Ion-immune-electric coupling 3D bionic conductive catheter and preparation method thereof

Abstract

The invention discloses an ion-immune-electric coupling 3D bionic conductive catheter and a preparation method and application thereof, and belongs to the technical field of biomedical materials. According to the catheter, a gelatin / poly-L-lactic acid / polypyrrole nanofiber scaffold serves as a substrate, tannic acid and magnesium ions are loaded in sequence, and a three-dimensional bionic structure with electrical conductivity, ion slow release and immunoregulation functions is formed. The conductivity of the catheter is matched with that of the natural spinal cord, Mg can be continuously released to reduce excitatory toxicity of neurons, and macrophages are synergistically regulated and controlled to be polarized to M2 phenotype through tannic acid, so that oxidative stress and inflammation are relieved. In-vitro experiments show that the catheter can promote neural stem cells to differentiate into neurons and inhibit activation of astrocytes. In a rat full-cross-section spinal cord injury model, when the catheter is implanted, axon regeneration, myelin sheath formation and synaptic occurrence can be remarkably promoted, movement and urinary function recovery are effectively improved, and an innovative treatment strategy is provided for spinal cord injury repair.

Description

Technical Field

[0001] This invention belongs to the field of biomedical materials and tissue engineering technology, specifically relating to a functionalized three-dimensional scaffold for nerve repair, particularly spinal cord injury repair. More specifically, this invention relates to a biomimetic catheter integrating conductivity, ion regulation, and immune modulation functions, as well as its preparation method and application. Background Technology

[0002] Complete spinal cord injury (SCI) disrupts neural conduction pathways and triggers a series of complex secondary pathological processes, including ion homeostasis imbalance, persistent neuroinflammation, and oxidative stress, which together constitute a microenvironment that inhibits nerve regeneration. Tissue-engineered scaffolds provide physical support and a bridge for SCI repair, but a single physical structure is insufficient to address the aforementioned multiple pathological challenges.

[0003] Existing technologies have explored introducing conductive materials (such as polypyrrole) into neural scaffolds to mimic the bioelectrical environment, loading anti-inflammatory factors to regulate immune responses, or supplementing magnesium ions (Mg²⁺) to antagonize excitotoxicity. However, these strategies often focus on only a single functional dimension. For example, a scaffold with only conductivity cannot effectively control calcium ion influx and neuronal apoptosis after injury; while relying solely on ion supplementation or drug release lacks the ability to reconstruct neural electrical signal transduction pathways. The repair of spinal cord injury requires the synergistic effect of electrical signal transduction, restoration of ion homeostasis, and immune-inflammatory regulation, but currently there is a lack of a comprehensive solution that can organically integrate the three major functional modules of "conduction" (electricity), "ion supplementation and regulation" (ion), and "immune regulation" (immunity).

[0004] Therefore, developing a three-dimensional biomimetic conduit capable of achieving synergistic coupling of "ions-immunity-electricity" to systematically reconstruct the electrical microenvironment, provide neuroprotection, and reverse the inhibitory immune microenvironment is of great significance for promoting the development of spinal cord injury repair technology. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide a 3D biomimetic conductive conduit with "ion-immunity-electricity" coupling and its preparation method. Through material design and multi-step functionalization, this conduit integrates a conductive network, an ion-release unit, and immunomodulatory molecules, aiming to synergistically promote neuroprotection, axonal regeneration, and functional recovery after spinal cord injury.

[0006] The technical solution adopted in this invention is: a method for preparing an ion-immune-electrocoupled 3D biomimetic conductive conduit, the core of which lies in a three-step functionalization construction: (1) Provide a conductive nanofiber scaffold containing biodegradable polymers and conductive polymers; (2) The conductive nanofiber scaffold is brought into contact with a tannic acid solution, so that the tannic acid is loaded onto the scaffold through intermolecular forces (such as hydrogen bonds) to obtain a conductive scaffold loaded with tannic acid. (3) The conductive scaffold loaded with tannic acid is brought into contact with a solution containing magnesium ions. The phenolic hydroxyl groups in the tannic acid molecule coordinate with the magnesium ions to stably load the magnesium ions onto the scaffold, and finally the ion-immune-electrocoupled 3D bionic conductive conduit is obtained.

[0007] The biodegradable polymer can be selected from at least one of gelatin, collagen, silk fibroin, chitosan, hyaluronic acid, poly-L-lactic acid (PLLA), polylactic-co-glycolic acid copolymer (PLGA), poly-ε-caprolactone (PCL), etc., to provide cells with good biocompatibility and a biomimetic extracellular matrix structure. The conductive polymer can be selected from at least one of polypyrrole (PPy), polyaniline (PANI), polythiophene (PTh), or their derivatives, to impart conductive properties to the scaffold and simulate the electrical microenvironment of neural tissue.

[0008] Preferably, step (1) is achieved by electrospinning. First, the biodegradable polymer and the conductive polymer are dissolved or dispersed in a suitable solvent (such as hexafluoroisopropanol) to form a spinning solution, and then electrospinning is performed to obtain a conductive nanofiber membrane. Subsequently, the fiber membrane is physically broken (e.g., sheared), homogenized in a dispersion, injected into a mold, freeze-dried, and then its three-dimensional porous structure is stabilized by chemical cross-linking (e.g., using glutaraldehyde), thereby obtaining a conductive nanofiber scaffold with suitable mechanical properties.

[0009] More preferably, the biodegradable polymer is a combination of gelatin and poly-L-lactic acid, and the mass ratio of the two can be adjusted in the range of (1-3):1. The conductive polymer is preferably polypyrrole nanoparticles (PPyNPs), and its final concentration in the spinning solution can be adjusted in the range of 1-10 wt% to balance conductivity and mechanical properties.

[0010] In step (2), the concentration of the tannic acid solution can be in the range of 1-20 mg / mL, and the contact time can be 0.5-48 hours. Tannic acid is a natural polyphenol with good antioxidant and anti-inflammatory properties, and its loading is intended to endow the scaffold with immunomodulatory and antioxidant functions.

[0011] In step (3), the magnesium ion-containing solution can be an aqueous solution of magnesium salts such as magnesium chloride and magnesium sulfate, with a magnesium ion concentration in the range of 1-30 mg / mL and a contact time of 0.5-48 hours. Magnesium ions (Mg²⁺) are endogenous antagonists of NMDA receptors, and their loading is intended to achieve sustained release to reduce neuronal excitotoxicity and calcium overload after injury.

[0012] The ion-immuno-electrocoupled 3D biomimetic conductive conduit prepared by the above method has an interconnected three-dimensional porous structure with a porosity preferably of 50-90%, which is beneficial for cell infiltration and nutrient exchange. Its conductivity is preferably 0.01-1 S / m, which matches the electrophysiological characteristics of nerve tissue. Tannic acid and magnesium ions were successfully loaded into the conduit, wherein the tannic acid loading (based on the total mass of the conduit) is preferably 0.5-15 wt%, and the magnesium ion loading is preferably 0.1-10 wt%.

[0013] The present invention also provides medical implants comprising the above-described catheters, and their use in the preparation of medicaments or medical devices for repairing nerve injuries (particularly spinal cord injuries).

[0014] The beneficial effects of this invention are as follows: 1) Functional integration and synergy: The three major functional modules of conductivity, ion sustained release (Mg²⁺) and immune regulation (tannic acid) are innovatively integrated into a single three-dimensional catheter, realizing a triple synergistic treatment strategy of "ion-immunity-electricity".

[0015] 2) Bionic structure and properties: The three-dimensional porous nanofiber scaffold constructed by electrospinning and freeze-drying highly simulates the topological structure of the natural extracellular matrix, while possessing conductivity and mechanical properties that match those of nerve tissue, providing an ideal physical and electrophysiological microenvironment for nerve regeneration.

[0016] 3) Clear biological mechanism: Electrical signal reconstruction: The conductive network restores the electrical signal conduction capability of the damaged area.

[0017] Neuroprotection: Continuously released Mg²⁺ effectively antagonizes NMDA receptors, reduces calcium ion influx and neuronal excitotoxicity, and inhibits apoptosis.

[0018] Regulation of the immune / oxidative microenvironment: Tannins exert antioxidant effects, scavenge reactive oxygen species (ROS), and promote macrophage polarization towards the reparative M2 phenotype, thereby reducing inflammatory responses.

[0019] Promoting neural regeneration: The above synergistic effects work together to reverse the inhibitory microenvironment, promote the differentiation of neural stem cells into neurons, inhibit glial scarring, and guide axonal regeneration and myelin formation.

[0020] 4) Significant in vitro and in vivo effects: In vitro experiments confirmed the good biocompatibility, neuroprotective effects, and immunomodulatory capabilities of the catheter. In a rat model of complete spinal cord injury, implantation of the catheter significantly promoted tissue repair (reducing cavities, promoting axonal and myelin regeneration) and neurological function recovery (improving motor scores and urinary function). Attached Figure Description

[0021] Figure 1This is a schematic diagram of the characterization and testing results of the 3D biomimetic conductive conduit according to a specific implementation method.

[0022] Figure 2 This is a schematic diagram showing the characteristics of the 3D biomimetic conductive catheter under physiological conditions and the results of conductivity performance testing in a specific implementation.

[0023] Figure 3 This is a schematic diagram of the biocompatibility test results of the 3D biomimetic conductive conduit according to a specific implementation method.

[0024] Figure 4 This is a schematic diagram illustrating the promoting nerve trunk differentiation and neuronal protection effects of a 3D biomimetic conductive conduit in a specific implementation.

[0025] Figure 5 This is a schematic diagram of a 3D biomimetic conductive catheter regulating the pathological microenvironment in a specific implementation.

[0026] Figure 6 This is a schematic diagram of the in vivo degradation results of the 3D biomimetic conductive catheter implanted in a specific implementation.

[0027] Figure 7 This is a schematic diagram of the in vivo compatibility test results of a 3D biomimetic conductive catheter implanted in a specific implementation.

[0028] Figure 8 This is a schematic diagram illustrating the recovery evaluation of a 3D bionic conductive catheter implanted in the body according to a specific implementation method.

[0029] Figure 9 This is a schematic diagram illustrating the functional recovery evaluation of a 3D bionic conductive catheter implanted in the body according to a specific implementation method.

[0030] Figure 10 These are swimming images of rats that underwent duct transplantation in various groups after SCI.

[0031] Figure 11 This is a characterization diagram of polypyrrole nanoparticles (PPyNPs) (transmission electron microscopy and energy dispersive spectroscopy). Detailed Implementation

[0032] The present invention will be further described below with reference to embodiments.

[0033] Example 1: This embodiment provides a method for preparing an ion-immune-electrocoupled 3D biomimetic conductive catheter (GPPTM catheter), the specific steps of which are as follows: (1) Provide conductive nanofiber scaffolds: (1a) Preparation of spinning solution: 0.4 g gelatin and 0.2 g poly-L-lactic acid (PLLA) were dissolved in 3.7 mL hexafluoroisopropanol (HFIP) and stirred overnight at room temperature to obtain a gelatin / PLLA solution. Polypyrrole nanoparticles (PPyNPs) were dispersed in HFIP at a concentration of 4% (w / v), homogenized by ultrasonication for 1 hour, and stirred overnight at room temperature to form a polypyrrole suspension. Subsequently, the gelatin / PLLA solution and the polypyrrole suspension were mixed at a volume ratio of 2:1 and stirred for 6 hours to finally obtain a uniform gelatin / PLLA / PPyNPs spinning solution.

[0034] (1b) Electrospinning: The spinning solution was loaded into a syringe and electrospinning was performed using a 22-G blunt needle (0.41 mm inner diameter) at a feed rate of 0.8 mL / h, a receiving distance of 18 cm, and a voltage of 20 kV. The fibers were collected on the rotating receiver to obtain a conductive nanofiber membrane (GPPNF).

[0035] (1c) Scaffold Formation and Crosslinking: The obtained conductive nanofiber membrane was cut into small pieces (approximately 1 cm × 1 cm) and dispersed in tert-butanol at a concentration of 2% (w / v). The mixture was homogenized at 25°C and 60 Hz for 15 minutes. The homogenized suspension was injected into a specific mold and frozen overnight at -80°C, followed by freeze-drying for 24 hours to obtain a three-dimensional porous scaffold preform. This preform was then crosslinked in a glutaraldehyde / anhydrous ethanol mixed solution (volume ratio 1:9) for 30 minutes. After crosslinking, it was washed three times with deionized water and then immersed in a 5% (w / v) glycine hydrochloric acid solution for 48 hours to neutralize residual aldehyde groups. Finally, it was washed with deionized water and freeze-dried to obtain the conductive nanofiber scaffold (denoted as GPP scaffold).

[0036] (2) Supported tannins: The GPP scaffold obtained in step (1) was immersed in 10 mL of tannic acid (TA) aqueous solution with a concentration of 6 mg / mL and stirred at room temperature for 30 minutes. After contact, it was washed three times with deionized water to remove unbound tannic acid, and then freeze-dried for 6 hours to obtain a conductive scaffold loaded with tannic acid (denoted as GPPT scaffold).

[0037] (3) Coordinated magnesium ions: The GPPT scaffold prepared in step (2) was immersed in 10 mL of an aqueous solution of magnesium chloride hexahydrate (MgCl2·6H2O) with a concentration of 8.1 mg / mL and stirred at room temperature for 30 minutes to allow magnesium ions to coordinate with the phenolic hydroxyl groups on the tannic acid. After the reaction was completed, the scaffold was thoroughly washed with deionized water and then freeze-dried to obtain the ion-immuno-electrocoupled 3D bionic conductive catheter (the 3D bionic conductive catheter prepared in this embodiment is referred to as the GPPTM catheter).

[0038] Example 2: This embodiment provides a method for preparing an ion-immune-electrocoupled 3D biomimetic conductive conduit, the specific steps of which are as follows: (1) Provide conductive nanofiber scaffolds: (1a) Preparation of spinning solution: 0.3 g gelatin and 0.3 g poly-L-lactic acid (PLLA) were dissolved in 4.0 mL hexafluoroisopropanol (HFIP) and stirred overnight at room temperature to obtain a gelatin / PLLA solution. Polypyrrole nanoparticles (PPyNPs) were dispersed in HFIP at a concentration of 3% (w / v), homogenized by ultrasonication for 1 hour, and stirred overnight at room temperature to form a polypyrrole suspension. Subsequently, the gelatin / PLLA solution and the polypyrrole suspension were mixed at a volume ratio of 3:1 and stirred for 6 hours to finally obtain a uniform gelatin / PLLA / PPyNPs spinning solution.

[0039] (1b) Electrospinning: The spinning solution was loaded into a syringe and electrospinning was performed using a 22-G blunt needle (inner diameter 0.41 mm) at a feed rate of 0.6 mL / h, a receiving distance of 15 cm and a voltage of 18 kV. The fibers were collected on the rotating receiver to obtain a conductive nanofiber membrane.

[0040] (1c) Scaffold Formation and Crosslinking: The obtained conductive nanofiber membrane was cut into small pieces (approximately 1 cm × 1 cm) and dispersed in tert-butanol at a concentration of 2% (w / v). The mixture was homogenized at 25°C and 60 Hz for 15 minutes. The homogenized suspension was injected into a specific mold and frozen at -80°C overnight, followed by freeze-drying for 24 hours to obtain a three-dimensional porous scaffold preform. This preform was then crosslinked in a glutaraldehyde / anhydrous ethanol mixed solution (volume ratio 1:9) for 30 minutes. After crosslinking, it was washed three times with deionized water, then immersed in a 5% (w / v) glycine hydrochloric acid solution for 48 hours to neutralize residual aldehyde groups. Finally, it was washed with deionized water and freeze-dried to obtain the conductive nanofiber scaffold.

[0041] (2) Supported tannins: The conductive scaffold obtained in step (1) was immersed in 10 mL of a 3 mg / mL aqueous solution of tannic acid (TA) and stirred at room temperature for 15 minutes. After contact, it was washed three times with deionized water to remove unbound tannic acid, and then freeze-dried for 6 hours to obtain a tannic acid-loaded conductive scaffold.

[0042] (3) Coordinated magnesium ions: The conductive scaffold loaded with tannic acid obtained in step (2) was immersed in 10 mL of a 5 mg / mL aqueous solution of magnesium chloride hexahydrate (MgCl2·6H2O) and stirred at room temperature for 60 minutes. After the reaction was completed, it was thoroughly washed with deionized water and finally freeze-dried to obtain the ion-immuno-electrocoupled 3D biomimetic conductive conduit.

[0043] Example 3: This embodiment provides another method for preparing ion-immune-electrocoupled 3D biomimetic conductive conduits, the specific steps of which are as follows: (1) Provide conductive nanofiber scaffolds: (1a) Preparation of spinning solution: 0.45 g of gelatin and 0.15 g of poly-L-lactic acid (PLLA) were dissolved in 3.5 mL of hexafluoroisopropanol (HFIP) and stirred overnight at room temperature to obtain a gelatin / PLLA solution. Polypyrrole nanoparticles (PPyNPs) were dispersed in HFIP at a concentration of 6% (w / v), homogenized by ultrasonication for 1 hour, and stirred overnight at room temperature to form a polypyrrole suspension. Subsequently, the gelatin / PLLA solution and the polypyrrole suspension were mixed at a volume ratio of 1.5:1 and stirred for 6 hours to finally obtain a uniform gelatin / PLLA / PPyNPs spinning solution.

[0044] (1b) Electrospinning: The spinning solution is loaded into a syringe, and electrospinning is performed using a 22-G blunt needle (inner diameter 0.41 mm) at a feed rate of 1.0 mL / h, a receiving distance of 20 cm, and a voltage of 22 kV. The fibers are collected on the rotating receiver to obtain a conductive nanofiber membrane.

[0045] (1c) Scaffold Formation and Crosslinking: The obtained conductive nanofiber membrane was cut into small pieces (approximately 1 cm × 1 cm) and dispersed in tert-butanol at a concentration of 2.5% (w / v). The mixture was homogenized at 25°C and 60 Hz for 15 minutes. The homogenized suspension was injected into a specific mold and frozen at -80°C overnight, followed by freeze-drying for 24 hours to obtain a three-dimensional porous scaffold preform. This preform was then crosslinked in a glutaraldehyde / anhydrous ethanol mixed solution (volume ratio 1:9) for 30 minutes. After crosslinking, the preform was washed three times with deionized water, then immersed in a 5% (w / v) glycine hydrochloric acid solution for 48 hours to neutralize residual aldehyde groups. Finally, it was washed with deionized water and freeze-dried to obtain the conductive nanofiber scaffold.

[0046] (2) Supported tannins: The conductive scaffold obtained in step (1) was immersed in 10 mL of a 10 mg / mL aqueous solution of tannic acid (TA) and stirred at room temperature for 60 minutes. After contact, it was washed three times with deionized water to remove unbound tannic acid, and then freeze-dried for 6 hours to obtain a tannic acid-loaded conductive scaffold.

[0047] (3) Coordinated magnesium ions: The conductive scaffold loaded with tannic acid obtained in step (2) was immersed in 10 mL of magnesium chloride hexahydrate (MgCl2·6H2O) aqueous solution with a concentration of 12 mg / mL and stirred at room temperature for 15 minutes. After the reaction was completed, it was thoroughly washed with deionized water and finally freeze-dried to obtain the ion-immuno-electrocoupled 3D biomimetic conductive conduit.

[0048] Comparative Example 1: This comparative example serves as a control experiment for Example 1, conducted according to the same steps and conditions as Example 1, except that only a GP scaffold (without conductive polymer) was prepared. The specific procedure is as follows: Provide nanofiber scaffolds: (a) Preparation of spinning solution: 0.4 g gelatin and 0.2 g poly-L-lactic acid (PLLA) were dissolved in 3.7 mL hexafluoroisopropanol (HFIP) and stirred overnight at room temperature to obtain a gelatin / PLLA spinning solution. (No conductive polymer suspension was prepared or added in this step.) (b) Electrospinning: The above spinning solution was loaded into a 5 mL syringe, placed on a syringe pump, and connected to the negative terminal of a high-voltage power supply through a 22-G blunt needle (0.41 mm inner diameter). The electrospinning parameters were set as follows: feed rate 0.8 mL / h, receiving distance 18 cm, and voltage 20 kV. The nanofibers were collected on a parallel rotating stainless steel rod at 600 rpm. The resulting nanofiber membrane (GPNF) was vacuum dried for 24 hours to completely remove HFIP.

[0049] (c) Scaffold Formation and Crosslinking: The obtained nanofiber membrane was cut into 1 cm × 1 cm pieces and dispersed in a 2% (w / v) tert-butanol solution. The mixture was homogenized at 25°C and 60 Hz for 15 minutes using a grinder. The homogenized suspension was then injected into a directional porous mold and frozen overnight at -80°C, followed by freeze drying for 24 hours. Next, the dried scaffold was crosslinked with a glutaraldehyde solution (25% glutaraldehyde solution and anhydrous ethanol mixed at a volume ratio of 1:9) for 30 minutes. After washing three times with deionized water, the scaffold was immersed in a 5% (w / v) glycine hydrochloric acid solution for 48 hours to remove residual aldehyde groups and improve biocompatibility. Finally, it was washed with deionized water and freeze-dried to obtain a nanofiber scaffold free of conductive polymers (denoted as the GP scaffold).

[0050] Comparative Example 2: This comparative example serves as a control experiment for Example 1, conducted according to the same steps and conditions as Example 1, except that only a GPP scaffold (conductive only, without tannic acid and magnesium ions) was prepared. The specific procedure is as follows: Provide conductive nanofiber scaffolds: (a) Preparation of spinning solution: 0.4 g gelatin and 0.2 g poly-L-lactic acid (PLLA) were dissolved in 3.7 mL hexafluoroisopropanol (HFIP) and stirred overnight at room temperature to obtain a gelatin / PLLA spinning solution. Polypyrrole nanoparticles (PPyNPs) were dispersed in HFIP at a concentration of 4% (w / v), homogenized by ultrasonication for 1 hour, and stirred overnight at room temperature to form a polypyrrole suspension. Subsequently, the gelatin / PLLA solution and the polypyrrole suspension were mixed at a volume ratio of 2:1 and stirred for 6 hours to finally obtain the gelatin / PLLA / PPyNPs spinning solution.

[0051] (b) Electrospinning: The spinning solution was loaded into a 5 mL syringe, placed on a syringe pump, and connected to the negative terminal of a high-voltage power supply via a 22-G blunt needle (0.41 mm inner diameter). The electrospinning parameters were set as follows: feed rate 0.8 mL / h, receiving distance 18 cm, and voltage 20 kV. The nanofibers were collected on a parallel rotating stainless steel rod at 600 rpm. The resulting conductive nanofiber membrane (GPPNF) was vacuum dried for 24 hours to completely remove HFIP.

[0052] (c) Scaffold Formation and Crosslinking: The obtained conductive nanofiber membrane was cut into 1 cm × 1 cm pieces and dispersed in a 2% (w / v) tert-butanol solution. The mixture was homogenized at 25°C and 60 Hz for 15 minutes using a grinder. The homogenized suspension was then injected into a directional porous mold and frozen overnight at -80°C, followed by freeze drying for 24 hours. Next, the dried scaffold was crosslinked with a glutaraldehyde solution (25% glutaraldehyde solution and anhydrous ethanol mixed at a volume ratio of 1:9) for 30 minutes. After washing three times with deionized water, the scaffold was immersed in a 5% (w / v) glycine hydrochloric acid solution for 48 hours to remove residual aldehyde groups and improve biocompatibility. Finally, it was washed with deionized water and freeze-dried to obtain the conductive nanofiber scaffold (denoted as GPP scaffold).

[0053] Comparative Example 3: This comparative example serves as a control experiment for Example 1, conducted according to the same steps and conditions as Example 1. The difference lies in that only a GPPT scaffold (conductive and loaded with tannic acid, without magnesium ions) is prepared. The specific scheme is as follows: (1) Provide conductive nanofiber scaffolds: (1a) Preparation of spinning solution: 0.4 g gelatin and 0.2 g poly-L-lactic acid (PLLA) were dissolved in 3.7 mL hexafluoroisopropanol (HFIP) and stirred overnight at room temperature to obtain a gelatin / PLLA solution. Polypyrrole nanoparticles (PPyNPs) were dispersed in HFIP at a concentration of 4% (w / v), homogenized by ultrasonication for 1 hour, and stirred overnight at room temperature to form a polypyrrole suspension. Subsequently, the gelatin / PLLA solution and the polypyrrole suspension were mixed at a volume ratio of 2:1 and stirred for 6 hours to finally obtain a uniform gelatin / PLLA / PPyNPs spinning solution.

[0054] (1b) Electrospinning: The spinning solution was loaded into a syringe and electrospinning was performed using a 22-G blunt needle (0.41 mm inner diameter) at a feed rate of 0.8 mL / h, a receiving distance of 18 cm, and a voltage of 20 kV. The fibers were collected on the rotating receiver to obtain a conductive nanofiber membrane (GPPNF).

[0055] (1c) Scaffold Formation and Crosslinking: The obtained conductive nanofiber membrane was cut into small pieces (approximately 1 cm × 1 cm) and dispersed in tert-butanol at a concentration of 2% (w / v). The mixture was homogenized at 25°C and 60 Hz for 15 minutes. The homogenized suspension was injected into a specific mold and frozen overnight at -80°C, followed by freeze-drying for 24 hours to obtain a three-dimensional porous scaffold preform. This preform was then crosslinked in a glutaraldehyde / anhydrous ethanol mixed solution (volume ratio 1:9) for 30 minutes. After crosslinking, it was washed three times with deionized water and then immersed in a 5% (w / v) glycine hydrochloric acid solution for 48 hours to neutralize residual aldehyde groups. Finally, it was washed with deionized water and freeze-dried to obtain the conductive nanofiber scaffold (denoted as GPP scaffold).

[0056] (2) Supported tannins: The GPP scaffold obtained in step (1) was immersed in 10 mL of tannic acid (TA) aqueous solution with a concentration of 6 mg / mL and stirred at room temperature for 30 minutes. After contact, it was washed three times with deionized water to remove unbound tannic acid, and then freeze-dried for 6 hours to obtain a conductive scaffold loaded with tannic acid (denoted as GPPT scaffold).

[0057] Experimental Design: I. Characterization of conductive nanofibers and 3D biomimetic conductive conduit systems: The surface morphology and chemical composition of each group of samples were analyzed using scanning electron microscopy (SEM, Hitachi, Japan). Based on the SEM images, the diameter and porosity of the nanofibers were measured using ImageJ software (USA). Simultaneously, energy-dispersive spectroscopy (EDS) was used to determine the elemental composition of the GPPTM.

[0058] Transmission electron microscopy (TEM, JEOL JEM-F200, Japan) was used to collect nanofibers on a carbon-coated copper grid to verify the loading of PPyNPs on the nanofibers.

[0059] Spectral analysis was performed in the wavelength range of 4000-400 cm⁻¹ using a Fourier transform infrared spectrometer (FTIR, Thermo Fisher Scientific, USA).

[0060] GPPTM was characterized using X-ray photoelectron spectroscopy (XPS, Thermo Scientific K-Alpha, USA) to determine its elemental composition and content.

[0061] Conductivity testing was performed using an ST2242 four-probe automated resistivity meter. The conductivity of GPPTM was measured at 37°C in saturated SBF-simulated body fluid (Solarbio, G0390) to simulate its conductivity in vivo. To evaluate the conductivity stability of GPPTM, it was placed in centrifuge tubes containing SBF-simulated body fluid, and conductivity was measured at 0, 7, 14, and 28°C. Its conductivity characteristics and electrical stability were recorded and analyzed.

[0062] To investigate the electrochemical performance of GPPTM, we characterized it using an electrochemical workstation (Zahner, Germany). A three-electrode system was employed, using 0.1 M phosphate-buffered saline (PBS, pH 7.4) as the electrolyte, consisting of a working electrode, a reference electrode (saturated Caromel electrode), and a counter electrode (platinum electrode). Electrochemical impedance spectroscopy (EIS) was performed at open circuit potential in the frequency range of 100 kHz to 0.01 Hz.

[0063] The contact angle of 10 μL of deionized water was measured using an SDC350KS water contact angle meter (Shengding, China) to evaluate the hydrophilicity of GPPTM.

[0064] The mechanical properties of GPPTM were tested using a universal testing machine (Sansi Yongheng, China). Samples were prepared as 5cm × 5cm blocks. Before testing, the samples were immersed in SBF simulated body fluid to simulate the physiological environment of the samples. After removal, testing was performed at a constant strain rate. Stress-strain curves were recorded and Young's modulus was calculated. For the determination of stent water absorption and expansion rate, the volume (V1) and weight (W1) of the dry stent were first measured. Then, the stent was immersed in distilled water and removed after 0.5, 3, 5, 15, 20, and 30 minutes, respectively. The volume (V2) and weight (W2) of the wet stent were measured. The formulas for calculating water absorption (Ww) and expansion rate (Vv) are as follows: Ww(%)=(W2-W1) / W1×100% (1) Vv(%)=(V2-V1) / V1×100% (2) To evaluate the release kinetics of magnesium ions, PBS solutions incubated with GPPTM scaffolds were collected at different time points at 37°C, and the concentration of magnesium ions in the solution was determined using inductively coupled plasma optical emission spectrometry (ICP-OES, Agilent Technologies, USA).

[0065] For the GPPTM degradation experiment, different groups of samples were completely immersed in 10 mL of simulated body fluid (SBF) at 37.0°C. The initial mass (W0) was recorded. After reaching the specified time point, the mass of the sample after vacuum drying (W1) was measured, and the degradation rate was calculated according to the formula DR = (W0- W1) / W0 × 100%.

[0066] II. Cell Culture: PC-12 cells were purchased from Pronosei Life Sciences Co., Ltd. (Wuhan) and cultured using PC-12 complete cell culture medium. Rat macrophages (BMDMs) were extracted from the femurs of 4-week-old SD rats and cultured in α-MEM medium containing 10% fetal bovine serum (FBS), 20 ng / mL macrophage colony-stimulating factor (M-CSF), penicillin, and streptomycin.

[0067] The isolation and culture of rat neural stem cells (NSCs) were performed as follows: The anterior-middle third of the brain (including the subventricular region and hippocampus) was isolated from rat embryos at gestation day 14 (E14). The NSCs were rinsed and soaked in HBSS buffer (Gibco, USA) containing 2% penicillin and antibiotics at 4°C. Subsequently, the vascularized meningeal layer was carefully dissected with ophthalmic scissors, digested with 0.125% EDTA (Gibco, USA) at 37°C for 5 minutes, filtered through a 70 μm filter, and then seeded into complete culture medium containing DMEM basal medium (Gibco, USA), 2% neuronal supplement B27 (Gibco, USA), glutamine (Glutamax, Gibco), and penicillin / streptomycin (Solarbio, China). Neurosphere formation was observed after 3-5 days of culture, followed by passage culture for subsequent experiments.

[0068] The isolation and culture procedures for rat cortical neurons were similar to those for NSCs, but only the cerebral cortex of fetal rats was isolated. The isolated cells were seeded into 12-well plates coated with poly-L-lysine, and after 4 hours, the medium was replaced with neuronal medium containing Neurobasal medium (Gibco, USA), 2% B27 supplement, 1% Glutamax, and penicillin / streptomycin. All cells were cultured at 37°C, 95% relative humidity, and 5% CO2, with the medium changed every 1–2 days. Furthermore, all in vitro experiments in this study employed Transwell chambers for co-culturing GPPTM with cells; that is, GPPTM was placed in the upper chamber, and cells were cultured in wells in the lower chamber.

[0069] Live / dead staining and cytoskeleton staining: To investigate the biocompatibility of GPPTM, PC12 cells were seeded in culture plates, and quantitative GPPTM was added above the culture chambers for co-culturing with the cells for 1, 2, and 3 days. Subsequently, the cells were stained with calcein AM and propidium iodide (PI, Beyotime, China) for 30 minutes, observed and photographed using a fluorescence microscope (QUANTA250, USA), and the images were analyzed using ImageJ software (USA). Using the same method, after co-culturing GPPTM with the scaffold for 24 hours, the cells were fixed with 4% paraformaldehyde for 20 minutes, washed three times with PBS, and permeabilized with 0.3% Triton-X for 15 minutes. PC12 cells were then stained with rhodamine-labeled phalloidin and Hoechst (Beyotime, China), and the cytoskeleton structure was observed using a fluorescence microscope. Three images were obtained for each experiment for analysis.

[0070] To assess the cell infiltration capacity of GPPTM, the morphology of PC12 cells on the scaffold was observed using scanning electron microscopy (SEM). The specific steps were as follows: PC12 cells were seeded in culture plates and co-cultured with GPPTM for 2 days. The cells were then fixed with 2.5% glutaraldehyde and dehydrated in a gradient of anhydrous ethanol solutions, followed by air-drying overnight. Finally, the samples were analyzed using SEM (Hitachi, Japan). Simultaneously, to assess the infiltration of PC12 cells into the scaffold, GPPTM was evaluated using fluorescent staining and hematoxylin-eosin (HE) staining. The specific procedures were as follows: After co-culturing PC12 cells with GPPTM for 48 hours, they were fixed with 4% paraformaldehyde (PFA) and dehydrated in a series of ethanol solutions. Subsequently, the dehydrated scaffold was embedded in paraffin and subjected to HE or fluorescent staining to analyze the infiltration of PC12 cells.

[0071] Blood compatibility of the GPP™ stents was assessed using a hemolysis analysis. The specific method was as follows: Blood samples were collected from anticoagulant tubes and co-incubated with each stent at 37°C for 4 hours. Phosphate-buffered saline (PBS) and Triton X-100 served as negative and positive controls, respectively. After centrifugation, the supernatant was transferred to a 96-well plate, and absorbance was measured using a microplate reader (SpectraMax M5, 540 nm). The percentage of hemolysis was calculated using the following formula: Hemolysis rate (%) = (Sample absorbance - Negative control absorbance) / (Positive control absorbance - Negative control absorbance) × 100.

[0072] The effect of GPPTM on the migration ability of PC12 cells was evaluated using a scratch healing assay. PC12 cells were seeded in culture plates and, after reaching 90% confluence, parallel scratches were performed using the tip of a 200 μL sterile pipette. Cells were then co-cultured with GPPTM and observed under a fluorescence microscope at 0 and 24 hours. Before observation, cells were incubated with calcein AM (Beyotime, China) in the dark for 30 minutes. The scratch width was measured using a fluorescence microscope, cell migration was recorded, and images were acquired. The scratch area was statistically analyzed using ImageJ software.

[0073] To investigate the effect of GPPTM on the proliferation characteristics of PC12 cells, the incorporation method using bromodeoxyuridine (BrdU) and 5-ethynyl-2'-deoxyuridine was employed to detect cell proliferation. The specific procedure was as follows: PC12 cells were co-cultured with GPPTM in Transwell chambers for 24 hours. Then, 10 μM EdU working solution was added to the wells of the plate, and incubation continued for another 2 hours. Subsequently, the cells were fixed with 4% paraformaldehyde for 20 minutes, washed three times with PBS, and then detected using the EdU-488 cell proliferation assay kit (Beyotime, China).

[0074] Rat bone marrow-derived macrophages (BMDMs) were seeded into the upper chamber of a Transwell plate (8.0 μm pores, Corning, 3422) in serum-free medium. Subsequently, medium containing GPP™ extract was added to the lower chamber. After co-culturing for 12 hours, cells were fixed and stained with crystal violet. After removing cells attached to the upper surface, the cells on the lower surface were photographed. BMDMs were seeded into 12-well plates and induced for 24 hours in medium containing lipopolysaccharide (LPS, 5 μg / mL), followed by 24 hours of further culture in medium containing GPP™. Cells were fixed with 4% paraformaldehyde and incubated with primary antibodies CD68 (1:400 dilution, ab303565, Abcam), CD86 (1:200 dilution, ET1606-50, HUABIO), and CD206 (1:400, ab300621, Abcam), respectively. After the samples were treated with the appropriate secondary antibody and DAPI, they were observed and photographed using a fluorescence microscope, and semi-quantitative analysis was performed using ImageJ software.

[0075] To assess the ability of GPPTM to scavenge reactive oxygen species (ROS), PC12 cells were seeded in 12-well plates, induced with LPS-containing medium for 24 hours, and then co-cultured with GPPTM for another 24 hours. ROS detection was performed using a DCFH-DA kit (Beyotime, China). After incubation at room temperature in the dark for 30 minutes, cell nuclei were labeled with Hoechst 33342 (Beyotime, C1022, China). Observation was performed under a fluorescence microscope, and quantitative analysis was conducted using ImageJ software. The mitochondrial membrane potential of PC12 cells was assessed using the same method: PC12 cells were seeded in well plates, induced with LPS-containing medium for 24 hours, and then co-cultured with GPPTM for another 24 hours. JC-1 solution (Solarbio, China) was prepared to working concentration and added to the well plates, incubated at 37°C for 20 minutes. After washing twice with JC-1 staining buffer and medium, staining was observed using an inverted fluorescence microscope, and semi-quantitative fluorescence analysis was performed using ImageJ software.

[0076] P1 generation NSCs were seeded in 24-well plates coated with poly-L-lysine and co-cultured with GPPTM for 7 days in a medium containing DMEM basal medium, 2% B27 supplement, 1% Glutamax, and penicillin / streptomycin. After cell fixation, the cells were incubated overnight with Tuj1 (1:500, Abcam, USA), GFAP (1:500, Abcam, USA), and Map-2 (1:100, 17490-1-AP, Proteintech), followed by immunofluorescence staining with the corresponding secondary antibodies. Cell nuclei were stained with DAPI. Images were captured under a fluorescence microscope, and the proportion of Tuj1 and Map-2 labeled neurons was analyzed using GraphPad Prism 9.0 (USA).

[0077] Neuronal culture medium containing 50 μM NMDA (Selleck, USA) was prepared to induce a calcium influx model, simulating the cytotoxic environment following spinal cord injury (SCI). Cortical neurons were seeded in 6-well plates coated with poly-L-lysine and cultured for 7 days, then replaced with medium containing 50 μM NMDA and cultured for another 24 hours, followed by co-culturing with GPPTM for 24 hours. Cells were incubated with Fluo-4 AM (4 μM, Beyotime, China) for 30 minutes, and the nuclei were stained with Hoechst 33342 at room temperature for 15 minutes. Fluorescence microscopy showed that intracellular Ca²⁺ concentration was directly proportional to fluorescence intensity, and the percentage of Fluo-4 AM positive cells in each group was analyzed. Using the same method, cells were incubated with Mg²⁺ probe working solution (Mag-520 am, 5 μM, Mocon Biotech) for 45 minutes, and the nuclei were stained with Hoechst 33342 for 15 minutes. Finally, images were captured using a fluorescence microscope.

[0078] The method for measuring neuronal mitochondrial membrane potential is as follows: First, cortical neurons were seeded in medium containing 50 μM NMDA and induced for 24 hours. Then, GPPTM was co-cultured with cortical neurons for 24 hours. Next, JC-1 solution was diluted to the working concentration and added to wells, and incubated at 37°C for 20 minutes. After incubation, the cells were washed twice with JC-1 staining buffer and medium. Finally, cell staining was observed using an inverted fluorescence microscope, and semi-quantitative fluorescence analysis was performed using ImageJ software.

[0079] Based on the above neuronal co-culture mode, to detect the neuroprotective effect of GPPTM in a neuroexcitotoxic environment, NMDA (50 μM) medium was used to replace the culture medium for 24 hours, followed by co-culture with GPPTM for another 24 hours. Neurons were stained with calcein AM and PI for 30 minutes, and images were observed and captured using a fluorescence microscope (QUANTA250, USA), and analyzed using ImageJ software (USA). Using the same method, cortical neurons were seeded in 6-well plates, cultured with NMDA medium for 24 hours, and then co-cultured with GPPTM for another 24 hours. Cleaved-caspase 3 (1:200, GB115733, Servicebio) and Tuj1 (1:500, ab78078, Abcam) were detected by immunofluorescence staining, followed by incubation with specific fluorescent secondary antibody at room temperature for 1 hour. After image capture, Cleaved-caspase 3-positive cells in each group of three images were counted and quantified.

[0080] All animal experiments were conducted in accordance with the experimental protocols approved by the Laboratory Animal Ethics Committee of Bengbu Medical University. Animal handling followed the regulations of the Institutional Animal Care and Use Committee (IACUC) of the university. Female Sprague-Dawley rats (weighing 180-220g) were selected and housed in an environment with constant temperature (23±2°C) and suitable humidity. The rats had free access to food and water under natural photoperiod (the feed did not contain calcium, magnesium, or other metal ions). According to the experimental protocol, a rat model of complete spinal cord injury was established by anesthesia with sodium pentobarbital (50mg / kg). Specific procedures included: shaving the hair on the back of each rat, making a 2cm incision to expose the T8-T10 vertebrae; performing a laminectomy at the T8-T10 segment, and performing a 2mm×2mm spinal cord transection at the T9-T10 segment. Experimental animals were randomly divided into 6 groups (n=20 per group): 1) Sham group: no SCI surgery performed; 2) Control group: no stent implanted after SCI surgery; 3) GP group: GP stent implanted after SCI surgery; 4) GPP group: GPP stent implanted after surgery; 5) GPPT group: GPPT stent implanted after surgery; 6) GPPTM group: GPPTM stent implanted after surgery. All surgical incisions were sutured using a layered suturing technique, carefully suturing muscles and fascia to ensure safe closure after stent implantation. Postoperatively, rats were placed under an incandescent lamp to aid in regaining consciousness and received penicillin anti-infection treatment for 3 days. Massage was performed twice daily, morning and evening, until the rats regained reflexive urination function. Postoperative general condition changes in each group of rats were continuously observed and recorded. After relevant assessments at weeks 2 and 12 postoperatively, all rats were euthanized, and corresponding spinal cord tissue samples were collected for immunofluorescence staining analysis.

[0081] The biodegradability and biocompatibility of GPPTM in vivo were assessed. Each scaffold was subcutaneously implanted into the back of rats, and animals were sacrificed at weeks 1, 2, 4, 8, 16, and 24 post-implantation. The scaffolds were removed, freeze-dried, and weighed. Peri-skin tissue was then collected, fixed with 4% paraformaldehyde, and subjected to fluorescent staining to assess pathological changes in the skin tissue.

[0082] Simultaneously, blood was collected from the medial canthal vein of rats 12 weeks post-surgery. Serum was separated after standing at room temperature for 30 min and centrifuged at 3000 rpm for 30 min. Serum Mg was measured using a commercial kit (Solarbio, China). 2+ Content. Renal function was assessed by serum creatinine (Cre) and uric acid (UA) concentrations, and liver function was assessed by alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities.

[0083] The BBB Motor Rating Scale was used to assess the recovery of motor function in rats after spinal cord injury. Throughout the assessment period, rats were allowed free movement in an open space, and their knee joint function, walking ability, trunk movement, and coordination were observed for 5 minutes each time. Two observers independently scored and recorded the rats weekly using the BBB scoring system (0-21 points). Simultaneously, rats in each group were placed on a grid with their heads facing upwards and their bodies parallel to the inclined plane, and their hind limb movements while crawling on the grid were recorded to assess hind limb function recovery.

[0084] Footprint analysis: Twelve weeks after scaffold implantation, the forelimbs and hindlimbs of rats were marked with blue and red ink, respectively. Subsequently, the rats were guided to crawl unidirectionally within the tube, and their movement trajectories were recorded in real time.

[0085] At the designated time point after SCI surgery, rats were anesthetized and fixed by cardiac perfusion with 0.9% saline and 4% paraformaldehyde. Anterior and posterior segments of the spinal cord were removed and photographed. The tissues were then dehydrated in 30% sucrose solution for cryoprotection. The tissues were embedded in OCT, cut into 20µm coronal sections, and stored at -80°C. HE and Masson staining were performed to assess the size of the spinal cord lesion cavity. Spinal cord sections were permeabilized with 0.3% Triton-X for 15 minutes, followed by blocking with 3% BSA for 2 hours. Sections were incubated overnight at 4°C with the appropriate primary antibody. After washing three times with PBS, they were incubated with the appropriate secondary antibody and DAPI. Images were acquired using fluorescence microscopy. The main antibodies used included: Tuj-1 (1:500, ab78078, Abcam), GFAP (1:500, ab68428, Abcam), CD68 (1:400, ab303565, Abcam), CD206 (1:400, ab300621, Abcam), CD86 (1:200, ET1606-50, HUABIO), GAP43 (1:500, ab75810, Abcam), MBP (1:500, ab218011, Abcam), Map-2 (1:100, 17490-1-AP, Proteintech), Syn (1:100, ET1606-56, HUABIO), and NEUN (1:500, 26975-1-AP). Proteintech, Cleaved-caspase (1:200, GB115733, Servicebio), and 5-HT (1:100, HA722503, HUABIO). Secondary antibodies included: goat anti-mouse IgG (Alexa 488, Abcam), goat anti-mouse IgG (Alexa 594, Abcam), goat anti-rabbit IgG (Alexa 488, Abcam), and goat anti-rabbit IgG (Alexa 594, Abcam). Furthermore, to assess the recovery of bladder function after spinal cord injury in each group of rats, bladder samples were collected, photographed, weighed, and further measured detrusor muscle thickness using HE staining and Masson staining. Finally, data analysis was performed using ImageJ software.

[0086] All data are expressed as mean ± standard deviation (SD). Each test was performed at least three times independently to ensure data validity. Statistical analysis was performed using GraphPad Prism software (version 9.0, USA). One-way ANOVA was used for multiple comparisons, and two-way unpaired Student's t-test was used for two-way comparisons. Statistical significance was defined as *p < 0.05, **p < 0.01, and ***p < 0.001.

[0087] Experimental results:

[0088] The characterization results of the polypyrrole nanoparticles are shown in [the table below]. Figure 11 Scanning electron microscopy and energy dispersive spectroscopy analysis showed that the average particle diameter was approximately 50 nm, with overlapping distributions of C, N, and O elements. The preparation of the GPPTM conductive conduit involved key steps including electrospinning, nanofiber homogenization, cross-linking and shaping, freeze-drying, TA loading, and Mg²⁺ coordination. First, two-dimensional GP nanofibers (GPNF) and GPP nanofibers (GPPNF) were prepared by electrospinning using gelatin / PLLA and gelatin / PLLA / PPyNPs spinning solutions, respectively. These were then shredded, homogenized at high speed in tert-butanol, molded, and freeze-dried to obtain uncrosslinked three-dimensional porous GP and GPP conduits. Considering the structural collapse problem caused by the hydrophilicity of gelatin upon contact with water, glutaraldehyde was used to crosslink the scaffold to stabilize the three-dimensional network and improve mechanical properties. To enhance biocompatibility, the crosslinked conduits were soaked in a 5% glutamate hydrochloric acid solution for 48 hours to remove residual glutaraldehyde. The GPP catheter was then immersed in a 6 mg / mL tannic acid solution for 30 minutes, washed, and lyophilized to obtain the GPPT catheter. Finally, it was placed in an 8.1 mg / mL magnesium chloride hexahydrate solution and stirred for 30 minutes, then washed and lyophilized to obtain the GPPTM three-dimensional biomimetic conductive catheter with a TA-Mg²⁺ coordination structure.

[0089] The morphology of various spun membranes and conduits during the preparation process was characterized using digital photography and scanning electron microscopy. Precise control of the nanofiber membrane (NF) structure was achieved through the spinning process. The doping of PPyNPs changed the nanofibers from white to black, indicating successful doping into the fiber membrane. Figure 1 A), SEM examination showed that PPyNps were uniformly dispersed and embedded in nanofibers (A), Figure 1 B). This uniformity not only enhances the conductivity of the material but also provides a solid structural foundation for subsequent functionalization. GPNF and GPPNF are formed from originally randomly oriented two-dimensional fiber membranes into unique three-dimensional structures through a series of treatments. SEM shows that all scaffolds have interconnected microporous structures, with randomly arranged fibers and a loose, porous structure, highly similar to the natural extracellular matrix. Figure 1(B) This facilitates cell adhesion, migration, growth, and nutrient exchange. Notably, the introduction of TA and Mg²⁺ did not disrupt the biomimetic structure of the fiber network.

[0090] Three-dimensional porous structures are generally considered key factors for cell adhesion / infiltration and nutrient transport in tissue-engineered materials. The complex spatial structure of the natural spinal cord requires a scaffold with a matching biomimetic microenvironment to precisely guide physiological neural regeneration and reconstruction. As intended by design, a GPP™ conductive conduit with a porous biomimetic structure was fabricated to mimic the spatial structure of the natural spinal cord. Axial SEM showed that it could precisely match and connect with the host spinal cord. Figure 1 C), radial SEM shows that the intraductal directional channel provides topological guidance for nerve cells and unobstructed space for axonal extension (C). Figure 1 D). TEM results showed that, compared to the smooth nanofibers in GPNF, the nanofibers in GPPNF exhibited a rough, granular surface, further confirming the embedding of PPyNPs. Figure 1 E). EDS elemental mapping shows that C, N, O, and Mg elements are uniformly distributed in GPPTM ( Figure 1 F). Fiber diameter analysis showed that the introduction of PPyNPs reduced the fiber diameter from 675.97 ± 246.21 nm to 303.18 ± 132.91 nm (F). Figure 1 H,I).

[0091] To further demonstrate the successful preparation of tannic acid and magnesium ions in the short fibers, Fourier transform infrared spectroscopy and XPS analysis were performed on the short fibers. The FTIR spectra of each group of catheters are as follows: Figure 1 As shown in Figure J, the broadening of the OH stretching vibration at 3300 cm⁻¹ indicates the formation of a hydrogen bond network; the absorption peak at 1620 cm⁻¹ originates from the synergistic effect of the C=N Schiff base and the O→Mg²⁺ coordination bond; the CH bending vibration of the aromatic ring at 750 cm⁻¹ confirms TA loading; and the Mg-O vibration peak at 645 cm⁻¹ further confirms successful Mg²⁺ coordination. The redshift of the CN stretching vibration at 1300 cm⁻¹ indicates the presence of strong hydrogen bonds between the TA and PPy chains. XPS analysis shows ( Figure 2 The 6% increase in nitrogen content and the appearance of the conjugated –N= peak in GPP confirm successful loading of PPyNPs; the oxygen content in GPPT increases to 32.38% while the nitrogen content decreases, proving successful TA loading; the appearance of a Mg signal and the decrease in oxygen content to 31.1% in GPPTM verify the coordination of Mg²⁺ with TA. High-resolution C1s spectra show four characteristic peaks (K). Figure 2 L), N 1s spectrum shows three components ( Figure 2 M), O 1s spectrum shows CO and C=O characteristic bonds ( Figure 2The Mg 1s signal at 1304 eV directly proves the coordination of Mg²⁺ (N). Figure 2 O). Fourier transform infrared analysis and XPS results also confirmed our successful fabrication of 3D biomimetic conductive conduits.

[0092] High porosity is a prerequisite for nutrient transport and exchange during cell growth and tissue remodeling. Porosity measurements showed that the porosity of GPPTM was 67.71 ± 2.08%, which was lower than that of GP (79.58% ± 2.21%). Figure 1 P), which may be related to the structural shrinkage caused by Mg²⁺ coordination-enhanced crosslinking. Although the introduction of bioactive molecules sacrificed some porosity, a more stable mechanical structure and controllable release kinetics were obtained. Degradation kinetics in a simulated in vivo environment (pH 7.35) showed ( Figure 1 Q), at week 12, the material residue rate in the GPPTM group (62.55% ± 2.79%) was significantly higher than that in the GP group (23.89% ± 1.27%). This indicates that the introduction of PPyNPs delayed the degradation of the material, possibly due to the stable chemical structure of PPyNPs and the physical cross-linking between them and the matrix. Generally, a rapid degradation rate is considered an advantage of biomaterials. However, for the chronic repair process following spinal cord injury, although the GPPTM catheter has a degradation cycle exceeding 24 weeks, this characteristic is precisely what allows it to provide durable mechanical support for chronic nerve tissue repair. This catheter can maintain its structural integrity in vivo for a long time, effectively bridging the spinal cord stump, providing a stable temporary matrix for cell adhesion and tissue regeneration, and ultimately degrading completely after fulfilling its mission, avoiding long-term physical interference with newly formed tissue. Furthermore, previous studies have shown that Mg... 2+ Levels of Mg²⁺ decreased significantly and persistently within the first 7 days following central nervous system injury. The Mg²⁺ release profile indicated that ( Figure 2 R), which is rapidly released in the first 5 days, reaches a stable period on the 7th day, and continues to be released for more than 14 days. This release characteristic is consistent with the early pathological stage of SCI and can effectively replenish the metal ion loss in the early stage of damage.

[0093] Using a mechanically matched scaffold to mimic the natural spinal cord can improve spinal cord development and reduce the risk of secondary injury to the surrounding undamaged spinal cord. Based on this concept, we developed the GPPTM catheter and aimed to evaluate its performance as an implant in a simulated body fluid environment. Test results showed that the wet GPPTM catheter exhibited excellent mechanical flexibility, and even after various deformations such as bending, twisting, and folding under external forces, it could still well recover its original shape. Figure 2 A, C). Previous studies have confirmed that neural stem cells differentiate more readily into neurons in softer scaffolds, while they tend to differentiate into astrocytes in rigider materials. Therefore, assessing the mechanical properties of the duct is crucial. Stress-strain curves indicate ( Figure 2 B), the compressive strength of wet ducts was significantly reduced, with the GP group showing the lowest modulus (1.17±0.04 kPa) and the GPPTM group showing the highest modulus (2.07±0.11 kPa). This may be related to the stable conjugated structure of PPyNPs and the TA-Mg²⁺ coordination-enhanced structure. Notably, the Young's modulus of all ducts was within the suitable mechanical range for neural tissue (600–3000 Pa), which is beneficial for regulating cell behavior and differentiation. Figure 2 D).

[0094] The wettability and water absorption of the scaffold are key physical properties affecting cell survival. Water contact angle tests showed that the GP scaffold exhibited optimal hydrophilicity, while the introduction of the hydrophobic conductive polymer PPyNPs increased the contact angle of the GPP group and significantly decreased its hydrophilicity. Figure 2 F). Nevertheless, all the catheters had contact angles less than 90°, demonstrating good overall hydrophilicity. Furthermore, as... Figure 2 As shown in E, the dry GPPTM reaches its maximum water absorption and expansion after 1 minute of contact with water. When the tube is placed on absorbent paper, the water inside the tube seeps out onto the absorbent paper. Figure 2 Ei), over time, the moisture is completely absorbed by the absorbent paper ( Figure 2 Eii) indicates that the scaffold's water absorption is reversible. Based on this characteristic, it can dynamically deliver nutrient molecules and drugs through periodic water absorption and release, while simultaneously absorbing and removing waste products generated by tissue metabolism during the repair process, thereby actively maintaining a microenvironment conducive to repair. Furthermore, the GPPTM catheter maintains its complete morphology and structural stability even under intense mechanical agitation. Figure 2 G). Differences exist in the water absorption and expansion rates of the different groups of catheters. Figure 2 (H), which is consistent with the hydrophilic results and may be related to the material composition and pore structure. These properties indicate that the catheter possesses ideal physical properties to support tissue repair and regeneration.

[0095] Conductive biomaterials play a positive role in spinal cord injury repair by promoting the conduction of endogenous bioelectrical signals. For example... Figure 2 As shown in Figure I, the conductivity of the PPyNP-doped GPP, GPPT, and GPPTM catheters, measured using the four-probe method, was significantly higher than that of the GP group, where no signal was detected. The GPPTM group exhibited the highest conductivity (0.181 ± 0.019 S / m), consistent with literature reports. Considering the complex biological environment in vivo, catheters require stable conductivity to transmit the long-term electrical signals needed by cells / tissues. A 28-day conductivity stability test was conducted in simulated body fluids, and the results showed no significant changes in conductivity across the groups. Figure 2J), indicating that GPPTM possesses long-term stability for application. The conductivity of the catheter was further evaluated using electrochemical impedance spectroscopy. Nyquist plot ( Figure 2 The results (K) show that the GP and GPP groups have the largest semicircular diameter in the high-frequency region, indicating higher charge transfer resistance; the GPPT group has a smaller semicircular diameter, while the GPPTM group has the smallest semicircular diameter, indicating the lowest charge transfer resistance. Nerve cells typically communicate with each other at frequencies from 300 Hz to 1 kHz. Low resistance facilitates the generation of endogenous bioelectrical signals between adjacent cells through the activity of ion channels and pumps, enabling rapid intercellular communication. As shown in the Bode plot (Figure 2L), the impedance of GPPTM at 1 kHz is only 18.4 Ω, lower than that of GPP and GPPT. It is noteworthy that in the integrated LED circuit experiment (… Figure 3 M), the LEDs driven by the GPPTM group have the highest brightness ( Figure 2 The results (N) are consistent with the aforementioned conductivity test results, which together verify its excellent electrical conductivity.

[0096] Nanofiber conduits, with their unique biomimetic structure, can highly mimic the topological and biochemical characteristics of the natural extracellular matrix, thus possessing the ability to regulate basic behaviors such as cell proliferation, migration, and secretion. Therefore, this study systematically evaluated the effects of different conduits on the biological behavior of PC12 cells, focusing on their biocompatibility, proliferative activity, and three-dimensional infiltration ability. Live / dead cell staining results showed ( Figure 3 A), cell viability remained above 90% in all duct groups throughout the culture process. Figure 3 G), the number of dead cells was negligible, indicating that the material had no significant cytotoxicity. Cytoskeleton staining further showed that the cells were fully extended and there were no significant differences between the groups ( Figure 3 B), further verifying the material's biocompatibility. Scratch assays were used to assess cell migration behavior ( Figure 3 C, H). After co-culturing for 24 hours, the migration rate of PC12 cells in the GPPTM group to the damaged area (62.24±0.95%) was higher than that in other groups. EDU proliferation assay showed ( Figure 3 (D, I) The number of proliferating cells in the GPPTM group was higher than that in the control and GP groups, suggesting that it has a cell proliferation-promoting effect. After co-culturing PC12 cells with GPPTM ducts for 3 days, cross-sectional HE staining showed the porous structure of the ducts and the ability of cells to infiltrate the scaffold along the pore structure. Figure 3 (E, F) This demonstrates that the duct supports effective cell infiltration and growth. These results collectively indicate that the GPPTM duct possesses good biocompatibility, providing a reliable in vitro experimental basis for subsequent spinal cord injury repair research.

[0097] Neural stem cells (NSCs) are pluripotent and self-renewing cells with the potential to differentiate into astrocytes and neurons. To assess the impact of different ducts on NSC differentiation, we detected the expression of early neuron markers Tuj-1, mature neuron marker MAP-2, and astrocyte marker GFAP using immunofluorescence staining. The results showed that ( Figure 4 (A–B) Compared to the Control and GP groups, NSCs treated with GPP and GPPT groups showed increased fluorescence signals and proportions of Tuj-1 and MAP-2 neurons, and decreased the proportion and weak fluorescence signal of GFAP in astrocytes. Notably, compared to other groups, the GPPTM group produced more Tuj-1 neurons, more MAP-2 neurons, and fewer GFAP astrocytes. Semi-quantitative analysis of fluorescence intensity further suggested that the GPP, GPPT, and GPPTM conductive conduit groups promoted neuronal expression and effectively inhibited GFAP expression. Figure 4 The above results indicate that the GPPTM duct can effectively guide neural stem cells to differentiate into neurons, inhibit their differentiation into astrocytes, and promote the extension of neuronal axons, thereby laying a favorable cellular foundation for in vivo neural regeneration.

[0098] To evaluate the neuroprotective effect of GPPTM ducts in vitro, we induced cortical neurons for 24 hours with the NMDA receptor-specific agonist N-methyl-D-aspartate (NMDA, 50 μM) to simulate the excitotoxic microenvironment caused by Ca2+ influx following spinal cord injury. Subsequently, neurons were co-cultured with the ducts of each group for 24 hours. Fluo-4 AM calcium ion fluorescence probe detection results showed that the fluorescence intensity of neurons in the Control and GP groups induced by NMDA was significantly higher than that in the GPP and GPPT groups, while GPPTM showed the lowest fluorescence intensity, suggesting that GPPTM effectively reduced the probe fluorescence intensity and inhibited calcium ion influx. Figure 4 C, L). Simultaneously, magnesium ion probe staining showed that the Mg²⁺ fluorescence intensity in neurons treated with GPPTM was 4.6 times that of the Control group (C, L). Figure 4 The results (D,M) indicate that neurons effectively absorb Mg²⁺ released from the ducts, resulting in enhanced function. These findings suggest that GPPTM exerts a neuroprotective effect by continuously releasing Mg²⁺, effectively antagonizing NMDA receptor-mediated Ca²⁺ influx, and mitigating the resulting excitotoxicity.

[0099] Mitochondrial membrane potential instability serves as an early indicator of apoptosis, while potential stability helps reduce cell death. To investigate the effect of GPPTM on excitotoxicity, we assessed the protective effect of each duct against NMDA-induced cortical neurons using JC-1 mitochondrial membrane potential staining. The results showed that ( Figure 4 In the control group treated with NMDA, mitochondrial membrane potential was significantly depolarized, manifested as a decrease in the proportion of JC-1 aggregates (red) and an increase in the level of monomers (green). However, after GPPTM intervention, the membrane potential significantly recovered, and the JC-1 red-green fluorescence ratio rebounded. Figure 4 The presence of N (N) indicates that it effectively alleviates NMDA-induced mitochondrial dysfunction, which plays a crucial role in inhibiting apoptosis. Live / dead cell staining further confirmed that both GPPT and GPPTM can reduce neuronal mortality and promote neuronal survival in an NMDA-induced toxic environment. Figure 4 F,O). Furthermore, Cleaved Caspase-3 staining showed ( Figure 4 In the control, GP, and GPP groups, apoptosis-related signals were significantly enhanced after NMDA treatment, while apoptosis was slightly reduced in the GPPT group, possibly related to the antioxidant effect of TA. The GPPTM group significantly reduced Cleaved Caspase-3 expression. Figure 4 The presence of P indicates that GPPTM possesses a clear anti-apoptotic ability. In summary, these results demonstrate that GPPTM effectively blocks the excitotoxic cascade through multiple mechanisms, including inhibiting Ca²⁺ overload, reducing mitochondrial depolarization, and decreasing neuronal apoptosis. This is of great significance for protecting neurons and promoting neurogenesis after spinal cord injury.

[0100] Neuroinflammation is one of the key factors leading to secondary degeneration of neurons and axons after spinal cord injury. In the early stage of injury, macrophages exhibit a mixed M1 / M2 phenotype. Specifically, macrophages located in the SCI region have difficulty transitioning from a pro-inflammatory phenotype to a pro-repair phenotype, severely affecting the neuronal recovery process. Therefore, we further verified the immunomodulatory role of GPPTM by examining its effects on macrophage polarization and inflammatory cytokine secretion. Transwell migration assay results showed that the cell count in the GPPTM group was significantly increased (…). Figure 5 A, H), indicating a substantial role in macrophage recruitment, consistent with previous studies. We phenotypically identified bone marrow-derived macrophages using surface markers CD68, CD86, and CD206 ( Figure 5 B, 5C). Immunofluorescence staining showed that in the LPS-induced inflammatory microenvironment in vitro, the proportion of M1 macrophages was higher in the Control, GP, and GPP groups, while GPPT and GPPTM treatments significantly reduced M1 phenotypic expression. Simultaneously, they promoted the increase of M2 phenotypic marker expression, indicating that GPPTM can guide macrophage transformation from M1 to M2. Figure 5 I, 5J). This is related to the catheter loading of polyphenols and metal ions with anti-inflammatory functions, and this trend was further confirmed at the cytokine level. Figure 5In the D, 5E group, the pro-inflammatory factor TNF-α decreased while the anti-inflammatory factor IL-10 increased. Figure 5 K, 5L). These results lay the experimental foundation for subsequent in vivo research on inflammation repair.

[0101] The effect of GPPTM on intracellular ROS levels in PC12 cells was assessed using the DCFH-DA probe. The results showed that ( Figure 5 Under LPS-induced inflammatory conditions, the Control group showed the highest intracellular ROS fluorescence intensity. In contrast, the GPP group exhibited a decrease in ROS fluorescence intensity, which may be attributed to the antioxidant capacity of the doped conductive polymer PPyNPs, consistent with previous literature reports. The GPPT and GPPTM groups further significantly reduced ROS fluorescence intensity, indicating that the loaded TA and Mg²⁺ exerted a stronger antioxidant activity through synergistic effects. Mitochondrial membrane potential detection results further support the above conclusions. Figure 5 G). LPS stimulation led to a significant increase in JC-1 monomer levels and a decrease in aggregate levels in both the Control and GP groups, reflecting mitochondrial membrane potential depolarization. GPP treatment restored the red / green fluorescence ratio of JC-1, consistent with changes in ROS levels. Figure 5 (N); GPPT and GPPTM treatment significantly promoted membrane potential repolarization, indicating that it can effectively alleviate oxidative stress and restore mitochondrial function under inflammatory conditions. These phenomena are closely related to the known inflammatory regulatory effects of TA and Mg²⁺. In summary, GPPTM exhibits significant antioxidant and anti-inflammatory capabilities in the pathological microenvironment, mainly attributed to the synergistic effect of TA and Mg²⁺. Overall, this "ion-electric coupling" composite material can reshape the pathological microenvironment after spinal cord injury by regulating macrophage polarization, inhibiting the release of inflammatory factors, and scavenging oxidative free radicals, thereby creating favorable conditions for nerve regeneration and circuit reconstruction.

[0102] The in vivo degradation behavior of the catheter was evaluated in a rat subcutaneous implantation model. Figure 6 A). Six weeks after implantation, the GP catheter had significantly degraded, while the GPP, GPPT, and GPPTM catheters were still detectable at 12 weeks, with a significantly lower degradation rate than the GP group. By 18 weeks, the diameter and thickness of the GPPTM catheter had decreased compared to before implantation, and the boundaries had become blurred, indicating that the material had undergone significant degradation; by 24 weeks, the catheter had almost completely degraded.

[0103] Histological analysis showed that hematoxylin-eosin (HE) staining revealed a small number of mononuclear inflammatory cells infiltrating the degrading duct interface. Figure 6B). Further observation showed that the polypyrrole chains broke into nanoparticles and were endocytosed by monocyte cytoplasm, suggesting that cells participated in its degradation process. One week after implantation, collagen fiber capsules formed around the catheters in all groups, which is a normal foreign body reaction; however, the thickness of the fiber capsules in the GPPTM group was significantly smaller than that in the GP group. By week 6, inflammatory cell infiltration was significantly reduced, especially in the GPPTM group, indicating that the TA-Mg²⁺ complex effectively alleviated the inflammatory response in the early stage of implantation. Its toxicity to major organs (heart, kidney, liver, lung, spleen) of rats was studied. Eight weeks after implantation, major organs of rats were collected and histologically evaluated. The cellular structure and morphology of these organs in all catheter groups were similar to those in the control group of normal rats, and no inflammatory infiltration or pathological changes were observed in these organs. Figure 7 A). Blood compatibility tests showed that the serum optical density values ​​of each catheter group were similar to those of the PBS control group, and significantly lower than those of the Triton-100X group ( Figure 7 B). Furthermore, the liver function indicators (ALT, AST) and kidney function indicators (BUN, UA) of the GP, GPP, GPPT, and GPPTM groups were not significantly different from those of the sham surgery group, indicating that the catheter did not cause systemic toxicity and demonstrating that the GPPTM catheter has good blood compatibility and meets the biosafety requirements for nerve repair materials.

[0104] To evaluate the therapeutic potential of the GPPTM catheter in vivo, we systematically analyzed its effects on promoting structural repair and functional recovery using a T9-T10 complete spinal cord transection model in SD rats. The surgical procedure was as follows: Figure 8 As shown in Figure A, after transection, the GPPTM conductive catheter was implanted into the normal spinal cord tissue connecting the two ends of the transection center. SD rats were randomly divided into 6 treatment groups: sham operation group, SCI, GP, GPP, GPPT, and GPPTM. Except for the Sham group, the BBB score of all groups decreased to 0 after surgery, indicating that the SCI model was successfully established. Figure 8 B). Two weeks after implantation, the GPPTM group score was significantly higher than other groups, suggesting that it played a repairing role in the early stage of injury by alleviating excitotoxicity, promoting macrophage M2 polarization, and improving the local microenvironment. By 12 weeks post-operation, the BBB score of the GPPTM group further improved to 9.333 ± 0.516, significantly better than the GPPT group (6.167 ± 0.752), GPP group (4.167 ± 0.983), GPP group (3.500 ± 0.547), and SCI group (2.833 ± 0.752).

[0105] Spinal cord injury often results in permanent loss of neurological function, and its recovery is highly dependent on the integrity of tissue structure reconstruction. Therefore, suitable artificial nerve conduits are needed to fill the injury gaps and provide a guiding microenvironment for tissue regeneration. Twelve weeks after conduit implantation, tissue sampling revealed that the conduits fused well with the host spinal cord tissue, significantly better than the control group without conduits. Macroscopic structural analysis showed that the GP conduit with its hierarchical pore structure effectively filled the injury defect, while the GPPTM conduit further enhanced tissue repair, a result consistent with HE staining analysis. Figure 8 C).

[0106] At 12 weeks post-surgery, footprint collection was used to further quantify the recovery of multidimensional motor function, and representative footprint analysis was conducted. Figure 8 (D) In ​​the SCI group, rats exhibited significant dragging of their hind limbs, while the GPPTM group showed clear footprints without dragging marks, and significantly improved coordination between the forepaws (blue) and hind paws (red). Furthermore, the GPPTM group demonstrated superior motor function in the ankle, knee, and hip joints compared to the SCI group. Compared to the uncoordinated walking trajectories and widespread dragging observed in the SCI, GP, and GPP groups, the GPPTM group achieved an intermittent walking pattern with weight-bearing support from the paws. Figure 6 E). Furthermore, we assessed the recovery of motor function in rats using inclined grid crawling, the inclined plane test (IPT), and planar grid crawling. During inclined grid climbing, rats in the GPPTM group occasionally exhibited forelimb-hindlimb coordination (…). Figure 8 F); In the inclined plane experiment, rats in the GPPTM group maintained better balance on steeper slopes (F); Figure 8 L), whose maximum tilt angle when moving 100 steps with its forelimbs and the number of steps taken with its hindlimbs were significantly better than other groups ( Figure 8 The results (M) indicate rapid recovery of hind limb muscle strength. These results are consistent with the BBB score, jointly confirming that GPPTM effectively promotes positive recovery of motor function.

[0107] Urinary system dysfunction and the resulting irreversible bladder pathological changes are among the most serious consequences of spinal cord injury, significantly reducing patients' quality of life. Therefore, the degree of urinary function recovery directly depends on the level of spinal cord nerve function repair and is a key end-point indicator for assessing treatment effectiveness. To assess bladder pathological changes, we collected bladder samples from rats in each group at week 12 post-surgery. Figure 8 As shown in G. Weighing results showed that the SCI group had the heaviest bladder weight, while the bladder weight decreased in all catheter intervention groups, with the GPPTM group showing the lowest weight. Figure 8 N). Gross photograph of the bladder and results of HE and Masson staining ( Figure 8(H, 8I) showed that the detrusor muscle was significantly thickened in the SCI group, while the detrusor muscle thickness in the GPPTM group was significantly lower than that in other intervention groups, approaching that of the sham surgery group, indicating that GPPTM can effectively prevent pathological damage. Simultaneously, histological analysis showed that the damaged area was significantly reduced in the GPPTM group, with a large number of serotonergic axons regenerating and traversing the damaged site (H, 8I). Figure 8 The GPPTM catheter, designed based on "ion-immune-electric coupling," showed no such effect in the SCI group, further confirming its promoting effect on functional recovery. The functional recovery trend was consistent across all groups (GPPTM > GPPT > GPP > GP > SCI), consistent with BBB scores and IPT results, highlighting the superior efficacy of the GPPTM catheter in synergistically promoting motor and urinary function recovery and achieving comprehensive nerve repair.

[0108] Functional recovery is closely related to neural structural repair and the immune microenvironment. For example... Figure 9 As shown in Figure A, cysts formed and gradually enlarged one week after transverse spinal cord injury (SCI). During SCI repair, macrophage polarization from pro-inflammatory M1 to anti-inflammatory M2 is crucial, but this process is often blocked after SCI. Therefore, we assessed the polarization status of macrophages in vivo using CD68, CD86, and CD206 immunofluorescence staining. The results showed that compared to the sham-operated group, the SCI group had a significantly increased CD68⁺ cell density at the injury site, indicating a severe inflammatory response in the early stages of injury. The GP group showed further increases in CD68 and CD86 fluorescence intensity, suggesting that GP catheters alone failed to improve local inflammation. In contrast, transplantation of conductive GPP and GPPT catheters significantly reduced CD68 and CD86 fluorescence intensity, attributed to the regulation of macrophage polarization by doping with antioxidant PPyNPs and TA. Notably, the GPPTM group showed the most significant effect in promoting M2 macrophage polarization, with significantly higher levels of CD206 expression compared to other groups. This promoted the transformation of inflammation after SCI from a pro-inflammatory state to an anti-inflammatory state, i.e., the conversion from M1 to M2. Figure 9(D, 9E). This indicates that the GPPTM catheter has significant anti-inflammatory function, which may stem from the fact that implanted GPPTM conductive catheters not only restore electrical signal transduction in vivo, but more importantly, significantly enhance the sensitivity of neurons to Mg²⁺ protection. Simultaneously, the electrical microenvironment provides suitable polarization conditions for immune cells, laying the physical foundation for the entire synergistic system. Specifically, TA promotes M1→M2 macrophage polarization; while Mg²⁺ itself creates a favorable environment as a neuroprotective agent. The synergistic effect of the TA-Mg²⁺ chelate further strengthens the dual immune regulation, creating a sustained anti-inflammatory microenvironment. By secreting anti-inflammatory cytokines, it enhances cell-catheter interactions in the immune microenvironment, thereby effectively guiding macrophages from M1 to M2 phenotype polarization and reducing local inflammatory responses. This synergistic effect generated by the "ion-immunity-electricity" triple coupling jointly regulates the pathological microenvironment after SCI, clearing obstacles for nerve regeneration and promoting nerve regeneration and neural circuit reconstruction after SCI.

[0109] Cell infiltration and fibrous structure of spinal cord tissue in each group were observed using H&E and Masson staining. H&E staining showed that the SCI group had obvious cavities and disordered tissue structure in the injury area; while the GP, GPP, GPPT, and GPPTM groups had injury sites filled with solid tissue, closely connected with the surrounding normal tissue, with uniform distribution of eosinophilic protein, and morphology similar to the sham-operated group. Figure 9 B). Masson staining results showed that obvious blue-stained fibrotic scars were visible in the SCI, GP, GPP, and GPPT groups, while only a small amount of collagen fiber positive staining was observed in the GPPTM group. Furthermore, dense fibrous scars at the SCI site were a major obstacle to axonal ingrowth into biomaterials. These results indicate that GPPTM transplantation can effectively enhance tissue regeneration capacity, reduce scar obstruction, and thus promote the coordinated recovery of motor function.

[0110] To further investigate the role of conductive catheters in spinal cord injury repair, we used Tuj1 (a marker of newborn neurons) and GFAP (a marker of glial scarring) for immunofluorescence staining of the injured area. The results showed that at 12 weeks post-surgery, the GPPTM group had a large number of Tuj1-positive cells in the injured area and adjacent regions, while such cells were scarce in the GP and SCI groups. Figure 9(C) indicates that the regenerative capacity of untreated neurons is limited. Meanwhile, GFAP-positive cells significantly aggregated in the SCI group's lesion area, forming glial scars that inhibit nerve ingrowth, with almost no Tuj1-positive neurons present in the center of the lesion. Quantitative analysis further revealed that, compared to the SCI group, the fluorescence intensity of GFAP and Tuj1 was significantly reversed in the GPP, GPPT, and GPPTM groups, with GPPTM showing significantly higher expression, indicating higher levels of Tuj-1 and lower levels of GFAP. This suggests that GPPTM treatment effectively alleviated the abnormal aggregation of astrocytes and demonstrated a significant neuroregenerative capacity. Figure 9 (F, 9G). This result is consistent with the experimental conclusions on the differentiation of neural stem cells into neurons in vitro, jointly confirming the synergistic effect of the conductive conduit system in improving the injury microenvironment and promoting nerve regeneration.

[0111] To evaluate the regulatory effects of GPPTM catheters on neural network reconstruction and glial scarring, we performed immunofluorescence double staining with Synapsin (SYN, a presynaptic marker) and GFAP. The results showed that, compared to the control group, the GPPTM group exhibited more SYN-positive signals at the lesion margin and inside the catheter. Figure 9 The H, 9I) results indicate significantly enhanced synapse formation and neural circuit reconstruction. Simultaneously, the significantly reduced GFAP fluorescence intensity suggests inhibited glial scar formation. Notably, newly formed SYN⁺ structures not only appeared in GFAP-negative regions but also adjacent to GFAP⁺ astrocyte processes. These results demonstrate that GPPTM can synergistically promote synapse formation and inhibit glial scarring, providing a crucial microenvironmental basis for axonal extension and functional recovery.

[0112] To investigate the protective effect of ducts on neuronal survival and structural integrity, we used NeuN (a marker of mature neuronal nuclear markers) and MAP-2 (a dendritic marker) for co-labeling. The results showed that the number of NeuN⁺ / MAP-2⁺ double-positive neurons in the GPP conductive group was significantly higher than that in the SCI and non-conductive GP groups. The GPPT group was superior to the GPP conductive group alone. Notably, the GPPTM group had the highest number of NeuN⁺ / MAP-2⁺ double-positive neurons. Figure 9(J, 9K) indicates that, based on the restoration of electrical signals in vivo, Mg²⁺ exerts a neuroprotective effect, effectively reducing secondary neuronal degeneration and promoting neuronal survival. TA then regulates the survival environment of surviving neurons. Further observation revealed that the dendritic structure of neurons in the GPPTM group was more complex, characterized by increased branches, longer extensions, and enhanced fluorescence signals; while the residual neurons in the SCI group exhibited degenerative morphologies such as weakened MAP-2 signals, dendritic breakage, or atrophy. These results collectively demonstrate that GPPTM treatment effectively maintains the integrity of dendritic structures while promoting neuronal survival.

[0113] Growth-associated protein 43 (GAP43) is a key marker of axonal regeneration and development. It is expressed at low levels in normal spinal cord but is significantly activated during repair, guiding the extension and integration of newly formed axons. To assess axonal regeneration and myelin repair, we performed immunofluorescence staining for GAP43 and myelin basic protein (MBP). The results showed that both GPPT and GPPTM significantly promoted GAP43⁺ axonal sprouting and MBP⁺ myelin regeneration in the damaged area. Figure 9 (L, 9M), confirming active axonal regeneration and myelin formation. The GPPTM group showed particularly significant effects, exhibiting denser GAP43⁺ axons and more extensive MBP⁺ myelin sheath coverage, suggesting gradual neural network reconstruction in the injured area. Quantitative analysis further showed that the proportion of MBP⁺ myelinated neurons in the GPPTM group reached 12.58%, approximately nine times that of the spinal cord injury control group, fully demonstrating its outstanding ability to promote myelin formation.

[0114] To evaluate the long-term restorative effect of the GPPTM catheter on motor function after complete spinal cord injury, we conducted a behavioral analysis using a swimming test at 12 weeks post-surgery. Figure 10 Compared to the sham-operated group, rats in the SCI group exhibited severely impaired hind limb motor function, dragging in the water and lacking coordinated paddling movements. In contrast, rats in the GPPTM treatment group demonstrated effective alternating or synchronized paddling, improved trunk stability, and significantly improved swimming trajectories. The recovery effect in the GPPTM group was superior to that in the GPPT group, with slight improvement observed in the GPP group, and the worst results in the GP and SCI groups. These behavioral results are consistent with the excellent axonal regeneration, myelination, and synaptic remodeling observed in the GPPTM group histologically, indicating that its "ion-immune-electric coupling" mechanism effectively translates into functional recovery while promoting structural repair.

[0115] Based on the above findings, we hypothesize that the mechanism by which the GPPTM conduit promotes nerve regeneration is closely related to its unique properties. This conductive conduit is not only a physical bridge and electrical signal transduction carrier for the injury gap, but also an active "regulatory platform," laying the physical and biological foundation for a synergistic repair system. It mimics the electrophysiological characteristics of the natural spinal cord, and its biomimetic electrical microenvironment provides familiar survival conditions for nerve cells. When neurons are in a healthy electrical active state, the function of their membrane ion channels and receptors is more normal, and the neuroprotective efficacy of Mg²⁺ as an NMDA receptor antagonist is significantly enhanced. Studies have shown that electrical signals can affect the chemotaxis and polarization of immune cells. The conductive microenvironment potentially guides infiltrating macrophages, creating the prerequisite for tannic acid (TA) to efficiently induce their polarization towards the M2 phenotype, thereby achieving a multiplier effect in immune regulation. After spinal cord injury, M1 macrophages and reactive oxygen species (ROS) together constitute an aggressive microenvironment, which not only directly damages vulnerable neurons but may even oxidize and degrade conductive polypyrrole, affecting its long-term stability. TA effectively eliminates the aggressive environment by efficiently scavenging ROS and promoting the conversion of M1 to M2 macrophages. While eliminating chemical corrosion of conductive materials, TA also ensures the long-term stability of the conductive scaffold, allowing it to continue functioning throughout the repair cycle. Magnesium ions (Mg²⁺) in this system are not only neuroprotective agents but also a core mediator connecting electrical signals and immune regulation. They competitively block NMDA receptors, inhibiting calcium overload and excitotoxicity at the source, a prerequisite for protecting neuronal survival. Maintaining neuronal survival and membrane potential stability is itself a significant contribution to the local electrophysiological environment, ensuring that signals transmitted by the conductive scaffold can be effectively received and responded to by healthy neurons. Further research clarifies that Mg²⁺, as an immune regulatory signaling molecule, directly assists TA in promoting M2 macrophage polarization, forming a synergistic effect at the immune level.

[0116] In summary, GPPTM promotes repair through a triple coupling mechanism: conductivity reconstructs the electrical microenvironment, providing a foundation for endogenous bioelectrical signal transduction; Mg²⁺ synergistically protects neurons in the acute phase and, in the chronic phase, works with TA to shape a microenvironment supporting regeneration, guiding axonal directional growth and myelin formation; TA regulates immunity and scavenges oxidative stress. These three elements form a self-reinforcing positive cycle: electrical enhancement enhances protective and regulatory efficacy, and protection and regulation, in turn, contribute to the stability of electrical signals. Ultimately, improved motor and urinary functions become the inevitable manifestation and final verification of this synergistic mechanism at the whole animal level.

[0117] Verification of the synergistic effect of "ion-immunity-electro" To evaluate the in vitro neuroprotective effect of GPPTM ducts, we treated cortical neurons for 24 h with the NMDA receptor-specific agonist N-methyl-D-aspartate (50 μM) to simulate the excitotoxic microenvironment induced by Ca²⁺ influx after spinal cord injury. Subsequently, the neurons were co-cultured with the ducts in each group for 24 h. Live / dead cell staining results showed that the apoptosis rates of neurons after NMDA induction were 29.16%, 28.47%, 18.58%, 12.30%, and 4.61% in the GP, GPP, GPPT, and GPPTM groups, respectively, indicating that GPPTM significantly reduced neuronal mortality and promoted survival in an excitotoxic environment. Furthermore, Cleaved Caspase-3 immunofluorescence staining further validated its anti-apoptotic effect. The mean fluorescence intensities of the control group, GP group, and GPP group were 3.198 ± 0.276, 2.622 ± 0.475, and 2.400 ± 0.420, respectively, indicating a significant enhancement of apoptosis signals after NMDA treatment. The intensity in the GPPT group decreased to 1.557 ± 0.414, possibly related to the antioxidant function of TA. The intensity in the GPPTM group further decreased to 0.556 ± 0.087, significantly inhibiting the expression of cleaved caspase-3, which was significantly lower than that in the Control, GP, GPP, and GPPT groups. This was attributed to the effects of TA and Mg. 2+ The synergistic effect of these substances has a significant anti-apoptotic effect and plays an important role in protecting neurons and promoting nerve regeneration after spinal cord injury.

[0118] To evaluate the therapeutic potential of the GPPTM catheter in vivo, we used a T9-T10 complete spinal cord transection model in SD rats to systematically analyze its effect on promoting structural repair and functional recovery. After surgical transection, the GPPTM conductive catheter was implanted into the normal spinal cord tissue connecting the two ends of the transection center. Except for the Sham group, the BBB scores of all groups dropped to 0 after surgery, indicating that the SCI model was successfully established. Two weeks after implantation, the GPPTM group score was significantly higher than other groups, suggesting that it played a repairing role in the early stage of injury by alleviating excitotoxicity, promoting macrophage M2 polarization, and improving the local microenvironment. By 12 weeks after surgery, the BBB score of the GPPTM group further improved to 9.333 ± 0.516, significantly better than the GPPT group (6.167 ± 0.752), GPP group (4.167 ± 0.983), GP group (3.500 ± 0.547), and SCI group (2.833 ± 0.752) (see Table 1). This demonstrates the significant advantages of GPPTM in vivo, achieving the best BBB score. Looking at the recovery trajectory, the GPPTM group showed a superior recovery trend compared to the control groups as early as 2 weeks post-injury, suggesting that its ion regulation (Mg²⁺) and immune regulation (TA) modules created a favorable microenvironment for neuronal function preservation and early repair by mitigating acute excitatory toxicity, inhibiting neuronal apoptosis, and controlling inflammatory responses, thus achieving better "initial protection." Until week 12, the GPPTM group significantly outperformed other groups in both the rate of BBB score improvement and the final recovery plateau. Animals exhibited a qualitative leap from limited ankle joint movement to frequent coordinated movements, and finally, stable weight-bearing walking. This sustained, high-order recovery of motor function strongly demonstrates the core role of electrical conductivity in guiding axonal regeneration, promoting neural signal transmission, and reconstructing neural circuits. Therefore, the comprehensive improvement in BBB scores across dimensions such as hindlimb joint mobility, trunk stability, coordination, and gait weight-bearing is the ultimate external manifestation of the synergistic effect of "ions-immunity-electricity": together they ensure that nerve signals can be generated, protected, effectively transmitted, and ultimately precisely executed.

[0119] Table 1: BBB motor function scores of rats in each group 12 weeks after surgery

[0120] Functional recovery is closely related to neural structural repair and the immune microenvironment. Cysts form and gradually enlarge one week after transverse spinal cord injury (SCI). During SCI repair, the polarization of macrophage phenotype from pro-inflammatory M1 to anti-inflammatory M2 is crucial, but this process is often blocked after SCI. Therefore, we assessed the polarization status of macrophages in vivo using CD68, CD86, and CD206 immunofluorescence staining. The results showed that compared to the sham-operated group, the CD68⁺ cell density at the injury site was significantly increased in the SCI group, indicating a severe inflammatory response in the early stages of injury. The fluorescence intensity of CD68 and CD86 was further increased in the GP group, suggesting that GP catheters alone failed to improve local inflammation. In contrast, transplantation of conductive GPP and GPPT catheters significantly reduced the fluorescence intensity of CD68 and CD86 (see Table 2), which is attributed to the regulation of macrophage polarization by doping with antioxidant PPyNPs and TA. Notably, the GPPTM group showed the most significant effect in promoting M2 macrophage polarization, with significantly higher CD206 expression levels than other groups, promoting the transformation of post-SCI inflammation from a pro-inflammatory to an anti-inflammatory state, i.e., M1 to M2 conversion. This indicates that the GPPTM catheter has significant anti-inflammatory function, which may stem from the fact that implanted GPPTM conductive catheters not only restore electrical signal transduction in vivo, but more importantly, significantly enhance the sensitivity of neurons to Mg²⁺ protection. Simultaneously, the electrical microenvironment provides suitable polarization conditions for immune cells, laying the physical foundation for the entire synergistic system. Specifically, TA promotes M1→M2 macrophage polarization; while Mg²⁺ itself creates a favorable environment as a neuroprotective agent. The synergistic effect of TA-Mg²⁺ chelates further enhances dual immune regulation, creating a sustained anti-inflammatory microenvironment. By secreting anti-inflammatory cytokines, it enhances cell-catheter interactions in the immune microenvironment, thereby effectively guiding macrophage polarization from the M1 to M2 phenotype and reducing local inflammatory responses. The synergistic effect generated by this triple coupling of "ion-immunity-electricity" jointly regulates the pathological microenvironment after SCI, clearing obstacles for nerve regeneration and promoting nerve regeneration and reconstruction of neural circuits after SCI.

[0121] Table 2: Fluorescence intensity of macrophage polarization markers in spinal cord injury areas of rats in each group 12 weeks post-surgery

[0122] Morphological analysis of spinal cord tissue showed that the GPPTM catheter significantly inhibited and repaired post-injury cavity formation. Compared with the sham-operated group (Sham, 1.393 ± 0.434%), the cavity area in the SCI model group was as high as 45.773 ± 2.820%, indicating that complete transection injury led to severe tissue loss. Although the cavity area in the GP group (41.053 ± 1.520%) and GPP group (35.606 ± 2.300%) was slightly reduced, there was no statistically significant difference compared with the SCI group, suggesting that the simple scaffold or conductive function has limited repair effect on tissue loss. Notably, the cavity area in the GPPT group was significantly reduced to 19.693 ± 1.952%, confirming that the introduction of TA promoted tissue repair through immunomodulation and antioxidant effects. The GPPTM group further reduced the cavity area to 15.693 ± 2.513% (see Table 3), showing the most significant effect among all treatment groups and a statistically significant difference compared to the GPPT group. This result directly confirms at the morphological level that the "ion-immune-electric" triple coupling strategy (GPPTM) has a clear synergistic enhancing effect in promoting tissue integration in the damaged area and reducing cavity formation.

[0123] Table 3: Percentage of relative cavity area in spinal cord injury region of rats in each group 12 weeks after surgery (%, n=3)

[0124] The recovery of urinary function was supported by key structural evidence: the bladder weight of rats in the GPPTM group recovered to 0.427 ± 0.059 g, which was significantly better than that in the SCI group (2.268 ± 0.084 g), GP group (1.723 ± 0.094 g), GPP group (0.7428 ± 0.114 g), and GPPT group (0.529 ± 0.041 g), and approached the level of the sham-operated group (0.350 ± 0.049 g) (see Table 4). This result profoundly reveals the synergistic repair mechanism of the "ion-immunity-electricity" triple function: the conductive network reconstructed the control circuit between the brain and the sacral spinal cord micturition center, laying the foundation for the recovery of coordinated micturition reflex; Mg²⁺ effectively protected the neurons innervating the bladder by blocking calcium overload, which is a prerequisite for functional execution; and the anti-inflammatory microenvironment shaped by TA significantly alleviated the chronic inflammation-driven fibrosis and pathological hypertrophy common in neurogenic bladder. The three components complement each other and work synergistically to reverse the typical pathological remodeling of neurogenic bladder, ultimately achieving a fundamental improvement in urinary function.

[0125] Table 4: Wet bladder weight of rats in each group 12 weeks after surgery (g, n=3)

[0126] The above experiments demonstrate that the core innovation and significant effects of the GPPTM catheter provided by this invention stem from the fact that the three functional dimensions of "ions (Mg²⁺), immunity (TA), and electricity (PPy conductive network)" are not independent but constitute a deeply coupled, interdependent, and positively amplified synergistic repair system. This synergy is specifically manifested in the integration and interaction at the following three levels: 1. The electrical microenvironment is the physical basis and efficiency amplifier for synergistic effects: The conductive network reconstructs the electrical signal conduction capacity of the damaged area, which not only provides a physical channel for neural circuit reconstruction, but more importantly, creates a dynamic biomimetic electrical microenvironment. This electrical microenvironment has a dual synergistic effect: (1) The stable membrane potential puts neurons in a healthier electrophysiological state, at which time the efficacy of Mg²⁺ as an NMDA receptor antagonist is significantly enhanced, that is, the electrical signal environment amplifies the neuroprotective effect of Mg²⁺. (2) Directional guidance of immune regulation: The conductive scaffold of the present invention provides suitable physical conditions for tannic acid (TA) to efficiently induce macrophages to polarize towards the repair-type M2 phenotype, realizing the synergy of "electrical signal preparation environment and precise TA regulation".

[0127] 2. Mg²⁺ and TA form the core of a neuroprotective-immune regulatory synergy: Mg²⁺ and TA have closely intertwined functions, forming a dual nucleus of protection and regulation. (1) In the early stage of injury, Mg²⁺ directly blocks excitotoxicity, laying the foundation for neuronal survival; at the same time, TA rapidly clears ROS and reduces oxidative stress. The two work together to inhibit secondary neuronal death through different pathways. (2) During the repair phase, Mg²⁺ itself acts as an immune regulatory signal, assisting and enhancing TA-induced polarization of M2 macrophages; while the anti-inflammatory environment shaped by TA further ensures the continuous stabilizing effect of Mg²⁺. The two work together to reverse the microenvironment from "inhibitory" to "supportive".

[0128] 3. The TA acts as a system stabilizer and a coordinating link: The antioxidant and anti-inflammatory functions of TA are key to maintaining the long-term stability of the entire synergistic system. It not only directly scavenges ROS and regulates immunity, but also indirectly protects the conductive component, polypyrrole (PPy), from the chemical attack of the inflammatory microenvironment, ensuring the durability and stability of the conductive network throughout the entire repair cycle. Therefore, TA is the link connecting and ensuring the long-term effective operation of both electrical and ionic functions.

[0129] The above three dimensions form a closed-loop positive feedback loop that enhances protection and regulation, thereby protecting and regulating the electrical signal and stabilizing it. Experiments in the examples and comparative cases show that the absence of any one function will cause this loop to break, resulting in a sharp decline in overall repair efficiency.

[0130] This invention successfully designed and constructed an innovative "ion-immune-electrocoupling" 3D biomimetic conductive conduit (GPPTM) for the synergistic repair of complete spinal cord injury. The GPPTM conduit exhibits mechanical and electrical properties matching those of natural spinal cord and possesses excellent biocompatibility, providing an ideal physical and electrophysiological scaffold for nerve regeneration. This system achieves a synergistic reversal of multiple pathological processes following injury by integrating the conductivity of polypyrrole nanoparticles, the antioxidant / anti-inflammatory properties of tannic acid (TA), and the neuroprotective function of magnesium ions (Mg²⁺). GPPTM effectively competitively blocks NMDA receptor-mediated calcium ion influx by continuously releasing Mg²⁺, reducing neuronal excitotoxicity and significantly inhibiting apoptosis. Simultaneously, this system effectively induces neural stem cells to differentiate into neurons and inhibits excessive activation of astrocytes, laying the foundation for nerve repair from both "protection" and "regeneration" perspectives. GPPTM actively modulates the immune response in the injured area, promoting macrophage polarization towards the reparative M2 phenotype while alleviating oxidative stress, thereby reversing a pro-inflammatory microenvironment that inhibits regeneration into an anti-inflammatory microenvironment that supports repair. In a rat model of complete transection spinal cord injury, GPPTM implantation significantly promoted axonal regeneration, myelination, and synapsis, and effectively inhibited the spread of glial scars. These significant structural repairs ultimately translated into substantial recovery of motor and urinary functions.

[0131] In summary, this invention not only demonstrates the immense potential of the GPPTM catheter as a highly efficient and multifunctional platform for treating complete spinal cord injury, but more importantly, it puts into practice and validates an innovative strategy of achieving synergistic repair by simultaneously modulating the three core dimensions of "electro-ion-immunity" through biomaterials. This "multidimensional coupling" therapeutic paradigm provides new theoretical guidance and application prospects for the future development of more complex neuroregenerative medicine solutions.

Claims

1. A method for preparing an ion-immune-electrocoupled 3D biomimetic conductive conduit, characterized in that, Includes the following steps: (1) Provide a conductive nanofiber scaffold containing biodegradable polymers and conductive polymers; (2) The conductive nanofiber scaffold is brought into contact with a tannic acid solution to load the tannic acid onto the scaffold, thereby obtaining a conductive scaffold loaded with tannic acid. (3) The conductive scaffold loaded with tannic acid is brought into contact with a solution containing magnesium ions, so that the magnesium ions are loaded onto the scaffold through coordination, thereby obtaining the ion-immune-electrocoupled 3D bionic conductive conduit.

2. The preparation method according to claim 1, characterized in that, The biodegradable polymer in step (1) includes at least one of gelatin, collagen, silk fibroin, chitosan, hyaluronic acid, poly-L-lactic acid, polylactic acid-glycolic acid copolymer or poly-ε-caprolactone; the conductive polymer includes at least one of polypyrrole, polyaniline, polythiophene or derivatives thereof.

3. The preparation method according to claim 1 or 2, characterized in that, Step (1) specifically includes: (1a) Dissolve or disperse the biodegradable polymer and the conductive polymer in a solvent to form a spinning solution; (1b) Electrospinning the spinning solution to obtain a conductive nanofiber membrane; (1c) The conductive nanofiber membrane is crushed, shaped and cross-linked to obtain the conductive nanofiber scaffold.

4. The preparation method according to claim 3, characterized in that, In step (1a), the biodegradable polymer includes gelatin and poly-L-lactic acid; the conductive polymer is polypyrrole nanoparticles; the mass ratio of gelatin to poly-L-lactic acid is (1-3):1; and the final concentration of polypyrrole nanoparticles in the spinning solution is 1-10 wt%.

5. The preparation method according to claim 3, characterized in that, In step (1b), the voltage of the electrospinning is 15-25 kV, the feed rate is 0.5-1.5 mL / h, and the receiving distance is 15-20 cm; in step (1c), the molding process includes injecting the broken fiber dispersion into a mold and then freeze-drying it; the crosslinking process includes crosslinking with glutaraldehyde.

6. The preparation method according to any one of claims 1-5, characterized in that, In step (2), the concentration of the tannic acid solution is 1-20 mg / mL, and the contact time is 0.5-48 hours; and / or, in step (3), the magnesium ion-containing solution is an aqueous solution of a magnesium salt, wherein the magnesium salt includes at least one of magnesium chloride, magnesium sulfate, magnesium nitrate, or magnesium gluconate, and the concentration of magnesium ions in the solution is 1-30 mg / mL, and the contact time is 0.5-48 hours.

7. A 3D biomimetic conductive conduit for ion-immune-electrocoupling, characterized in that, include: Three-dimensional porous nanofiber scaffold formed by a composite of biodegradable polymers and conductive polymers; Tannic acid loaded on the support; And magnesium ions that bind to the tannic acid through coordination.

8. The ion-immune-electrocoupled 3D biomimetic conductive catheter according to claim 7, characterized in that, The catheter is prepared by any one of claims 1-6; the catheter has a three-dimensional porous structure with a porosity of 50-90% and an electrical conductivity of 0.01-1 S / m; the catheter is loaded with tannic acid and magnesium ions; based on the total mass of the catheter, the loading of tannic acid is 0.5-15 wt% and the loading of magnesium ions is 0.1-10 wt%.

9. A medical implant, characterized in that, The ion-immune-electrocoupled 3D biomimetic conductive conduit comprising any one of claims 7 or 8.

10. The use of the ion-immune-electrocoupled 3D biomimetic conductive catheter of any one of claims 7 or 8, or the medical implant of claim 9, in the preparation of a medicament or medical device for repairing nerve damage.

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