Patent Document 2 describes an implantable neural probe having a base material made of Parylene. Non-Patent Document 2 describes glial reactions to electrodes implanted in the brain using an implantable neural probe.

[0006] Srikantharajah, K., Medinaceli Quintela, R., Doerenkamp, ​​K. et al. Minimally-invasive insertion strategy and in vivo evaluation of multi-shank flexible intracortical probes. Sci Rep 11, 18920 (2021). https: / / doi.org / 10.1038 / s41598-021-97940-xSalatino, JW, Ludwig, KA, Kozai, TDY et al. Glial responses to implanted electrodes in the brain. Nat Biomed Eng 1, 862-877 (2017). https: / / doi.org / 10.1038 / s41551-017-0154-1

[0007] When measuring neural activity using an implantable neural probe, the probe must be implanted in the body. This physically damages the neural tissue. Furthermore, an inflammatory reaction of cells surrounding the implantable neural probe placed in the body can cause fibrous tissue hypertrophy. This hypertrophy significantly reduces the electrical signal measurement and / or input capabilities of the implantable neural probe. For this reason, it has been difficult to accurately measure and / or input electrical signals over a long period of time using conventional implantable neural probes.

[0008] Furthermore, conventional implantable neural probes include a base material made of a hard material and having a shape such as a pin-holder or a flat plate, and an electrode that is exposed at the tip of the base material and placed inside a living body. When the electrode of such an implantable neural probe is placed inside a living body to measure neural activity, the base material of the implantable neural probe cannot follow the movement of the living tissue, which makes the neural tissue susceptible to damage and also makes it susceptible to hypertrophy of fibrous tissue due to an inflammatory reaction of the cells.

[0009] For this reason, in recent years, studies have been conducted to suppress the inflammatory reaction of cells present around an implantable neural probe placed in a living body by using a flexible material as the base material of the implantable neural probe. Also, as a method of suppressing the inflammatory reaction of cells present around an implantable neural probe placed in a living body, studies have been conducted to reduce the cross-sectional area of ​​the implantable neural probe to reduce the relative shear movement between the neural tissue and the implantable neural probe.

[0010] However, conventional implantable neural probes have not been able to sufficiently suppress the hypertrophy of fibrous tissue caused by the inflammatory reaction of cells present around the implantable neural probe placed in a living body. Therefore, there has been a demand for an implantable neural probe that can effectively suppress the inflammatory reaction of cells present around the implantable neural probe placed in a living body.

[0011] The present invention has been made in consideration of the above circumstances, and aims to provide an implantable neural probe that can suppress inflammatory reactions of cells present around the implantable neural probe placed in a living body.

[0012] In order to solve the above problems, the following means are provided: An implantable neural probe according to one aspect of the present invention includes a substrate, wiring formed on the substrate, an insulating layer covering the wiring, an electrode provided at one end of the wiring and exposed on the surface, and an immunomodulatory layer provided on the surface of the insulating layer at least on an implantation region to be implanted in a living body, the immunomodulatory layer being a surface-treated film formed by bonding functional groups derived from an immunomodulator to the surface of the insulating layer.

[0013] The implantable neural probe of the present invention includes an immunomodulatory layer disposed on the surface of an insulating layer at least in the region to be implanted in a living body, the immunomodulatory layer being a surface-treated film formed by bonding functional groups derived from an immunomodulator to the surface of the insulating layer. Therefore, when placed in a living body, the implantable neural probe can effectively suppress inflammatory reactions of cells present around the implantable neural probe, thereby suppressing the hypertrophy of fibrous tissue caused by the inflammatory reactions of cells. Therefore, the implantable neural probe can be used to measure and / or input electrical signals for a long period of time.

[0014] FIG. 1(a) is a schematic plan view showing an implantable neural probe according to a first embodiment of the present invention, and FIG. 1(b) is an enlarged plan view showing a portion of FIG. 1(a). FIG. 2 is a schematic cross-sectional view of the implantable neural probe shown in FIG. 1(b) along line II'. FIG. 3 shows an example of the chemical structure of an immunomodulatory layer 4, which is a surface-treated film 4 formed by bonding functional groups derived from an immunomodulatory substance, such as docosahexaenoic acid (DHA), to the surface of an insulating layer 3 made of parylene C. The functional groups derived from the immunomodulatory substance are bonded to the surface of the insulating layer 3 via linking groups derived from (3-aminopropyl)triethoxysilane, a silane coupling agent having an amino group. FIGS. 4(a) to 4(d) are process diagrams illustrating an example of a manufacturing method for the implantable neural probe 10 shown in FIGS. 1(a), 1(b), and 2, and are cross-sectional views showing the portion corresponding to FIG. 2. FIGS. 5(a) to 5(d) are perspective views illustrating other examples of the implantable neural probe of the present invention. Fig. 6 is a graph showing the Fourier transform infrared spectroscopy spectra of the surface of the substrate after the first step and the test specimen of Example 1. Fig. 7 is a graph showing the Fourier transform infrared spectroscopy spectra of the surface of the substrate after the first step and the test specimen of Example 1. Fig. 8 is a graph showing the measurement results of the amounts of inflammatory cytokines in Example 1 and Comparative Example 1.

[0015] In order to solve the above problems, the present inventors have focused on immune cells that initiate cellular inflammatory responses and conducted extensive research as described below. That is, when an implantable neural probe is placed in a living body, immune cells present around the implantable neural probe recognize the implantable neural probe as a foreign body, initiating an inflammatory response as an immune response. Therefore, simply using a flexible material as the base material of the implantable neural probe and reducing the cross-sectional area of ​​the implantable neural probe has a limited effect in suppressing the inflammatory response of cells present around the implantable neural probe.

[0016] Therefore, the present inventors have intensively investigated the possibility of forming an immunomodulatory layer containing an immunomodulatory substance on the outer surface of an implantable neural probe, which inhibits or avoids the activation of immune cells that initiate inflammatory responses in cells, thereby suppressing the inflammatory responses of cells present around the implantable neural probe. As a result, they have found that the immunomodulatory layer can be formed by binding functional groups derived from the immunomodulatory substance to at least the implantation region of the surface of the insulating layer that covers the wiring of the implantable neural probe, which is to be implanted in a living body, and have arrived at the present invention.

[0017] The present invention includes the following aspects: [1] An implantable neural probe comprising a substrate, wiring formed on the substrate, an insulating layer covering the wiring, an electrode provided at one end of the wiring and exposed on the surface, and an immunomodulatory layer provided on the surface of the insulating layer at least on an implantation region to be implanted in a living body, wherein the immunomodulatory layer is a surface-treated film formed by bonding functional groups derived from an immunomodulator to the surface of the insulating layer.

[0018] [2] The implantable neural probe according to [1], wherein the immunomodulatory substance is one or more selected from ω3 fatty acids, 3,4,5-trihydroxybenzoic acid, phenolic acid, dopamine, γ-aminobutyric acid, sericin, serine, sialic acid, hyaluronic acid, and derivatives thereof.

[0019] [3] An implantable neural probe according to [1], in which a functional group derived from an immunomodulatory substance is bound to the surface of the insulating layer via a linking group derived from a silane coupling agent.

[0020] [4] The implantable neural probe described in [1], wherein the base material and the insulating layer are each made of one or more materials selected from polyimide resin, polyparaxylene resin, and polydimethylsiloxane resin.

[0021] The implantable neural probe of the present invention will be described in detail below with reference to the drawings as appropriate. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity. Therefore, the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited to them. Appropriate modifications can be made within the scope of the present invention.

[0022] [Implantable neural probe] Fig. 1(a) is a schematic plan view showing an implantable neural probe according to a first embodiment of the present invention, and Fig. 1(b) is an enlarged plan view showing a part of Fig. 1(a). Fig. 2 is a schematic cross-sectional view taken along line II' of the implantable neural probe shown in Fig. 1(b).

[0023] The implantable neural probe 10 of this embodiment is a thin film type having a substantially uniform thickness. The planar shape and cross-sectional shape of the implantable neural probe 10 can be appropriately determined depending on the number of electrodes 5, the purpose of the implantable neural probe 10, etc.

[0024] 1(a), the implantable neural probe 10 of this embodiment has a tip portion 10a, which is an implantable region to be implanted in a living body and has an electrode 5, a base portion 10b, which has a connector 6, and a belt-like connecting portion 10c connecting the tip portion 10a and the base portion 10b. A known connector can be used as the connector 6. The connector 6 is electrically connected to an external device, such as an electrical signal measuring device and / or an electrical signal input device, via a wiring member such as a known cable (not shown).

[0025] The planar shape of the connecting portion 10c can be, for example, a strip shape with a width of 300 μm to 5000 μm and a length of 1 mm to 50 mm. ２ ~0.1mm ２ It can be a substantially rectangular shape of 1500 μm ２ ~2000μm ２ It is preferable that the connecting portion 10c has a substantially rectangular shape with a cross-sectional area of ​​1500 μm ２ If the cross-sectional area of ​​the connecting portion 10c is 2000 μm or more, the implantable neural probe 10 tends to have sufficient strength and is easy to handle. ２ If it is less than this, the cross-sectional area of ​​the portion of the implantable neural probe 10 that is implanted in the living body will be small, and the inflammatory reaction of cells present around the implantable neural probe 10 can be more effectively suppressed.

[0026] The planar shape of the tip portion 10a can be, for example, a shape with a length of 200 μm to 2000 μm and a width that gradually narrows toward the tip. The angle formed by the tip of the tip portion 10a can be, for example, an acute angle of 10° to 90°. The cross-sectional shape of the tip portion 10a can be, for example, a substantially rectangular shape with a cross-sectional area that gradually decreases toward the tip. The thickness of the tip portion 10a can be substantially constant, or can gradually become thinner toward the tip.

[0027] The base 10b may have a substantially constant width and a planar shape including a connector installation region where the connector 6 is located and a narrowing region whose width gradually narrows from the connector installation region toward the connecting portion 10c. The length of the base 10b may be, for example, 10 mm to 300 mm. The width of the connector installation region may be, for example, 10 mm to 300 mm.

[0028] As shown in Figures 1(a), 1(b) and 2, the implantable neural probe 10 of this embodiment includes a substrate 1, wiring 2 formed on the substrate 1, an insulating layer 3 covering the wiring 2, an electrode 5 provided at the end of the wiring 2 opposite the connector 6 and exposed on the surface of the implantable neural probe 10, and an immune modulatory layer 4 provided on the tip portion 10a, which is the implantation region on the surface of the insulating layer 3 that is implanted in a living body.

[0029] 2, in this embodiment, the immunomodulatory layer 4 is provided not only on the surface of the insulating layer 3 of the tip portion 10a but also on the surface of the base material 1 of the tip portion 10a opposite to the insulating layer 3. Therefore, when the implantable neural probe 10 is placed in a living body, the contact surfaces with the living body on the insulating layer 3 side and the base material 1 side of the implantable neural probe 10 implanted in the living body are the surfaces on which the immunomodulatory layer 4 is formed, and the inflammatory reaction of cells present around the implantable neural probe 10 can be more effectively suppressed.

[0030] In this embodiment, as shown in Figures 1(b) and 2, an example will be given in which the immune-adjusting layer 4 is provided only on the tip portion 10a, which is the implantation area on the surface of the insulating layer 3 that will be implanted in a living body, and on the surface of the substrate 1 of the tip portion 10a opposite the insulating layer 3, but it is sufficient that the immune-adjusting layer 4 is provided at least on the implantation area on the surface of the insulating layer 3 that will be implanted in a living body.

[0031] That is, the immune adjusting layer 4 may be provided only on the surface of the insulating layer 3 arranged in the tip portion 10a, or may be provided extending from the surface of the insulating layer 3 arranged in the tip portion 10a to the surface of the insulating layer 3 arranged in the connecting portion 10c or the base portion 10b. Furthermore, the immune adjusting layer 4 does not have to be provided on the surface of the substrate 1 opposite to the insulating layer 3, or may be provided only on the surface of the substrate 1 in the tip portion 10a opposite to the insulating layer 3, or may be provided extending from the surface of the substrate 1 in the tip portion 10a opposite to the insulating layer 3 to the surface of the substrate 1 in the connecting portion 10c or the base portion 10b opposite to the insulating layer 3.

[0032] 1(b) and 2, in this embodiment, the region (tip portion 10a) on the surface of the insulating layer 3 where the immune-modulating layer 4 is provided overlaps in plan view with the region (tip portion 10a) on the surface of the substrate 1 opposite the insulating layer 3 where the immune-modulating layer 4 is provided. Therefore, the immune-modulating layer 4 can be easily formed without protecting or masking the region where the immune-modulating layer 4 is not to be formed, by immersing the region where the immune-modulating layer 4 is to be formed in a solution of a silane coupling agent and an immune-modulating substance, which will be described later, used to form the immune-modulating layer 4.

[0033] The thickness of the substrate 1 can be appropriately determined depending on the material forming the substrate 1, etc. The thickness of the substrate 1 can be, for example, 1 μm to 15 μm, and is preferably 3 μm to 5 μm. When the thickness of the substrate 1 is 3 μm or more, the implantable neural probe 10 tends to have sufficient strength and is easy to handle. Furthermore, when the thickness of the substrate 1 is 5 μm or less, the implantable neural probe 10 tends to have a small cross-sectional area at the portion implanted in the living body, and the inflammatory response of cells present around the implantable neural probe 10 can be more effectively suppressed.

[0034] A known material can be used as the substrate 1. Examples of the substrate 1 include one or more materials selected from silicone resins, polyimide resins, polyparaxylene resins, polydimethylsiloxane resins, etc. Among these, the substrate 1 is preferably one or more materials selected from polyimide resins, polyparaxylene resins, and polydimethylsiloxane resins. This is because the substrate 1 has flexibility and can more effectively suppress inflammatory reactions of cells present around the implantable neural probe 10.

[0035] In the implantable neural probe 10 of this embodiment, an immune-modulating layer 4 is also provided on the surface of the substrate 1 opposite the insulating layer 3, so it is preferable that the substrate 1 be made of a material to which functional groups derived from immune-modulating substances are easily bonded, such as polyparaxylene-based resin, and it is particularly preferable that the substrate 1 be made of polyparaxylene-based resin, as this is a material to which functional groups derived from immune-modulating substances are easily bonded, has good flexibility, and has good biocompatibility and biological stability.

[0036] In this embodiment, the substrate 1 is described as consisting of only one substrate layer, but the substrate 1 may also be a laminate of two or more substrate layers. When the substrate 1 is a laminate of two or more substrate layers, it is preferable that the substrate forming the surface of the laminate opposite to the insulating layer 3 is made of a material to which functional groups derived from an immunomodulatory substance can easily bind.

[0037] As shown in FIG. 2, the wiring 2 is formed on the substrate 1. As shown in FIGS. 1(a) and 1(b), the wiring 2 electrically connects a plurality of electrodes 5 (five in the example shown in FIG. 1(b)) to the connector 6. The wiring 2 may be made of a known conductive material such as chromium (Cr), gold (Au), titanium (Ti), or aluminum (Al). Among these conductive materials, the wiring 2 is preferably made of gold, since this can more effectively suppress inflammatory reactions of cells present around the implantable neural probe 10.

[0038] As shown in Fig. 1(b), the electrodes 5 are provided on the ends of the plurality of wires 2 (five in the example shown in Figs. 1(a) and 1(b)) opposite the connector 6. All of the plurality of electrodes 5 are provided on the tip 10a of the implantable neural probe 10, which is the implanted region implanted in the living body. As shown in Fig. 2, the electrodes 5 are exposed on the surface of the substrate 1 facing the insulating layer 3.

[0039] In this embodiment, an example in which five electrodes 5 are provided will be described, but the number of electrodes 5 is not particularly limited and may be 1 to 4, or 6 or more. In addition, in this embodiment, an example in which five electrodes 5 are arranged at equal intervals in a row approximately along the center of the length of the tip portion 10a will be described, as shown in Figure 1(b), but the arrangement of the electrodes 5 is not particularly limited.

[0040] The electrode 5 can be made of known electrode materials such as chromium (Cr), gold (Au), titanium (Ti), and aluminum (Al). Among these, the electrode 5 is preferably made of gold, since this can more effectively suppress the inflammatory reaction of cells present around the implantable neural probe 10. The electrode 5 and the wiring 2 may be made of the same material, or may be made of different materials. When the electrode 5 and the wiring 2 are made of the same material, the electrode 5 and the wiring 2 can be efficiently formed simultaneously, which is preferable.

[0041] The insulating layer 3 covers the wires 2 and insulates the wires 2 from the environment surrounding the implantable neural probe 10 implanted in a living body. The thickness of the insulating layer 3 can be determined appropriately depending on the material forming the insulating layer 3, etc. The thickness of the insulating layer 3 can be, for example, 0.5 μm to 5 μm, and is preferably 1 μm to 1.5 μm. When the thickness of the insulating layer 3 is 1 μm or more, the wires 2 can be sufficiently insulated from the surrounding environment. In addition, the implantable neural probe 10 tends to have sufficient strength and is easy to handle. Furthermore, when the thickness of the insulating layer 3 is 1.5 μm or less, the cross-sectional area of ​​the portion implanted in a living body of the implantable neural probe 10 tends to be small, and inflammatory responses of cells present around the implantable neural probe 10 can be more effectively suppressed.

[0042] The insulating layer 3 may be made of one or more materials selected from silicone resins, polyimide resins, polyparaxylene resins, polydimethylsiloxane resins, etc. Among these, the insulating layer 3 is preferably made of a material to which functional groups derived from immunomodulators, such as polyparaxylene resins, are easily bonded.

[0043] Furthermore, the insulating layer 3 is preferably made of a flexible material such as polyimide resin, polyparaxylene resin, or polydimethylsiloxane resin, because this can more effectively suppress the inflammatory reaction of cells present around the implantable neural probe 10.

[0044] The insulating layer 3 is particularly preferably made of a polyparaxylene-based resin, which is a material to which functional groups derived from immunomodulators are easily bonded, has good flexibility, and is excellent in biocompatibility and biological stability. Examples of polyparaxylene-based resins include Parylene N, Parylene C, Parylene D, and Parylene HT. Parylene C is the most preferred because it has excellent insulating properties and good barrier properties against moisture and chemicals.

[0045] The insulating layer 3 and the substrate 1 may be made of the same material or different materials, which is preferable because the insulating layer 3 and the substrate 1 are made of the same material, since this provides good adhesion between the insulating layer 3 and the substrate 1.

[0046] In this embodiment, the insulating layer 3 is described as consisting of only one insulating layer, but the insulating layer 3 may also be a laminate of two or more insulating layers. When the insulating layer 3 is a laminate of two or more insulating layers, it is preferable that the insulating layer forming the surface of the laminate opposite to the substrate 1 is made of a material to which functional groups derived from an immunomodulatory substance can easily bind.

[0047] 1(a) and 2, the immunomodulating layer 4 is provided on the surface of the insulating layer 3 of the tip portion 10a and on the surface of the substrate 1 of the tip portion 10a opposite to the insulating layer 3. The immunomodulating layer 4 is a surface-treated film in which functional groups derived from an immunomodulating substance are bonded to the surface of the insulating layer 3 and the surface of the substrate 1 opposite to the insulating layer 3.

[0048] Examples of immunomodulators include one or more selected from ω3 fatty acids, 3,4,5-trihydroxybenzoic acid (gallic acid), sialic acids such as N-acetylneuraminic acid (Neu5Ac), phenolic acids, dopamine, γ-aminobutyric acid, sericin, serine, hyaluronic acid, and derivatives thereof. Among these, immunomodulators are preferably compounds having a carboxy group (—COOH), and ω3 fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are preferred because they exhibit high antioxidant activity and have the function of activating nerve cells.

[0049] The immunomodulating layer 4 preferably contains a functional group derived from the immunomodulating substance and a linking group derived from a silane coupling agent that is bonded to the surface of the insulating layer 3 and the surface of the substrate 1 opposite to the insulating layer 3. This is because the immunomodulating layer 4 can be easily formed by a method in which the surface of the insulating layer 3 that has been reacted with the silane coupling agent and the surface of the substrate 1 opposite to the insulating layer 3 are reacted with the immunomodulating substance.

[0050] The silane coupling agent in the linking group derived from the silane coupling agent is preferably a silane coupling agent having an amino group, such as (3-aminopropyl)triethoxysilane or (3-aminopropyl)trimethoxysilane. The reason for this is that when the immunomodulator is a compound having a carboxy group (-COOH), the amino group (-NH ２ ) with the carboxy group of the immunomodulator, functional groups derived from the immunomodulator can be easily bound to the surface of insulating layer 3 and the surface of substrate 1 opposite insulating layer 3.

[0051] The immunomodulatory layer 4 is, for example, a surface-treated film in which functional groups derived from an immunomodulatory substance made of docosahexaenoic acid (DHA) are bonded to the surface of the insulating layer 3 made of Parylene C and to the surface of the substrate 1 opposite the insulating layer 3. When the functional groups derived from the immunomodulatory substance are bonded to the surface of the insulating layer 3 and to the surface of the substrate 1 opposite the insulating layer 3 via linking groups derived from a silane coupling agent having an amino group, which is (3-aminopropyl)triethoxysilane, the immunomodulatory layer 4 has the chemical structure shown in Figure 3.

[0052] The immunomodulatory layer 4 may contain the condensing agent and / or esterifying agent used in forming the immunomodulatory layer 4. For example, when one or more selected from docosahexaenoic acid (DHA), gallic acid (3,4,5-trihydroxybenzoic acid), and N-acetylneuraminic acid (Neu5Ac) are used as the immunomodulatory substance, the immunomodulatory layer 4 may contain 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC.HCl) or the like as the condensing agent, and N-hydroxysuccinimide (NHS) or the like as the esterifying agent.

[0053] [Method for Manufacturing Implantable Neural Probe] The implantable neural probe 10 of this embodiment can be manufactured, for example, by the following manufacturing method. Figures 4(a) to 4(d) are process diagrams for explaining an example of a method for manufacturing the implantable neural probe 10 shown in Figures 1(a), 1(b), and 2, and are cross-sectional views showing the part corresponding to Figure 2.

[0054] To manufacture the implantable neural probe 10 of this embodiment, first, a base material 1 having a predetermined thickness is formed by a known method, as shown in Fig. 4(a). Next, a conductive film that will become the wiring 2 and electrodes 5 is formed on the base material 1 by a known method. After that, the conductive film is patterned by photolithography to form the wiring 2 and electrodes 5 having predetermined shapes, as shown in Fig. 4(b). Then, the base material 1 on which the wiring 2 and electrodes 5 are formed is cut by a known method so that the planar shape of the base material 1 corresponds to the planar shape of the implantable neural probe 10.

[0055] 4(c), an insulating layer 3 is formed to a predetermined thickness by a known method on the entire surface of the substrate 1 on which the wiring 2 and the electrodes 5 are formed. For example, when the insulating layer 3 is made of parylene C, it can be formed by a vapor deposition method.

[0056] Next, as shown in Figure 4(d), an immunomodulating layer 4 is provided on the surface of the insulating layer 3 and on the surface of the substrate 1 opposite the insulating layer 3. In this embodiment, an example will be described in which the immunomodulating layer 4 is provided on the surface of the insulating layer 3 of the tip portion 10a and on the surface of the substrate 1 opposite the insulating layer 3 at the same time. The immunomodulating layer 4 can be formed, for example, by a method that involves reacting the surface of the insulating layer 3 of the tip portion 10a and the surface of the substrate 1 opposite the insulating layer 3 with a silane coupling agent (step 1), and then reacting functional groups derived from the silane coupling agent with functional groups possessed by the immunomodulator (step 2).

[0057] (First Step) In the first step, oxygen plasma treatment is performed as a pretreatment on the surface of the insulating layer 3 in the region where the immunomodulatory layer 4 is to be provided (in this embodiment, the surface of the tip portion 10a (see Figure 1(b)), which is the implantation region to be implanted in a living body), and on the surface of the base material 1 of the tip portion 10a opposite the insulating layer 3. For example, the oxygen plasma treatment is preferably performed by irradiating with 100 W of power for 10 to 120 seconds. Thereafter, the tip portion 10a that has been subjected to the oxygen plasma treatment is immersed in a silane coupling agent. This causes the silane coupling agent to react with the surface of the insulating layer 3 of the tip portion 10a and the surface of the base material 1 opposite the insulating layer 3.

[0058] In this embodiment, after the first step, the surface of the insulating layer 3 and the surface of the substrate 1 opposite to the insulating layer 3 are preferably washed with ethanol and / or water. This makes it possible to remove unreacted silane coupling agent and by-products from the surface of the insulating layer 3 and the surface of the substrate 1 opposite to the insulating layer 3 after the first step.

[0059] (Step 2) In step 2, first, an immunomodulator solution is prepared by activating the immunomodulator with a condensing agent and / or an esterifying agent. Then, the insulating layer 3 of the tip portion 10a, which has been reacted with the silane coupling agent, and the surface of the substrate 1 opposite the insulating layer 3 are immersed in the immunomodulator solution to react the functional groups derived from the silane coupling agent with the functional groups possessed by the immunomodulator. This results in the formation of an immunomodulator layer 4, a surface-treated film in which the functional groups derived from the immunomodulator are bonded (modified) to the surface of the insulating layer 3 and the surface of the substrate 1 opposite the insulating layer 3 via the linking groups derived from the silane coupling agent.

[0060] In this embodiment, after the second step, the surface of the insulating layer 3 and the surface of the base material 1 of the tip portion 10a opposite to the insulating layer 3 are preferably washed with ethanol and / or water, thereby removing unreacted immunomodulators and by-products from the surface of the insulating layer 3 and the surface of the base material 1 of the tip portion 10a opposite to the insulating layer 3 after the second step.

[0061] Thereafter, for example, a mask is formed by a known method in the area excluding the area where the electrode 5 is to be formed in a plan view, and the insulating layer 3 and the immunomodulatory layer 4 provided on the electrode 5 are removed by plasma treatment or laser treatment, thereby exposing the electrode 5 on the surface of the implantable neural probe 10. Through the above steps, the implantable neural probe 10 of this embodiment is obtained.

[0062] In this embodiment, as described above, an example has been given of a method in which the insulating layer 3 and the immunomodulating layer 4 provided on the electrode 5 are removed to expose the electrode 5 after forming the immunomodulating layer 4, but the insulating layer 3 provided on the electrode 5 may be removed to expose the electrode 5 on the surface, and then the immunomodulating layer 4 may be formed. In this case, a mask is formed on the electrode 5 exposed on the surface using a known method, and then the immunomodulating layer 4 is formed.

[0063] Furthermore, in this embodiment, as described above, an example has been given in which the substrate 1 on which the wiring 2 and electrodes 5 are formed is cut into a shape corresponding to the planar shape of the implantable neural probe 10, but the wiring 2, electrodes 5, insulating layer 3, and immunomodulatory layer 4 may be formed on a substrate 1 having a shape corresponding to the planar shape of the implantable neural probe 10, or after forming the insulating layer 3 and immunomodulatory layer 4, the implantable neural probe 10 may be cut into a predetermined planar shape.

[0064] Furthermore, in this embodiment, the above-described first and second steps are performed to form an immunomodulatory layer 4 in which functional groups derived from an immunomodulator are bound to the surface of the insulating layer 3 and to the surface of the base material 1 of the tip portion 10a opposite the insulating layer 3 via linking groups derived from a silane coupling agent. However, the immunomodulatory layer 4 may be any surface-treated film in which functional groups derived from an immunomodulator are bound to the surface of the insulating layer 3. Therefore, the immunomodulatory layer 4 may be a surface-treated film in which functional groups derived from an immunomodulator are directly bound to the surface of the insulating layer 3 using one or more methods selected from the group consisting of a method using the Buchwald-Hartwig amination reaction, a method using the Friedel-Crafts reaction, and a method using a polymerization initiator. Alternatively, the immunomodulatory layer 4 may be a surface-treated film in which linking groups are introduced to the surface of the insulating layer 3 using one or more of the above methods, and then functional groups derived from an immunomodulator are bound via the linking groups by a separate chemical reaction.

[0065] Furthermore, in this embodiment, the thin-film type implantable neural probe 10 shown in Figures 1(a) and 1(b) has been used as an example, but the shape of the implantable neural probe is not limited to the thin-film type implantable neural probe 10 shown in Figures 1(a) and 1(b), and may be, for example, one having the shape shown in Figures 5(a) to 5(d).

[0066] Figures 5(a) to 5(d) are perspective views illustrating other examples of the implantable neural probe of the present invention. Figure 5(a) is a pin-frog-type implantable neural probe 11. Figure 5(b) is a flat-plate-type implantable neural probe 12. Figure 5(c) is a thin-wire-type implantable neural probe 13. Figure 5(d) is a mesh-type implantable neural probe 14.

[0067] The implantable neural probes 11, 12, 13, and 14 shown in Figures 5(a) to 5(d), like the implantable neural probe 10 shown in Figures 1(a) and 1(b), include a substrate, wiring formed on the substrate, an insulating layer covering the wiring, an electrode 5 provided at one end of the wiring and exposed on the surface, and an immune-modulating layer provided on the implantation region of the insulating layer that will be implanted in the living body.

[0068] [Method of Using the Implantable Neural Probe] When the implantable neural probe 10 of this embodiment is used to measure the firing of neurons in the brain of an animal such as a rat, it can be used in the following manner: First, an animal such as a rat is anesthetized to expose the brain, and the implantable neural probe 10 is placed in the brain tissue.

[0069] When the base material 1 and insulating layer 3 of the implantable neural probe 10 are made of a flexible material, the implantable neural probe 10 is placed in brain tissue using a guide. The guide can be a rod-shaped object with sufficient rigidity, such as a glass capillary or a thin stainless steel wire. Specifically, the implantable neural probe 10 is attached to the guide using a known method, and then inserted together with the guide into a predetermined position in the animal's brain tissue. The guide is then removed from the brain tissue, leaving the implantable neural probe 10 in place in the brain tissue.

[0070] Next, the connector 6 of the implantable neural probe 10 is electrically connected to an electrical signal measuring device via a wiring member such as a known cable. Also, a reference electrode such as a silver-silver chloride electrode is placed on the surface of the animal's biological tissue, separate from the implantable neural probe 10. Then, the electrical signal from the electrode 5 of the implantable neural probe 10 is measured, and the firing of the nerve cell is measured from the change in the potential difference between the electrode 5 and the reference electrode.

[0071] The implantable neural probe 10 of this embodiment has an immune-modulating layer 4 provided on the surface of the insulating layer 3 in an implantation region that will be implanted in a living body. The immune-modulating layer 4 is a surface-treated film formed by bonding functional groups derived from immune-modulating substances to the surface of the insulating layer 3. Therefore, when the implantable neural probe 10 of this embodiment is placed in a living body, the inflammatory reaction of cells present around the implantable neural probe 10 can be effectively suppressed.

[0072] For example, when the implantable neural probe 10 of this embodiment is placed in brain tissue, the immunomodulatory effect of the immunomodulatory layer 4 on microglia, which are immune cells present in the brain tissue, suppresses activation of microglia, which is one type of immune response. As a result, hypertrophy of fibrous tissue caused by inflammatory reactions of cells in the brain tissue is sufficiently suppressed. This makes it difficult for the reduction in measurement sensitivity of electrical signals and / or the reduction in input accuracy of electrical signals that accompanies the hypertrophy of fibrous tissue to occur, allowing the implantable neural probe 10 to accurately measure and / or input electrical signals for a long period of time.

[0073] The above describes the embodiments of the present invention in detail, but each configuration and combination thereof in each embodiment is an example, and additions, omissions, substitutions, and other modifications of the configurations are possible within the scope that does not deviate from the spirit of the present invention.

[0074] Example 1: A circular substrate (in plan view) made of parylene C, 15 mm in diameter and 1 μm thick, was prepared by thermal chemical vapor deposition. An immunomodulatory layer (4) was then formed over the entire surface of the substrate. The immunomodulatory layer (4) was formed by reacting the surface of the substrate with a silane coupling agent (step 1) and then reacting functional groups derived from the silane coupling agent with functional groups possessed by an immunomodulator (step 2).

[0075] (Step 1) First, as a pretreatment, the surface of the substrate was subjected to oxygen plasma treatment by irradiating it with oxygen plasma at 100 W for 40 seconds. The oxygen plasma-treated substrate was then immersed in a silane coupling agent solution for 1 hour, allowing the substrate surface to react with the silane coupling agent. The silane coupling agent solution was prepared by the following method. A silane coupling agent consisting of (3-aminopropyl)triethoxysilane (APTES) was dissolved in ethanol to obtain an ethanol solution containing (3-aminopropyl)triethoxysilane at a concentration of 5% by mass. The pH of the ethanol solution was then adjusted using hydrochloric acid to obtain a silane coupling agent solution with a pH of 5. The surface of the substrate after Step 1 was then washed with ethanol.

[0076] (Step 2) An immunomodulator consisting of docosahexaenoic acid (DHA) was dissolved in ethanol to a concentration of 800 mmol / L to prepare a first solution. An ethanol solution containing 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl), a condensing agent, and N-hydroxysuccinimide (NHS), an esterifying agent, each containing 1.2 equivalents of the immunomodulator molecule, was also prepared to prepare a second solution. The first and second solutions were then mixed, and the immunomodulator was activated by reacting with the condensing agent and esterifying agent, thereby obtaining an immunomodulator solution containing 400 mmol / L of the immunomodulator.

[0077] The substrate washed after the first step was then immersed in an immunomodulator solution for 1 hour to allow the functional groups derived from the silane coupling agent to react with the functional groups of the immunomodulator, forming an immunomodulatory layer. The surface of the substrate after the formation of the immunomodulatory layer was then washed with ethanol to obtain a test specimen for Example 1.

[0078] The surface of the specimen of Example 1 thus obtained was measured by a colorimetric method using a 0.5% by mass ninhydrin solution to measure the amount of functional groups derived from the immunomodulator (DHA) and the amount of linking groups derived from the silane coupling agent (APTES) bound to the surface. As a result, the amount of linking groups derived from the silane coupling agent (APTES) bound to the surface was 14.3 nmol / cm ２ and the amount of functional groups derived from the immunomodulator (DHA) is 13.3 nmol / cm ２ It was.

[0079] Furthermore, the surface of the substrate after the first step and the surface of the test specimen of Example 1 were analyzed using a Fourier transform infrared spectrometer (product name: FT / IR-4X, manufactured by JASCO Corporation). The results are shown in Figures 6 and 7. Figures 6 and 7 are graphs showing the Fourier transform infrared spectroscopic spectra of the surface of the substrate after the first step and Example 1. In Figures 6 and 7, the solid line shows the results of the surface of the substrate after the first step, and the dotted line shows the results of Example 1.

[0080] As shown in Figure 6, a peak derived from the C=O of ketone, which is thought to be due to the thermal chemical vapor deposition of Parylene C, was observed in the substrate after the first step. Also, as shown in Figure 6, in the specimen of Example 1, the peak derived from the absorption of C=O shifted to a lower wavenumber compared to the substrate after the first step, suggesting the formation of an amide bond. From this, it was confirmed that in the specimen of Example 1, a chemical bond was formed via an amide bond due to the reaction between the immunomodulatory substance docosahexaenoic acid (DHA) and the silane coupling agent APTES.

[0081] 7, the height of the peak derived from the absorption of the C═C double bond is higher in the test specimen of Example 1 compared to the substrate after step 1. This is presumably because the second step causes docosahexaenoic acid (DHA), an immunomodulator, to bind to the surface of the substrate after step 1, thereby increasing the absorption derived from the double bond in DHA.

[0082] From these findings, it was confirmed that in the second step, by immersing the substrate after the first step in an immunomodulatory substance solution obtained by mixing a first solution containing the immunomodulator docosahexaenoic acid (DHA) with a second solution containing the condensing agent 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and the esterifying agent N-hydroxysuccinimide (NHS), a surface treatment film (immunomodulatory layer) was formed on the surface of the substrate made of Parylene C, in which functional groups derived from the immunomodulator made of docosahexaenoic acid (DHA) were bonded (modified).

[0083] Comparative Example 1 The substrate made of Parylene C used in Example 1 was used as a test specimen in Comparative Example 1.

[0084] "Evaluation of foreign body reaction of immune cells" The foreign body reaction of immune cells to the test specimens of Example 1 and Comparative Example 1 was evaluated by the method described below. Mouse microglia were placed as immune cells at 6 × 10 cells per test specimen of Example 1 and Comparative Example 1 together with a medium (culture solution). ４ cells / cm ２ Seed and incubate in 5% CO ２ After culturing for 6 hours at 37°C in air containing β-amycin, lipopolysaccharide was added to the medium at a concentration of 20 ng / ml to activate the immune response of microglia.

[0085] After the culture was completed, the cell supernatant was used to quantify the inflammatory cytokines by enzyme-linked immunosorbent assay. The results are shown in Figure 8. Figure 8 is a graph showing the measurement results of the inflammatory cytokine amounts in Example 1 and Comparative Example 1. ＊＊ "p<0.01" indicates that the results of Example 1 and Comparative Example 1 are statistically significant at the 1% level.

[0086] As shown in Figure 8, the test specimen of Example 1, in which an immunomodulatory layer was formed on a substrate made of Parylene C, showed significantly reduced production of inflammatory cytokines compared to the test specimen of Comparative Example 1, in which an immunomodulatory layer was not formed on a substrate made of Parylene C. This is presumably because the immunomodulatory effect of the immunomodulatory layer suppressed the activation of microglia, which is one component of the immune response, thereby suppressing the production of inflammatory cytokines from immune cells.

Claims

1. An implantable neural probe comprising a substrate, wiring formed on the substrate, an insulating layer covering the wiring, an electrode provided at one end of the wiring and exposed on the surface, and an immunomodulatory layer provided on at least the implantation area of ​​the insulating layer that will be implanted in a living body, wherein the immunomodulatory layer is a surface-treated film formed by bonding functional groups derived from immunomodulatory substances to the surface of the insulating layer.

2. The implantable neural probe according to claim 1, wherein the immunomodulatory substance is one or more selected from the group consisting of omega-3 fatty acids, 3,4,5-trihydroxybenzoic acid, phenolic acid, dopamine, γ-aminobutyric acid, sericin, serine, sialic acid, hyaluronic acid, and derivatives thereof.

3. The implantable neural probe of claim 1, wherein a functional group derived from an immunomodulatory substance is bound to the surface of the insulating layer via a linking group derived from a silane coupling agent.

4. The implantable neural probe according to claim 1, wherein the substrate and the insulating layer are each made of one or more materials selected from the group consisting of polyimide resin, polyparaxylene resin, and polydimethylsiloxane resin.

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