Cartilage injuries from trauma or degenerative diseases such as osteoarthritis pose a major clinical challenge because cartilage has a limited intrinsic healing capacity. Tissue engineering has emerged as a promising strategy to restore function, and the scaffold is a critical component that provides a temporary supportive environment for cell attachment, proliferation, and matrix deposition. Among various fabrication techniques, electrospinning has gained particular attention for its ability to produce fibrous scaffolds that closely mimic the nanoscale architecture of the natural extracellular matrix (ECM). This article explores the innovations in scaffold fabrication using electrospinning for cartilage repair, covering the fundamentals, recent advances, and future directions.

Understanding Electrospinning in Tissue Engineering

Electrospinning is a versatile and scalable technique that uses an electric field to draw polymer solutions or melts into ultrafine fibers with diameters ranging from a few nanometers to micrometers. The basic setup includes a syringe pump, a high-voltage power supply, a needle or spinneret, and a grounded collector. When a high voltage is applied, the polymer droplet at the needle tip becomes charged, forming a Taylor cone. Once the electrostatic forces overcome the solution’s surface tension, a fine jet is ejected. The solvent evaporates during the jet’s travel, and the solidified fibers are deposited on the collector as a nonwoven mat.

Key process parameters include applied voltage, flow rate, collector distance, polymer concentration, and solution conductivity. These parameters directly influence fiber morphology, diameter distribution, alignment, and porosity—properties that are essential for guiding cell behavior and tissue formation in cartilage repair. For instance, aligned fibers can mimic the anisotropic structure of certain cartilage regions, while random fibers offer isotropic support for cell infiltration.

The Role of Electrospun Scaffolds in Cartilage Regeneration

Articular cartilage is a highly specialized tissue with a complex zonal architecture: the superficial zone has collagen fibers parallel to the surface; the middle zone contains randomly oriented fibers; and the deep zone has fibers perpendicular to the subchondral bone. Additionally, the ECM composition varies with depth, influencing the mechanical and biochemical properties. Electrospinning allows the recreation of these zonal structures through techniques like multilayer deposition, dual-collector methods, and co-electrospinning of different materials. By emulating the native ECM, electrospun scaffolds provide topographical and biochemical cues that promote chondrocyte phenotype maintenance and new matrix synthesis.

Key Advantages of Electrospun Scaffolds for Cartilage Repair

The popularity of electrospinning in cartilage tissue engineering stems from several distinct advantages over conventional scaffold fabrication methods such as solvent casting, freeze-drying, and gas foaming.

  • High surface-area-to-volume ratio: The nanofiber network provides an extensive surface for cell adhesion and nutrient diffusion, supporting higher cell densities and uniform distribution.
  • Structural mimicry of native ECM: The fibrous architecture closely resembles the collagen fibrils in cartilage, providing contact guidance and signaling cues that promote chondrogenic differentiation and ECM deposition.
  • Biocompatibility and biodegradability: A wide range of natural and synthetic polymers—collagen, gelatin, silk fibroin, chitosan, polycaprolactone (PCL), poly(lactic-co-glycolic acid) (PLGA), and poly(L-lactic acid) (PLLA)—can be electrospun into scaffolds. Many of these materials degrade over time at rates that can be tuned to match new tissue formation.
  • Customization: Fiber diameter, alignment, and porosity can be adjusted to meet specific mechanical and biological requirements. For example, increasing fiber diameter can improve compressive strength, while aligning fibers enhances tensile properties in a preferred direction.
  • Controlled release of bioactive molecules: Electrospinning can encapsulate growth factors, cytokines, drugs, or nucleic acids within the fibers for sustained, localized delivery. This spatiotemporal control enhances regenerative efficacy and reduces systemic side effects.
  • Scalability: Electrospinning is a continuous process that can be scaled up for industrial production using multi-nozzle systems and rotating mandrels, making it viable for clinical translation.

These advantages have been demonstrated in numerous preclinical studies. For instance, electrospun PCL scaffolds seeded with mesenchymal stem cells (MSCs) have shown improved cartilage repair in rabbit models, with enhanced hyaline-like cartilage formation and integration with host tissue.

Recent Innovations in Electrospinning Techniques for Cartilage Repair

While conventional electrospinning produces random fiber mats, recent innovations have expanded the capabilities of the technique, enabling the fabrication of more sophisticated scaffolds that better match the structural and biological complexity of native cartilage.

Composite and Hybrid Scaffolds

To overcome the limitations of single-polymer scaffolds—such as insufficient mechanical strength or lack of bioactivity—researchers have developed composite electrospun mats. These hybrids combine two or more materials, often including bioactive ceramics or nanoparticles. For example, incorporating hydroxyapatite (HA) or bioactive glass into polymer fibers improves compressive stiffness and supports mineralization, which is beneficial for osteochondral interface repair. Similarly, blending synthetic polymers with natural ECM components (e.g., collagen, hyaluronic acid, or chondroitin sulfate) enhances cell adhesion and chondrogenesis. A study published in Acta Biomaterialia demonstrated that hyaluronic acid–grafted PCL fibers promoted greater glycosaminoglycan (GAG) deposition by chondrocytes compared to unmodified PCL.

Multilayered and Gradient Scaffolds

Articular cartilage is not homogeneous; it has distinct zones with varying mechanical properties, collagen orientation, and proteoglycan content. To replicate this hierarchy, researchers have developed multilayered scaffolds via sequential electrospinning or by combining electrospinning with other fabrication methods. For instance, a three-layered scaffold can have a random fiber layer for the middle zone, aligned fibers for the superficial zone, and a denser layer or microporous structure for the deep zone. Co-electrospinning of two or more polymer solutions simultaneously allows the creation of blends with zonal gradients in composition. A recent study in Journal of Tissue Engineering and Regenerative Medicine used a rotating mandrel collector to produce scaffolds with gradient transverse alignment, mimicking the depth-dependent orientation pattern of collagen.

Coaxial and Emulsion Electrospinning

Coaxial electrospinning uses two concentric needles to produce core–shell fibers. The core can contain a drug or growth factor, while the shell provides mechanical stability and degradation control. This technique allows for the encapsulation of delicate bioactive molecules without exposing them to harsh organic solvents. For cartilage repair, transforming growth factor-β1 (TGF-β1) or insulin-like growth factor-1 (IGF-1) can be encapsulated in the core for sustained release, enhancing chondrogenic differentiation of seeded stem cells. Emulsion electrospinning is a simpler alternative that creates a similar core–shell structure by emulsifying an aqueous phase (containing the bioactive agent) into a polymer solution. Both methods have shown promise in maintaining bioactivity and achieving prolonged release profiles.

Electrospinning with 3D Printing Hybrids

While electrospinning produces fine fibers, it generally yields thin mats (micrometers to a few millimeters). For repairing large cartilage defects, thicker, more porous scaffolds are needed. Combining electrospinning with 3D printing (melt electrowriting) allows the fabrication of hierarchical structures: a 3D-printed melt fiber framework provides macroporosity and structural integrity, while electrospun nanofibers fill the interstices to provide cell-instructive surfaces. A study in Advanced Healthcare Materials showed that such hybrid scaffolds improved cell infiltration and cartilage-like tissue formation in a rabbit osteochondral defect model compared to electrospun mats alone.

Stem Cell–Laden Electrospun Scaffolds

Electrospun scaffolds can serve as carriers for stem cells, either by seeding cells after fabrication or by incorporating them during electrospinning (e.g., using cell electrospraying). The latter approach, known as bio-electrospinning, allows for the creation of cell-laden fibers, though it requires careful control of voltage and flow to maintain viability. More commonly, MSCs are seeded onto electrospun mats and induced toward chondrogenic lineage. Scaffolds functionalized with specific peptides (e.g., RGD, collagen-binding peptides) or growth factors can direct stem cell fate without soluble inductive factors. Recent work has also explored the use of decellularized ECM-derived materials as electrospinning substrates, providing a native biochemical milieu that primes MSCs for chondrogenesis.

Applications in Specific Cartilage Repair Contexts

Electrospun scaffolds are being investigated for various types of cartilage defects, including articular cartilage, meniscus, and osteochondral lesions.

Articular Cartilage Repair

For focal chondral defects, electrospun scaffolds can be implanted as cell-free or cell-seeded constructs. In a rabbit model, electrospun PCL/gelatin scaffolds seeded with autologous chondrocytes promoted healing of full-thickness defects with hyaline-like tissue after 12 weeks. In a larger animal model (sheep), electrospun collagen scaffolds loaded with BMP-7 improved the quality of repair tissue at 6 months, with better integration than untreated controls. Human clinical trials are still limited, but pilot studies using electrospun collagen–hyaluronic acid membranes for cartilage repair have shown safety and potential efficacy in small patient cohorts.

Meniscus Repair

The meniscus is a fibrocartilaginous structure with a complex, circumferentially aligned collagen network. Electrospinning can produce aligned fiber scaffolds that mimic the meniscal architecture. In vitro studies using aligned PLGA fibers have shown that meniscus fibrochondrocytes align along the fiber direction and deposit oriented ECM. Animal models of meniscal injury have demonstrated that electrospun PCL scaffolds seeded with MSCs can promote regeneration and prevent joint degeneration. Recent innovations include creating tubular scaffolds by electrospinning onto a rotating mandrel, which can be used as meniscal substitutes, and incorporating antibacterial agents to reduce infection risk.

Osteochondral Repair

Osteochondral defects involve both cartilage and subchondral bone. Bilayered or gradient scaffolds are ideal for this application. Electrospinning allows the fabrication of a composite scaffold with a nanofibrous cartilage layer and a more porous, stiff bone layer. For instance, a bilayer scaffold composed of an electrospun PCL–collagen layer for cartilage and a 3D-printed tricalcium phosphate layer for bone has shown promise in rabbit osteochondral defects. The electrospun layer guides chondrogenesis while the bone layer supports osseointegration and blood vessel ingrowth.

Challenges and Future Directions

Despite significant progress, several hurdles remain before electrospun scaffolds become routine clinical tools for cartilage repair.

Mechanical Properties

Native cartilage is subjected to compressive, shear, and tensile loads. Electrospun scaffolds often lack the compressive stiffness of cartilage, especially when wet, because of their high porosity. Strategies to improve mechanical performance include crosslinking fiber networks (chemically or via heat), reinforcing with nano-fillers (nanotubes, nanocellulose), or designing interlocked fiber architectures. However, adding more material or increasing fiber diameter may reduce porosity and cell infiltration, so a balance must be achieved.

Cell Infiltration and Homogeneous Seeding

The small pore size of electrospun mats (typically 1–10 μm) restricts cell penetration, forcing cells to remain on the surface. This leads to non-uniform tissue formation. Recent approaches to improve infiltration include using sacrificial fibers (e.g., electrospinning polyethylene oxide or gelatin that can be leached out), cryogenic electrospinning to create hierarchical porosity, and incorporating microspheres as spacers. Melt electrowriting, which produces larger fibers (50–200 μm) with well-defined pores, is another promising solution that is often combined with electrospinning.

Long-Term Integration and Degradation

Scaffolds must degrade at a rate that matches new tissue deposition. If degradation is too fast, the scaffold loses support before tissue maturation; if too slow, it may inhibit tissue remodeling and cause chronic inflammation. Moreover, the degradation byproducts should be non-toxic and easily cleared. Polymers like PCL degrade slowly (2–4 years), while PLGA degrades faster (weeks to months). Blending polymers with different degradation rates can produce tunable profiles. Additionally, incorporating antioxidant or anti-inflammatory molecules can mitigate the foreign body response and improve long-term outcomes.

Regulatory and Manufacturing Considerations

Translation to clinical use requires reproducible manufacturing under good manufacturing practices (GMP). Electrospinning is sensitive to environmental conditions (humidity, temperature), and scaling up without quality fluctuations is challenging. Multi-nozzle systems and automated monitoring are being developed to address this. From a regulatory standpoint, electrospun scaffolds intended for cartilage repair are classified as medical devices or combination products (if they contain drugs, cells, or growth factors). Clear guidelines for preclinical testing—including mechanical characterization, biocompatibility, and in vivo evaluation in relevant animal models—are still evolving.

Smart and Responsive Materials

Future directions aim to create “intelligent” scaffolds that respond to physiological signals. For example, scaffolds containing enzymes (e.g., matrix metalloproteinase–cleavable crosslinkers) can be remodeled by invading cells. Temperature- or pH-responsive polymers could release growth factors at inflamed sites. Another exciting frontier is the incorporation of conductive nanomaterials to facilitate electrical stimulation, which has been shown to enhance chondrocyte proliferation and matrix synthesis. While still in the early research stage, these smart materials hold promise for dynamic, patient-specific treatments.

Conclusion

Electrospinning has become a cornerstone technology for fabricating scaffolds in cartilage tissue engineering. Its ability to create nanofiber networks that reproduce the native ECM, combined with advances in composite materials, multilayered structures, and controlled release, has brought us closer to clinically viable cartilage repair solutions. However, challenges related to mechanical strength, cell infiltration, long-term integration, and scalability must be overcome. The integration of electrospinning with additive manufacturing, stem cell therapies, and smart biomaterials points toward a future where customized, off-the-shelf scaffolds can effectively restore cartilage function and improve patient outcomes. As research continues, interdisciplinary collaboration among material scientists, biologists, engineers, and clinicians will be essential to translate these innovations from bench to bedside.