Novel fabricated matrix via electrospinning for tissue engineering

A doxycycline-loaded microfiber of poly-metformin/PCL for eradicating melanoma stem cells

Nowadays, electrospun fibrous mats are used as drug delivery systems for loading of potential drugs in order to kill cancer cells. In the study, a skin patch for treating melanoma cancer after surgery was made using polycaprolactone and polymetformin microfibers that were loaded with doxycycline (PolyMet/PCL@DOX), an anti-cancer stem cell agent. The morphology, structure, mechanical characteristics, swelling, and porosity of the electrospun microfibers were examined. Drug release andanticancereffectiveness of PolyMet/PCL@DOXwas evaluated against A375 melanoma cancer stem cells using the MTS, Flow cytometry, colony formation and CD44 expression assays. Scanning electron microscopy (SEM) verified the micro fibrous structure with a diameter of about 2.31 µm. The porosity and swelling percentages for microfibers was 73.5 % and 2.9 %, respectively. The tensile strength at the breaking point was equal to 3.84 MPa. The IC50 of PolyMet/PCL@DOX was 7.4 μg/mL. The survival rate of A375 cells after 72 h of PolyMet/PCL@DOX treatment was 43.9 %. The colony formation capacity of A375 cells decreased after PolyMet/PCL@DOX treatment. The level of CD44 expression in the PolyMet/PCL@DOX group decreased compared to the control group. Generally, PolyMet/PCL@DOX microfibers can be a promising candidate as a patch after surgery to eradicate cancer stem cells, effectively.

Optimizing PCL/PLGA Scaffold Biocompatibility Using Gelatin from Bovine, Porcine, and Fish Origin

This research introduces a novel approach by incorporating various types of gelatins, including bovine, porcine, and fish skin, into polycaprolactone and poly (lactic-co-glycolic acid) using a solvent casting method. The films are evaluated for morphology, mechanical properties, thermal stability, biodegradability, hemocompatibility, cell adhesion, proliferation, and cytotoxicity. The results show that the incorporation of gelatins into the films alters their mechanical properties, with a decrease in tensile strength but an increase in elongation at break. This indicates that the films become more flexible with the addition of gelatin. Gelatin incorporation has a limited effect on the thermal stability of the films. The composites with the gelatin show higher biodegradability with the highest weight loss in the case of fish gelatin. The films exhibit high hemocompatibility with minimal hemolysis observed. The gelatin has a dynamic effect on cell behavior and promotes long-term cell proliferation. In addition, all composite films reveal exceptionally low levels of cytotoxicity. The combination of the evaluated parameters shows the appropriate level of biocompatibility for gelatin-based samples. These findings provide valuable insights for future studies involving gelatin incorporation in tissue engineering applications.

Bioresorbable films of polycaprolactone blended with poly(lactic acid) or poly(lactic-co-glycolic acid)

Recent complications on the use of polypropylene meshes for hernia repair has led to the development of meshes or films, which were based on resorbable polymers such as polycaprolactone (PCL), polylactic acid (PLA) and poly(lactic-co-glycolic acid) (PLGA). These materials are able to create suitable bioactive environment for the growth and development of cells. In this research, we mainly focused on the relations among structure, mechanical performance and biocompatiblity of PCL/PLA and PCL/PLGA and blends prepared by solution casting. The films were characterized regarding the chemical structure, morphology, physicochemical properties, cytotoxicity, biocompatibility and cell growth. All the films showed high tensile strength ranging from 9.5 to 11.8 MPa. SAXS showed that the lamellar stack structure typical for PCL was present even in the blend films while the morphological parameters of the stacks varied slightly with the content of PLGA or PLA in the blends. WAXS indicated preferential orientation of crystallites (and thus, also the lamellar stacks) in the blend films. In vitro studies revealed that PCL/PLGA films displayed better cell adhesion, spreading and proliferation than PCL/PLA and PCL films. Further the effect of blending on the degradation was investigated, to understand the significant variable within the process that could provide further control of cell adhesion. The results showed that the investigated blend films are promising materials for biomedical applications.

Desalination technologies, membrane distillation, and electrospinning, an overview

Water is a critical component for humans to survive, especially in arid lands or areas where fresh water is scarce. Hence, desalination is an excellent way to effectuate the increasing water demand. Membrane distillation (MD) technology entails a membrane-based non-isothermal prominent process used in various applications, for instance, water treatment and desalination. It is operable at low temperature and pressure, from which the heat demand for the process can be sustainably sourced from renewable solar energy and waste heat. In MD, the water vapors are gone through the membrane's pores and condense at permeate side, rejecting dissolved salts and non-volatile substances. However, the efficacy of water and biofouling are the main challenges for MD due to the lack of appropriate and versatile membrane. Numerous researchers have explored different membrane composites to overcome the above-said issue, and attempt to develop efficient, elegant, and biofouling-resistant novel membranes for MD. This review article addresses the 21st-century water crises, desalination technologies, principles of MD, the different properties of membrane composites alongside compositions and modules of membranes. The desired membrane characteristics, MD configurations, role of electrospinning in MD, characteristics and modifications of membranes used for MD are also highlighted in this review.

State-of-the-art review of advanced electrospun nanofiber yarn-based textiles for biomedical applications

The pandemic of the coronavirus disease 2019 (COVID-19) has made biotextiles, including face masks and protective clothing, quite familiar in our daily lives. Biotextiles are one broad category of textile products that are beyond our imagination. Currently, biotextiles have been routinely utilized in various biomedical fields, like daily protection, wound healing, tissue regeneration, drug delivery, and sensing, to improve the health and medical conditions of individuals. However, these biotextiles are commonly manufactured with fibers with diameters on the micrometer scale (> 10 μm). Recently, nanofibrous materials have aroused extensive attention in the fields of fiber science and textile engineering because the fibers with nanoscale diameters exhibited obviously superior performances, such as size and surface/interface effects as well as optical, electrical, mechanical, and biological properties, compared to microfibers. A combination of innovative electrospinning techniques and traditional textile-forming strategies opens a new window for the generation of nanofibrous biotextiles to renew and update traditional microfibrous biotextiles. In the last two decades, the conventional electrospinning device has been widely modified to generate nanofiber yarns (NYs) with the fiber diameters less than 1000 nm. The electrospun NYs can be further employed as the primary processing unit for manufacturing a new generation of nano-textiles using various textile-forming strategies. In this review, starting from the basic information of conventional electrospinning techniques, we summarize the innovative electrospinning strategies for NY fabrication and critically discuss their advantages and limitations. This review further covers the progress in the construction of electrospun NY-based nanotextiles and their recent applications in biomedical fields, mainly including surgical sutures, various scaffolds and implants for tissue engineering, smart wearable bioelectronics, and their current and potential applications in the COVID-19 pandemic. At the end, this review highlights and identifies the future needs and opportunities of electrospun NYs and NY-based nanotextiles for clinical use.

Continuous Microfiber Wire Mandrel-Less Biofabrication for Soft Tissue Engineering Applications

Suture materials are the most common bioimplants in surgical and clinical practice, playing a crucial role in wound healing and tendon and ligament repair. Despite the assortment available on the market, sutures are still affected by significant disadvantages, including failure in mimicking the mechanical properties of the tissue, excessive fibrosis, and inflammation. This study introduces a mandrel-less electrodeposition apparatus to fabricate continuous microfiber wires of indefinite length. The mandrel-less biofabrication produces wires, potentially used as medical fibers, with different microfiber bundles, that imitate the hierarchical organization of native tissues, and tailored mechanical properties. Microfiber wire morphology and mechanical properties are characterized by scanning electron microscopy, digital image processing, and uniaxial tensile test. Wires are tested in vitro on monocyte/macrophage stimulation and in vivo on a rat surgical wound model. The wires produced by mandrel-less deposition show an increased M2 macrophage phenotype in vitro. The in vivo assessment demonstrates that microfiber wires, compared to the medical fibers currently used, reduce pro-inflammatory macrophage response and preserve their mechanical properties after 30 days of use. These results make this microfiber wire an ideal candidate as a suture material for soft tissue surgery, suggesting a crucial role of microarchitecture in more favorable host response.

Electrospun Antibacterial Nanomaterials for Wound Dressings Applications

Chronic wounds are caused by bacterial infections and create major healthcare discomforts; to overcome this issue, wound dressings with antibacterial properties are to be utilized. The requirements of antibacterial wound dressings cannot be fulfilled by traditional wound dressing materials. Hence, to improve and accelerate the process of wound healing, an antibacterial wound dressing is to be designed. Electrospun nanofibers offer a promising solution to the management of wound healing, and numerous options are available to load antibacterial compounds onto the nanofiber webs. This review gives us an overview of some recent advances of electrospun antibacterial nanomaterials used in wound dressings. First, we provide a brief overview of the electrospinning process of nanofibers in wound healing and later discuss electrospun fibers that have incorporated various antimicrobial agents to be used in wound dressings. In addition, we highlight the latest research and patents related to electrospun nanofibers in wound dressing. This review also aims to concentrate on the importance of nanofibers for wound dressing applications and discuss functionalized antibacterial nanofibers in wound dressing.

A Review on Electrospun Nanofibers Based Advanced Applications: From Health Care to Energy Devices

Electrospun nanofibers have been exploited in multidisciplinary fields with numerous applications for decades. Owing to their interconnected ultrafine fibrous structure, high surface-to-volume ratio, tortuosity, permeability, and miniaturization ability along with the benefits of their lightweight, porous nanofibrous structure, they have been extensively utilized in various research fields for decades. Electrospun nanofiber technologies have paved unprecedented advancements with new innovations and discoveries in several fields of application including energy devices and biomedical and environmental appliances. This review article focused on providing a comprehensive overview related to the recent advancements in health care and energy devices while emphasizing on the importance and uniqueness of utilizing nanofibers. A brief description regarding the effect of electrospinning techniques, setup modifications, and parameters optimization on the nanofiber morphology was also provided. The article is concluded with a short discussion on current research challenges and future perspectives.

Electrospun Nanofibrous Membranes for Tissue Engineering and Cell Growth

In biotechnology, the field of cell cultivation is highly relevant. Cultivated cells can be used, for example, for the development of biopharmaceuticals and in tissue engineering. Commonly, mammalian cells are grown in bioreactors, T-flasks, well plates, etc., without a specific substrate. Nanofibrous mats, however, have been reported to promote cell growth, adhesion, and proliferation. Here, we give an overview of the different attempts at cultivating mammalian cells on electrospun nanofiber mats for biotechnological and biomedical purposes. Starting with a brief overview of the different electrospinning methods, resulting in random or defined fiber orientations in the nanofiber mats, we describe the typical materials used in cell growth applications in biotechnology and tissue engineering. The influence of using different surface morphologies and polymers or polymer blends on the possible application of such nanofiber mats for tissue engineering and other biotechnological applications is discussed. Polymer blends, in particular, can often be used to reach the required combination of mechanical and biological properties, making such nanofiber mats highly suitable for tissue engineering and other biotechnological or biomedical cell growth applications.

Application of textile technology in tissue engineering: A review

One of the key elements in tissue engineering is to design and fabricate scaffolds with tissue-like properties. Among various scaffold fabrication methods, textile technology has shown its unique advantages in mimicking human tissues' properties such as hierarchical, anisotropic, and strain-stiffening properties. As essential components in textile technology, textile patterns affect the porosity, architecture, and mechanical properties of textile-based scaffolds. However, the potential of various textile patterns has not been fully explored when fabricating textile-based scaffolds, and the effect of different textile patterns on scaffold properties has not been thoroughly investigated. This review summarizes textile technology development and highlights its application in tissue engineering to facilitate the broader application of textile technology, especially various textile patterns in tissue engineering. The potential of using different textile methods such as weaving, knitting, and braiding to mimic properties of human tissues is discussed, and the effect of process parameters in these methods on fabric properties is summarized. Finally, perspectives on future directions for explorations are presented. STATEMENT OF SIGNIFICANCE: Recently, biomedical engineers have applied textile technology to fabricate scaffolds for tissue engineering applications. Various textile methods, especially weaving, knitting, and braiding, enables engineers to customize the physical, mechanical, and biological properties of scaffolds. However, most textile-based scaffolds only use simple textile patterns, and the effect of different textile patterns on scaffold properties has not been thoroughly investigated. In this review, we cover for the first time the effect of process parameters in different textile methods on fabric properties, exploring the potential of using different textile methods to mimic properties of human tissues. Previous advances in textile technology are presented, and future directions for explorations are presented, hoping to facilitate new breakthroughs of textile-based tissue engineering.

Textile-based sandwich scaffold using wet electrospun yarns for skin tissue engineering

One of the key elements in tissue engineering is to design and fabricate scaffolds with tissue-like properties. However, mimicking the strain-stiffening property of human tissues by using synthetic materials is still a challenge in scaffold fabrication since most synthetic materials exhibit strain-softening behavior. To address this challenge, we propose a textile-based sandwich scaffold to mimic strain-stiffening behavior observed in human tissues. For this purpose, we first fabricate polycaprolactone (PCL) yarns by wet electrospinning. Then, we crochet PCL yarns into a textile fabric. Finally, we fabricate the sandwich scaffold by embedding the textile fabric inside two electrospun mats. The wet electrospun PCL yarns induce cellular alignment and elongation. The textile-based sandwich scaffold exhibits strain-stiffening behavior. By changing process parameters during the yarn fabrication and textile process, we can adjust the maximum stress of the scaffold from 3.74 to 11.82 MPa, the maximum strain from 0.16 to 2.37, and the elastic modulus from 2.10 to 18.05 MPa, all within the ranges of that of human skin. The scaffold is also able to support cell proliferation and infiltration after optimizing the thickness of the outer layers of the sandwich scaffold. This study validates the potential of the textile-based sandwich scaffold to mimic the physical, mechanical, and biological properties of human skin and other tissues.

Using Wet Electrospun PCL/Gelatin/CNT Yarns to Fabricate Textile-Based Scaffolds for Vascular Tissue Engineering

Incorporating conductive materials in scaffolds has shown advantages in regulating adhesion, mitigation, and proliferation of electroactive cells for tissue engineering applications. Among various conductive materials, carbon nanotubes (CNTs) have shown great promises in tissue engineering because of their good mechanical properties. However, the broad application of CNTs in tissue engineering is limited by current methods to incorporate CNTs in polymers that require miscible solvents to dissolve CNTs and polymers or CNT surface modification. These methods either limit polymer selections or adversely affect the properties of polymer/CNT composites. Here, we report a novel method to fabricate polymer/CNT composite yarns by electrospinning polycaprolactone/gelatin into a bath of CNT dispersion and extracting electrospun fibers out of the bath. The concentration of CNTs in the bath affects the thermal and mechanical properties and the yarns' degradation behavior. In vitro biological test results show that within a limited range of CNT concentrations in the bath, the yarns exhibit good biocompatibility and the ability to guide cell elongation and alignment. We also report the design and fabrication of a vascular scaffold by knitting the yarns into a textile fabric and combining the textile fabric with gelatin. The scaffold has similar mechanical properties to native vessels and supports cell proliferation. This work demonstrates that the wet electrospun polymer/CNT yarns are good candidates for constructing vascular scaffolds and provides a novel method to incorporate CNTs or other functional materials into biopolymers for tissue engineering applications.

A review of recent progress in polymeric electrospun nanofiber membranes in addressing safe water global issues

With rapid advancement in water filtration materials, several efforts have been made to fabricate electrospun nanofiber membranes (ENMs). ENMs play a crucial role in different areas of water treatment due to their several advantageous properties such as high specific surface area, high interconnected porosity, controllable thickness, mechanical robustness, and wettability. In the broad field of water purification, ENMs have shown tremendous potential in terms of permeability, rejection, energy efficiency, resistance to fouling, reusability and mechanical robustness as compared to the traditional phase inversion membranes. Upon various chemical and physical modifications of ENMs, they have exhibited great potential for emerging applications in environment, energy and health sectors. This review firstly presents an overview of the limiting factors influencing the morphology of electrospun nanofibers. Secondly, it presents recent advancements in electrospinning processes, which helps to not only overcome drawbacks associated with the conventional electrospinning but also to produce nanofibers of different morphology and orientation with an increased rate of production. Thirdly, it presents a brief discussion about the recent progress of the ENMs for removal of various pollutants from aqueous system through major areas of membrane separation. Finally, this review concludes with the challenges and future directions in this vast and fast growing area.

Electrostatic Self-Assembly of Composite Nanofiber Yarn

Electrospinning polymer fibers is a well-understood process primarily resulting in random mats or single strands. More recent systems and methods have produced nanofiber yarns (NFY) for ease of use in textiles. This paper presents a method of NFY manufacture using a simplified dry electrospinning system to produce self-assembling functional NFY capable of conducting electrical charge. The polymer is a mixture of cellulose nanocrystals (CNC), polyvinyl acrylate (PVA) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). When treated with ethylene glycol (EG) to enhance conductivity, fibers touching the collector plate align to the applied electrostatic field and grow by twisting additional nanofiber polymers injected by the jet into the NFY bundle. The longer the electrospinning continues, the longer and more uniformly twisted the NFY becomes. This process has the added benefit of reducing the electric field required for NFY production from >2.43 kV cm⁻¹ to 1.875 kV cm⁻¹.

Nanonet-nano fiber electrospun mesh of PCL-chitosan for controlled and extended release of diclofenac sodium

Electrospun nanofiber (EN) technology has been used in the past to generate electrostatically charged multilayer-nanofibers. This platform offers versatile applications including in tissue engineering, drug delivery, wound dressings, and high-efficiency particulate air filters. In this study, we synthesized for the first time nanonet-nanofiber electrospun meshes (NNEMs) of polycaprolactone (PCL)-chitosan (CH) using EN technology. The fabricated NNEMs were utilized for high payload delivery and controlled release of a water-soluble drug. Diclofenac Sodium (DS), a hydrophilic anti-inflammatory drug, was selected as a model drug because of its high aqueous solubility and poor compatibility with insoluble polymers. Various compositions of DS drug-loaded NNEMs (DS-NNEMs) were synthesized. The physicochemical properties such as structure, morphology, and aqueous stability and the chemical properties of DS-NNEMs were evaluated. High drug entrapment efficiency and concentration-dependent drug release patterns were investigated for up to 14 days. Furthermore, the biocompatibility of the DS-NNEMs was tested with NIH 3T3 cells. The physicochemical characterization results showed that the DS drug is a key contributing factor in the generation of nanonet-nanofiber networks during electrospinning. DS-NNEMs also enhanced 3T3 cell adhesion, viability, and proliferation in the nanonet-nano fiber network through the controlled release of DS. The presented EN technology-based biodegradable NNEM material is not only limited for the controlled release of hydrophilic anti-inflammatory drugs, but also can be a suitable platform for loading and release of antiviral drugs.

A novel hemostat and antibacterial nanofibrous scaffold based on poly(vinyl alcohol)/poly(lactic acid)

Today, an advanced wound dressing with the ability of blood clotting and antibacterial activity is the main subject of many studies to consider their necessity in modern society. In this study, it was aimed to present a novel scaffold with both abilities simultaneously. Poly(vinyl alcohol)/poly(lactic acid) nanofibrous scaffolds containing ceftriaxone antimicrobial agent (PVA-CTX/PLA) and tranexamic acid coagulant (PVA-CTX-TXA/PLA) were fabricated by electrospinning method. Morphology, antimicrobial activity, blood coagulation and bioavailability indexes, and swelling ability (gel formation) of produced samples were determined. Morphological results showed that the hybrid nanofibers were form successfully. The antibacterial efficiency of them against Gram-negative ( Escherichia coli) and Gram-positive ( Staphylococcus aureus) bacteria was more than 90% for PVA-CTX/PLA and it reached 100% for PVA-CTX-TXA/PLA. Both PVA-CTX-TXA/PLA and PVA-TXA/PLA scaffolds showed acceptable blood coagulation ability with an average absorption of 0.043 and 0.036 nm, respectively. PVA-CTX-TXA/PLA scaffolds had a gel formation ability of about 45 min. All scaffolds were successful in cell proliferation (L929 fibroblast cell) after 48 h.

Polyvinyl Butyral (PVB) Nanofiber/Nanoparticle-Covered Yarns for Antibacterial Textile Surfaces

In this study, nanoparticle-incorporated nanofiber-covered yarns were prepared using a custom-made needle-free electrospinning system. The ultimate goal of this work was to prepare functional nanofibrous surfaces with antibacterial properties and realize high-speed production. As antibacterial agents, we used various amounts of copper oxide (CuO) and vanadium (V) oxide (V₂O₅) nanoparticles (NPs). Three yarn preparation speeds (100 m/min, 150 m/min, and 200 m/min) were used for the nanofiber-covered yarn. The results indicate a relationship between the yarn speed, quantity of NPs, and antibacterial efficiency of the material. We found a higher yarn speed to be associated with a lower reduction in bacteria. NP-loaded nanofiber yarns were proven to have excellent antibacterial properties against Gram-negative Escherichia coli (E. coli). CuO exhibited a greater inhibition and bactericidal effect against E. coli than V₂O₅. In brief, the studied samples are good candidates for use in antibacterial textile surface applications, such as wastewater filtration. As greater attention is being drawn to this field, this work provides new insights regarding the antibacterial textile surfaces of nanofiber-covered yarns.

Tropoelastin-Coated Tendon Biomimetic Scaffolds Promote Stem Cell Tenogenic Commitment and Deposition of Elastin-Rich Matrix

Tendon tissue engineering strategies that recreate the biophysical and biochemical native microenvironment have a greater potential to achieve regeneration. Here, we developed tendon biomimetic scaffolds using mechanically competent yarns of poly-ε-caprolactone, chitosan, and cellulose nanocrystals to recreate the inherent tendon hierarchy from a nano-to-macro scale. These were then coated with tropoelastin (TROPO) through polydopamine (PDA) linking, to mimic the native extracellular matrix (ECM) composition and elasticity. Both PDA and TROPO coatings decreased surface stiffness without masking the underlying substrate. We found that human adipose-derived stem cells (hASCs) seeded onto these TROPO biomimetic scaffolds more rapidly acquired their spindle-shape morphology and high aspect ratio characteristic of tenocytes. Immunocytochemistry shows that the PDA and TROPO-coated surfaces boosted differentiation of hASCs toward the tenogenic lineage, with sustained expression of the tendon-related markers scleraxis and tenomodulin up to 21 days of culture. Furthermore, these surfaces enabled the deposition of a tendon-like ECM, supported by the expression of collagens type I and III, tenascin, and decorin. Gene expression analysis revealed a downregulation of osteogenic and fibrosis markers in the presence of TROPO when compared with the control groups, suggesting proper ECM deposition. Remarkably, differentiated cells exposed to TROPO acquired an elastogenic profile due to the evident elastin synthesis and deposition, contributing to the formation of a more mimetic matrix in comparison with the PDA-coated and uncoated conditions. In summary, our biomimetic substrates combining biophysical and biological cues modulate stem cell behavior potentiating their long-term tenogenic commitment and the production of an elastin-rich ECM.

Fabricated tropoelastin-silk yarns and woven textiles for diverse tissue engineering applications

Electrospun yarns offer substantial opportunities for the fabrication of elastic scaffolds for flexible tissue engineering applications. Currently available yarns are predominantly made of synthetic elastic materials. Thus scaffolds made from these yarns typically lack cell signaling cues. This can result in poor integration or even rejection on implantation, which drive demands for a new generation of yarns made from natural biologically compatible materials. Here, we present a new type of cell-attractive, highly twisted protein-based yarns made from blended tropoelastin and silk fibroin. These yarns combine physical and biological benefits by being rendered elastic and bioactive through the incorporation of tropoelastin and strengthened through the presence of silk fibroin. Remarkably, the process delivered multi-meter long yarns of tropoelastin-silk mixture that were conducive to fabrication of meshes on hand-made frames. The resulting hydrated meshes are elastic and cell interactive. Furthermore, subcutaneous implantation of the meshes in mice demonstrates their tolerance and persistence over 8 weeks. This combination of mechanical properties, biocompatibility and processability into diverse shapes and patterns underscores the value of these materials and platform technology for tissue engineering applications. STATEMENT OF SIGNIFICANCE: Synthetic yarns are used to fabricate textile materials for various applications such as surgical meshes for hernia repair and pelvic organ prolapse. However, synthetic materials lack the attractive biological and physical cues characteristic of extracellular matrix and there is a demand for materials that can minimize postoperative complications. To address this need, we made yarns from a combination of recombinant human tropoelastin and silk fibroin using a modified electrospinning approach that blended these proteins into functional yarns. Prior to this study, no protein-based yarns using tropoelastin were available for the fabrication of functional textile materials. Multimeter-long, uniform and highly twisted yarns based on these proteins were elastic and cell interactive and demonstrated processing to yield textile fabrics. By using these yarns to weave fabrics, we demonstrate that an elastic human matrix protein blend can deliver a versatile platform technology to make textiles that can be explored for efficacy in tissue repair.

Bromelain-loaded chitosan nanofibers prepared by electrospinning method for burn wound healing in animal models

Bromelain is a mixture of proteolytic enzymes present in all tissues of pineapple (Ananas comosus). It is known as an efficient debriding agent in burn treatment. In this study, the efficiency of bromelain-loaded chitosan nanofibers for burn wounds repair was investigated in animal model. Chitosan nanofibers containing bromelain (2% and 4% w/v) were prepared by electrospinning method. The physicochemical characteristics of the synthetized nanofibers were evaluated. The release profile and activity of bromelain loaded in nanofibers were also assayed. Cytotoxicity test was carried out using Alamar blue. The burn healing effect of chitosan-2% w/v bromelain nanofiber was studied in the induced burn wounds in rats for 21 days. The efficacy of treatment was assessed by reduction of burn wound area and histological characteristics at different times. Chitosan-2% w/v bromelain showed the better physicochemical properties and release profile as well as low cytotoxicity than chitosan-4% w/v bromelain. The results also indicated that chitosan-2% w/v bromelain nanofiber was more efficient to heal burn skin compared to chitosan nanofiber alone in the animal model tested. The present study concludes that chitosan-2% w/v bromelain nanofiber possesses great wound healing activity and could be considered as an effective natural topical burn wound healing treatment.

Pyridine as an additive to improve the deposition of continuous electrospun filaments

Electrospun filaments are leading to a new generation of medical yarns that have the ability to enhance tissue healing through their biophysical cues. We have recently developed a technology to fabricate continuous electrospun filaments by depositing the submicron fibres onto a thin wire. Here we investigate the influence of pyridine on the fibre deposition. We have added pyridine to polydioxanone solutions at concentrations ranging from 0 to 100 ppm, increasing the conductivity of the solutions almost linearly from 0.04 uS/cm to 7 uS/cm. Following electrospinning, this led to deposition length increasing from 1 cm to 14 cm. The samples containing pyridine easily underwent cold drawing. The strength of drawn filaments increased from 0.8 N to 1.5 N and this corresponded to a decrease in fibre diameter, with values dropping from 2.7 μm to 1 μm. Overall, these findings are useful to increase the reliability of the manufacturing process of continuous electrospun filaments and to vary their biophysical properties required for their application as medical yarns such as surgical sutures.

Biofabrication of Electrospun Scaffolds for the Regeneration of Tendons and Ligaments

Tendon and ligament tissue regeneration and replacement are complex since scaffolds need to guarantee an adequate hierarchical structured morphology, and non-linear mechanical properties. Moreover, to guide the cells' proliferation and tissue re-growth, scaffolds must provide a fibrous texture mimicking the typical of the arrangement of the collagen in the extracellular matrix of these tissues. Among the different techniques to produce scaffolds, electrospinning is one of the most promising, thanks to its ability to produce fibers of nanometric size. This manuscript aims to provide an overview to researchers approaching the field of repair and regeneration of tendons and ligaments. To clarify the general requirements of electrospun scaffolds, the first part of this manuscript presents a general overview concerning tendons' and ligaments' structure and mechanical properties. The different types of polymers, blends and particles most frequently used for tendon and ligament tissue engineering are summarized. Furthermore, the focus of the review is on describing the different possible electrospinning setups and processes to obtain different nanofibrous structures, such as mats, bundles, yarns and more complex hierarchical assemblies. Finally, an overview concerning how these technologies are exploited to produce electrospun scaffolds for tendon and ligament tissue applications is reported together with the main findings and outcomes.

A polypropylene mesh modified with poly-ε-caprolactone nanofibers in hernia repair: large animal experiment

Purpose

Incisional hernia repair is an unsuccessful field of surgery, with long-term recurrence rates reaching up to 50% regardless of technique or mesh material used. Various implants and their positioning within the abdominal wall pose numerous long-term complications that are difficult to treat due to their permanent nature and the chronic foreign body reaction they trigger. Materials mimicking the 3D structure of the extracellular matrix promote cell adhesion, proliferation, migration, and differentiation. Some electrospun nanofibrous scaffolds provide a topography of a natural extracellular matrix and are cost effective to manufacture.

Materials and methods

A composite scaffold that was assembled out of a standard polypropylene hernia mesh and poly-ε-caprolactone (PCL) nanofibers was tested in a large animal model (minipig), and the final scar tissue was subjected to histological and biomechanical testing to verify our in vitro results published previously.

Results

We have demonstrated that a layer of PCL nanofibers leads to tissue overgrowth and the formation of a thick fibrous plate around the implant. Collagen maturation is accelerated, and the final scar is more flexible and elastic than under a standard polypropylene mesh with less pronounced shrinkage observed. However, the samples with the composite scaffold were less resistant to distracting forces than when a standard mesh was used. We believe that the adverse effects could be caused due to the material assembly, as they do not comply with our previous results.

Conclusion

We believe that PCL nanofibers on their own can cause enough fibroplasia to be used as a separate material without the polypropylene base, thus avoiding potential adverse effects caused by any added substances.

Electrospun Composites of Polycaprolactone and Porous Silicon Nanoparticles for the Tunable Delivery of Small Therapeutic Molecules

This report describes the use of an electrospun composite of poly(ε-caprolactone) (PCL) fibers and porous silicon (pSi) nanoparticles (NPs) as an effective system for the tunable delivery of camptothecin (CPT), a small therapeutic molecule. Both materials are biodegradable, abundant, low-cost, and most importantly, have no known cytotoxic effects. The composites were treated with and without sodium hydroxide (NaOH) to investigate the wettability of the porous network for drug release and cell viability measurements. CPT release and subsequent cell viability was also investigated. We observed that the cell death rate was not only affected by the addition of our CPT carrier, pSi, but also by increasing the rate of dissolution via treatment with NaOH. This is the first example of loading pSi NPs as a therapeutics nanocarrier into electronspun PCL fibers and this system opens up new possibilities for the delivery of molecular therapeutics.

Regenerative Engineering of the Rotator Cuff of the Shoulder

Rotator cuff tears often heal poorly, leading to re-tears after repair. This is in part attributed to the low proliferative ability of the resident cells (tendon fibroblasts and tendon-stem cells) upon injury to the rotator cuff tissue and the low vascularity of the tendon insertion. In addition, surgical outcomes of current techniques used in clinical settings are often suboptimal, leading to the formation of neo-tissue with poor biomechanics and structural characteristics, which results in re-tears. This has prompted interest in a new approach, which we term as "Regenerative Engineering", for regenerating rotator cuff tendons. In the Regenerative Engineering paradigm, roles played by stem cells, scaffolds, growth factors/small molecules, the use of local physical forces, and morphogenesis interplayed with clinical surgery techniques may synchronously act, leading to synergistic effects and resulting in successful tissue regeneration. In this regard, various cell sources such as tendon fibroblasts and adult tissue-derived stem cells have been isolated, characterized, and investigated for regenerating rotator cuff tendons. Likewise, numerous scaffolds with varying architecture, geometry, and mechanical characteristics of biologic and synthetic origin have been developed. Furthermore, these scaffolds have been also fabricated with biochemical cues (growth factors and small molecules), facilitating tissue regeneration. In this Review, various strategies to regenerate rotator cuff tendons using stem cells, advanced materials, and factors in the setting of physical forces under the Regenerative Engineering paradigm are described.

The Thickness of Electrospun Poly (ε-Caprolactone) Nanofibrous Scaffolds Influences Cell Proliferation

Nanofibrous scaffolds have morphological similarities to native extracellular matrix and have been considered as candidate scaffolds in tissue engineering. However, there is no report on the effect of the thickness of nanofibrous scaffold on cell behavior. In this study poly (∊-caprolactone) (PCL) nanofibrous scaffolds with thicknesses of 0.1 and 0.6 mm were fabricated by electrospinning. Properties of PCL nanofibrous scaffolds were measured by contact angle and air permeability measurements while the morphology of the nanofibers was observed by SEM. Mouse embryonal carcinoma stem cells (P19), monkey epithelial kidney cells (Vero), Chinese hamster ovary cells (CHO) and mouse mesenchymal stem cells (MSCs) were seeded on PCL nanofibrous scaffolds with thicknesses of 0.1 and 0.6 mm. Air permeability measurements showed that air permeability decreases with the increase in the thickness of nanofibrous scaffolds, and contact angle measurements revealed a contact angle of 118° for electrospun PCL nanofibers. The MTT assays showed that the proliferation of the cells was influenced by the thickness of the nanofibrous scaffold. Scaffolds with a thickness of 0.6 mm were found to provide a better substrate for cell proliferation, possibly due to more dimensional stability. Therefore, regardless of cell origin, thicker scaffolds provide a better substrate for cell proliferation, possibly due to the higher dimensional stability and tightness of thicker scaffolds.

3D Mimicry of Native-Tissue-Fiber Architecture Guides Tendon-Derived Cells and Adipose Stem Cells into Artificial Tendon Constructs

Tendon and ligament (T/L) function is intrinsically related with their unique hierarchically and anisotropically organized extracellular matrix. Their natural healing capacity is, however, limited. Here, continuous and aligned electrospun nanofiber threads (CANT) based on synthetic/natural polymer blends mechanically reinforced with cellulose nanocrystals are produced to replicate the nanoscale collagen fibrils grouped into microscale collagen fibers that compose the native T/L. CANT are then incrementally assembled into 3D hierarchical scaffolds, resulting in woven constructions, which simultaneously mimic T/L nano-to-macro architecture, nanotopography, and nonlinear biomechanical behavior. Biological performance is assessed using human-tendon-derived cells (hTDCs) and human adipose stem cells (hASCs). Scaffolds nanotopography and microstructure induce a high cytoskeleton elongation and anisotropic organization typical of tendon tissues. Moreover, the expression of tendon-related markers (Collagen types I and III, Tenascin-C, and Scleraxis) by both cell types, and the similarities observed on their expression patterns over time suggest that the developed scaffolds not only prevent the phenotypic drift of hTDCs, but also trigger tenogenic differentiation of hASCs. Overall, these results demonstrate a feasible approach for the scalable production of 3D hierarchical scaffolds that exhibit key structural and biomechanical properties, which can be advantageously explored in acellular and cellular T/L TE strategies.

Multilayered Engineered Tissue Sheets for Vascularized Tissue Regeneration

A major hurdle in engineering thick and laminated tissues such as skin is how to vascularize the tissue. This study introduces a promising strategy for generating multi-layering engineered tissue sheets consisting of fibroblasts and endothelial cells co-seeded on highly micro-fibrous, biodegradable polycaprolactone membrane. Analysis of the conditions for induction of the vessels in vivo showed that addition of endothelial cell sheets into the laminated structure increases the number of incorporated cells and promotes primitive endothelial vessel growth. In vivo analysis of 11-layered constructs showed that seeding a high number of endothelial cells resulted in better cell survival and vascularization 4 weeks after implantation. Within one week after implantation in vivo, red blood cells were detected in the middle section of three-layered engineered tissue sheets composed of polycaprolactone/collagen membranes. Our engineered tissue sheets have several advantages, such as easy handling for cell seeding, manipulation by stacking each layer, a flexible number of cells for next-step applications and versatile tissue regeneration, and automated thick tissue generation with proper vascularization.

Paediatric nanofibrous bioprosthetic heart valve

The search for an optimal aortic valve implant with durability, calcification resistance, excellent haemodynamic parameters and ability to withstand mechanical loading is yet to be met. Thus, there has been struggled to fabricate bio-prosthetics heart valve using bioengineering. The consequential product must be resilient with suitable mechanical features, biocompatible and possess the capacity to grow. Defective heart valves replacement by surgery is now common, this improves the value and survival of life for a lot of patients. The recent paediatric heart valve implant is suboptimal due to their inability of somatic growth. They usually have multiple surgeries to change outgrown valves. Short-lived valve bio-prostheses occurring in older patients and younger ones who more usually need the replacement of its damaged heart with prosthesis led to a new invasive surgical interventions with an improved quality of life. The authors propose that nanofibre scaffold for paediatric tissue-engineered heart valve will meet most of these conditions, most particularly those related to somatic growth, and, as the nanofibre scaffold is eroded, new valve is produced, the valve matures in the child until adulthood.

Electrospun nanofibre bundles and yarns for tissue engineering applications: A review

Nanofibre membranes produced through the electrospinning process have been studied extensively over the past decade for a number of high demand applications including use as tissue engineered scaffolds. Despite possessing desirable properties including high surface area to volume ratios and enhanced mechanical properties, they ultimately suffer from a lack of cellular infiltration. Variations on the process include the production of highly aligned filaments of electrospun fibres referred to as bundles and yarns. Nanofibre bundle and yarn-based scaffolds have been shown to demonstrate superior cell infiltration rates compared to traditional electrospun nonwovens while also offering the capability to be incorporated into a wider array of post-processing technologies. In this review, fibre collection techniques currently employed within the literature for the fabrication of electrospun bundles and yarns along with their applications in the field of tissue engineering will be discussed.

Recent advances in electrospun nanofibers for wound healing

Electrospun nanofibers represent a novel class of materials that show great potential in many biomedical applications including biosensing, regenerative medicine, tissue engineering, drug delivery and wound healing. In this work, we review recent advances in electrospun nanofibers for wound healing. This article begins with a brief introduction on the wound, and then discusses the unique features of electrospun nanofibers critical for wound healing. It further highlights recent studies that have used electrospun nanofibers for wound healing applications and devices, including sutures, multifunctional dressings, dermal substitutes, engineered epidermis and full-thickness skin regeneration. Finally, we finish with conclusions and future perspective in this field.

Investigating the use of curcumin-loaded electrospun filaments for soft tissue repair applications

Electrospun filaments represent a new generation of medical textiles with promising applications in soft tissue repair. A potential strategy to improve their design is to combine them with bioactive molecules. Curcumin, a natural compound found in turmeric, is particularly attractive for its antioxidant, anti-inflammatory, and antimicrobial properties. However, investigating the range of relevant doses of curcumin in materials designed for tissue regeneration has remained limited. In this paper, a wide range of curcumin concentrations was explored and the potential of the resulting materials for soft tissue repair applications was assessed. Polydioxanone (PDO) filaments were prepared with various amounts of curcumin: 0%, 0.001%, 0.01%, 0.1%, 1%, and 10% (weight to weight ratio). The results from the present study showed that, at low doses (≤0.1%), the addition of curcumin has no influence on the spinning process or on the physicochemical properties of the filaments, whereas higher doses lead to smaller fiber diameters and improved mechanical properties. Moreover, filaments with 0.001% and 0.01% curcumin stimulate the metabolic activity and proliferation of normal human dermal fibroblasts (NHDFs) compared with the no-filament control. However, this stimulation is not significant when compared to the control filaments (0%). Highly dosed filaments induce either the inhibition of proliferation (with 1%) or cell apoptosis (with 10%) as a result of the concentrations of curcumin found in the medium (9 and 32 μM, respectively), which are near or above the known toxicity threshold of curcumin (~10 μM). Moreover, filaments with 10% curcumin increase the catalase activity and glutathione content in NHDFs, indicating an increased production of reactive oxygen species resulting from the large concentration of curcumin. Overall, this study suggested that PDO electrospun filaments loaded with low amounts of curcumin are more promising compared with higher concentrations for stimulating tissue repair. This study also highlighted the need to explore lower concentrations when using polymers as PDO, such as those with polycaprolactone and other degradable polyesters.

Laminin-coated nerve guidance conduits based on poly(l-lactide-co-glycolide) fibers and yarns for promoting Schwann cells’ proliferation and migration

A laminin-coated and yarn-encapsulated PLGA nerve guidance conduit for Schwann cells’ proliferation and migration.

Current Status of Tissue-Engineered Scaffolds for Rotator Cuff Repair

Rotator cuff tears continue to be at significant risk for re-tear or for failure to heal after surgical repair despite the use of a variety of surgical techniques and augmentation devices. Therefore, there is a need for functionalized scaffold strategies to provide sustained mechanical augmentation during the critical first 12-weeks following repair, and to enhance the healing potential of the repaired tendon and tendon-bone interface. Tissue engineered approaches that combine the use of scaffolds, cells, and bioactive molecules towards promising new solutions for rotator cuff repair are reviewed. The ideal scaffold should have adequate initial mechanical properties, be slowly degrading or non-degradable, have non-toxic degradation products, enhance cell growth, infiltration and differentiation, promote regeneration of the tendon-bone interface, be biocompatible and have excellent suture retention and handling properties. Scaffolds that closely match the inhomogeneity and non-linearity of the native rotator cuff may significantly advance the field. While substantial pre-clinical work remains to be done, continued progress in overcoming current tissue engineering challenges should allow for successful clinical translation.

Synthesis and characterization of multiwalled CNT-PAN based composite carbon nanofibers via electrospinning

Electrospun fibrous membranes find place in diverse applications like sensors, filters, fuel cell membranes, scaffolds for tissue engineering, organic electronics etc. The objectives of present work are to electrospun polyacrylonitrile (PAN) nanofibers and PAN–CNT nanocomposite nanofibers and convert into carbon nanofiber and carbon-CNT composite nanofiber. The work was divided into two parts, development of nanofibers and composite nanofiber. The PAN nanofibers were produced from 9 wt% PAN solution by electrospinning technique. In another case PAN–CNT composite nanofibers were developed from different concentrations of MWCNTs (1–3 wt%) in 9 wt% PAN solution by electrospinning. Both types of nanofibers were undergone through oxidation, stabilization, carbonization and graphitization. At each stage of processing of carbon and carbon-CNT composite nanofibers were characterized by SEM, AFM, TGA and XRD. It was observed that diameter of nanofiber varies with processing parameters such as applied voltage tip to collector distance, flow rate of solution and polymer concentrations etc. while in case of PAN–CNT composite nanofiber diameter decreases with increasing concentration of CNT in PAN solution. Also with stabilization, carbonization and graphitization diameter of nanofiber decreases. SEM images shows that the minimum fiber diameter in case of 3 wt% of CNT solution because as viscosity increases it reduces the phase separation of PAN and solvent and as a consequence increases in the fiber diameter. AFM images shows that surface of film is irregular which give idea about mat type orientation of fibers. XRD results show that degree of graphitization increases on increasing CNT concentration because of additional stresses exerting on the nanofiber surface in the immediate vicinity of CNTs. TGA results shows wt loss decreases as CNT concentration increases in fibers.

Acellular Bioactivity of Sol-Gel Derived Borate Glass-Polycaprolactone Electrospun Scaffolds

Recently, sol-gel derived borate glasses (BGs) have shown unprecedented conversion rates to bone-like mineral (hydroxycarbonated apatite). In an effort to explore their potential applications in bone tissue engineering, this study reports on the fabrication and characterization of BG particle incorporated electrospun "- polycaprolactone (PCL) fibrous composites. The electrospinning technique successfully incorporated PCL fibres with BG particles at 2.5 and 5 w/v%, with the higher BG loading creating a three-dimensional cotton-wool like morphology. Dynamic vapour sorption showed greater extents of mass change with BG content attributable to water sorption, and indicating greater reactivity in the composite systems. In vitro bioactivity was investigated in simulated body fluid for up to 7 days. Scanning electron microscopy, Fourier-transform infrared spectroscopy and xray diffraction indicated apatite formation in the 5 w/v% incorporated composite scaffold, which initiated as early as day 3. In summary, sol-gel derived BGs incorporatedfibrous electrospun PCL composites indicate rapid reactivity and bioactivity with potential applications in mineralized tissue engineering.

Online stretching of directly electrospun nanofiber yarns

An online stretching during electrospinning of nanofiber yarn can considerably improve yarn production rate, quality and mechanical strength.

Fabrication of continuous electrospun filaments with potential for use as medical fibres

Soft tissue injuries represent a substantial and growing social and economic burden. Medical fibres are commonly used to repair these injuries during surgery. Patient's outcomes are, however, not promising with around 40% of surgical repairs failing within the first few months after surgery due to poor tissue regeneration. The application of nanofibrous filaments and yarns as medical fibres and scaffolds has been suggested to improve soft tissue regeneration and enhance the quality of the repair. However, due to a lack of robustness and reliability of the current fabrication methods, continuous nanofibrous filaments cannot be manufactured and scaled up in industrial settings and are not currently available for clinical use. We have developed a robust and automated method that enables the manufacture of continuous electrospun filaments and which has the potential to be integrated into existing textile production lines. The technology uses a wire guide to form submicrofibres in a dense, narrow mesh which can be detached as a long and continuous thread. The thread can then be stretched and used to create multifilament yarns which can imitate the hierarchical architecture of tissues such as tendons and ligaments. Electrospun polydioxanone yarns produced by this method showed improved cellular proliferation and adhesion when compared to medical monofilament fibres in current clinical use. In vivo, the electrospun yarns showed a good safety profile with mild foreign body reaction and complete degradation within 5 months after implantation. These results suggest that this filament collection method has the potential to become a useful platform for the fabrication of future medical textiles.

Significant improvement of biocompatibility of polypropylene mesh for incisional hernia repair by using poly-ε-caprolactone nanofibers functionalized with thrombocyte-rich solution

Incisional hernia is the most common postoperative complication, affecting up to 20% of patients after abdominal surgery. Insertion of a synthetic surgical mesh has become the standard of care in ventral hernia repair. However, the implementation of a mesh does not reduce the risk of recurrence and the onset of hernia recurrence is only delayed by 2–3 years. Nowadays, more than 100 surgical meshes are available on the market, with polypropylene the most widely used for ventral hernia repair. Nonetheless, the ideal mesh does not exist yet; it still needs to be developed. Polycaprolactone nanofibers appear to be a suitable material for different kinds of cells, including fibroblasts, chondrocytes, and mesenchymal stem cells. The aim of the study reported here was to develop a functionalized scaffold for ventral hernia regeneration. We prepared a novel composite scaffold based on a polypropylene surgical mesh functionalized with poly-ε-caprolactone (PCL) nanofibers and adhered thrombocytes as a natural source of growth factors. In extensive in vitro tests, we proved the biocompatibility of PCL nanofibers with adhered thrombocytes deposited on a polypropylene mesh. Compared with polypropylene mesh alone, this composite scaffold provided better adhesion, growth, metabolic activity, proliferation, and viability of mouse fibroblasts in all tests and was even better than a polypropylene mesh functionalized with PCL nanofibers. The gradual release of growth factors from biocompatible nanofiber-modified scaffolds seems to be a promising approach in tissue engineering and regenerative medicine.