A systematic study of solution and processing parameters on nanofiber morphology using a new electrospinning apparatus

Evaluation of Gelatin-Based Poly(Ester Urethane Urea) Electrospun Fibers Using Human Mesenchymal and Neural Stem Cells

Previously, a new biodegradable poly(ester urethane urea) was synthesized based on polycaprolactone-diol and fish gelatin (PU-Gel). In this work, the potential of this new material for neural tissue engineering is evaluated. Membranes with randomly oriented fibers and with aligned fibers are produced using electrospinning and characterized regarding their mechanical behavior under both dry and wet conditions. Wet samples exhibit a lower Young's modulus than dry ones and aligned membranes are stiffer and more brittle than those randomly oriented. Cyclic tensile tests are conducted and high values for recovery ratio and resilience are obtained. Both membranes exhibited a hydrophobic surface, measured by the water contact angle (WCA). Human mesenchymal stem cells from umbilical cord tissue (UC-MSCs) and human neural stem cells (NSCs) are seeded on both types of membranes, which support their adhesion and proliferation. Cells stained for the cytoskeleton and nucleus in membranes with aligned fibers display an elongated morphology following the alignment direction. As the culture time increased, higher cell viability is obtained on randomfibers for UC-MSCs while no differences are observed for NSCs. The membranes support neuronal differentiation of NSCs, as evidenced by markers for a neuronal filament protein (NF70) and for a microtubule-associated protein (MAP2).

Electrospun poly(lactic acid) membranes with defined pore size to enhance cell infiltration

Electrospun membranes are compact structures with small pore sizes that hinder cell infiltration, resulting in membranes with cells attached only to the external surface rather than throughout the entire volume. Thus, there is a need to increase the pore size of electrospun membranes maintaining their structural similarity to the extracellular matrix. In this work, we used glucose crystals embedded in polyethylene oxide (PEO) fibers to create large pores in poly(lactic acid) (PLA) electrospun membranes to allow for cellular infiltration. The PEO fibers containing glucose crystals of different sizes (>50, 50-100 and 100-150 μm) and in varying concentrations (10, 15 and 20 %) were co-electrospun with PLA fibers and subsequently leached out using distilled water. PLA fibrous membranes without glucose crystals were also produced as controls. The membranes were examined for their morphology, mechanical properties, and potential to support the proliferation of fibroblasts. In addition, the immune response to the membranes was evaluated using monocyte-derived macrophages. The glucose crystals were uniformly distributed in the PLA membranes and their removal created open pores without collapsing the structure. Although a reduced Young's modulus was observed for membranes produced using higher glucose crystal concentrations and larger crystal sizes, the structural integrity remained intact, and the values are still suitable for tissue engineering. In vitro results showed that the scaffolds supported the adhesion and proliferation of fibroblasts and the pores created in the PLAmembranes were large enough for fibroblasts infiltration and colonization of the entire scaffold without inducing an inflammatory response.

The Synergetic Effect of 3D Printing and Electrospinning Techniques in the Fabrication of Bone Scaffolds

The primary goal of bone tissue engineering is to restore and rejuvenate bone defects by using a suitable three-dimensional scaffold, appropriate cells, and growth hormones. Various scaffolding methods are used to fabricate three-dimensional scaffolds, which provide the necessary environment for cell activity and bone formation. Multiple materials may be used to create scaffolds with hierarchical structures that are optimal for cell growth and specialization. This study examines a notion for creating an optimal framework for bone regeneration using a combination of the robocasting method and the electrospinning approach. Research indicates that the integration of these two procedures enhances the benefits of each method and provides a rationale for addressing their shortcomings via this combination. The hybrid approach is anticipated to provide a manufactured scaffold that can effectively replace bone defects while possessing the necessary qualities for bone regeneration.

The Challenge of E-Spinning Sub-Millimeter Tubular Scaffolds-A Design-of-Experiments Study for Fiber Yield Improvement

In tissue engineering, electrospinning has gained significant interest due to its highly porous structure with an excellent surface area to volume ratio and fiber diameters that can mimic the structure of the extracellular matrix. Bioactive substances such as growth factors and drugs are easily integrated. In many applications, there is an important need for small tubular structures (I.D. < 1 mm). However, fabricating sub-millimeter structures is challenging as it reduces the collector area and increases the disturbing factors, leading to significant fiber loss. This study aims to establish a reliable and reproducible electrospinning process for sub-millimeter tubular structures with minimized material loss. Influencing factors were analyzed, and disturbance factors were removed before optimizing control variables through the design-of-experiments method. Structural and morphological characterization was performed, including the yield, thickness, and fiber arrangement of the scaffold. We evaluated the electrospinning process to enhance the manufacturing efficiency and reduce material loss. The results indicated that adjusting the voltage settings and polarity significantly increased the fiber yield from 8% to 94%. Variations in the process parameters also affected the scaffold thickness and homogeneity. The results demonstrate the complex relationship between the process parameters and provide valuable insights for optimizing electrospinning, particularly for the cost-effective and reproducible production of small tubular diameters.

Optimization of Electrospinning Parameters for Lower Molecular Weight Polymers: A Case Study on Polyvinylpyrrolidone

Polyvinylpyrrolidone (PVP) is a synthetic polymer that holds significance in various fields such as biomedical, medical, and electronics, due to its biocompatibility and exceptional dielectric properties. Electrospinning is the most commonly used tool to fabricate fibers because of its convenience and the wide choice of parameter optimization. Various parameters, including solution molarity, flow rate, voltage, needle gauge, and needle-to-collector distance, can be optimized to obtain the desired morphology of the fibers. Although PVP is commercially available in various molecular weights, PVP with a molecular weight of 130,000 g/mol is generally considered to be the easiest PVP to fabricate fibers with minimal challenges. However, the fiber diameter in this case is usually in the micron regime, which limits the utilization of PVP fibers in fields that require fiber diameters in the nano regime. Generally, PVP with a lower molecular weight, such as 10,000 g/mol and 55,000 g/mol, is known to present challenges in fiber preparation. In the current study, parameter optimization for PVP possessing molecular weights of 10,000 g/mol and 55,000 g/mol was carried out to obtain nanofibers. The electrospinning technique was utilized for fiber fabrication by optimizing the above-mentioned parameters. SEM analysis was performed to analyze the fiber morphology, and quantitative analysis was performed to correlate the effect of parameters on the fiber morphology. This research study will lead to various applications, such as drug encapsulation for sustained drug release and nanoparticles/nanotubes encapsulation for microwave absorption applications.

Biodegradable trimethyl chitosan nanofiber mats by electrospinning as bioabsorbable dressings for wound closure and healing

The paper aimed to prepare quaternary chitosan-based nanofibers as bioabsorbable wound dressings. To this aim, fully biodegradable chitosan/N,N,N-trimethyl chitosan (TMC) nanofibers were designed and prepared via electrospinning, using poly(ethylene glycol) as sacrificial additive. The new biomaterials were structurally and morphologically characterized by FTIR and NMR spectroscopy, thermogravimetric analysis, X-ray diffraction and scanning electron microscopy, and their properties required for wound dressings application were investigated and discussed in detail. Thus, the nanofiber behavior was investigated by swelling, dynamic vapor sorption, and in vitro biodegradation in media mimicking the wound exudate. The mechanical properties were analysed from the stress-strain curves, the bioadhesivity from the texture analysis and the mucoadhesivity from the Zeta potential and transmittance measurements. The antimicrobial activity was assessed against S. aureus and E. coli strains, and the biocompatibility was tested in vitro on normal human dermal fibroblasts, and in vivo on rats. The application of the fiber mats with the best balance of properties as dressings on deep burn wound models in rats showed wound closure and active healing, with fully restoration of epithelia. It was concluded that the combination of chitosan with TMC into nanofibers provides new potential bioabsorbable wound dressing, opening new perspectives in regenerative medicine.

Preparation and Characterization of Electrospun Polysaccharide FucoPol-Based Nanofiber Systems

The electrospinnability of FucoPol, a bacterial exopolysaccharide, is presented for the first time, evaluated alone and in combination with other polymers, such as polyethylene oxide (PEO) and pullulan. The obtained fibers were characterized in terms of their morphological, structural and thermal properties. Pure FucoPol fibers could not be obtained due to FucoPol’s low water solubility and a lack of molecular entanglements. Nanofibers were obtained via blending with PEO and pullulan. FucoPol:PEO (1:3 w/w) showed fibers with well-defined cylindrical structure, since the higher molecular weight of PEO helps the continuity of the erupted jet towards the collector, forming stable fibers. WAXS, DSC and TGA showed that FucoPol is an amorphous biopolymer, stable until 220 °C, whereas FucoPol-PEO fibers were stable until 140 °C, and FucoPol:pullulan fibers were stable until 130 °C. Interestingly, blended components influenced one another in intermolecular order, since new peaks associated to intermolecular hierarchical assemblies were seen by WAXS. These results make FucoPol-based systems viable candidates for production of nanofibers for packaging, agriculture, biomedicine, pharmacy and cosmetic applications.

Biotechnological Applications of Polymeric Nanofiber Platforms Loaded with Diverse Bioactive Materials

This review article highlights the critical research and formative works relating to nanofiber composites loaded with bioactive materials for diverse applications, and discusses the recent research on the use of electrospun nanofiber incorporating bioactive compounds such as essential oils, herbal bioactive components, plant extracts, and metallic nanoparticles. Inevitably, with the common advantages of bioactive components and polymer nanofibers, electrospun nanofibers containing bioactive components have attracted intense interests for their applications in biomedicine and cancer treatment. Many studies have only concentrated on the production and performance of electrospun nanofiber loaded with bioactive components; in this regard, the features of different types of electrospun nanofiber incorporating a wide variety of bioactive compounds and their developing trends are summarized and assessed in the present article, as is the feasible use of nanofiber technology to produce products on an industrial scale in different applications.

Review on Electrospun Nanofiber-Applied Products

Electrospinning technology, which was previously known as a scientific interdisciplinary research approach, is now ready to move towards a practice-based interdisciplinary approach in a variety of fields, progressively. Electrospun nanofiber-applied products are made directly from a nonwoven fabric-based membranes prepared from polymeric liquids involving the application of sufficiently high voltages during electrospinning. Today, electrospun nanofiber-based materials are of remarkable interest across multiple fields of applications, such as in electronics, sensors, functional garments, sound proofing, filters, wound dressing and scaffolds. This article presents such a review for summarizing the current progress on the manufacturing scalability of electrospun nanofibers and the commercialization of electrospun nanofiber products by dedicated companies globally. Despite the clear potential and limitless possibilities for electrospun nanofiber applications, the uptake of electrospinning by the industry is still limited due to the challenges in the manufacturing and turning of electrospun nanofibers into physical products. The recent developments in the field of electrospinning, such as the prominent nonwoven technology, personal views and the potential path forward for the growth of commercially applied products based on electrospun nanofibers, are also highlighted.

Oxygen Plasma Treated-Electrospun Polyhydroxyalkanoate Scaffolds for Hydrophilicity Improvement and Cell Adhesion

Poly(hydroxyalkanoates) (PHAs) with differing material properties, namely, the homopolymer poly(3-hydroxybutyrate), P(3HB), the copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate), P(3HB-co-3HV), with a 3HV content of 25 wt.% and a medium chain length PHA, and mcl-PHA, mainly composed of 3-hydroxydecanoate, were studied as scaffolding material for cell culture. P(3HB) and P(3HB-co-3HV) were individually spun into fibers, as well as blends of the mcl-PHA with each of the scl-PHAs. An overall biopolymer concentration of 4 wt.% was used to prepare the electrospinning solutions, using chloroform as the solvent. A stable electrospinning process and good quality fibers were obtained for a solution flow rate of 0.5 mL h⁻¹, a needle tip collector distance of 20 cm and a voltage of 12 kV for P(3HB) and P(3HB-co-3HV) solutions, while for the mcl-PHA the distance was increased to 25 cm and the voltage to 15 kV. The scaffolds’ hydrophilicity was significantly increased under exposure to oxygen plasma as a surface treatment. Complete wetting was obtained for the oxygen plasma treated scaffolds and the water uptake degree increased in all treated scaffolds. The biopolymers crystallinity was not affected by the electrospinning process, while their treatment with oxygen plasma decreased their crystalline fraction. Human dermal fibroblasts were able to adhere and proliferate within the electrospun PHA-based scaffolds. The P(3HB-co-3HV): mcl-PHA oxygen plasma treated scaffold highlighted the most promising results with a cell adhesion rate of 40 ± 8%, compared to 14 ± 4% for the commercial oxygen plasma treated polystyrene scaffold Alvetex^TM. Scaffolds based on P(3HB-co-3HV): mcl-PHA blends produced by electrospinning and submitted to oxygen plasma exposure are therefore promising biomaterials for the development of scaffolds for tissue engineering.

Effect of the Mixing Region Geometry and Collector Distance on Microbubble Formation in a Microfluidic Device Coupled with ac-dc Electric Fields

In this work, we report a significant advance in the preparation of monodisperse microbubbles using a combination of microfluidic and electric field technologies. Microbubbles have been employed in various fields such as biomedical engineering, water purification, and food engineering. Many techniques have been investigated for their preparation. Of these, the microfluidic T-junction has shown great potential because of the high degree of control it has over processing parameters and the ability to produce monodisperse microbubbles. Two main lines of investigation were conducted in this work-the effect of varying the mixing region distance (M_x) and the influence of altering the tip-to-collector distance (D_x) when an ac-dc field is applied. It was found that when M_x was decreased from 200 to 100 μm, the microbubble diameter also decreased from 128 ± 3 to 88 ± 5 μm due to an increase in shear stress as a result of a reduction in surface area. Similarly, decreasing the tip-to-collector distance results in an increase in the electric field strength experienced at the nozzle, facilitating further reduction of the bubble diameter from 111 ± 1 to 86 ± 1 μm at an ac voltage of 6 kV P-P and an applied dc voltage of 6 kV. Experiments conducted with the optimal parameters identified from these previous experiments enabled further reduction of the microbubble diameter to 18 ± 2 μm. These results suggest that a unique combination of parameters can be employed to achieve particular microbubble diameters to suit various applications.

A Review on Properties of Natural and Synthetic Based Electrospun Fibrous Materials for Bone Tissue Engineering

Bone tissue engineering is an interdisciplinary field where the principles of engineering are applied on bone-related biochemical reactions. Scaffolds, cells, growth factors, and their interrelation in microenvironment are the major concerns in bone tissue engineering. Among many alternatives, electrospinning is a promising and versatile technique that is used to fabricate polymer fibrous scaffolds for bone tissue engineering applications. Copolymerization and polymer blending is a promising strategic way in purpose of getting synergistic and additive effect achieved from either polymer. In this review, we summarize the basic chemistry of bone, principle of electrospinning, and polymers that are used in bone tissue engineering. Particular attention will be given on biomechanical properties and biological activities of these electrospun fibers. This review will cover the fundamental basis of cell adhesion, differentiation, and proliferation of the electrospun fibers in bone tissue scaffolds. In the last section, we offer the current development and future perspectives on the use of electrospun mats in bone tissue engineering.

The Use of Finite Element Analyses to Design and Fabricate Three-Dimensional Scaffolds for Skeletal Tissue Engineering

Computational modeling has been increasingly applied to the field of tissue engineering and regenerative medicine. Where in early days computational models were used to better understand the biomechanical requirements of targeted tissues to be regenerated, recently, more and more models are formulated to combine such biomechanical requirements with cell fate predictions to aid in the design of functional three-dimensional scaffolds. In this review, we highlight how computational modeling has been used to understand the mechanisms behind tissue formation and can be used for more rational and biomimetic scaffold-based tissue regeneration strategies. With a particular focus on musculoskeletal tissues, we discuss recent models attempting to predict cell activity in relation to specific mechanical and physical stimuli that can be applied to them through porous three-dimensional scaffolds. In doing so, we review the most common scaffold fabrication methods, with a critical view on those technologies that offer better properties to be more easily combined with computational modeling. Finally, we discuss how modeling, and in particular finite element analysis, can be used to optimize the design of scaffolds for skeletal tissue regeneration.

Parametric Study of Electrospun Cellulose Acetate in Relation to Fibre Diameter

The objective was to identify the main factors and interactions influencing the fibre diameter in the production of electrospun cellulose acetate (CA) webs. A systematic parameter study was completed for producing electrospun CA fibres that were substantially free of bead defects and the effect of different process parameters during electrospinning CA were evaluated in respect of mean fibre diameter. The experiments were planned using factorial designs. Altogether three parameters, each at three levels, were selected for this study. The results indicate that polymer concentration, voltage and flow rate interact so that the magnitude of any change in the mean fibre diameter is dependent upon the level of the other factors. Furthermore, stable electrospinning conditions for CA were confirmed using an acetone: N, N-dimethylacetamide (DMAc) (2:1) solvent system that minimised the presence of structural defects in the web and promoted uniform fibre diameters.

Blends of shellac as nanofiber formulations for wound healing

Shellac is being used in food, pharmaceutical, and agricultural industries. It is seldom used for biomedical applications due to its poor mechanical property and instability. We designed thermoresponsive shellac-based bioactive nanofiber mats that mimic extracellular matrix to extend their utility in wound healing. Various blend compositions of shellac, gelatin, and poly(N-isopropylacrylamide) enriched with a bioactive agent, nadifloxacin, were prepared and nanofiber mats were fabricated. The morphology of the nanofiber formation was influenced by the concentration of polymer, drug, and polymer blend composition. Polymer–drug interactions and thermal and crystalline properties of nanofiber mats were analyzed. The shellac/gelatin/poly(N−isopropylacrylamide) blend of composition 3%/7%/3% (w/v) was chosen to evaluate in vitro drug release. Release studies recorded slow, constant, and sustained release for 140 h. The release kinetics and mechanism confirmed zero-order release with resultant r2 values greater than 0.99, and the Korsmeyer–Peppas release exponent ( n) was slightly higher than 0.8, which indicated that drug diffusion was anomalous or non-Fickian type and drug release followed diffusion involving chain stretching. Indirect cytotoxicity studies recorded insignificant toxicity against normal human fibroblast cells. In vivo studies demonstrated that drug-loaded nanofiber mats were more suitable for faster tissue regeneration as compared to nanofiber mats without drug and commercial nadifloxacin cream.

Biomaterials-based nanofiber scaffold: targeted and controlled carrier for cell and drug delivery

Nanofiber scaffold formulations (diameter less than 1000 nm) were successfully used to deliver the drug/cell/gene into the body organs through different routes for an effective treatment of various diseases. Various fabrication methods like drawing, template synthesis, fiber-mesh, phase separation, fiber-bonding, self-assembly, melt-blown, and electrospinning are successfully used for fabrication of nanofibers. These formulations are widely used in various fields such as tissue engineering, drug delivery, cosmetics, as filter media, protective clothing, wound dressing, homeostatic, sensor devices, etc. The present review gives a detailed account on the need of the nanofiber scaffold formulation development along with the biomaterials and techniques implemented for fabrication of the same against innumerable diseases. At present, there is a huge extent of research being performed worldwide on all aspects of biomolecules delivery. The unique characteristics of nanofibers such as higher loading efficiency, superior mechanical performance (stiffness and tensile strength), controlled release behavior, and excellent stability helps in the delivery of plasmid DNA, large protein drugs, genetic materials, and autologous stem-cell to the target site in the future.

Nanofibrous poly(lactide-co-glycolide) membranes loaded with diamond nanoparticles as promising substrates for bone tissue engineering

BACKGROUND

Nanofibrous scaffolds loaded with bioactive nanoparticles are promising materials for bone tissue engineering.

METHODS

In this study, composite nanofibrous membranes containing a copolymer of L-lactide and glycolide (PLGA) and diamond nanoparticles were fabricated by an electrospinning technique. PLGA was dissolved in a mixture of methylene chloride and dimethyl formamide (2:3) at a concentration of 2.3 wt%, and nanodiamond (ND) powder was added at a concentration of 0.7 wt% (about 23 wt% in dry PLGA).

RESULTS

In the composite scaffolds, the ND particles were either arranged like beads in the central part of the fibers or formed clusters protruding from the fibers. In the PLGA-ND membranes, the fibers were thicker (diameter 270 ± 9 nm) than in pure PLGA meshes (diameter 218 ± 4 nm), but the areas of pores among these fibers were smaller than in pure PLGA samples (0.46 ± 0.02 μm(2) versus 1.28 ± 0.09 μm(2) in pure PLGA samples). The PLGA-ND membranes showed higher mechanical resistance, as demonstrated by rupture tests of load and deflection of rupture probe at failure. Both types of membranes enabled the attachment, spreading, and subsequent proliferation of human osteoblast-like MG-63 cells to a similar extent, although these values were usually lower than on polystyrene dishes. Nevertheless, the cells on both types of membranes were polygonal or spindle-like in shape, and were distributed homogeneously on the samples. From days 1-7 after seeding, their number rose continuously, and at the end of the experiment, these cells were able to create a confluent layer. At the same time, the cell viability, evaluated by a LIVE/DEAD viability/cytotoxicity kit, ranged from 92% to 97% on both types of membranes. In addition, on PLGA-ND membranes, the cells formed well developed talin-containing focal adhesion plaques. As estimated by the determination of tumor necrosis factor-alpha levels in the culture medium and concentration of intercellular adhesion molecule-1, MG-63 cells, and RAW 264.7 macrophages on these membranes did not show considerable inflammatory activity.

CONCLUSION

This study shows that nanofibrous PLGA membranes loaded with diamond nanoparticles have interesting potential for use in bone tissue engineering.