A polymer solution (10% w/v) was prepared by dissolving Poly(ε-caprolactone) (PCL; Sigma Aldrich, United Kingdom, Cat. No. 440744-500G) in a solvent mixture of dichloromethane (DCM; Sigma Aldrich, United Kingdom) and N,N-dimethylformamide (DMF; Fisher Scientific, United Kingdom) at a 7:3 volume ratio. The solution was stirred continuously for 24 h at room temperature until fully dissolved.

Electrospinning was performed using a Fluidnatek® LE-500 electrospinning system (Bioinicia, Spain), equipped with dual syringe pumps, two oppositely charged 21G stainless steel needles, a rotating funnel collector, and an automated take-up reel (Figure 1A). The needles were placed 175 mm from the funnel collector, and voltages of −8 kV and +12 kV were applied to each needle, respectively. Polylactic acid (PLA) (NatureWorks, Ingeo Extend 4950D United States) multifilament yarn (warp-grade) was continuously fed through the centre of the rotating funnel, enabling electrospun nanofibres to deposit evenly around the PLA core, resulting in a continuous, stable core-sheath nanofibre yarn structure. Nanofibre yarns were collected onto the reel at a controlled winding speed between 14 and 18 rpm. A representative image of the PLA-PCL yarn package collected over a 2-h run is shown in Figure 1B.

Woven scaffold structures were fabricated using an Arm Patronic semi-automated loom (Figure 1Ci) (ARM AG CH-2507 Biglen) equipped with an electronic dobby mechanism for precise control over individual warp yarn movements (Figure 1Cii). PLA multifilament yarns were used as warp material, and the previously fabricated electrospun PLA-PCL core-sheath nanofibre yarns served as the weft material (Figure 1Ciii). Warp yarns and warp beams were prepared using a Hergeth Hollingsworth sample warper and subsequently threaded individually through the heald wires and frames. A reed density of 10 dents/cm was selected, and the warp yarns were threaded at a density of 2 ends/dent, resulting in a final warp density of 20 ends/cm. The weaving was performed at a constant warp tension to ensure uniform fabric quality. Multiple woven structures were produced to investigate how weave architecture influences scaffold properties. These structures included plain weave, 2 × 2 twill weave, sateen weave (R = 8, S = 5), broken twill (1/7 S with alternating 5 × 5 S-diagonal and 3 × 3 Z-diagonal), and shadow twill (warp repeat Rwp = 22, weft repeat Rwf = 3). While Figure 1D, shows a tubular scaffolds fabricated in a plain weave structure, consisting of PCL-PLA core–sheath yarns in the weft and PLA yarns in the warp, produced with customisable diameters.

Morphological characteristics of core-sheath nanofibre yarns and woven scaffolds were examined using scanning electron microscopy (SEM; Tescan Vega3, United Kingdom) at 5 kV and a working distance of 12–25 mm. Samples were gold/palladium coated (10 nm thickness) prior to imaging. Fibre diameters and alignment were quantified using ImageJ from SEM images at ×500 magnification (n = 10). Yarn linear density (tex) was measured according to BS EN ISO 2060:1995 via the skein method. PLA-PCL core-sheath nanofibre yarns (10 m skeins) from five batches were weighed, averaged, and compared to reference yarns. Mechanical properties were determined on individual yarns to characterise tensile behaviour prior to scaffold fabrication, enabling determination of baseline yarn properties independent of scaffold architecture. Tests were performed using an Instron 5565 tensile tester (5 N load cell) following BS EN ISO 2062:2009 standards. Tensile tests were conducted at 250 mm/min crosshead speed, applying a pre-load of 0.5 cN/tex to determine yarn tenacity, with at least three replicates per yarn type. Further, tensile strength (σ) of the yarns was calculated using the measured tenacity and the known material density (ρ) values of polymers PLA (1.25 g/cm³) and PCL (1.145 g/cm³) using the following formula: σ = T e n a c i t y × ρ

The woven scaffold cover factor was calculated from warp and weft yarn densities and diameters. Surface roughness of scaffolds was analysed using a digital microscope (Keyence VHX-5000, United Kingdom) at ×10 magnification (n = 5). Height profiles were captured in warp and weft directions, calculating mean peak-to-valley heights (Rz). The woven scaffold cover factor was calculated from warp and weft yarn densities and diameters. Scaffold relative porosity was determined gravimetrically, measuring laser-cut samples (10 × 10 mm) and applying polymer density values to compute porosity.

Water contact angles were evaluated with a Drop Shape Analyser (Krüss DSA100, Germany). A 1 µL water droplet was applied to scaffold surfaces (n = 5 per scaffold type), and angle changes were continuously recorded until absorption to assess scaffold hydrophilicity.

For biological evaluations, scaffolds were laser-cut into 10 × 10 mm samples, sterilised with ethanol (70%) and UV exposure (45 min/side), washed with PBS, and air-dried. Human umbilical vein endothelial cells (HUVECs) and human oesophageal smooth muscle cells (HOeSMCs) were used for biological evaluation. HUVECs were cultured in Endothelial Cell Growth Medium 2 (PromoCell, C-22011) supplemented with Supplement Mix (C-39216), L-glutamine, and 1% penicillin-streptomycin. HOeSMCs were maintained in high-glucose DMEM (Sigma-Aldrich, D5796) supplemented with 10% fetal bovine serum, 1% Antibiotic-Antimycotic, and L-glutamine. All cells were cultured at 37 °C in a humidified incubator with 5% CO₂ and passaged at 80%–90% confluence. Dry scaffolds were seeded using a low-volume droplet method, 10 µL droplets. of cell suspension were evenly applied per scaffold, followed by a 2-h incubation at 37 °C to promote attachment. HUVECs were seeded at a density of 7.5 × 10³ cells/cm², while HOeSMCs were seeded at 4 × 10³ cells/cm². After the initial attachment phase, 500 µL of the appropriate complete medium was added to each well.

Cell viability was assessed at 24 h, 4 days, and 7 days using the LIVE/DEAD™ Viability/Cytotoxicity Kit (L3224, Life Technologies Ltd., United Kingdom), following the manufacturer’s instructions. Each scaffold was incubated in 300 µL of this solution for 30 min at 37 °C in the dark. After incubation, samples were gently washed with PBS to remove unbound dye and immediately imaged using a Leica SP8 confocal microscope (Leica Microsystems Ltd., Milton Keynes, United Kingdom). Samples were imaged using a Leica SP8 confocal microscope (Leica Microsystems Ltd., United Kingdom). Cell metabolic activity was quantified using a resazurin reduction assay (Resazurin sodium salt, R7017, Sigma-Aldrich, United Kingdom). A resazurin stock solution was prepared in PBS and diluted 1:10 (v/v) in complete culture medium immediately before use. Scaffolds were rinsed in once PBS, transferred to fresh wells containing 1 mL of the working solution, incubated for 3 h at 37 °C in a humidified incubator with 5% CO₂. Following incubation, 200 µL of supernatant from each well was transferred to a black 96-well plate. Fluorescence was measured at 560 nm excitation and 590 nm emission using a FLUOROstar OPTIMA plate reader (BMG LabTech, Germany). Blank controls were used to correct background signal. Cell proliferation was assessed by total DNA content using the Quant-iT™ PicoGreen™ dsDNA Assay Kit (P7589, Thermo Fisher Scientific, United Kingdom), according to the manufacturer’s protocol. Samples were subjected to three freeze–thaw cycles, lysed in 1% Triton X-100 (X100, Sigma-Aldrich, United Kingdom) in TE buffer, and incubated for 3 h on a rocking platform at room temperature. Lysates were mixed with diluted PicoGreen reagent, and fluorescence was measured at 485 nm excitation and 520 nm emission using the FLUOROstar OPTIMA plate reader. DNA concentrations were calculated using a standard curve generated from known dsDNA standards.

All statistical analyses were performed using GraphPad Prism (Version 10.4.2 (534), March 29, 2025) and Microsoft Excel 2025. For comparisons involving more than two groups, statistical significance was assessed by one-way ANOVA with Tukey’s multiple comparisons post hoc test. A p-value of <0.05 was considered statistically significant. Data are presented as mean ± standard error of the mean (SEM). Biological assays were conducted with two independent experiments; each performed in technical triplicates. Mechanical testing was performed on three independent yarn or scaffold samples per group. Morphological analyses (e.g., fibre diameter, pore size) were based on measurements from ten randomly selected SEM fields per sample across three independent samples.

The core-sheath yarn structure was successfully fabricated using conjugate electrospinning, combining a PLA multifilament core with an electrospun PCL nanofibre sheath. This approach produced a stable, continuous yarn with a well-defined architecture. SEM images confirmed the distinct morphological differences between the PLA core (Figures 2Ai,ii) and the PCL sheath (Figures 2Aiii,iv). The PLA multifilament core consisted of smooth, uniform filaments measuring 13 µm in diameter. In contrast, the electrospun PCL sheath comprised randomly distributed fibres with a mean diameter of 851.78 ± 253.23 nm (Figure 2B), within the biomimetic range known to support cellular adhesion and proliferation, particularly in vascular tissue engineering, tendon repair, and ECM-mimetic scaffolds (Mo et al., 2004; Han et al., 2019; Flavia et al., 2022; Shaohua et al., 2017; Qi et al., 2023). Quantitative analysis of scaffold porosity was conducted using particle analysis in FIJI (ImageJ) by applying threshold-based segmentation to SEM images. Analysis showed that the PCL nanofibre sheath had a mean pore area of 5.73 ± 0.69 µm² and a surface porosity of 24.1% ± 1.27%. In contrast, the PLA multifilament core exhibited significantly larger inter-filament pore areas (94.19 ± 40.25 µm²) and a lower surface porosity of 9.92% ± 0.59% (Figure 2D). These fibres exhibit axial alignment (∼10°) relative to the multifilament core (Figure 2C), contributing to a uniform sheath layer approximately 9.98 ± 4.30 µm thick. Quantitative analysis of scaffold porosity was conducted using particle analysis in FIJI (ImageJ) by applying threshold-based segmentation to SEM images. Analysis showed that the PCL nanofibre sheath had a mean pore area of 5.73 ± 0.69 µm² and a surface porosity of 24.1% ± 1.27%. In contrast, the PLA multifilament core exhibited significantly larger inter-filament pore areas (94.19 ± 40.25 µm²) and a lower surface porosity of 9.92% ± 0.59% (Figure 2D). To assess their suitability of tissue engineering applications, preliminary biocompatibility assessment of the PLA-PCL scaffolds using 3T3 fibroblasts was conducted. Differences in fibre diameter and pore area influenced seeded 3T3 fibroblast behaviour on the two yarn types (Figure 2E). On the electrospun PCL nanofibre sheath, the smaller fibre diameters and pore sizes promoted surface-level spreading and cytoplasmic extension (Figure 2Ei). In contrast, the larger diameter PLA multifilament yarns and wider inter-filament pores supported cell alignment along individual filaments and facilitated infiltration into the yarn interior (Figure 2Eii), suggesting distinct features of scaffold interaction based on architectural fibre structure.

Mechanical testing highlighted key advantages of the PLA–PCL core-sheath yarn structure (Figures 3A–D). The hybrid PLA–PCL core-sheath yarn demonstrated a tenacity of 3.90 dN/tex (487.10 MPa tensile strength) and a breaking strain of 32%, outperforming pure PCL nanofibre yarns, which exhibited greater extensibility (84.72%) but significantly lower tensile strength (0.93 dN/tex or 107.26 MPa). Previous studies show that electrospun aligned PCL nanofibre yarns achieve maximum single-yarn forces of only 5.16 ± 0.04 cN (∼0.052 N/tex), underscoring their mechanical limitations (Yang Q. et al., 2022). Although bundling multiple PCL yarns increases the total force (up to 3.31 ± 0.37 N for 50 yarns), it does not fully overcome the intrinsic weakness of the material (Yang Q. et al., 2022). Melt-spun PLA filaments typically achieve tenacities between 20 and 30 cN/tex, influenced by polymer crystallinity and molecular orientation, but remain mechanically inferior compared to the hybrid system (Yang Y. et al., 2022). The integration of a PLA multifilament core with a PCL nanofibre sheath to create a core-sheath yarn results in a scalable structure suitable for engineering tubular textile scaffolds. The enhanced mechanical performance of the core-sheath yarn, compared to a PCL nanofibre yarn, is primarily attributed to the PLA multifilament core, which functions as the principal load-bearing component. In contrast, the surrounding PCL nanofibre sheath contributes to stress distribution and elasticity by mitigating localised stress concentrations and buffering tensile loads. This dual-component interaction enhances energy dissipation and ductility, consistent with observations in other multi-scale yarn architectures (Chen et al., 2022). The addition of the PCL nanofibre sheath resulted in a slight increase in strain compared to the PLA multifilament core alone, which displayed a break tenacity and strain of 3.67 dN/tex and 30.6% respectively. Although these minor mechanical improvements to the PLA multifilament core yarns were observed by the addition of PCL nanofiber sheaths, they were not statistically different. Young’s modulus values further supported these trends: the core-sheath yarn exhibited a modulus of 0.47 dN/tex, nearly identical to that of the PLA core (0.45 dN/tex), confirming that the composite’s stiffness is predominantly governed by the core. In contrast, the PCL yarn displayed a considerably lower modulus (0.064 dN/tex), reflecting its compliant nature. Overall, the PLA–PCL core-sheath yarn, with its intermediate modulus, and enhanced strength/elasticity, offers favourable properties for engineered woven scaffolds intended to leverage anisotropic mechanical behaviour. Although the tensile tests in this study were performed on individual yarns and therefore do not provide direct measurements of scaffold-level anisotropy, it is well established in textile mechanics literature that woven fabrics inherently exhibit anisotropic behaviour (Hu and Xin, 2008). This results from the directional arrangement of yarns and the structural characteristics influenced by the weave architecture. Such anisotropy is particularly relevant in the design of tubular scaffolds, where differential mechanical responses along warp and weft directions can be strategically engineered to tailor strength, compliance, and deformation characteristics to meet the specific functional demands of target tissues.

Scaffolds were fabricated using an ArmPatronic dobby loom, producing five weave patterns: plain, 2 × 2 twill, sateen, broken twill, and shadow twill. PLA multifilament yarns were used as warp in all cases (20 ends/cm), while PLA or PLA–PCL yarns were used as weft. The PLA plain weave, composed entirely of PLA yarns, served as the control (Figures 4A,B). These weave patterns were selected to explore how textile structures affect scaffold mechanics and biological response. Each offers distinct advantages. Plain weave, with its high interlacing density, offers structural stability and uniform pore distribution, potentially enhancing cell infiltration. Twill and sateen weaves introduce varied float lengths and surface textures, which may impact scaffold flexibility and support directional or uniform cell growth. Broken twill and shadow twill introduce subtle 3D structures and gradient porosities that resemble the surface folds and heterogeneous textures of native tissues like the oesophagus or trachea. These features can provide mechanical support while offering topographical cues that influence cell attachment, orientation, and function. The difference in weaving patterns also demonstrated to influence surface roughness and wettability of the fabricated yarns. Average surface roughness increased with weave complexity (Figure 4C). Broken twill showed the highest roughness (73.5 ± 6.4 µm), followed by twill (65.2 ± 5.1 µm), while PLA plain had the lowest (32.6 ± 4.7 µm). Twill, broken twill, and shadow twill weaves showed higher Rz values due to longer floats and irregular interlacing (Becerir et al., 2016). Surface roughness also increased with PLA–PCL yarns compared to PLA alone, reflecting the influence of material composition (Akgun, 2015). These results demonstrate that by modulating weave pattern complexity, the degree of yarn interlacement and resulting surface topography can be precisely tuned to engineer scaffold surfaces with tailored roughness for specific biological responses (Beyene and Kumelachew, 2022). Furthermore, contact angle measurements showed significant variation across weaves where wettability correlated with surface roughness, porosity, and material composition. (Figure 4D). Increased hydrophilicity is generally favourable for cell attachment and spreading, as it promotes the adsorption of adhesive proteins like fibronectin and preserves integrin-binding motifs essential for adhesion and cytoskeletal organization (Webb et al., 1998). PLA plain exhibited a low contact angle (35°) and complete droplet absorption within 70s, indicating high hydrophilicity. PLA–PCL plain showed moderate hydrophobicity (98°) with delayed absorption over several minutes. In contrast, the sateen weave displayed pronounced hydrophobicity (131°), with minimal droplet spread and no measurable absorption over the observation period.

Constructional parameters for each weave structure, including weft densities, fabric thickness and cover factor were also measured for the different types of weaves (Table 1). Generally, fabrics with lower cover factors, such as PLA-PCL Plain Weave (43.77%), have more open area, while higher cover factors, like Broken Twill (75.37%) and Sateen (64.99%), indicate denser woven structures that enhance mechanical stability and limit permeability. Cover factor is calculated based on the yarn density and diameter in both the warp and weft directions, representing the proportion of fabric surface covered by yarns.

The lower tightness of the PLA–PCL plain weave compared with PLA plain, despite identical loom settings, is attributed to differences in yarn properties. The additional PCL sheath likely deformed differently under loom beat-up motion, producing slightly larger inter-yarn spacing. This variation may have influenced surface roughness and pore geometry (Figure 4C) and is considered in interpreting scaffold morphology and function.

Biocompatibility is a key component for any scaffold used for tissue engineering and regenerative medicine applications. While PCL and PLA are widely recognized for their cytocompatibility and clinical potential (Woodruff and Hutmacher, 2010; Santoro et al., 2016), scaffold architecture can also markedly influence cell organisation. Surface topography, fibre arrangement, and pore geometry can affect cell adhesion, viability, and proliferation (Dalby et al., 2007; Anselme, 2000). Here, we evaluated how different weave structures have the capacity to support cell viability and metabolic activity across multiple cell types, recognising that both morphological and topographical cues can modulate cellular responses. The three-dimensional yarn architecture and through-thickness pores of the woven scaffolds produced complex surface topographies and multiple focal planes, which, in combination with the specific weave pattern, influenced cell organisation. Cells were frequently observed bridging yarn intersections or extending into the scaffold volume, resulting in organisation patterns that varied with the underlying weave geometry. Due to the intricacy of these architectures, conventional two-dimensional coverage measurements were not applied, as they may misrepresent cellular arrangement in such structures. Instead, qualitative fluorescence microscopy was used to evaluate cell viability and morphology, as indicators of functional organisation. LIVE/DEAD staining at days 1, 4, and 7 confirmed consistently high viability on all scaffolds (Figures 5A,B). HUVECs and HOeSMCs showed distinct attachment patterns depending on weave and fibre type. In PLA plain weaves, HUVECs and HOeSMCs exhibited a relatively uniform spatial distribution along both warp and weft yarns. In contrast, PLA–PCL plain weaves showed a more pronounced yarn-dependent pattern, with live cells preferentially located on warp yarns and fewer on the PCL nanofibre-sheathed weft. This likely reflects reduced adhesion to PCL-rich regions, where the dense nanofibrous sheath limits infiltration, compared to the open, porous PLA multifilament core, which frequently supported cell ingrowth. In more complex patterns, twill, broken twill, and shadow twill patterns showed less uniform cell arrangements. For HUVECs, which tended to be clustered in flatter regions between yarn intersections, suggesting preferential attachment to these areas over more elevated or irregular topographies. HOeSMCs, by comparison, generally aligned along the yarn axis across all weaves, with orientation changes observed at yarn intersections, reflecting adaptation to local surface geometry. Sateen weaves promoted more linear alignment along the weft, but showed reduced cell attachment during early culture, especially for HUVECs. Cell morphology and organisation were assessed using phalloidin staining of actin filaments (Figure 5C). Cell alignment and organisation were influenced by both fibre type and weave pattern. PLA multifilament yarns encouraged alignment along the filament axis and enabled infiltration between filaments (Figures 5Ci–iv), with phalloidin staining revealing continuous actin filaments spanning between neighbouring cells, indicative of close contact and suggesting the potential for network formation, while PCL nanofibre sheaths appeared to support more random, surface-level spreading, consistent with their smaller pores and lack of a dominant fibre orientation (Figure 5Cv-viii). Metabolic analysis and cell growth differences were also observed in cells seeded on different weave types. Increased metabolic activity was observed over 14 days for all cell types, with PLA plain weaves consistently showing the highest values by day 14. PLA–PCL plain and shadow twill supported moderate activity, while sateen and broken twill started with lower levels but also increased over time (Figure 5D). In SMC cultures, some weave types, particularly PLA plain, showed significantly higher metabolic activity (p < 0.05), whereas differences among HUVECs were less pronounced. Proliferation assessed via PicoGreen assay was consistent with metabolic activity as proliferation was observed to increased significantly on PLA plain (p < 0.001), with HUVECs, HOeSMCs, and HDFs showing the highest proliferation. PLA-PCL plain showed a moderate increase (p < 0.05). Twill and sateen had lower DNA content, suggesting it was less able to promote proliferation compared to other type of weaves (Figure 5E). Nonetheless, all scaffold types supported high cell viability and metabolic activity, confirming their overall cytocompatibility.