A recent study published in Advanced Materials Technologies introduced a microfluidic spinning process to create poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS) microfibers.
Researchers used a polydimethylsiloxane (PDMS) microfluidic chip with a laser-written nozzle to spin fibers from a commercial PEDOT:PSS solution, offering a new approach to fabricating conductive fibers for nerve repair applications.
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Background
Peripheral nerve injuries can cause significant disability, often requiring surgical intervention to reconnect severed nerves. When direct suturing is not possible, nerve guidance conduits (NGCs) or grafts help bridge the gap. However, the limited availability of nerve grafts and the complexity of additional surgeries drive research into synthetic alternatives.
Microfibrous fillers are promising for synthetic NGCs because they mimic the natural anisotropic structure of nerves, provide mechanical support, and promote axonal growth. Conductive materials, such as PEDOT polymers, enhance nerve regeneration by offering electrical stimulation while maintaining biocompatibility, flexibility, and biodegradability.
Developing PEDOT:PSS Microfibers
Researchers fabricated microfluidic chips using PDMS through soft lithography, creating a system for controlled fiber spinning. A commercial PEDOT:PSS solution served as the spinning dope, and fiber collection was optimized by adjusting the spindle’s rotational speed to ensure smooth, stable fiber formation.
The surface morphology and diameter of the fibers were analyzed using field emission scanning electron microscopy (FESEM). Tensile strength was assessed using a custom-built setup with a precision scale and micromanipulator arm, while additional mechanical properties were examined through nanoindentation.
Conductivity was measured via cyclic voltammetry, with the fibers acting as working electrodes against a platinum mesh counter-electrode. The active electrode surface was determined by measuring fiber dimensions under light microscopy.
To evaluate biocompatibility, researchers tested L929 mouse fibroblast adhesion, migration, and proliferation on the microfiber meshes. Cytotoxicity was assessed by comparing metabolic activity in fibroblasts cultured with and without PEDOT:PSS NGCs using a cell proliferation assay.
Key Findings: Stable, Conductive, and Biocompatible Fibers
SEM imaging confirmed that the PEDOT:PSS microfibers had a uniform diameter, smooth surface, and minimal defects. Researchers found that fiber diameter could be controlled by adjusting the flow rates of the spinning dope and shear fluid.
Increasing the total flow rate reduced clogging risks, but exceeding a threshold prevented proper fiber formation. At lower flow rates, the spinning process became unstable.
The system produced microfibers with diameters ranging from 1.2 to 3 µm, with thinner fibers proving too fragile for collection. Despite their small size, the mechanical properties of the PEDOT:PSS fibers were comparable to those of pure PEDOT:PSS.
However, handling individual fibers remained difficult due to their low absolute strength, necessitating the use of fiber bundles for improved stability and bulk handling.
The fibers had a Young’s modulus of 1.22 ± 0.11 MPa, making them suitable for supporting migrating cells. Tensile tests showed they provided structural support against shear, compression, and stretching forces.
Cyclic voltammetry demonstrated the fibers’ electrode stability in electrolyte solutions, revealing their safe operating range, charge storage capacity, and potential resistance to unwanted reactions. Additionally, researchers determined the “water window,” defining the voltage range in which the fibers could function without degradation.
Biocompatibility tests showed no signs of cytotoxicity, with L929 fibroblasts successfully adhering to and proliferating on the fibers. The results suggest that PEDOT:PSS fibers could support axonal ingrowth and Schwann cell migration within NGCs, enhancing nerve regeneration outcomes.
The fibers were softer than other conductive scaffolds used for nerve repair but remained easy to handle, making them practical as fillers in nerve guidance conduits. The proposed microfluidic spinning method offers a controlled approach to studying how topographical, mechanical, and electrical factors influence neuroregeneration.
Journal Reference
Geiger, M., et al. (2025). Microfluidic Spinning of PEDOT: PSS Microfibers for Nerve Guidance Conduits. Advanced Materials Technologies. DOI: 10.1002/admt.202401996, https://advanced.onlinelibrary.wiley.com/doi/10.1002/admt.202401996
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