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An implantable scaffold pre-seeded with cells needs to remain viable and encourage rapid angiogenesis in order to replace injured tissues, especially for tissue defect repairs. We created a bioartificial adipose graft composed of an electrospun 3D nanofibrous scaffold and fat tissue excised from New Zealand white rabbits. Cell viability and angiogenesis potential of the bioartificial substitute were examined during four weeks of culture in Dulbecco's Modified Eagle Medium by immunohistochemical staining with LIVE/DEAD® cell kit and PECAM-1 antibody, respectively. In addition, a Matrigel® assay was performed to examine the possibility of blood vessels sprouting from the bioartificial graft. Our results showed that cells within the graft were viable and vascular tubes were present at week 4, while cells in a fat tissue block were dead in vitro. In addition, capillaries were observed sprouting from the graft into the Matrigel, demonstrating its angiogenic potential. We expect that improved cell viability and angiogenesis in the bioartificial substitute, compared to intact autologous graft, could potentially contribute to its survival following implantation. Copyright © 2012 John Wiley & Sons, Ltd.

Two different techniques were used to fabricate nanoparticle-reinforced nanofibrous scaffolds with different organizations of the minerals. First, a three-dimensional (3D) cylindrical nanofibrous scaffold made of poly- l -lactide and poly( l -lactide)/collagen (1:1) was fabricated using a modified electrospinning method. An alternating dipping method and a flow version of it were used to mineralize the 3D scaffolds. Flow mineralization was found to significantly improve the distribution of the mineral nanoparticles throughout the 3D nanofibrous scaffold, while mineral nanoparticles were found only on the periphery of the static mineralized scaffold. As a result of the mineral nanoparticle distribution, the compressive strength and modulus of the flow mineralized scaffold was found to be significantly greater than that of the static mineralized scaffold, despite having a lower mineral content. Energy-dispersive X-ray analysis and X-ray diffraction studies suggest that the mineral was composed of heterogeneous phases of calcium phosphates. This study demonstrates the importance of hierarchical and deliberate organization of the nanocomponents to optimize the mechanical properties, as is often found in nature.

A new technology based on the liquid support system is introduced for fabricating continuous twisted nanofibrous yarn. In this novel technique, the electrospun yarn was collected from the top of the water vortex such that it can be twisted simultaneously during yarn production. Our study demonstrated the feasibility of the technique for producing continuous twisted yarn from well aligned nanofibers. It is shown that the system can be modified to have different yarn counts with various twists. Further, significant improvement can be seen in the strength and strain when nanofibrous yarn is twisted compared to non-twisted yarn. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers

Nanostructured materials with high aspect ratio and one-dimensional (ID) morphology are nature’s choices when high degree of functional performances and flexible properties are concerned. Two examples are extracellular matrices in tissues of living organism, and light harvesting rods of the retina and chlorophyll. Electrospinning (E-spinning) is a simple processing technique that allows fabrication of high aspect ratio nanofibers (NFs) in a commercial scale. Electrospun nanofibers (E-spun NFs) combine a number of physical properties such as guided electron transport, strain-induced electronic properties, high mechanical strength, high degree of flexibility, large specific surface area, high electron and thermal diffusivity, and tailorable pore distribution. Our laboratory has been involved in fabrication of E-spun polymeric, inorganic, and polymer-nanocomposite fibers in random, aligned, cross-aligned, sheaths, tubes, yarns, core/shell, and trilayer morphologies. This article focuses on application of the E-spun fibers in the areas of clean energy, water treatment, and regenerative medicine in the authors’ laboratory. In addition, the article briefly reviews the progress made in these areas using E-spun NFs.

Nanofibers are ideally suited to form a scaffold where multi-functional components can be hierarchically organized. Development in electrospinning in terms of fiber construction and organization, materials selection and incorporation, and post-spinning modifications have pathed the way for future developments of advanced composite systems. A nanocomposite system with up to five distinct levels of organization can be constructed using electrospun fibers. At the first level is a composite nanofiber. The second level is a second layer of composite material coated over the core composite nanofiber. Surface modification of the nanofiber will give the third level. The fourth level of organization is by arranging the nanofibers to form an assembly. Finally at the last level, the nanofiber assembly can be encapsulated within a matrix or form a bulk structure of a pre-determined shape. Examples of how hierarchically organized multifunctional nanocomposite can be used in healthcare, environmental and defense and security is discussed.

Quick establishment of a confluent and stable endothelial cells (ECs) layer in the lumen of vascular grafts is critical for long-term patency of small-diameter vascular grafts. The objective of the study was to fabricate tubular nanofiber scaffolds, incorporate ECs onto the lumen of the scaffolds, and establish an animal model to prove the basic concept of using the scaffolds as vascular grafts. Poly(L-lactic acid)-co-poly(epsilon-caprolactone) P(LLA-CL 70:30) tubular nanofiber scaffolds were fabricated by electrospinning onto a rotating mandrel. Collagen was coated onto the scaffolds after air plasma treatment. Structure and mechanical property of the scaffolds were studied by scanning electron microscopy and tensile stress measurement, respectively. Human coronary artery endothelial cells (HCAECs) were rotationally seeded onto the lumen of the scaffolds at the speed of 6 rpm for 4 h through a customized seeding device, followed with static culture. Results showed evenly distributed and well-spread HCAECs throughout the lumen of the scaffold from 1 day onward to 10 days after seeding. Further, HCAECs maintained phenotypic expression of PECAM-1. To prove the basic concept of using the scaffolds as vascular grafts, acellular tubular P(LLA-CL) nanofiber scaffolds (inner diameter 1 mm) were implanted into rabbits to replace the inferior superficial epigastric veins. Results showed the scaffolds sustained the surgical process, kept the structure integrity, and showed the patency for 7 weeks.

Electrospinning is known to be a highly versatile process which is able to produce fibers made out of different compositions with diameter of a few microns down to several nanometers. Current electrospinning technology generally involves the deposition of fibers onto a solid substrate although in some cases, a liquid coagulation bath is used to collect the fibers. However, a liquid collector may offer several advantages over a solid substrate. A novel electrospun fiber manipulation process through the use of a water vortex is described in this communication where continuous yarn was made from electrospun fibers. Preliminary studies on some parameters such as solution feed rate and solution concentration and their impact on fabrication of the yarn and the fiber morphology were carried out.

Collagen and glycosaminoglycan (GAG) are native constituents of human tissues and are widely utilized to fabricate scaffolds serving as an analog of native extracellular matrix (ECM).The development of blended collagen and GAG scaffolds may potentially be used in many soft tissue engineering applications since the scaffolds mimic the structure and biological function of native ECM. In this study, we were able to obtain a novel nanofibrous collagen–GAG scaffold by electrospinning with collagen and chondroitin sulfate (CS), a widely used GAG. The electrospun collagen–GAG scaffold exhibited a uniform fiber structure in nano-scale diameter. By crosslinking with glutaraldehyde vapor, the collagen–GAG scaffolds could resist from collagenase degradation and enhance the biostability of the scaffolds. This led to the increased proliferation of rabbit conjunctiva fibroblast on the scaffolds. Incorporation of CS into collagen nanofibers without crosslinking did not increase the biostability but still promoted cell growth. In conclusion, the electrospun collagen–GAG scaffolds, with high surface-to-volume ratio, may potentially provide a better environment for tissue formation/biosynthesis compared with the traditional scaffolds.

Maintaining functions of endothelial cells in vitro is a prerequisite for effective endothelialization of biomaterials as an approach to prevent intimal hyperplasia of small-diameter vascular grafts. The aim of this study was to design suitable nanofiber meshes (NFMs) that further maintain the phenotype and functions of human coronary artery endothelial cells (HCAECs). Collagen-coated random and aligned poly(L-lactic acid)-co-poly(epsilon-caprolactone) (P(LLA-CL)) NFMs were fabricated using electrospinning. Mechanical testing showed that tensile modulus and strength were greater for the aligned P(LLA-CL) NFM than for the random NFM. Spatial distribution of the collagen in the NFMs was visualized by labeling with fluorescent dye. HCAECs grew along the direction of nanofiber alignment and showed elongated morphology that simulated endothelial cells in vivo under blood flow. Both random and aligned P(LLA-CL) NFMs preserved phenotype (expression of platelet endothelial cell adhesion molecule-1, fibronectin, and collagen type IV in protein level) and functions (complementary DNA microarray analysis of 112 genes relevant to endothelial cell functions) of HCAECs. The P(LLA-CL) NFMs are potential materials for tissue-engineered vascular grafts that may enable effective endothelialization.

Although there are many methods of fabricating nanofibres, electrospinning is perhaps the most versatile process. Materials such as polymer, composites, ceramic and metal nanofibres have been fabricated using electrospinning directly or through post-spinning processes. However, what makes electrospinning different from other nanofibre fabrication processes is its ability to form various fibre assemblies. This will certainly enhance the performance of products made from nanofibres and allow application specific modifications. It is therefore vital for us to understand the various parameters and processes that allow us to fabricate the desired fibre assemblies. Fibre assemblies that can be fabricated include nonwoven fibre mesh, aligned fibre mesh, patterned fibre mesh, random three-dimensional structures and sub-micron spring and convoluted fibres. Nevertheless, more studies are required to understand and precisely control the actual mechanics in the formation of various electrospun fibrous assemblies.

Nanofibers are able to form a highly porous mesh and their large surface-to-volume ratio improves performance for many applications. Electrospinning has the unique ability to produce nanofibers of different materials in various fibrous assemblies. The relatively high production rate and simplicity of the setup makes electrospinning highly attractive to both academia and industry. A variety of nanofibers can be made for applications in energy storage, healthcare, biotechnology, environmental engineering, and defense and security.

Despite recent advances in electrospinning, creating highly ordered structure through the use of electrospun fibres is not possible. This is due to the chaotic motion of the electrospinning jet which means that the deposition location of the fibres covers a few centimetres radius. As a result, applications for electrospun fibres are restricted to applications where precise positioning is not required. However, through the use of steel blades to control the electric field, it is now possible to create a fibre bundle made of highly aligned nanofibres where the ends of the fibre bundle are fixed during electrospinning. The creation of highly ordered structures made of electrospun fibre bundles is now possible since the fibre bundle is robust enough to be handled, and it is also easy to transfer the fibre bundle onto a substrate. More importantly, with the two ends of the fibre bundle known, automating the transfer of the fibre bundle onto a substrate is a possibility.

Electrospinning offers an avenue to produce small diameter tubes made out of nanofibres. However, to date, most tubes from electrospun fibres have been either random fibres or from sheets that were rolled into tubes. Although there have been suggestions of getting tubes made of circumferentially aligned fibres, this is the first time that a method used to create a tube made of diagonally aligned electrospun fibres has been described. This tube was formed by depositing fibres on a rotating tube during electrospinning to give a resultant tube with uniform thickness and superior all round mechanical strength without any line of weakness. A knife-edged auxiliary electrode was given a charge that was opposite to that of the charge given to the needle to create an electrostatic field that encouraged fibre alignment on a rotating tube collector. A tubular structure made of nanofibres aligned in a diagonal direction was produced through electrospinning.

An implantable scaffold pre-seeded with cells needs to remain viable and encourage rapid angiogenesis in order to replace injured tissues, especially for tissue defect repairs. We created a bioartificial adipose graft composed of an electrospun 3D nanofibrous scaffold and fat tissue excised from New Zealand white rabbits. Cell viability and angiogenesis potential of the bioartificial substitute were examined during four weeks of culture in Dulbecco's Modified Eagle Medium by immunohistochemical staining with LIVE/DEAD® cell kit and PECAM-1 antibody, respectively. In addition, a Matrigel® assay was performed to examine the possibility of blood vessels sprouting from the bioartificial graft. Our results showed that cells within the graft were viable and vascular tubes were present at week 4, while cells in a fat tissue block were dead in vitro. In addition, capillaries were observed sprouting from the graft into the Matrigel, demonstrating its angiogenic potential. We expect that improved cell viability and angiogenesis in the bioartificial substitute, compared to intact autologous graft, could potentially contribute to its survival following implantation.

A novel nanofibrous construct for promoting peripheral nerve repair was fabricated and tested in a rat sciatic nerve defect model. The conduit is made out of bilayered nanofibrous membranes with the nanofibers longitudinally aligned in the lumen and randomly oriented on the outer surface. The intra-luminal guidance channel is made out of aligned nanofibrous yarns. In addition, biomolecules such as laminin and nerve growth factor were incorporated in the nanofibrous nerve construct to determine their efficacy in in vivo nerve regeneration. Muscle reinnervation, withdrawal reflex latency, histological, axon density and electrophysiology tests were carried out to compare the efficacy of nanofibrous constructs with an autograft. Our study showed mixed results when comparing the artificial constructs with an autograft. In some cases, the nanofibrous conduit with aligned nanofibrous yarn as an intra-luminal guidance channel performs better than the autograft in muscle reinnervation and withdrawal reflex latency tests. However, the axon density count is highest in the autograft at mid-graft. Functional recovery was improved with the use of the nerve construct which suggested that this nerve implant has the potential for clinical usage in reconstructing peripheral nerve defects.

The natural extracellular matrix (ECM) is a complex structure that is built to meet the specific requirements of the tissue and organ. Primarily consisting of nanometer diameter fibrils, ECM may contain other vital substances such as proteoglycans, glycosaminoglycan and various minerals. Current research in tissue engineering involves trying to replicate the ECM such that it provides the environment for tissue regeneration. Electrospinning is a versatile process that results in nanofibers by applying a high voltage to electrically charge a liquid. A variety of polymers and other substances have been incorporated into the artificial nanofibrous scaffold. Surface modification and cross-linking of the nanofibers are some ways to improve the biocompatibility and stability of the scaffold. Electrospun scaffolds with oriented nanofibers and other assemblies can be constructed by modifying the electrospinning setup. Using electrospinning, researchers are able to specifically tailor the electrospun scaffold to meet the requirements of the tissue that they seek to regenerate. In vitro and in vivo experiments demonstrate that electrospun scaffolds hold great potential for tissue engineering applications.

Fabrication of nanofibrous scaffolds with well-defined architecture mimicking native extracellular matrix analog has significant potentials for many specific tissue engineering and organs regeneration applications. The fabrication of aligned collagen nanofibrous scaffolds by electrospinning was described in this study. The structure and in vitro properties of these scaffolds were compared with a random collagen scaffold. All the collagen scaffolds were first crosslinked in glutaraldehyde vapor to enhance the biostability and keep the initial nano-scale dimension intact. From in vitro culture of rabbit conjunctiva fibroblast, the aligned scaffold exhibited lower cell adhesion but higher cell proliferation because of the aligned orientation of fibers when compared with the random scaffold. And the alignment of the fibers may control cell orientation and strengthen the interaction between the cell body and the fibers in the longitudinal direction of the fibers.

The development of blended collagen and glycosaminoglycan (GAG) scaffolds can potentially be used in many soft tissue engineering applications since the scaffolds mimic the structure and biological function of native extracellular matrix (ECM). In this study, we were able to obtain novel nanofibrous collagen-GAG scaffolds by electrospinning collagen blended with chondroitin sulfate (CS), a widely used GAG, in a mixed solvent of trifluoroethanol and water. The electrospun collagen-GAG scaffold with 4% CS (COLL-CS-04) exhibited a uniform fiber structure with nanoscale diameters. A second collagen-GAG scaffold with 10% CS consisted of smaller diameter fibers but exhibited a broader diameter distribution due to the different solution properties in comparison with COLL-CS-04. After cross-linking with glutaraldehyde vapor, the collagen-GAG scaffolds became more biostable and were resistant to collagenase degradation. This is evidently a more favorable environment allowing increased proliferation of rabbit conjunctiva fibroblast on the scaffolds. Incorporation of CS into collagen nanofibers without cross-linking did not increase the biostability but still promoted cell growth. The potential of applying the nanoscale collagen-GAG scaffold in tissue engineering is significant since the nanodimension fibers made of natural ECM mimic closely the native ECM found in the human body. The high surface area characteristic of this scaffold may maximize cell-ECM interaction and promote tissue regeneration faster than other conventional scaffolds.

Electrospun collagen-blended poly(L-lactic acid)-co-poly(epsilon-caprolactone) [P(LLA-CL), 70:30] nanofiber may have great potential application in tissue engineering because it mimicks the extracellular matrix (ECM) both morphologically and chemically. Blended nanofibers with various weight ratios of polymer to collagen were fabricated by electrospinning. The appearance of the blended nanofibers was investigated by scanning electron microscopy and transmission electron microscopy. The nanofibers exhibited a smooth surface and a narrow diameter distribution, with 60% of the nanofibers having diameters between 100 and 200 nm. Attenuated total reflectance-Fourier transform infrared spectra and X-ray photoelectron spectroscopy verified the existence of collagen molecules on the surface of nanofibers. Human coronary artery endothelial cells (HCAECs) were seeded onto the blended nanofibers for viability, morphogenesis, attachment, and phenotypic studies. Five characteristic endothelial cell (EC) markers, including four types of cell adhesion molecule and one EC-preferential gene (von Willebrand factor), were studied by reverse transcription-polymerase chain reaction. Results showed that the collagen-blended polymer nanofibers could enhance the viability, spreading, and attachment of HCAECs and, moreover, preserve the EC phenotype. The blending electrospinning technique shows potential in refining the composition of polymer nanofibers by adding various ingredients (e.g., growth factors) according to cell types to fabricate tissue-engineering scaffold, particularly blood vessel-engineering scaffold.

An introduction to electrospinning and nanofibers , An introduction to electrospinning and nanofibers , کتابخانه دیجیتال جندی شاپور اهواز

Endothelialization of biomaterials is a promising way to prevent intimal hyperplasia of small-diameter vascular grafts. The aim of this study was to design a nanofiber mesh (NFM) that facilitates viability, attachment and phenotypic maintenance of human coronary artery endothelial cells (HCAECs). Collagen-coated poly(L-lactic acid)-co-poly(epsilon-caprolactone) P(LLA-CL 70:30) NFM with a porosity of 64-67% and a fiber diameter of 470+/-130 nm was fabricated using electrospinning followed by plasma treatment and collagen coating. The structure of the NFM was observed by SEM and TEM, and mechanical property was studied by tensile test. The presence of collagen on the P(LLA-CL) NFM surface was verified by X-ray photoelectron spectroscopy (XPS) and quantified by colorimetric method. Spatial distribution of the collagen in the NFM was visualized by labelling with fluorescent probe. The collagen-coated P(LLA-CL) NFM enhanced the spreading, viability and attachment of HCAECs, and moreover, preserve HCAEC's phenotype. The P(LLA-CL) NFM is a potential material for tissue engineered vascular graft.

In this paper, various three-dimensional (3D) nanofibrous structures were constructed based on liquid support systems and alteration of the solution charge property. Structures fabricated from the liquid support system include a nanofibrous ring and spindle-shaped nanofibrous ones. The ease of fabricating fluffy, randomly organized nanofibrous structure by altering the charge capacity of the electrospun solution is also demonstrated. The set-up conditions for the design of the nanofibrous structures using these techniques are discussed.