Preparation of three-dimensional multilayer ECM-simulated woven/knitted fabric composite scaffolds for potential tissue engineering applications

Abstract

The extracellular matrix (ECM), with its multilayer fiber structure, regulates diverse functions including cell proliferation, migration, differentiation and tissue regeneration effects. To mimic and replace the native ECM, the structures and properties of three single-layer fabric substrates including warp/weft-knitted and woven fabrics were analyzed, then two-layer warp/weft-knitted composite fabrics prepared by polyurethane (PU) bonding, and woven composite fabrics prepared by polycaprolactone (PCL)/collagen solution bonding or PU bonding, were studied. After PCL/collagen solution bonding or PU bonding, properties such as pore diameter, air permeability, stress and the contact angle of composite fabrics decreased by some degree, while fiber diameter, thickness and the thermal conductivity of composite fabrics increased. In combination with fiber diameter, pore diameter and physical properties, we know that warp- or weft-knitted composite fabrics are ideal scaffolda for potential applications in nerve, myocardium and tendon tissue engineering.

Keywords

ECM fabrication materials multilayer composite fabric properties

The extracellular matrix (ECM), with its multilayer structure, and chondrocytes varying in organization and phenotype with depth from the articular surface, is responsible for governing the functional properties of tissues.¹ The ECM of cardiac tissue has a fibrous structure that varies in collagen alignment throughout the left ventricle wall to the heart muscle.² The structure of the ECM can interact with cells and regulate diverse functions, including cell proliferation, migration, differentiation and tissue regeneration.³

The field of tissue engineering has two major motivations: (a) to grow cells in constructs for replacement of organs and (b) to create experimental models of tissues (ultimately of organs and animals) for in vitro studies (e.g. in drug development, toxicology, pharmacokinetics and radiation biology), which could replace more expensive and more complex in vivo models.⁴ Development of three-dimensional (3D) scaffolds aims to simply mimic and replace the native ECM, allowing the diffusion of nutrients, metabolites and soluble factors by controlling pore size and morphology, porosity, mechanical properties, surface properties and biodegradability for the initiation of tissue regeneration upon cell seeding.⁵

To be clinically effective, synthetic environments with biomaterials must replicate, as closely as possible, the main characteristics of the native ECM at a cellular and subcellular scale.⁶ Synthetic or natural biomaterials are commonly utilized to provide mechanical support, and 3D environments for cellular growth and function.⁷ The pore sizes of scaffolds are optimized to regulate cell binding, migration and ingrowth, and large pores allow effective nutrient supply, gas diffusion and metabolic waste removal, but can also lead to low cell attachment and intracellular signaling, while small pores do the opposite.⁸ All these properties are important for scaffolds, and by utilizing cell-laden ﬁbers during the assembly process, cellular distribution can be finely controlled.⁷

Researchers have tended to focus on the design of electrospun biodegradable multilayer scaffolds that involve varying either the polymer type or constructional properties in each layer, which, in turn, have revealed the importance of layer interactions and their composite effects on the final multilayer grafts.⁹ For example, Enis et al. described the fabrication of biodegradable single-layer tubular scaffolds from polycaprolactone and poly-L-lactide caprolactone polymers composed of either randomly distributed or, preferably, radially oriented fibers.⁹ Histological evaluation of the 3D printing scaffold revealed a tri-layered structure consisting of distinct epithelial, connective tissue and bone layers, replicating normal oral tissue architecture to closely simulate the native oral hard and soft tissues.¹⁰

Other methods have also been reported for the preparation of scaffolds to simulate ECM. A microfluidic device generated submillimetre hollow hydrogel spheres, encapsulating cells and coated internally to reconstitute the ECM.¹¹ Polyelectrolyte multilayer assemblies of silicon-carbonated hydroxyapatite nanopowders and collagen type I were used to enhance cell–material interactions.¹² Polyethylene terephthalate yarns were used to produce an expandable warp-knitted synthetic hybrid fabric (SHF), the SHF exhibited satisfactory tensile and suture retention strength for surgical implantation, and inflammatory reactions were minimal with no calcium deposition.¹³ However, the ability of these approaches to achieve precise control over the spatial distribution of pore size and interconnectivity, and mechanical and structural properties has been limited.⁷

The effect of specific surface area has been overcome in larger pores due to the importance of cell migration and proliferation, as has been seen histologically in scaffolds. Larger pores reduce cell aggregations along the edges of the scaffold, and promote cell proliferation and migration into the center of the scaffold; the smallest pores show both reduced cell attachment and the poorest rate of cell migration.¹⁴ Increasing cell viability with decreasing pore size would not be expected to continue as pore size would eventually drop to the point where cells could no longer fit into the pores, and a linear relationship has been found between cell attachment and specific surface area indicating that, over the range of pore sizes studied (95.9–150.5 µm), short-term osteoblast MC3T3 cell viability is governed by the specific surface area available for binding.¹⁵ If pores are too small cell migration is limited, resulting in the formation of a cellular capsule around the edges of the scaffold, which can limit the diffusion of nutrients and removal of waste, resulting in necrotic regions within the construct.¹⁴

Textile technologies have recently attracted great attention as potential biofabrication tools for the engineering of tissue constructs, as fibrous porous structures could be designed and engineered to attain the required properties to simulate the ECM for tissue engineering applications, such as the physiochemical characteristics of fibers, microarchitecture and mechanical properties of the fabrics such as knitting, weaving and braiding of fabrics.¹⁶ Anisotropic mechanical properties of scaffolds could lead to precise control over the distribution of different cell types within their constructs.¹⁷

Fabric scaffolds and their composites have been studied. For example, Gao et al.¹⁸ prepared polylactic acid/tussah silk ﬁbroin electrospun nanoﬁber woven multilayer fabrics and then used mineralization to obtain composite scaffolds; biological assay results showed that the mineralization and multilayer fabric structures signiﬁcantly increased cell adhesion and proliferation, and enhanced mesenchymal stem cell diffrentiation toward osteoblasts. Wu et al.¹⁹ produced a novel composite scaffold consisting of nano- and micro-scale fibrous woven fabrics and 3D hydrogels, to improve mechanical strength, physical structural anisotropy and support the growth of human aortic valve interstitial cells for the maintenance of valve cell phenotypes. Ribeiro et al.²⁰ manufactured silk fibroin/polyethylene terephthalate weft-knitted space composite fabrics with homogeneous pore distribution and storage modulus values, higher angiogenic effects and tissue ingrowth for bone regeneration applications. Nemoto et al.¹³ made a composite warp-knitted fabric composed of poly-L-lactic acid and polyethylene terephthalate yarns, after which the fabric was cross-linked with gelatin to induce smooth muscle cell tissue connections containing vasa vasorum across the patch in the aorta and inferior vena cava. While the preparation method of multilayer composite fabric scaffolds in our research were different from mineralized electrospun nanoﬁber woven multilayer fabrics, woven fabric/3D hydrogel composite scaffolds, weft-knitted space composite fabrics and warp-knitted fabrics cross-linked with gelatin, it was able to simulate the multilayer structure of the ECM and regulate fiber diameter, pores and physical properties for potential tissue engineering applications.

In this paper, to mimic and replace the multilayer structure of the native ECM, the structures and properties of three single-layer fabric substrates including warp/weft-knitted fabric and woven fabrics were analyzed first, then two-layer warp/weft-knitted composite fabrics were prepared by polyurethane (PU) bonding, and woven composite fabrics prepared by polycaprolactone (PCL)/collagen solution bonding or PU bonding, were studied.

Experiments

Substrates

Three different polyester scaffold substrates of woven, weft-knitted and warp-knitted fabrics were provided from Foshan Nanhai Danming Fabric Company, Dongguan Lichun Textile Co. Ltd and Zhejiang Yiyang New Materials Co., Ltd, respectively. The substrates were plain weave fabric, plain knitted fabric and queenscord stitch composite warp-knitted fabric, respectively.

Preparation of two-layer composite fabric scaffolds

According to the method of Feng²¹ and the preparation of PCL/collagen solution by Middleton et al.,²² 0.8 g PCL (Shenzhen Esun Industrial Co., Ltd) and 0.8 g collagen (Shanghai Makclin Biochemical Co., Ltd) were simultaneously put into 20 mL hexafluoroisopropanol (Hangzhou Hete Chemical Technology Co., Ltd) to produce 8% (v/w) solvent. A brush was completely dipped into the solution and brushed gently onto the woven fabric surface in the manner of coating, then the other woven fabric without solvent was covered by plating and dried naturally to prepare the two-layer woven composite fabric scaffold (shortened to woven fabrics+PCL/collagen). In such cases, bioadhesive PU (Shanghai Jiaheng Chemical Co., Ltd) was directly used to prepare three different composite fabric scaffolds: woven fabrics+PU (woven composite fabric), warp-knitted fabrics+PU (warp-knitted composite fabric) and weft-knitted fabrics+PU (weft-knitted composite fabric) in a process similar to that described above for woven fabrics+PCL/collagen (Figure 1).

Figure 1.

Schematic diagram of preparation of the composite fabric scaffold.

Characterization

Macroscopic surface topographies of samples were observed by DXS-10 optical microscope (OM, China) at a size of 7 × 7 cm². The JFC-1600 sputtering apparatus was used to gold plate small samples for 50 s, then surfaces and cross-sectional morphologies of samples 0.25 cm² in size were characterized by JSM-5610LV scanning electron microscope (SEM, Japan).

Measurement of fiber diameter and pore diameter was conducted as described in our previous papers.^23–25 Thickness was measured by a YG141D digital thickness gauge under the condition of 200 cN weight and 10 s time. Air permeability of scaffolds was measured by a YG461E permeability tester at 20 cm² size and 200 Pa pressure. The static water contact angle of sample (5 × 2 cm, length × width) was measured by a contact angle measuring system (Krüss, Germany) with 2 µL deionized water. An Instron 3367 mechanical universal testing machine, manufactured by the American Instron company, was used to measure warp direction stress and strain at the breaking point under 100 mm/min speed and 10 × 4 cm² clamping size. Conductivity properties was characterized by DM3068 digital multimeter (Beijing RIGOL electric technology Co. Ltd, China) at a size of 10 × 10 cm². Heat conduction properties were measured by a TPS2500S Thermal Constant Analyzer (Hot Disk Company, Sweden) with 14.67 mm probe radius, 600 mW heating power and 80 s test time.

Statistical analysis

The experimental data were expressed as mean ± standard deviation, and the significant differences between groups were analyzed by using one-way analysis of variance (ANOVA) using Origin 8.0 software. The statistical significance was set as p < 0.05 and p < 0.01.

Results and discussion

Surface morphology

Preparation of the two-layer composite fabric scaffolds is shown in Figure 1. Woven fabric is very well arranged and has a compact structure, with the pores barely visible in such an alternating arrangement. There were many short fiber ends on the surface of the weft-knitted fabric, and there were also some elongated pores in this knitted structure. The warp-knitted fabric has a flat surface with no short filaments and a well-proportioned pore structure (Figure 2). In the plain woven fabric, each weft passed over one warp then under the following warp, in the weft-knitted fabric stitches from the same yarn were arranged horizontally, while in the warp-knitting fabric stitches from the same yarn were arranged vertically.⁷

Figure 2.

(a) Woven, (b) weft-knitted and (c) warp-knitted fabrics. (d), (e) and (f) show their corresponding images taken by scanning electron microscope.

In Figure 3, the fiber surface is relatively smooth and the fiber bundle has a relatively stable shape enabling it to form a porous structure. For the woven fabric, the yarn is intersected to generate a micropattern with straight line topography. In contrast, for the weft- and warp-knitted fabrics, buckling of the yarns forms a looped arrangement and a porous structure. The versatilities of the textile structures enabled their architectures to be tailored by controlling the fiber size and orientation, pore size and geometry, pore interconnectivity, total porosity and surface topography.⁷

Figure 3.

Scanning electron microscope images of (a) woven fabric, (b) and (c) weft-knitted fabric, and (d) warp-knitted fabric. Optical microscope images of (e) warp-knitted fabric and (f) weft-knitted fabric. (g) Lapping diagram and (h) loop structure of warp-knitted fabric.

When two-layer woven fabrics were bonded by PCL/collagen solution (Figure 4(a) 1–2), a slightly flat and compact structure formed and a porous film appeared on the fiber surface. We also attempted to use PCL/collagen solution to prepare a knitted fabric composite scaffold; however, the bonding effect was not ideal in the case of large porosity, missing solvents and poor bonding effects. In such situations, three different composite fabric scaffolds, like woven, warp- and weft-knitted fabrics, were produced by bioadhesive PU bonding (Figure 4(a)3, (b)1–3 and (c)1–3). It could be found that the PU bonding topographies of the three scaffolds were similar regarding porous structure and basic fiber morphology, but were obviously different from the PCL/collagen bonding topography. After being subjected to the same pressure force, the topographies of fibers in the woven fabric were compact with small pores, while the warp- and weft-knitted fabrics appeared to have a porous structure between fibers and layers. PU adhesive could stay on the surface or infiltrate into the pores of the warp-knitted fabric, leading to smaller and fewer pores in comparison to the weft-knitted fabric.

Figure 4.

Scanning electron microscope images of ((a)1 and 2) woven fabrics + polycaprolactone/collagen, ((a)3) woven fabrics+polyurethane, ((b)1–3) weft-knitted fabrics + polyurethane and ((c)1–3) warp-knitted fabrics+polyurethane.

Cross-sectional morphology

The differences in surface topography were obvious, and complete fiber morphologies, and stable and uniform internal structures can be seen in Figure 5. However, the internal morphologies of the woven fabric and the warp/weft-knitted fabrics were different, and the woven composite fabric produced a more compact structure regarding minor pores. Textile fabrics have some advantages, such as high flexibility and an ability to create 3D complex structures for knitted fabrics, and woven fabrics have the ability to create constructs with anisotropic properties such as low porosity and less flexibility.⁷

Figure 5.

Cross-sectional scanning electron microscope images of ((a)1 and 2) woven fabrics+polycaprolactone/collagen, ((b)1–3) woven fabrics + polyurethane, ((c)1–3) weft-knitted fabrics + polyurethane (weft-knitted composite fabric) and ((d)1–2) warp-knitted fabrics + polyurethane (warp-knitted composite fabric).

Structural and physical properties of substrates

Comparison of fiber diameter, pore diameter, thickness, air permeability, contact angle, stress–strain, electrical conductivity and temperature–time relationship of single-layer fabric substrates is shown in Figure 6. Fiber diameters of warp-knitted, weft-knitted and woven fabrics were 15.38 ± 1.09, 11.87 ± 0.38 and 8.33 ± 0.47 µm, respectively. Pore diameters of the three fabric substrates were 145.29 ± 52.76, 194.17 ± 69.59 µm and 5.46 ± 2.64 µm, respectively. Weft-knitted fabric had a larger pore diameter and smaller fiber diameter than the warp-knitted fabric (p < 0.01), and woven fabric had the smallest fiber diameter and pore diameter (p < 0.01), which is consistent with the results reported by Akbari et al.⁷

Figure 6.

Characterization of single-layer fabric scaffolds. (a) Fiber diameter (N = 20), (b) pore diameter (N = 20), (c) thickness (N = 3), (d) air permeability (N = 3), (e) contact angle (N = 3), (f) stress–strain curve, (g) stress (N = 3), (h) electrical conductivity (N = 3) and (i) temperature–time relationship (N = 3). * and ** denote signiﬁcant difference at the p < 0.05 and p < 0.01 level, respectively.

The thickness and air permeability of the weft-knitted fabric were larger than for the warp-knitted and woven fabrics (p < 0.01), and the variation in air permeability was due to its smaller fiber and larger pore diameters. Macro pores gave real correlation with air permeability by taking in account all of characteristics of pores that participated in loose energy, i.e. the lengths of pores, structure, tortuosity and bottle necks.²⁶

Contact angles of woven and weft-knitted fabrics were 61.60 ± 3.42° and 128.05 ± 1.42°, respectively. The value for the woven fabric was similar to that reported in the study by Wang et al.,²⁷ in that the fabric possessed a partial hydrophilic property because of chemical groups in its pore structures. The droplets penetrated into the internal pores of the warp-knitted fabric showing no value.

It could be seen from the stress–strain curve that stress on the warp-knitted, weft-knitted and woven fabric was 29.14 ± 1.91, 33.03 ± 0.40 and 149.07 ± 7.43 MPa, respectively. The woven fabric had the largest amount of stress (p < 0.01) due to its small pores and compact structure. Knitting creates structures by intertwining yarns or threads in a series of connected loops in 2D or 3D complex patterns; such structures can provide mechanical strength both in- and across-plane.²⁸

There was no significant difference in electrical conductivity among the samples, because polyester fibers in the fabrics were basically non-conductive in the case of large resistance. The sequence of thermal conductivity (weft-knitted fabric > warp-knitted fabric > woven fabric), was basically around 0.05, which is a low value for polyesters.

Structure and physical properties of composite scaffolds

Comparisons of fiber diameter, pore diameter, thickness, air permeability, contact angle, stress–strain, electrical conductivity and temperature–time relationship of the composite fabric scaffolds are shown in Figure 7. Fiber diameter of fabrics before and after adhesion varied in different degrees, warp-knitted fabric (15.38 ± 1.09 µm vs 15.53 ± 1.48 µm), weft-knitted fabric (11.87 ± 0.38 µm vs 12.00 ± 0.58 µm) and woven fabric (8.33 ± 0.47 µm vs 7.46 ± 0.87 µm for PCL/collagen and 8.33 ± 0.47 µm vs 10.48 ± 0.79 µm for PU). The fiber diameter of fabrics bonded by PU had some increases as a result of solvent attached to fibers, while showed a decrease for PCL/collagen bonding in case of some fibers were dissolved by solvent.

Figure 7.

Properties of composite fabric scaffolds. (a) Fiber diameter (N = 20), (b) pore diameter (N = 3), (c) thickness (N = 3), (d) air permeability (N = 3), ((e) and (f)) contact angle (N = 3), (g) stress–strain curve, (h) stress (N = 3), (i) electrical cinductivity (N = 3) and (j) temperature–time relationship (N = 3). * and ** denote signiﬁcant difference at p < 0.05 and p < 0.01, respectively.

Pore diameter of four two-layer composite fabrics was 1.78 ± 0.77 µm, 3.94 ± 1.39 µm, 94.83 ± 32.30 µm and 192.50 ± 19.50 µm, respectively, showing some degrees of decrease in comparison with their corresponding single layer fabric substrate, in which weft-knitted composite fabric had larger pore diameter among them (p < 0.01).

Thickness of four composite fabrics had significant differences (p < 0.01), showing values of composite fabric were larger than its corresponding single-layer fabric, in which weft-knitted fabric possessed the maximum result.

Air permeability of composite fabrics decreased after solvent bonding and weft-knitted composite fabric had larger values than other fabrics (warp/weft-knitted composite fabric vs woven composite fabric at p < 0.01, warp-knitted composite fabric vs weft-knitted composite fabric at p < 0.05 and p > 0.01). Variation of air permeability was consistent with pore diameter that larger pore diameter could produce bigger air flow.

Weft-knitted composite fabric possessed larger contact angle than other composite fabrics (p < 0.01), water droplets morphology appeared onto surface of warp-knitted fabric in the case of decreased pore diameter to retain water droplet.

Stress of warp-knitted composite fabric, weft-knitted composite fabric and woven composite fabric was 28.02 ± 3.34 MPa, 17.92 ± 0.40 MPa, 76.58 ± 16.94 MPa (for PCL/collagen) and 91.86 ± 11.84 MPa (for PU), respectively. For the same woven fabric, PU adhesive bonding effect was better than PCL/collagen solvent. Woven composite fabric had the largest stress among them (p < 0.01) in case of small pores and compact structure, which was similar to the variation of substrate fabric. We found that mechanical properties of two-layer composite fabrics did not improve significantly after lamination, mainly due to the interlamination slip and no complete fracture only separation between layers in the stretching.

There was no significant difference in electrical conductivity except two woven composite fabrics, because polyester fibers in fabrics were basically non-conductive in the case of large resistance. The sequence of thermal conductivity was weft-knitted composite fabric > warp-knitted composite fabric > woven composite fabric, and values were basically around 0.0005 μA in a low thermal conductivity of polyesters, which was similar to comparison results of substrate fabrics in front.

Discussion

Micro/nanofibrous structures have been applied widely in various tissue engineering applications because the topological structures are similar to the ECM, which encourages a high degree of cell adhesion and growth via a multilayered fibrous scaffold.²⁹ The natural ECM, which consists of a complex microfibril physical structure and various proteins, has several functions; it provides physical support to cells, supplies various bioactive cues that modulated cell proliferation and differentiation, and produces a flexible physical environment that enables vascularization and new tissue formation by tissue dynamic processes.³⁰

Different from Messori’s research,³¹ in this paper, the structures and properties of three single-layer fabric substrate, including warp/weft-knitted and woven fabrics, were analyzed first, then two-layer warp/weft-knitted and woven composite fabrics were prepared to simulate the multilayer structure of the ECM (Figure 8). The fiber diameter, pore diameter, thickness, air permeability, contact angle, stress–strain, electrical conductivity and temperature–time relationships of the of single-layer fabric substrates and two-layer composite fabrics were studied.

Figure 8.

Three-dimensional multilayer extracellular matrix-simulated composite fabric scaffolds.

Significant advances have been made in the development of polymeric materials for biomedical applications. Synthetic biomaterials are generally biologically inert, have more predictable properties and batch-to-batch uniformity advantages, and are devoid of many of the disadvantages of natural polymers.³² Typical synthetic polymers used in biomedical applications are hydrophobic polyesters.³³ Nemoto et al.¹³ developed a new warp-knitted fabric made of polyester yarns exhibiting sufficient mechanical properties for safe surgical implantation and avoidance of deformity in canine aorta, and in situ vascular tissue regeneration was achieved with favorable integration in pediatric congenital cardiac surgery. With reference to these results, this study also used polyester fiber scaffolds.

As for the three single-layer fabric substrates, we had a limited number of options from which to choose the fabrics. Single-layer woven fabric has a smaller fiber diameter, pore diameter, thickness, air permeability, contact angle and thermal conductivity, yet can take greater stress in comparison with warp/weft-knitted fabric. Weft-knitted composite fabric possesses greater pore diameter, thickness, air permeability, contact angle and thermal conductivity than warp-knitted and woven composite fabrics, while the electrical conductivity of these four composite fabrics had no obvious difference. Variations of composite fabric properties were similar to those of single-layer fabric substrates, in a way that was determined by the structures and properties of the single-layer fabrics.

After PCL/collagen or PU bonding, pore diameter, air permeability, stress and contact angle had some degrees of decrease while fiber diameter caused by PU bonding, thickness and the thermal conductivity of the composite fabrics increased. Electrical conductivities of the single-layer fabric substrates and composite fabrics were so small that there were no significant differences.

The single-layer woven fabric substrate and its composite fabric had the largest stress among these four composite fabrics. The structure generated from weaving technique is stronger and exhibits higher dimensional stability compared to knitted fabrics. Knitted textile substrates are more extensible and compliant than their woven and knitted counterparts, and possess remarkably higher porosity and relatively reduced thickness compared to woven scaffolds.³⁴ In the weaving technique, warps and wefts interweave into each other at right angles to generate a textile structure with controlled morphology, and physical and mechanical properties.³⁴ As a result, the pore diameters of woven composite fabrics are so small that cells may have difficulty in migrating and growing into the scaffold, while composite warp/weft-knitted fabrics do not have this problem.

The compositions, mechanical properties, surface topographies and 3D geometrical features of biomaterials may provide bioactive cues that act together to synergistically regulate cell behaviors and guide tissue/organ development, and mechanical information that may modulated cell proliferation by activating mitogenic signaling pathways.³⁵ For different tissue engineering applications, such as articular cartilage, tendons and ligaments, vascular grafts, anterior cruciate ligaments and bone, tensile stresses of woven/knitted fabric scaffolds were 67–85 MPa, 97.2 N, and 3.3–5.4, 1.07–19.3 and 1.7-4.1 MPa, respectively.²⁸ In our study, woven composite fabric (76.58 ± 16.94 MPa and 91.86 ± 11.84 MPa) had larger stress than composite warp/weft-knitted fabric (28.02 ± 3.34/17.92 ± 0.40 MPa) in the case of different fiber diameters, pore diameters and thickness. Moreover, the stresses of woven composite and warp/weft-knitted fabrics were larger than in a previous report.²⁸ In combination with fiber diameter, pore diameter and other physical properties, especially mechanical properties, we know that composite warp- or weft-knitted fabrics are more suitable for potential applications in tissue engineering.

Conclusions

To mimic and replace the native multilayer structure of the ECM, three different single-layer fabric substrates, including warp/weft-knitted and woven fabrics, were ananlyzed first and then used to prepare two-layer composite fabric scaffolds. After PCL/collagen solution bonding or PU bonding, the pore diameter, air permeability, stress and contact angle of warp/weft-knitted and woven fabric composite scaffolds all decreased to some degree, while the fiber diameter of composite scaffolds prepared by PU bonding, and the thickness and thermal conductivity of composite scaffolds prepared by PCL/collagen solution or PU bonding increased. Through comparison of the structures and properties of the composite scaffolds, the resulted indicated that warp- or weft-knitted fabric composite scaffolds had relatively ideal pore strutures and physical properties, could effectively simulate the ECM and may have potential applications in nerve, myocardium and tendon tissue engineering.

Footnotes

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship and/or publication of this article.

Funding

The authors disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This project was financially supported by Zhejiang Sci-Tech University Scientific Research Project (Grant No. 16012055-Y), the Key Laboratory of Advanced Textile Materials and Manufacturing Technology (Zhejiang Sci-Tech University), Ministry of Education (Grant No. 2016QN06), Zhejiang Sci-Tech University (Engineering Research Center of Clothing of Zhejiang Province) (Grant No. 2018FZKF07), The Open Project Program of Key Laboratory of Eco-textiles, Ministry of Education, Jiangnan University (Grant No. KLET1711), Fujian Key Laboratory of Novel Functional Textile Fibers and Materials, Minjiang University (Grant No. FKLTFM1817), and the State Key Laboratory of Molecular Engineering of Polymers, Fudan University (Grant No. K2019-04).

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