Implantable neural electrode for long-term electrophysiological signal monitoring, method for preparing same, and use thereof
By employing a hydrogel insulating encapsulation layer and aerosol printing technology on the neural electrodes, the biocompatibility and mechanical mismatch issues of traditional neural electrodes have been resolved, enabling stable and high-precision recording of long-term electrophysiological signals.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- TSINGHUA SHENZHEN INTERNATIONAL GRADUATE SCHOOL
- Filing Date
- 2025-02-28
- Publication Date
- 2026-07-30
AI Technical Summary
Traditional neural electrodes suffer from poor biocompatibility, mechanical mismatch leading to neuronal damage and signal instability during long-term implantation, and it is difficult to fabricate high-precision, high-electrode-density neural electrode arrays.
The device employs two layers of hydrogel insulating encapsulation. Electrode sites, connecting lines, and pads are formed using aerosol printing technology. Conductive hydrogel provides electrical connectivity and good biocompatibility, while the hydrogel insulating encapsulation provides hydrophilicity and stability.
The neural electrodes that enable long-term electrophysiological signal monitoring have good biocompatibility and stability, can continuously monitor in vivo for one year, and can accurately record and stimulate brain region signals.
Smart Images
Figure CN2025079877_30072026_PF_FP_ABST
Abstract
Description
An implantable neural electrode for long-term electrophysiological signal monitoring, its preparation method and application Technical Field
[0001] This application relates to the field of medical device technology, and in particular to an implantable neural electrode for long-term electrophysiological signal monitoring, its preparation method, and its application. Background Technology
[0002] In the interdisciplinary field of biomedicine and neuroscience, there are very few biomaterials and electronic interfaces capable of chronic implantation and precise decoding of neural activity. Two-dimensional planar electrode arrays have been developed for minimally invasive electrophysiological recording and stimulation of brain activity, commonly known as electrocorticography (ECoG) neural electrodes. However, traditional ECoG electrode arrays are typically based on metals such as silicon (Si) or platinum (Pt). While they can effectively capture signals, they face challenges in long-term implantation. The long-term presence of these foreign materials can trigger persistent immune responses and even lead to damage and death of neurons near the electrodes. The Young's modulus of traditional electrodes is typically measured in GPa, while the modulus of the brain is 0.5–1.2 MPa, and the modulus of gray / white matter is 1–1.5 kPa. This mechanical difference exacerbates the challenges to the biocompatibility of implantable devices. Furthermore, the mechanical mismatch between the electrode and the brain can lead to uneven strain distribution, shear motion, and positioning disorder during implantation, thereby altering physiological responses and impairing signal fidelity. Furthermore, traditional encapsulation materials such as polyimide and parylene, while possessing excellent insulating properties, lack adhesion to brain tissue due to their hydrophobic nature. Insufficient adhesion often exacerbates tissue damage caused by mechanical mismatch during long-term implantation of neural electrodes, thereby compromising the stability and lifespan of the neural interface.
[0003] Furthermore, fabricating implantable neural electrode arrays with high precision and high electrode density remains another challenge. Conductive polymer-based hydrogels, such as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS), are excellent materials for conductive layers in neural electrodes due to their tunable mechanical and electrical properties and structural stability in biological environments. However, patterning conductive hydrogels to fabricate neural electrodes with linewidths in the micrometer range also presents a challenge. Recent studies have shown that 3D printing and photolithography have demonstrated some assistance in patterning conductive hydrogels, but photoresists and developers can affect the biocompatibility of the materials. Summary of the Invention
[0004] To at least overcome one of the problems existing in the prior art, one objective of this application is to provide an implantable neural electrode for long-term electrophysiological signal monitoring. A second objective of this application is to provide a method for preparing the implantable neural electrode for long-term electrophysiological signal monitoring. A third objective of this application is to provide an electrophysiological signal monitoring device, including the neural electrode or a neural electrode prepared by the method described above. The implantable neural electrode for long-term electrophysiological signal monitoring of this application includes upper and lower hydrogel insulating encapsulation layers, and electrode sites, connecting lines, and pads between the upper and lower hydrogel insulating encapsulation layers. The electrode sites and the pads are connected by the connecting lines. The electrode sites, connecting lines, and pads, formed using aerosol printing technology, provide reliable electrical connections for the neural electrode. The conductive hydrogel provides the neural electrode with the ability to capture minute electrophysiological signals and apply electrical stimulation. The hydrogel insulating encapsulation layer, with good hydrophilicity and wet tissue adhesion, provides the neural electrode with good biocompatibility and long-term recording stability.
[0005] Therefore, this application adopts the following technical solution:
[0006] The first aspect of this application provides an implantable neural electrode for long-term electrophysiological signal monitoring. The neural electrode includes upper and lower hydrogel insulating encapsulation layers, and an electrode site, a connecting line, and a pad between the upper and lower hydrogel insulating encapsulation layers. The electrode site and the pad are connected by the connecting line.
[0007] Preferably, the electrode sites, connecting lines, and pads are all made of conductive hydrogel.
[0008] Preferably, the upper and lower hydrogel insulating encapsulation layers have the same material composition;
[0009] Preferably, the material composition of the upper and lower hydrogel insulating encapsulation layers includes an insulating polymer and hydrogel;
[0010] Preferably, the insulating polymer is an insulating polymer that has undergone plasma surface modification.
[0011] Preferably, the raw material composition of the conductive hydrogel includes conductive ink and hydrogel;
[0012] The conductive ink, the hydrogel, and the insulating polymer can all be obtained using existing technologies, and this application does not limit them.
[0013] Preferably, the conductivity of the conductive ink is 4800–5200 S / cm. More preferably, the conductivity of the conductive ink is about 5000 S / cm.
[0014] Preferably, the conductive ink is a modified poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). More preferably, the conductive ink is the EG and LiTFSI modified PEDOT:PSS conductive ink disclosed in the invention patent application "PEDOT:PSS / EG / LiTFSI conductive ink and ultra-flexible electrode and method for monitoring electrophysiological signals" (CN114574040A). The preparation method of this PEDOT:PSS / EG / LiTFSI conductive ink includes: modifying the PEDOT:PSS solution with ethylene glycol and lithium bis(trifluoromethanesulfonyl)imide, wherein the viscosity of the PEDOT:PSS / EG / LiTFSI conductive ink is 1-1000 cP and the surface tension is 30-40 mN / m.
[0015] Preferably, the raw material components of the hydrogel include sodium alginate and polyacrylamide. More preferably, the raw material components of the hydrogel are the peelable polyacrylamide / sodium alginate ultrathin hydrogel disclosed in the invention patent application "A peelable ultrathin hydrogel, preparation method and application" (CN113754897A).
[0016] Preferably, the insulating polymer is selected from at least one of parylene, polyethylene terephthalate, polyimide, and polydimethylsiloxane. More preferably, the insulating polymer is selected from at least one of parylene, polyethylene terephthalate, and polyimide. Even more preferably, the insulating polymer is selected from parylene.
[0017] Preferably, the diameter of the electrode site is 50 μm to 200 μm. More preferably, the diameter of the electrode site is 80 μm to 120 μm.
[0018] Preferably, the line width of the connecting line is 20μm to 100μm. More preferably, the line width of the connecting line is 20μm to 80μm. Even more preferably, the line width of the connecting line is 30μm to 50μm.
[0019] Preferably, the diameter of the pad is 100μm to 2000μm. More preferably, the diameter of the pad is 200μm to 2000μm. Even more preferably, the diameter of the pad is 500μm to 1000μm.
[0020] The electrode sites can perform real-time signal monitoring and stimulation of the implanted brain region, and the pads can transmit the recorded electrophysiological signals to electronic devices for decoding and analysis.
[0021] A second aspect of this application provides a method for preparing a neural electrode according to the first aspect of this application, comprising the following steps:
[0022] (1) A hydrogel insulating encapsulation layer was prepared by combining a surface-modified insulating polymer with a hydrogel.
[0023] (2) The electrode sites, connecting lines and pads are obtained by printing on the hydrogel surface of the hydrogel insulating encapsulation layer using aerosol printing technology.
[0024] (3) A hydrogel insulating encapsulation layer is covered on the upper surface of the electrode sites, connecting lines, and pads, and etched to obtain electrode sites and pad openings, thereby obtaining the neural electrode.
[0025] Preferably, in step (1), the surface modification of the insulating polymer is performed using O2 plasma. After O2 plasma modification, many oxygen-containing functional groups are generated on the surface of the insulating polymer. These functional groups can form hydrogen bonds with the hydrogel to improve the bonding strength between the two.
[0026] Preferably, in step (1), the surface modification time is 2 min to 10 min.
[0027] Preferably, in step (1), the method for preparing the hydrogel includes the following steps:
[0028] S1: Peel off one of the two hydrophobic modified release films attached to both sides of the peelable hydrogel, so that one side of the hydrogel substrate is exposed, while the other unpeeled hydrophobic modified release film plays a role in fixing the shape of the hydrogel.
[0029] S2: Place the hydrogel with one side exposed on a hot plate and heat it to dry it. Preferably, the heating temperature is 50℃~90℃; more preferably, the heating temperature is 60℃~70℃. The purpose of heating and drying is to increase the Young's modulus of the hydrogel and to separate it from another unpeeled hydrophobic modified release film.
[0030] S3: Place the dried hydrogel, which has been separated from another unpeeled hydrophobically modified release membrane, into deionized water to allow it to fully swell; preferably, the swelling time is 1 min to 40 min; more preferably, the swelling time is 5 min to 20 min.
[0031] S4: The fully swollen hydrogel is removed from the deionized water in a shape-preserving manner, which may be done by means of a base material; preferably, the base material may be polyethylene terephthalate, polyimide, polydimethylsiloxane and a sieve; more preferably, the removal is done by means of a pre-soaked sieve so that excess deionized water is drained out when the fully swollen hydrogel is removed from the deionized water in a shape-preserving manner.
[0032] Preferably, in step (1), the method for preparing the hydrogel insulating encapsulation layer includes the following steps:
[0033] The fully swollen hydrogel is shape-conservatively transferred to the surface of an insulating polymer modified with O2 plasma, and then placed on a hot stage for heating to promote water evaporation and hydrogel fixation. Preferably, the heating temperature is 50°C to 90°C; more preferably, the heating temperature is 60°C to 70°C.
[0034] Preferably, in step (3), the etching is performed using a mask plasma etching method, and the mask is made of polydimethylsiloxane / polyimide.
[0035] Preferably, in step (3), the process flow for opening the hole includes:
[0036] S1: Based on the electrode sites and pads of the neural electrodes, the photomask is patterned using laser lithography.
[0037] S2: Cover the upper and lower surfaces of the electrode sites, connecting lines, and pads with hydrogel insulating encapsulation layers respectively. After aligning the patterned mask with the electrode sites and pads, open holes are made in the electrode sites and pads. The process for making the holes is plasma etching.
[0038] A third aspect of this application provides an electrophysiological signal monitoring device, including a neural electrode prepared by the method described in the first aspect of this application or the method described in the second aspect of this application.
[0039] Compared with the prior art, the beneficial effects of this application are:
[0040] This application provides an implantable neural electrode for long-term electrophysiological signal monitoring. Specifically, the implantable neural electrode for long-term electrophysiological signal monitoring prepared by the above method has good electrical properties and excellent flexibility. After being implanted into the cerebral cortex of mice, it has good conformal adhesion and can monitor the normal physiological activities of mice. In addition, by means of the volume capacitance of the conductive hydrogel, electrical stimulation can be successfully applied to specific brain regions.
[0041] This application provides an implantable neural electrode for long-term electrophysiological signal monitoring. No biotoxic materials were introduced during its fabrication. Thanks to the high biocompatibility and biofriendliness of the materials, this neural electrode exhibits excellent biocompatibility and can be continuously monitored in vivo for up to one year. Therefore, this implantable neural electrode for long-term electrophysiological signal monitoring has significant application value for studying signal responses and neural circuits in various brain regions, providing a valuable tool for long-term in vivo monitoring. Attached Figure Description
[0042] The present application will be further described below with reference to the accompanying drawings and embodiments, wherein:
[0043] Figure 1 illustrates the flexibility and mechanical compliance of the neural electrode prepared in Example 1.
[0044] Figure 2 shows the stress-strain curves of the neural electrode in Example 1 under dry and swollen conditions.
[0045] Figure 3 shows the cell fluorescence images of the neural electrode and the blank control group in Example 1 after culturing in the extract for 1 day, 3 days, 5 days and 7 days.
[0046] Figure 4 shows the in vitro cytotoxicity test of the neural electrode in Example 1.
[0047] Figure 5 shows the in vivo biocompatibility fluorescence image of the neural electrode in Example 1.
[0048] Figure 6 is a comparison of fluorescence intensity between the implanted and unimplanted areas of the neural electrode in Example 1.
[0049] Figure 7 is a schematic diagram of the neural electrodes covering the left hemisphere of the mouse brain in Example 1.
[0050] Figure 8 shows the neural responses of mice during spontaneous whisker movement captured by neural electrodes in Example 1.
[0051] Figure 9 shows the neural response of mice when the neural electrodes in Example 1 are electrically stimulated.
[0052] Figure 10 shows the electrophysiological signal waveforms captured by all channels of the neural electrode in Example 1 on the first day after implantation in a New Zealand rabbit.
[0053] Figure 11 shows the decoding of different band signals captured by all channels of the neural electrode in Example 1 on the first day after implantation in a New Zealand rabbit.
[0054] Figure 12 shows the signal intensity versus frequency under three different physiological conditions after implantation of the neural electrode in New Zealand rabbits on day 1 and day 365 in Example 1. Detailed Implementation
[0055] The following detailed description of the contents of this application is provided through specific embodiments and test examples, but is not limited to all the arguments and data.
[0056] The conductive ink is the EG and LiTFSI modified PEDOT:PSS conductive ink disclosed in the invention patent application "PEDOT:PSS / EG / LiTFSI conductive ink and ultra-flexible electrode and method for monitoring electrophysiological signals" (CN114574040A). The preparation method of this PEDOT:PSS / EG / LiTFSI conductive ink includes modifying a PEDOT:PSS solution with ethylene glycol and lithium bis(trifluoromethanesulfonyl)imide. The viscosity of this PEDOT:PSS / EG / LiTFSI conductive ink is 1–1000 cP, and the surface tension is 30–40 mN / m.
[0057] The raw material components of the hydrogel are the peelable polyacrylamide / sodium alginate ultrathin hydrogel disclosed in the invention patent application "A peelable ultrathin hydrogel, preparation method and application" (CN113754897A), and its preparation method is carried out according to the preparation process of Example 1.
[0058] The insulating polymer is parylene.
[0059] It is particularly important to emphasize that, unless otherwise specified, the raw materials, reagents or devices used in this application are all available from conventional commercial sources.
[0060] In this application, “about” means that the numerical error range is within 2%.
[0061] Example 1:
[0062] A method for preparing a neural electrode includes the following steps:
[0063] S1: Peel off one of the two hydrophobic modified release films that were prepared in Example 1 of CN113754897A and attached to both sides of the peelable hydrogel, so that one side of the hydrogel substrate is exposed, while the other unpeeled hydrophobic modified release film plays a role in fixing the shape of the hydrogel.
[0064] S2: Place the hydrogel with one side exposed on a hot plate and heat it at 60°C to dry it, so as to increase the Young's modulus of the hydrogel and promote its separation from another unpeeled hydrophobic modified release film.
[0065] S3: Place the dried hydrogel, which has been separated from another unpeeled hydrophobic modified release membrane, into deionized water and soak for 20 minutes to allow it to swell completely.
[0066] S4: Using a sieve, the fully swollen hydrogel is removed from the deionized water in a shape-preserving manner, and the excess deionized water is drained through the sieve.
[0067] S5: The surface of parylene is modified using O2 plasma to generate oxygen-containing functional groups on its surface;
[0068] S6: The hydrogel is transferred conformally to the surface of parylene modified by O2 plasma, and then placed on a hot stage and heated at 60°C to promote the evaporation of water and the fixation of hydrogel, thus obtaining a hydrogel insulating encapsulation layer.
[0069] S7: The PEDOT:PSS / EG / LiTFSI conductive ink from Example 1 of CN114574040A is placed in the ink cartridge of an aerosol printer. The electrode pattern is printed on the hydrogel surface of the hydrogel insulating encapsulation layer according to the design, to obtain electrode sites, connecting lines, and pads. The electrode sites and pads are connected by connecting lines. The diameter of the electrode site in contact with the cerebral cortex is 100μm; the diameter of the pad connected to the circuit board is 700μm; and the line width of the connecting line is 40μm.
[0070] S8: Based on the electrode sites and pads of the neural electrodes, the PDMS / PI mask is patterned using laser lithography.
[0071] S9: A hydrogel insulating encapsulation layer is covered on the upper surface of the electrode sites, connecting lines, and pads. After aligning the patterned mask with the electrode sites and pads, plasma etching is used to create openings in the electrode sites and pads to obtain the neural electrodes.
[0072] Material performance testing:
[0073] The neural electrodes obtained in Example 1 were subjected to mechanical, electrical, and biocompatibility tests, and the specific results are as follows:
[0074] (1) Figure 1 shows the flexibility and mechanical compliance of the neural electrode prepared in Example 1. As can be seen from Figure 1, the neural electrode can be bent into any shape and fits perfectly with the irregular surface, thanks to the good flexibility and mechanical compliance of the hydrogel insulating encapsulation layer.
[0075] (2) Figure 2 shows the stress-strain curves of the neural electrode in Example 1 under dry and swollen conditions. Figure 2a shows the dry state, and Figure 2b shows the swollen state. As shown in Figure 2a, the elongation at break of the dry neural electrode is 13.57%, and the Young's modulus is 245 MPa. As shown in Figure 2b, since the hydrogel absorbs water during implantation, thus reducing its own Young's modulus, although the elongation at break of the fully swollen implantable electrode does not change significantly (10.35%), its Young's modulus decreases by an order of magnitude to 61.3 MPa. Therefore, whether in the dry state or the fully swollen state, the elongation at break of the neural electrode meets the range of deformation caused by daily brain activity (10%), and the introduction of hydrogel can act as a dissipative layer during stretching, effectively reducing the overall Young's modulus of the neural electrode.
[0076] (3) Figure 3 shows the cell fluorescence images of the neural electrode and blank control group after 1, 3, 5 and 7 days of culture in the extract. The neural electrode prepared in Example 1 was tested for in vitro cytotoxicity using rat cortical neuron cells, complete rat cortical neuron cell culture medium, and DAPI fluorescence staining. The experimental procedure was as follows: 0.25% trypsin containing EDTA (Gibco) was added to rat cortical neuron cells (Wuhan Procell Biotechnology Co., Ltd.) preserved in rat cortical neuron cell culture medium. The culture flask was then placed in a 37℃, 5% CO2 incubator for 3-5 minutes to digest the cells and allow them to detach from the cell wall. To obtain the neural electrode culture medium extract, the cells were cultured at 3cm... 2 The neural electrodes were precisely cut at a ratio of / mL and immersed in complete culture medium for rat cortical neurons, then placed in a 37℃, 5% CO2 incubator for at least 24 hours. During the extraction process, the detached rat cortical neurons were completely dispersed in the culture medium and seeded into 96-well plates, which were then incubated at 37℃, 5% CO2 for 24 hours to allow them to adhere. After obtaining the extract, the complete culture medium for rat cortical neurons in the 96-well plates was replaced with the extract, while the complete culture medium for rat cortical neurons in the control group remained unchanged. After incubation at 37℃, 5% CO2 for 1, 3, 5, and 7 days, the cells were characterized by DAPI fluorescence staining. As shown in Figure 3, the rat cortical neurons were in good condition, and no cell reduction was observed compared to the control group on day 7. Furthermore, the Cell Count Kit-8 (CCK-8) assay showed that after 7 days of culture, cell viability did not decrease significantly in six different concentrations of extraction media (4%, 7%, 13%, 25%, 50%, and 100%) (Figure 4). This demonstrates that the neural electrode of this application exhibits low in vitro cytotoxicity.
[0077] (4) In vivo immunofluorescence analysis was performed in a rat model. The specific procedures were as follows: To assess chronic biocompatibility in vivo, rats were anesthetized by intraperitoneal injection of sodium pentobarbital solution (40-50 mg / kg). Before the operation, it was necessary to confirm that the animal had reached a state of analgesia (surgical anesthesia period), characterized by the gradual inhibition of respiration, circulation, muscle tone, and protective reflexes. The anesthetized animals were perfused at weeks 4, 8, 12, and 16 after the implantation of the neural electrodes and fixed with phosphate-buffered saline (PBS, Beingmate China) and 4% paraformaldehyde (PFA, Beingmate China). The entire brain was dissected and preserved with paraformaldehyde at 4°C for 24 h, and then fixed with 30% sucrose solution (1×PBS) at 4°C for 48 h. The dehydrated brain was then frozen at the optimal cutting temperature (OCT, Sakura, USA) and a 40 μm slice containing the motor cortex was cut from the coronal direction using a cryostat (Leica, CM1950, USA). Brain slices were washed three times with PBS and blocked at room temperature (5% BSA and 0.3% Triton X-100) for 2 h. They were then incubated overnight at 4°C with primary antibodies (anti-Iba1, 1:1000, rabbit, Invitrogen; anti-GFAP, 1:300, IgG1, Cell Signaling) diluted in PBST (0.3% Triton X-100) to label microglia and astrocytes. As shown in Figure 5, no morphological abnormalities were observed in astrocytes and microglia compared to the non-implanted sites throughout the entire implantation period. Furthermore, Figure 6, showing a comparison of fluorescence intensity between the implanted and non-implanted areas of the neural electrodes in Example 1, indicates that the fluorescence intensity levels of these three markers at the implanted site were comparable to those at the non-implanted electrode array sites throughout the 16-week observation period. This demonstrates that the neural electrodes of this application exhibit excellent electrical stability, good in vivo biocompatibility, and low in vitro cytotoxicity, making them suitable for in vivo signal monitoring in organisms.
[0078] (5) The neural electrode prepared in Example 1 was implanted into the brain of a mouse to verify whether the neural electrode could be used for recording and applying stimulation of normal electrophysiological activities in mice. The specific operation is as follows:
[0079] Before surgery, mice were anesthetized by intraperitoneal injection of 1% sodium pentobarbital solution (60-80 mg / kg). At the start of surgery, the mouse's head was fixed and the hair on the skull surface was shaved. After disinfecting with povidone-iodine and incising the skin on the skull surface, the exposed area was carefully wiped with hydrogen peroxide to remove soft tissue from the skull surface. After the skull was fully exposed, the skull surface was wiped with clean cotton balls and then dried with a bulb syringe until the skull sutures were clearly visible. One to two skull screws were implanted above the cerebellum as a ground reference. Before implantation, the brain was adjusted to ensure that the animal's brain height was consistent and the left and right sides were flat. A skull screw was implanted above the cerebellum as a ground wire. Then, the left brain of the rat was opened with a dental drill, and the exposed area should be slightly larger than the implanted electrodes. Damage to brain tissue should be minimized during the craniotomy. The electrode array implantation area was then exposed through craniotomy and removal of the dura mater. As shown in Figure 7, the neural electrodes of this application can effectively cover key areas of the left hemisphere of the C57BL / 6 mouse brain, including the motor cortex, somatosensory cortex, and visual cortex. Due to its high electrode density, this neural electrode for long-term electrophysiological signal monitoring can comprehensively capture brain activity, providing a valuable tool for large-scale understanding and regulation of brain function. Figure 8a is a schematic diagram of the neural response captured by the neural electrodes of Example 1 during spontaneous beard movement in C57BL / 6 mice. As shown in Figure 8b, the small white circles represent the distribution of 128 electrode sites on the cerebral cortex. It can be seen that beard movement evoked different response characteristics in multiple cortical regions. Notably, the primary motor cortex (M1), secondary motor cortex (M2), and secondary visual cortex (V2) all showed signal responses during beard movement, indicating that these cortices are widely involved in these sensorimotor functions. Furthermore, the primary somatosensory cortex (S1), which plays a key role in beard movement control, also showed significant activity. Each time the beard moves, the spectrum shown in Figure 8c produces a distinct peak and a corresponding change in amplitude.
[0080] (6) Direct stimulation of specific brain regions can elucidate functional connections and information flow within neural networks. Therefore, using the same mouse model, this application used two electrodes located in the S1 region to provide bidirectional square wave currents with opposite phases for directional stimulation, as shown in Figure 9a. During stimulation, the remaining electrodes could simultaneously record the response of the cerebral cortex electrophysiological signals generated by the stimulation (Figure 9b), demonstrating the multifunctionality of the neural electrodes of Example 1, which can both apply stimulation and simultaneously record signals. In addition, different waveforms could be recorded in the M1, S1, and V2 cortices (Figure 9c). Among them, the channel located in S1 closest to the stimulation site showed the most obvious response, characterized by an initial sharp drop in potential, followed by an increase, and then a gradual return to baseline. The electrode located in M1 showed the opposite trend, due to its proximity to the opposite-phase stimulation, resulting in a lower amplitude and a longer time to return to baseline. The electrode placed in the V2 cortex responded to bidirectional currents from both stimulation points, with the potential initially rising sharply with the stimulation pulse, then rapidly decreasing with the negative stimulation, and then gradually returning to baseline. The results showed that the neural electrode could accurately record the electrophysiological signals generated by normal physiological activities in mice, and the high electrode density could comprehensively capture brain activity. Furthermore, this neural electrode could successfully apply electrical stimulation to the implanted area and record the electrophysiological signal response simultaneously with the stimulation. Therefore, this neural electrode provides a valuable tool for large-scale understanding and regulation of brain function.
[0081] (7) The neural electrode from Example 1 was implanted into the rabbit brain to verify whether the neural electrode could be used for long-term monitoring of signals generated by normal electrophysiological activities in rabbits. The specific operation is as follows:
[0082] Before surgery, New Zealand rabbits were anesthetized with propofol (10 mg / kg) intravenously (10 mg / ml). Once breathing was stable and muscles were relaxed, they were placed on a heating pad. During surgery, a nasal cone was used, and anesthesia was maintained with 3% isoflurane in oxygen. Sterile eye ointment was applied to the rabbit's eyes to reduce the risk of corneal irritation and dehydration during surgery. At the start of surgery, the rabbit's head was stabilized, and the hair on the skull surface was shaved. After disinfecting with povidone-iodine and incising the skin on the skull surface, the exposed area was carefully wiped with hydrogen peroxide, and soft tissue on the skull surface was removed. After the skull was fully exposed, the skull surface was wiped with clean cotton balls and then dried with an ear syringe to make the skull sutures clearly visible. Six to seven cranial screws were implanted in the rabbit's left hemisphere to more firmly fix the dental adhesive, and four additional grounding wires were inserted to prevent damage to the grounding wires during long-term implantation. The right side of the rabbit's brain was opened with a dental drill, exposing an area slightly larger than the implanted electrodes. Damage to brain tissue should be minimized during the craniotomy. After opening the skull with sharp forceps and removing the meninges, sterilized neuroelectrodes were implanted into the exposed area. The removed skull was sterilized, replaced at the craniotomy site, and sealed with bio-adhesive. Once the bio-adhesive dried, a self-designed shielded electrode box was fixed to the rabbit's brain using dental cement. Post-surgery, the rabbit was given a subcutaneous injection of meloxicam (sc, 0.2 mg / kg) for pain relief and a subcutaneous injection of enrofloxacin (sc, 2.5 mg / kg). The rabbit was placed on a warm blanket and returned to its cage only after full recovery.
[0083] Figure 10 shows the electrophysiological signal waveforms captured by all channels of the neural electrodes of Example 1 on the first day after implantation in New Zealand rabbits. On the first day after implantation, all channels displayed the electrophysiological signals generated by the freely moving New Zealand rabbits during normal physiological activities, with slight differences in the signals recorded between each channel. Various behavioral states of the freely moving New Zealand rabbits were categorized into exploratory behavior, stereotyped behavior, and resting behavior to study the cortical electrical signal responses during different physiological activities. As shown in Figure 11, the signal responses in different frequency bands during different physiological activities of the New Zealand rabbits showed significant differences. For example, in the resting behavior state, the signal response in the delta band (1–4 Hz) was the strongest, while the signal changes in the exploratory and stereotyped behavior states also intensified with increasing frequency. Notably, in the stereotyped behavior state, the response was mainly concentrated in the beta band (13–30 Hz) and weakened with increasing frequency. Conversely, in the exploratory behavior state, the signal power increased with increasing frequency, reaching a peak in the gamma band (30–120 Hz). This observation demonstrates that the neural electrode can accurately capture neural activity across a wide frequency range associated with different states. Subsequently, this application recorded the long-term electrophysiological activity of a freely moving rabbit. As shown in Figure 12, the neural electrode successfully recorded cortical electrical signals generated in the New Zealand rabbit during three different physiological activities on day 1 and day 365, thus demonstrating the electrode's ability to stably record electrophysiological signals over a year-long study period.
[0084] Obviously, the above embodiments of this application are merely examples for clearly illustrating this application, and are not intended to limit the implementation of this application. For those skilled in the art, other variations or modifications can be made based on the above description. Any obvious variations or modifications derived from the technical solutions of this application, such as changing the diameter of the electrode site, the line width of the connecting line, or the diameter of the pad, the raw material composition of the hydrogel, etc., are still within the protection scope of this application.
Claims
1. A neural electrode, characterized in that, The neural electrode includes upper and lower hydrogel insulating encapsulation layers, and electrode sites, connecting lines, and pads between the upper and lower hydrogel insulating encapsulation layers. The electrode sites and the pads are connected by the connecting lines. The electrode sites, connecting lines, and pads are all made of conductive hydrogel. The upper and lower hydrogel insulating encapsulation layers have the same material composition. The material composition of the upper and lower hydrogel insulating encapsulation layers includes insulating polymers and hydrogels; The insulating polymer is an insulating polymer that has undergone plasma surface modification.
2. The neural electrode according to claim 1, characterized in that, The conductive hydrogel is composed of conductive ink and hydrogel. The conductive ink is a modified poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate).
3. The neural electrode according to claim 1, characterized in that, The raw material components of the hydrogel include sodium alginate and polyacrylamide.
4. The neural electrode according to claim 1, characterized in that, The insulating polymer is selected from at least one of poly(p-xylene), polyethylene terephthalate, polyimide, and polydimethylsiloxane.
5. The neural electrode according to claim 1, characterized in that, The diameter of the electrode site is 50 μm to 200 μm; And / or, the line width of the connecting line is 20μm to 100μm; And / or, the diameter of the pad is 100μm to 2000μm.
6. The method for preparing a neural electrode according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) A hydrogel insulating encapsulation layer was prepared by combining a surface-modified insulating polymer with a hydrogel. (2) The electrode sites, connecting lines and pads are obtained by printing on the hydrogel surface of the hydrogel insulating encapsulation layer using aerosol printing technology. (3) A hydrogel insulating encapsulation layer is covered on the upper surface of the electrode sites, connecting lines, and pads, and etched to obtain electrode sites and pad openings, thereby obtaining the neural electrode.
7. The method for preparing a neural electrode according to claim 6, characterized in that, In step (1), the surface modification is performed using O2 plasma.
8. The method for preparing a neural electrode according to claim 6, characterized in that, In step (1), the surface modification time is 2 min to 10 min.
9. The method for preparing a neural electrode according to claim 6, characterized in that, In step (3), the etching is performed using a mask plasma etching method, and the mask is made of polydimethylsiloxane / polyimide.
10. An electrophysiological signal monitoring device, comprising a neural electrode as described in any one of claims 1 to 5 or a neural electrode prepared by the method described in claims 6 to 9.