The design trend in tissue-engineering scaffolds based on nanomechanical properties of individual electrospun nanofibers (original) (raw)
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Journal of the Mechanical Behavior of Biomedical Materials, 2016
Electrospun nanofibers are a promising material for ligamentous tissue engineering, however weak mechanical properties of fibers to date have limited their clinical usage. The goal of this work was to modify electrospun nanofibers to create a robust structure that mimics the complex hierarchy of native tendons and ligaments. The scaffolds that were fabricated in this study consisted of either random or aligned nanofibers in flat sheets or rolled nanofiber bundles that mimic the size scale of fascicle units in primary tensile bearing soft musculoskeletal tissues. Altering nanofiber orientation and geometry significantly affected mechanical properties; most notably aligned nanofiber sheets had the greatest modulus; 125% higher than that of random nanofiber sheets; and 45% higher than aligned nanofiber bundles. Modifying aligned nanofiber sheets to form aligned nanofiber bundles also resulted in approximately 107% higher yield stresses and 140% higher yield strains. The mechanical properties of aligned nanofiber bundles were in the range of the mechanical properties of the native ACL: modulus = 158 ± 32 MPa, yield stress = 57 ± 23 MPa and yield strain = 0.38 ± 0.08. Adipose derived stem cells cultured on all surfaces remained viable and proliferated extensively over a 7 day culture period and cells elongated on nanofiber bundles. The results of the study suggest that aligned nanofiber bundles may be useful for ligament and tendon tissue engineering based on their mechanical properties and ability to support cell adhesion, proliferation, and elongation.
Mechanical enhancement of nanofibrous scaffolds through polyelectrolyte complexation
Nanotechnology, 2013
Optimization of mechanical properties is required in applications of tissue-engineered scaffolds. In this study, a polyelectrolyte complexation approach is proposed to improve the mechanical properties of the nanofibrous scaffolds. Through an electrospun chitosan/gelatin (CG) model system, it is demonstrated that the storage modulus of CG nanofiber-based complex membranes is over 10 3 -fold higher than that of neat chitosan or gelatin membranes. Further, an annealing process was found to promote the conjugation of the oppositely charged polymers and thus the tensile modulus of CG membranes is 1.9-fold elevated. When the molar ratio of aminoglucoside units in chitosan to carboxyl units in gelatin is 1:1, the complex nanofiber-based membranes (CG2) display the highest mechanical strength. In addition, the complex membranes reveal an excellent swelling capacity. By comparing the CG membranes electrospun with cast, it is deduced that the complexation is one of the main contributing factors to the improvement in mechanical properties. FTIR and DSC analyses confirm that more molecular interactions took place in the complexation. SEM observation clearly displays the electrospinnability of the complex. Therefore, polyelectrolyte complexation is an effective strategy for enhancing mechanical properties of nanofibrous scaffolds. These mechanically enhanced chitosan/gelatin nanofibrous membranes have wider applications than wound dressing.
The mechanical stress–strain properties of single electrospun collagen type I nanofibers
Acta Biomaterialia, 2010
Knowledge of the mechanical properties of electrospun fibers is important for their successful application in tissue engineering, material composites, filtration and drug delivery. In particular, electrospun collagen has great potential for biomedical applications due to its biocompatibility and promotion of cell growth and adhesion. Using a combined atomic force microscopy (AFM)/optical microscopy technique, the single fiber mechanical properties of dry, electrospun collagen type I were determined. The fibers were electrospun from a 80 mg ml À1 collagen solution in 1,1,1,3,3,3-hexafluro-2-propanol and collected on a striated surface suitable for lateral force manipulation by AFM. The small strain modulus, calculated from threepoint bending analysis, was 2.82 GPa. The modulus showed significant softening as the strain increased. The average extensibility of the fibers was 33% of their initial length, and the average maximum stress (rupture stress) was 25 MPa. The fibers displayed significant energy loss and permanent deformations above 2% strain.
Mechanical Considerations for Electrospun Nanofibers in Tendon and Ligament Repair
Advanced healthcare materials, 2018
Electrospun nanofibers possess unique qualities such as nanodiameter, high surface area to volume ratio, biomimetic architecture, and tunable chemical and electrical properties. Numerous studies have demonstrated the potential of nanofibrous architecture to direct cell morphology, migration, and more complex biological processes such as differentiation and extracellular matrix (ECM) deposition through topographical guidance cues. These advantages have created great interest in electrospun fibers for biomedical applications, including tendon and ligament repair. Electrospun nanofibers, despite their nanoscale size, generally exhibit poor mechanical properties compared to larger conventionally manufactured polymer fiber materials. This invites the question of what role electrospun polymer nanofibers can play in tendon and ligament repair applications that have both biological and mechanical requirements. At first glance, the strength and stiffness of electrospun nanofiber grafts appea...
Current approaches to electrospun nanofibers for tissue engineering
Biomedical Materials, 2013
The ultimate goal of tissue engineering is to replace damaged tissues by applying engineering technology and the principles of life sciences. To successfully engineer a desirable tissue, three main elements of cells, scaffolds and growth factors need to be harmonized. Biomaterial-based scaffolds serve as a critical platform both to support cell adhesion and to deliver growth factors. Various methods of fabricating scaffolds have been investigated. One recently developed method that is growing in popularity is called electrospinning. Electrospinning is known for its capacity to make fibrous and porous structures that are similar to natural extracellular matrix (ECM). Other advantages to electrospinning include its ability to create relatively large surface to volume ratios, its ability to control fiber size from micro-to nano-scales and its versatility in material choice. Although early work with electrospun fibers has shown promise in the regeneration of certain types of tissues, further modification of their chemical, biological and mechanical properties would permit future advancements. In this paper, current approaches to the development of modular electrospun fibers as scaffolds for tissue engineering are discussed. Their chemical and physical characteristics can be tuned for the regeneration of specific target tissues by co-spinning of multiple materials and by post-modification of the surface of electrospun fibers. In addition, topology or structure can also be controlled to elicit specific responses from cells and tissues. The selection of proper polymers, suitable surface modification techniques and the control of the dimension and arrangement of the fibrous structure of electrospun fibers can offer versatility and tissue specificity, and therefore provide a blueprint for specific tissue engineering applications.
Electrospun of polymer/bioceramic nanocomposite as a new soft tissue for biomedical applications
Journal of Asian Ceramic Societies, 2015
Iranian Gum Tragacanth (IGT) is among the most natural polymers which has interesting properties such as nontoxic nature, biodegradability and high resistance to bacterial attacks making it applicable for tissue scaffolds, protective clothing, and wound healing. In the current work, polyvinyl alcohol (PVA)/IGT nanocomposite fibre is prepared by using the electrospinning (ELS) technique in an aqueous solution with different volume ratios of 60/40, 70/30, 80/20, and 90/10. To enhance the chemical and mechanical stability of the produced samples, different amounts of nanoclay powder (1% and 3%) are added also to the solution. The blended nanofibres are characterized by scanning electron microscopy (SEM), Fouriertransform infrared (FTIR), and bioactivity evaluation in phosphate buffered saline (PBS) and simulated body fluid (SBF) solutions. The FTIR analysis indicated that PVA and IGT may have H + bonding interactions. The results revealed that with a higher amount of IGT, a superior degradation as well as a higher chemical and biological stability could be obtained in the nanobiocomposite blend fibres. Furthermore, the blend nanofibre samples of 80/20 and 3% nanoclay powder exhibit a significant improvement during evaluation of its properties.
Electrospun nanofiber blend with improved mechanical and biological performance
International journal of nanomedicine, 2018
Here, electrospun fibers based on a blend of polycaprolactone (PCL), poly(ethylene glycol) (PEG), and gelatin methacryloyl (GelMA) were developed. The careful choice of this polymer combination allowed for the preparation of a biomaterial that preserved the mechanical strength of PCL, while at the same time improving the hydrophilicity of the blended material and human osteoblast maturation. The morphology, chemical structure, wettability, and mechanical properties before and after UV photocrosslinking were evaluated. Furthermore, human osteoblasts (hFOB) were cultivated for up to 21 days on the scaffolds, and their potential to upregulate cell proliferation, alkaline phosphatase (ALP) activity, and calcium deposition were investigated. Contact angle measurement results showed that the developed scaffolds presented hydrophilic properties after PEG and GelMA incorporation before (25°) and after UV photocross-linking (69°) compared to pure PCL (149°). PCL:PEG:GelMA-UV displayed a slig...
Braided and Stacked Electrospun Nanofibrous Scaffolds for Tendon and Ligament Tissue Engineering
Tissue engineering. Part A, 2017
Tendon and ligament injuries are a persistent orthopedic challenge given their poor innate healing capacity. Nonwoven electrospun nanofibrous scaffolds composed of polyesters have been used to mimic the mechanics and topographical cues of native tendons and ligaments. However, nonwoven nanofibers have several limitations that prevent broader clinical application, including poor cell infiltration, as well as tensile and suture-retention strengths that are inferior to native tissues. In this study, multilayered scaffolds of aligned electrospun nanofibers of two designs-stacked or braided-were fabricated. Mechanical properties, including structural and mechanical properties and suture-retention strength, were determined using acellular scaffolds. Human bone marrow-derived mesenchymal stem cells (MSCs) were seeded on scaffolds for up to 28 days, and assays for tenogenic differentiation, histology, and biochemical composition were performed. Braided scaffolds exhibited improved tensile a...
Polymers, 2018
In this paper, it is shown that pure chitosan nanofibers and films were prepared with success in 0.5 M acetic acid as solvent using poly (ethylene oxide) (PEO) at different yields, allowing electrospinning of the blends. After processing, a neutralization step of chitosan followed by water washing is performed, preserving the initial morphology of chitosan materials. The influence of the yield in PEO in the blend on the degree of swelling and hydrophilicity of films and nanofibers is demonstrated. Then, the mechanical behavior of blended nanofibers and films used as reference are determined for small stress applied in the linear domain by DMA and by uniaxial traction up to rupture. The dried and wet states are covered for the first time. It is shown that the mechanical properties are increased when electrospinning is performed in the presence of PEO up to a 70/30 chitosan/PEO weight ratio even after PEO extraction. This result can be explained by a better dispersion of the chitosan in the presence of PEO.
Electrospun polycaprolactone matrices with tensile properties suitable for soft tissue engineering
Artificial cells, nanomedicine, and biotechnology, 2015
The extracellular environment is a complex network of functional and structural components that impart chemical and mechanical stimuli that affect cellular function and fate. Cell differentiation on three dimensional scaffolds is also determined by the modulus of the substrate. Electrospun PCL nanofibers, which mimic the extra cellular matrix, have been developed with a wide variety of solvents and their combinations. The various studies have revealed that the solvents used influence the physical and mechanical properties, resulting in scaffolds with Young's modulus in the range of 1.8-15.4 MPa, more suitable for engineering of hard tissue like bone. The current study describes the use of benign binary solvent-generated fibrous scaffolds with a Young's modulus of 36.05 ± 13.08 kPa, which is almost 50 times lower than that of scaffolds derived from the commonly used solvents, characterized with myoblast, which can be further explored for applications in muscle and soft tissue...