Effects of Working Parameters on Electrospinning

Application of a PLA/PBAT/Graphite sensor obtained by electrospinning on determination of 2,4,6-trichlorophenol

The widespread use of pesticides requires effective detection and quantification tools to improve monitoring of environmental quality. Electrochemical sensors offer a fast and sensitive response, and can also be optimized by combining several constituents and techniques, including biodegradable materials, being useful in the determination of chemical agents from environmental samples. Here, we produced a polymer-based sensor for 2,4,6-trichlorophenol determination, through electrospinning of poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blend with graphite. The graphite-containing fibres were thermally treated and wetted in mineral oil, thus forming a paste, used as an electrode in the electrochemical sensor. The thermal analysis indicated a disorganization of the polymeric chains between the aromatic carbon chain of the PBAT polymer, resulting in a material with low enthalpy, lower crystallinity and greater thermal degradability after insertion of graphite in polymeric fibres. NIR spectra revealed changes related to the carbonyls of the polymeric ester groups. Cyclic voltammetry and square wave voltammetry techniques were applied to study the electrochemical behaviour of developed sensor. The thermal treatment of graphite-containing fibres increased the adhesion surface in which occurs the adsorption of the analyte on the electrode, which improved the peak current in the electrochemical tests. The PLA/PBAT/Graphite sensor applied to determination of 2,4,6-TCP presented the detection and quantification limits of 7.84 × 10-8 mol L-1 (0.0155 mg L-1) and 2.36 × 10-7 mol L-1 (0.0466 mg L-1) with a linearity response of 1.00 × 10-7 mol L-1 and 2.00 × 10-6 mol L-1 with correlation coefficient of 0.993 (r2).

Environmental concerns on the use of the electrospinning technique for the production of polymeric micro/nanofibers

The production of micro and nanofibers through the electrospinning technique is a well assessed technology that finds application in a variety of fields. Indeed, the specific features of electrospun fibers, as well as the possibility to be modelled and functionalized, ensure their great versatility. In the last decades, the widespread use of electrospun fibers promoted studies related to the evaluation of both human health and environmental risks associated to their handling and exposure. However, to date, the environmental impact strictly related to the use of the manufacturing process has been barely considered. Therefore, the present work aims to assess the environmental impacts of the electrospinning technology used to produce micro and nanofibers. To this purpose, a model polymer was systematically electrospun, varying the main system, process and external parameters, that control the electrospinning technique. A simplified life cycle assessment analysis was finally used to evaluate how the fibrous morphology, closely linked to the choice of the technological parameters, intrinsically affected the environmental impacts.

An Insight into Viscosity and Conductivity in the Formulation of Co-axial Electrospun Carica papaya Leaf Extract

Objective: This research aimed to investigate the application of the coaxial electrospun method for the production of natural extracts (papaya leaf extract) fibre films. This was achieved through utilising different polymers and with a focus on the conductivity and the viscosity of polymer solutions as critical parameters to generate successful fibres. Significance: Electrospinning is a promising trending manufacturing method for incorporating thermolabile herbal extracts using coaxial electrospun features. However, the complexity of the electrospinning process and the feasibility of the product required precise scrutiny. Methods: The electrospinning solution parameters (conductivity and viscosity) were evaluated by employing various ratios of Eudragit L100 (EL100) and Eudragit L100-55 (EL100-55) pre-spinning polymeric blend solutions. The electrospinning process and ambient parameters were optimised. Following that, the in-silico physicochemical properties of phytochemical marker, rutin, were illustrated using SwissADME web tool. Both freeze-dried Carica papaya leaf extract and its produced films were characterised using Scanning Electron Microscopy (SEM), Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR), polarised light microscopy, and X-Ray Powder Diffraction (XRPD). Results: The optimal values of conductivity (≈40-44 × 10-4 S/m) and viscosity (≈32-42 × 10-3 Pa·s) were determined for producing evenly distributed and small fibre diameters in SEM images. These parameters significance was highlighted in acquiring and maintaining adequate tangential stress for fibre elongation, which would consequently affect the morphology and diameter of the fibres formed. Conclusion: In conclusion, the solution, process, and ambient parameters are significant in developing natural extracts into films via electrospinning technology, and this includes the promising Carica papaya leaf extract films produced by coaxial electrospinning.

Electrospun Chitosan-Based Nanofibrous Coating for the Local and Sustained Release of Vancomycin

As the population ages, the number of vascular surgery procedures performed increases. Older adults often have multiple comorbidities, such as diabetes and hypertension, that increase the risk of complications from vascular surgery including vascular graft infection (VGI). VGI is a serious complication with significant morbidity, mortality, and healthcare costs. Here, we aimed to develop a nanofibrous chitosan-based coating for vascular grafts loaded with different concentrations of the vancomycin antibiotic vancomycin (VAN). Blending chitosan with poly(vinyl alcohol) or poly(ethylene oxide) copolymers improved solubility and ease of spinning. Thermal gravimetric analysis and Fourier transform infrared spectroscopy confirmed the presence of VAN in the nanofibrous membranes. Kinetics of VAN release from the nanofibrous mats were evaluated using high-performance liquid chromatography, showing a burst followed by sustained release over 24 h. To achieve longer sustained release, a poly(lactic-co-glycolic acid) coating was applied, resulting in extended release of up to 7 days. Biocompatibility assessment using human umbilical vein endothelial cells demonstrated successful attachment and viability of the nanofiber patches. Our study provides insights into the development of a drug delivery system for vascular grafts aimed at preventing infection during implantation, highlighting the potential of electrospinning as a promising technique in the field of vascular surgery.

Affordable lab-scale electrospinning setup with interchangeable collectors for targeted fiber formation

The electrospinning method is increasingly in demand due to its capability to produce fibers in the nanometer to micrometer range, with applications in diverse fields including biomedical, filtration, energy storage, and sensing. Many of these applications demand control over fiber layout and diameter. However, a standard flat plate collector yields random fibers with limited control over diameter and density. Other viable solutions offering a higher level of control are either scarce or substantially expensive, impeding the accessibility of this vital technique. This study addresses the challenge by designing an affordable laboratory-scale electrospinning setup with interchangeable collectors, enabling the creation of targeted fibers from random, aligned, and coiled. The collectors include the standard flat plate and two additional designs, which are a rotating drum and a spinneret tip collector. The rotating drum collector has adjustable speed control to collect aligned fibers and exhibits stability even at high rotational speeds. The spinneret tip collector was designed to produce helically coiled fibers. The setup was validated by directed fiber formation using polycaprolactone (PCL), a biodegradable and FDA-approved polymer. Overall, the uniqueness of the design lies in its affordability, modifiability, and replicability using readily available materials, thus extending the reach of the electrospinning technique.

Charge Storage Mechanism in Electrospun Spinel-Structured High-Entropy (Mn0.2 Fe0.2 Co0.2 Ni0.2 Zn0.2 )3 O4 Oxide Nanofibers as Anode Material for Li-Ion Batteries

High-entropy oxides (HEOs) have emerged as promising anode materials for next-generation lithium-ion batteries (LIBs). Among them, spinel HEOs with vacant lattice sites allowing for lithium insertion and diffusion seem particularly attractive. In this work, electrospun oxygen-deficient (Mn,Fe,Co,Ni,Zn) HEO nanofibers are produced under environmentally friendly calcination conditions and evaluated as anode active material in LIBs. A thorough investigation of the material properties and Li+ storage mechanism is carried out by several analytical techniques, including ex situ synchrotron X-ray absorption spectroscopy. The lithiation process is elucidated in terms of lithium insertion, cation migration, and metal-forming conversion reaction. The process is not fully reversible and the reduction of cations to the metallic form is not complete. In particular, iron, cobalt, and nickel, initially present mainly as Fe3+ , Co3+ /Co2+ , and Ni2+ , undergo reduction to Fe0 , Co0 , and Ni0 to different extent (Fe < Co < Ni). Manganese undergoes partial reduction to Mn3+ /Mn2+ and, upon re-oxidation, does not revert to the pristine oxidation state (+4). Zn2+ cations do not electrochemically participate in the conversion reaction, but migrating from tetrahedral to octahedral positions, they facilitate Li-ion transport within lattice channels opened by their migration. Partially reversible crystal phase transitions are observed.

Fabrication and characterization of anti-rosacea 3D nanofibrous customized sheet masks as a novel scaffold for repurposed use of spironolactone with pre-clinical studies

The repurposed oral use of spironolactone (SP) as an anti-rosacea drug faces many challenges that hinder its efficacy and compliance. In this study, a topically applied nanofibers (NFs) scaffold was evaluated as a promising nanocarrier that enhances SP activity and avoids the friction routine that exaggerates rosacea patients' inflamed, sensitive skin. SP-loaded poly-vinylpyrrolidone (40% PVP) nanofibers (SP-PVP NFs) were electrospun. Scanning electron microscopy showed that SP-PVP NFs have a smooth homogenous surface with a diameter of about 426.60 nm. Wettability, solid state, and mechanical properties of NFs were evaluated. Encapsulation efficiency and drug loading were 96.34% ± 1.20 and 11.89% ± 0.15, respectively. The in vitro release study showed a higher amount of SP released over pure SP with a controlled release pattern. Ex vivo results showed that the permeated amount of SP from SP-PVP NFs sheets was 4.1 times greater than that of pure SP gel. A higher percentage of SP was retained in different skin layers. Moreover, the in vivo anti-rosacea efficacy of SP-PVP NFs using croton oil challenge showed a significant reduction in erythema score compared to the pure SP. The stability and safety of NFs mats were proved, indicating that SP-PVP NFs are promising carriers of SP.

Optimal delivery of poorly soluble drugs using electrospun nanofiber technology: Challenges, state of the art, and future directions

Poor aqueous solubility of both, existing drug molecules and those which are currently in the developmental stage, have posed a great challenge to pharmaceutical scientists because they often exhibit poor dissolution behavior and subsequent poor and erratic bioavailability. This has triggered extensive research to explore nanotechnology-based technology platforms for possible rescue. Recently, nanofibers have been exploited widely for diverse biomedical applications including for drug delivery. Electrospun nanofibers are capable of preserving the homogeneously loaded therapeutic agents in amorphous state potentialy impairing devitrification. The present review aims at providing an overview of the various key factors that affect the electrospinning process and characteristics of the nanofibers while fabrication of drug loaded nanofibers for poorly soluble drug candidates. The review explores various methodological advancements in the electrospinning process and set-ups for production scale-up. The various types of electrospun nanofibers (like simple matrix, core-sheath, Janus, and inclusion complex nanofibers) that have been exploited for the delivery of poorly soluble drugs are also critically assessed. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Structure and magnetism of electrospun porous high-entropy (Cr1/5Mn1/5Fe1/5Co1/5Ni1/5)3O4, (Cr1/5Mn1/5Fe1/5Co1/5Zn1/5)3O4 and (Cr1/5Mn1/5Fe1/5Ni1/5Zn1/5)3O4 spinel oxide nanofibers

High-entropy oxide nanofibers, based on equimolar (Cr,Mn,Fe,Co,Ni), (Cr,Mn,Fe,Co,Zn) and (Cr,Mn,Fe,Ni,Zn) combinations, were prepared by electrospinning followed by calcination. The obtained hollow nanofibers exhibited a porous structure consisting of interconnected nearly strain-free (Cr_1/5Mn_1/5Fe_1/5Co_1/5Ni_1/5)₃O₄, (Cr_1/5Mn_1/5Fe_1/5Co_1/5Zn_1/5)₃O₄ and (Cr_1/5Mn_1/5Fe_1/5Ni_1/5Zn_1/5)₃O₄ single crystals with a pure Fd3̄m spinel structure. Oxidation state of the cations at the nanofiber surface was assessed by X-ray photoelectron spectroscopy and cation distributions were proposed satisfying electroneutrality and optimizing octahedral stabilization. The magnetic data are consistent with a distribution of cations that satisfies the energetic preferences for octahedral vs. tetrahedral sites and is random only within the octahedral and tetrahedral sublattices. The nanofibers are ferrimagnets with relatively low critical temperature more similar to cubic chromites and manganites than to ferrites. Replacing the magnetic cations Co or Ni with non-magnetic Zn lowers the critical temperature from 374 K (Cr,Mn,Fe,Co,Ni) to 233 and 105 K for (Cr,Mn,Fe,Ni,Zn) and (Cr,Mn,Fe,Co,Zn), respectively. The latter nanofibers additionally have a low temperature transition to a reentrant spin-glass-like state.

Qualifying the contribution of fiber diameter on the acrylate-based electrospun shape memory polymer nano/microfiber properties

Fibrous shape memory polymers (SMPs) have received growing interest in various applications, especially in biomedical applications, which offer new structures at the microscopic level and the potential of enhanced shape deformation of SMPs. In this paper, we report on the development and investigation of the properties of acrylate-based shape memory polymer fibers, fabricated by electrospinning technology with the addition of polystyrene (PS). Fibers with different diameters are manufactured using four different PS solution concentrations (25, 30, 35, and 40 wt%) and three flow rates (1.0, 2.5, and 5.0 μL min-1) with a 25 kV applied voltage and 17 cm electrospinning distance. Scanning electron microscope (SEM) images reveal that the average fiber diameter varies with polymer concentration and flow rates, ranging from 0.655 ± 0.376 to 4.975 ± 1.634 μm. Dynamic mechanical analysis (DMA) and stress-strain testing present that the glass transition temperature and tensile values are affected by fiber diameter distribution. The cyclic bending test directly proves that the electrospun SMP fiber webs are able to fully recover; additionally, the recovery speed is also affected by fiber diameter. With the combination of the SMP material and electrospinning technology, this work paves the way in designing and optimizing future SMP fibers properties by adjusting the fiber diameter.

Electrospun Poly (Vinyl Alcohol) Nanofibrous Mat Loaded with Green Propolis Extract, Chitosan and Nystatin as an Innovative Wound Dressing Material

Purposes

The objective of this work was to produce and characterise biodegradable poly (vinyl alcohol) (PVA) nanofibre loaded with green propolis extract (GPE), chitosan (CS) and nystatin (NYS) alone and in mixtures as a potential wound dressing material.

Methods

The GPE, NYS and CS1% were loaded in electrospinning compositions based on PVA 7%, 8% and 12% solubilised in milli-Q water or a mixture of water and glacial acetic acid. The electrospinning compositions without actives (blank) and those loaded with actives were characterised by determining the pH, electrical conductivity and rheological properties. An image analysis procedure applied to photomicrographs obtained by scanning electronic microscopy (SEM) allowed the determination of the nanofibres' diameter distribution and average surface porosity. The disintegration time and swelling ratio of the nanofibre mats were also determined.

Results

The physicochemical parameters of the electrospinning compositions (pH, electrical conductivity and rheology) and the incorporated active ingredients (GPE, CS and NYS) affected the electrospun nanofibre mats properties. The electrospun nanofibres' mean diameters and surface porosity ranged from 151.5 to 684.5 nm and from 0.29 ± 0.04 to 0.50 ± 0.05. The PVA/CS electrospun nanofibres fibres exhibited the smallest diameters, high surface porosity, water absorption capacity and disintegration time. The characteristics of the PVA/CS nanofibres mat associated with the biodegradability of the polymers make them a novel material with the potential to be applied as wound and burn dressings.

Preparation of PCL Electrospun Fibers Loaded with Cisplatin and Their Potential Application for the Treatment of Prostate Cancer

Prostate cancer is a global fatal type of cancer. It is a type of cancer that affect men. Signs and symptoms of the disease include blood in the urine, pain when one micturates, and difficulties in penis erection. Cisplatin chemotherapy is a principal treatment normally given to the prostate cancer patients. Nonetheless, on its own, cisplatin loses efficacy once administered due to liver pass effects and other biochemical attacks. In this paper, we looked at preparation of PCL nanoparticles loaded with cisplatin and their potential for the treatment of prostate cancer. PCL nanoparticles protect cisplatin from biochemical attack, thus increasing drug efficacy. Incorporation of P-glycoprotein inhibitors in PCL nanoparticles (NPs) loaded with cisplatin could improve prostate cancer treatment even more.

Optimizing the structural properties of electrospun polyimide membranes by response surface method

Recently, there has been a rising tendency for the fabrication of membranes using the electrospinning method because it can control the properties of the fibrous mats by changing the parameters of the process. For this reason, in the current research, polyimide (PI) membranes were fabricated by the electrospinning method. The effect of electrospinning parameters on the content of porosity and tensile properties of the electrospun PI mats were investigated. Solution concentration, device voltage, and feed rate were considered the process parameters. Response surface methodology was adopted to design the electrospinning experiments. The results showed that the feed rate had the most contribution to the content of porosity of electrospun PI membranes which increased by decreasing the feed rate. On the other hand, the polymer concentration had a remarkable effect on the tensile strength. Indeed, the tensile strength improved as the solution concentration increased. The optimized electrospinning parameters to achieve both the highest porosity (97.66%) and the highest tensile strength (2.25 MPa) in the PI membrane were as follows: solution concentration 16.78%wt, device voltage 17 kV, and feed rate 1.4 mL h−1. The experimental results were in good agreement with the predicted values.

Immobilization of α-amylase in ethylcellulose electrospun fibers using emulsion-electrospinning method

α-Amylase encapsulated in water in oil (W/O) emulsion was prepared using poly ethylene glycol (PEG 10000) (2%w/v) as water phase and ethylcellulose (EC) in ethyl acetate as oil phase at the ratio of 10:90 v/v. Next, the electrospun fibers were prepared by mixing enzyme loaded emulsion with EC solution (20%w/v) in acetic acid/ethyl acetate (20:80 v/v) at the 2:1 ratio. The emulsion showed good physical stability. The immobilized enzyme showed high activity across a board range of pHs and temperatures. The storage stability of the immobilized enzyme was 2 fold of free enzyme activity after 45 days. The residual activity of immobilized α-amylase onto of fibers after 10 and 15 repeated cycles, was approximately 100% and 50%, respectively. The results of this study indicated that the α-amylase loaded EC fibers have acceptable activity against harsh conditions and excellent reusability.

Understanding multiscale structure-property correlations in PVDF-HFP electrospun fiber membranes by SAXS and WAXS

Electrospinning is a versatile technique to produce nanofibrous membranes with applications in filtration, biosensing, biomedical and tissue engineering. The structural and therefore physical properties of electrospun fibers can be finely tuned by changing the electrospinning parameters. The large parameter window makes it challenging to optimize the properties of fibers for a specific application. Therefore, a fundamental understanding of the multiscale structure of fibers and its correlation with their macroscopic behaviors is required for the design and production of systems with dedicated applications. In this study, we demonstrate that the properties of poly(vinylidene fluoride-co-hexafluoro propylene) (PVDF-HFP) electrospun fibers can be tuned by changing the rotating drum speed used as a collector during electrospinning. Indeed, with the help of multiscale characterization techniques such as scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS), and wide-angle X-ray scattering (WAXS), we observe that increasing the rotating drum speed not only aligns the fibers but also induces polymeric chain rearrangements at the molecular scale. Such changes result in enhanced mechanical properties and an increase of the piezoelectric β-phase of the PVDF-HFP fiber membranes. We detect nanostructural deformation behaviors when the aligned fibrous membrane is uniaxially stretched along the fiber alignment direction, while an increase in the alignment of the fibers is observed for randomly aligned samples. This was analyzed by performing in situ SAXS measurements coupled with uniaxial tensile loading of the fibrous membranes along the fiber alignment direction. The present study shows that fibrous membranes can be produced with varying degrees of fiber orientation, piezoelectric β-phase content, and mechanical properties by controlling the speed of the rotating drum collector during the fiber production. Such aligned fiber membranes have potential applications for neural or musculoskeletal tissue engineering.

Preparation and Evaluation of Polyvinylpyrrolidone Electrospun Nanofiber Patches of Pioglitazone for the Treatment of Atopic Dermatitis

Nanofibers have many promising biomedical applications. They can be used for designing transdermal and dermal drug delivery systems. This project aimed to prepare and characterize polyvinylpyrrolidone-based nanofibers as a dermal and transdermal drug delivery system using pioglitazone. Pioglitazone is an oral antidiabetic drug. In addition, it can act as an inflammatory process modulator, making it a good candidate for managing different skin inflammatory conditions such as atopic dermatitis, skin ulcers, and diabetic foot wound healing. Several nanofiber formulations were prepared using the electrospinning method at different drug loadings, polyvinylpyrrolidone concentrations, and flow rates. A cast film with the exact composition of selected nanofiber formulations was prepared as a control. Nanofibers were characterized using a scanning electron microscope to calculate the diameter. Fourier-transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and powder X-ray diffraction were performed for physical and biochemical characterizations. In vitro release, drug loading efficiency, and swelling studies were performed. Ex vivo permeation studies were performed using Franz diffusion cells with or without applying a solid microneedle roller. Round uniform nanofibers with a smooth surface were obtained. The diameter of nanofibers was affected by the drug loading and polymer concentration. Fourier-transform infrared spectra showed a potential physical interaction between the drug and the polymer. According to X-ray diffraction, pioglitazone existed in an amorphous form in prepared nanofibers, with partial crystallinity in the casted film. Nanofibers showed a higher swelling rate compared to the casted film. The drug dissolution rate for nanofibers was 2.3-folds higher than the casted films. The polymer concentration affected the drug dissolution rate for nanofibers; however, drug loading and flow rate did not affect the drug dissolution rate for nanofibers. The application of solid microneedles slightly enhances the total amount of drug permeation. However, it did not affect the flux of the drug through the separated epidermis layer for pioglitazone. The drug permeation flux in nanofibers was approximately five times higher than the flux of the casted film. It was observed that pioglitazone is highly retained in skin layers. Graphical abstract.

Near-Field Electrospinning: Crucial Parameters, Challenges, and Applications

Near-field electrospinning (NFES) is a micro- or nanofiber production technology based on jetting molten polymer or polymer solution. Thanks to the programmable collector and nozzle movement, it can generate designed patterns in the presence of an electric field. Despite a few shortcomings of NFES, its high resolution, simplicity, precision, high throughput, reproducibility, and low costs have convinced researchers to employ it for various purposes. Furthermore, as the paradigm of fiber-based structures shifts from random textures toward delicate designs, NFES can bridge the gap between existing inefficient processes and aspired technologies for precise patterning. NFES facilitates the production of ultrafine nanofibers because it can be used to fabricate them in every laboratory. These robust fibers are convenient tools for small and additive manufacturing. As such, NFES is considered a potent additive fabrication technology that facilitates the production of complicated patterns as well. It is suggested that near-field electrospun fibers exhibit outstanding results in various applications, owing to their precise and controllable positioning. Meanwhile, the ongoing development of NFES has yet to reach its climax, making it attractive for further research. In this review, the basic principles of NFES, derivatives, limitations, and applications in nanomanufacturing, tissue engineering, microscale electronics, biosensors, and optics are presented.

Implantable magnetic nanofibers with ON-OFF switchable release of curcumin for possible local hyperthermic chemotherapy of melanoma

Implantable thermo-responsive drug-loaded magnetic nanofibers (NFs) have attracted great interest for localized thermo-chemotherapy of cancer tissue/cells. From this perspective, smart polymeric electrospun NFs co-loaded with magnetic nanoparticles (MNPs) and a natural polyphenol anticancer agent, curcumin (CUR), were developed to enhance the local hyperthermic chemotherapy against melanoma, the most serious type of skin cancer. CUR/MNPs-loaded thermo-sensitive electrospun NFs exhibited alternating magnetic field (AMF)-responsive heat generation and "ON-OFF" switchable heating capability. Besides, corresponding to the reversible alterations in the swelling ratio, the "ON-OFF" switchable discharge of CUR from the magnetic NFs was detected in response to the "ON-OFF" switching of AMF application. Due to the combinatorial effect of hyperthermia and release of CUR after applying an AMF ("ON" state) for 600 s on the second and third days of incubation time, the viability of the B16F10 melanoma cancer cells exposed to the CUR/MNPs-NFs was reduced by 40% and 17%, respectively. Taken together, the macroscopic and nanoscale features of the smart NFs led to the creation of a reversibly adjustable structure that enabled hyperthermia and facile switchable release of CUR for eradication of melanoma cancer cells.

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.

Nanomagnetite- and Nanotitania-Incorporated Polyacrylonitrile Nanofibers for Simultaneous Cd(II)- and As(V)-Ion Removal Applications

This work reports the fabrication of nanomagnetite- and nanotitania-incorporated polyacrylonitrile nanofibers (MTPANs) by an electrospinning process, which has the potential to be used as a membrane material for the selective removal of Cd(II) and As(V) in water. The fiber morphology was characterized by scanning electron microscopy (SEM). The incorporation of nanomagnetite and nanotitania in the composite fiber matrix was confirmed by energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. The fibers doped with nanomagnetite and nanotitania (MPAN and TPAN fibers, respectively), as well as MTPAN and neat polycrylonitrile (PAN) fibers, after thermally stabilizing at 275 °C in air, were assessed for their comparative As(V)- and Cd(II)-ion removal capacities. The isotherm studies indicated that the highest adsorption of Cd(II) was shown by MTPAN, following the Langmuir model with a q m of 51.5 mg/m2. On the other hand, MPAN showed the highest As(V)adsorption capacity, following the Freundlich model with a K F of 0.49. The mechanism of adsorption of both Cd(II) and As(V) by fibers was found to be electrostatically driven, which was confirmed by correlating the point of zero charges (PZC) exhibited by fibers with the pH of maximum ion adsorptions. The As(V) adsorption on MPAN occurs by an inner-sphere mechanism, whereas Cd(II) adsorption on MTPAN is via both surface complexation and an As(V)-assisted inner-sphere mechanism. Even though the presence of coexistent cations, Ca(II) and Mg(II), has been shown to affect the Cd(II) removal by MTPAN, the MTPAN structure shows >50% removal efficiency even for minute concentrations (0.5 ppm) of Cd(II) in the presence of high common ion concentrations (10 ppm). Therefore, the novel polyacrylonitrile-based nanofiber material has the potential to be used in polymeric filter materials used in water purification to remove As(V) and Cd(II) simultaneously.

Assessment of structural, biological and drug release properties of electro-sprayed poly lactic acid-dexamethasone coating for biomedical applications

The efficacy of an implant is highly depends on its coating characteristics mainly determined by polymer properties and coating technique. Electro-spraying is an inexpensive and versatile coating technique with various advantages for biomedical application. In this study, the efficacy of electro-sprayed (ES) poly lactic acid (PLA)-dexamethasone (DEX) coatings for medical implants was evaluated and compared with spin-coated samples as control. Structural properties of coatings were investigated using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). Confocal and scanning electron microscopy (SEM), contact angle measurement and nanoindentation tests were used to study surface properties. Coating degradation rate and drug release profile were studied for 40 days. Cell viability experiments were also performed on human endothelial (HUVEC) and smooth muscle cells (HUASMC) using MTT assay and SEM. XRD and DSC analysis showed electro-spraying significantly reduce PLA and DEX crystallinity. Surface studies showed ES coatings has significantly higher hydrophobicity and roughness with microbead-nanofiber morphology vs. micro-nanoporous structure of spin-coated samples. Initial burst release of DEX was 22% and 10% after 6 h and total release was 71% and 46% after 40 days for ES and spin-coated samples, respectively. HUVEC viability of ES samples was higher than spin-coated ones after 1 and 4 days. However, dexamethasone release profile reduced HUASMC proliferation in ES PLA-DEX samples in comparison to spin-coated after 1 and 3 days. In conclusion, in vitro results showed potential of ES PLA-DEX as a biocompatible and efficient anti-inflammatory coating with suitable drug release profile for future applications such as coronary drug eluting stents.

Biomimicking spider webs for effective fog water harvesting with electrospun polymer fibers

Fog is an underestimated source of water, especially in regions where conventional methods of water harvesting are impossible, ineffective, or challenging for low-cost water resources. Interestingly, many novel methods and developments for effective water harvesting are inspired by nature. Therefore, in this review, we focused on one of the most researched and developing forms of electrospun polymer fibers, which successfully imitate many fascinating natural materials for instance spider webs. We showed how fiber morphology and wetting properties can increase the fog collection rate, and also observed the influence of fog water collection parameters on testing their efficiency. This review summarizes the current state of the art on water collection by fibrous meshes and offers suggestions for the testing of new designs under laboratory conditions by classifying the parameters already reported in experimental set-ups. This is extremely important, as fog collection under laboratory conditions is the first step toward creating a new water harvesting technology. This review summarizes all the approaches taken so far to develop the most effective water collection systems based on electrospun polymer fibers.

Near-field electrospinning polycaprolactone microfibers to mimic arteriole-capillary-venule structure

The ability to create three-dimensional (3D) cell-incorporated constructs for tissue engineering has progressed tremendously. One of the major challenges that limit the clinical applications of tissue engineering is the inability to form sufficient vascularization of capillary vessels in the 3D constructs. The lack of a functional capillary network for supplying nutrients and oxygen leads to poor cell viability. This paper presents the near-field electrospinning (ES) technique to fabricate a branched microfiber structure that mimics the morphology of capillaries. Polycaprolactone solution was electrospun onto a sloped collector that resulted in morphological and geometric variation of the fibers. With proper control over the solution viscosity and the electrospinning voltage, a single fiber was scattered into a branched fiber network and then converged back to a single fiber on the collector. The obtained fibers have a diameter of less than 100 microns at the two ends with coiled and branched fibers of less than 10 microns that mimics the arteriole-capillary-venule structure. The formation of such a structure in the near-field ES strongly depends on the solution viscosity. Low viscosity solutions form beads and discontinuous lines thus cannot be used to achieve the desired structure. The branching of PCL fiber occurs due to an electrohydrodynamic instability. The transition from the straight large fiber to smaller coiled/branched fibers is not instantaneous and stretches over a horizontal region of 1.5 cm. The current work shows the feasibility of electrospinning the stem-branch-stem fibrous structure by adopting a valley-shaped collector with potentials for tissue engineering applications.

Poly(Glycerol Sebacate) in Biomedical Applications-A Review of the Recent Literature

Poly(glycerol sebacate) (PGS) continues to attract attention for biomedical applications owing to its favorable combination of properties. Conventionally polymerized by a two-step polycondensation of glycerol and sebacic acid, variations of synthesis parameters, reactant concentrations or by specific chemical modifications, PGS materials can be obtained exhibiting a wide range of physicochemical, mechanical, and morphological properties for a variety of applications. PGS has been extensively used in tissue engineering (TE) of cardiovascular, nerve, cartilage, bone and corneal tissues. Applications of PGS based materials in drug delivery systems and wound healing are also well documented. Research and development in the field of PGS continue to progress, involving mainly the synthesis of modified structures using copolymers, hybrid, and composite materials. Moreover, the production of self-healing and electroactive materials has been introduced recently. After almost 20 years of research on PGS, previous publications have outlined its synthesis, modification, properties, and biomedical applications, however, a review paper covering the most recent developments in the field is lacking. The present review thus covers comprehensively literature of the last five years on PGS-based biomaterials and devices focusing on advanced modifications of PGS for applications in medicine and highlighting notable advances of PGS based systems in TE and drug delivery.

Biomedical Applications of Electrospun Graphene Oxide

Graphene oxide (GO) has broad potential in the biomedical sector. The oxygen-abundant nature of GO means the material is hydrophilic and readily dispersible in water. GO has also been known to improve cell proliferation, drug loading, and antimicrobial properties of composites. Electrospun composites likewise have great potential for biomedical applications because they are generally biocompatible and bioresorbable, possess low immune rejection risk, and can mimic the structure of the extracellular matrix. In the current review, GO-containing electrospun composites for tissue engineering applications are described in detail. In addition, electrospun GO-containing materials for their use in drug and gene delivery, wound healing, and biomaterials/medical devices have been examined. Good biocompatibility and anionic-exchange properties of GO make it an ideal candidate for drug and gene delivery systems. Drug/gene delivery applications for electrospun GO composites are described with a number of examples. Various systems using electrospun GO-containing therapeutics have been compared for their potential uses in cancer therapy. Micro- to nanosized electrospun fibers for wound healing applications and antimicrobial applications are explained in detail. Applications of various GO-containing electrospun composite materials for medical device applications are listed. It is concluded that the electrospun GO materials will find a broad range of biomedical applications such as cardiac patches, medical device coatings, sensors, and triboelectric nanogenerators for motion sensing and biosensing.

Vitamin D3-loaded electrospun cellulose acetate/polycaprolactone nanofibers: Characterization, in-vitro drug release and cytotoxicity studies

Vitamin D deficiency is now a global health problem; despite several drug delivery systems for carrying vitamin D due to low bioavailability and loss bioactivity. Developing a new drug delivery system to deliver vitamin D₃ is a strong incentive in the current study. Hence, an implantable drug delivery system (IDDS) was developed from the electrospun cellulose acetate (CA) and ε-polycaprolactone (PCL) nanofibrous membrane, in which the core of implants consists of vitamin D₃-loaded CA nanofiber (CAVD) and enclosed in a thin layer of the PCL membrane (CAVD/PCL). CA nanofibrous mat loaded with vitamin D₃ at the concentrations of 6, 12, and 20% (w/w) of vitamin D₃ were produced using electrospinning. The smooth and bead-free fibers with diameters ranged from 324 to 428 nm were obtained. The fiber diameters increased with an increase in vitamin D₃ content. The controlled drug release profile was observed over 30-days, which fit with the zero-order model (R² > 0.96) in the first stage. The mechanical properties of IDDS were improved. Young's modulus and tensile strength of CAVD/PCL (dry) were161 ± 14 and 13.07 ± 2.5 MPa, respectively. CA and PCL nanofibers are non-cytotoxic based on the results of the in-vitro cytotoxicity studies. This study can further broaden in-vivo study and provide a reference for developing a new IDDS to carry vitamin D₃ in the future.

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.

Synthesis of nano-fibers containing nano-curcumin in zein corn protein and its physicochemical and biological characteristics

Curcumin contains many biological activities as a natural bioactive substance, however, its low solubility stands as a huge bioavailability disadvantage. Recently, different methods have been developed for utilizing the tremendous medicinal properties of this material. In this study, an Oil/Water nano-emulsion of curcumin (Nano-CUR) has been woven in zein polymer at three percentages of 5%, 10%, and 15% (v/v). We have investigated the physicochemical properties of nanofibers (NFs) including FESEM, FTIR, tensile strength, encapsulation efficiency, and release profile, as well as biological properties. According to the data, the NFs have been observed to become significantly thinner and more uniformed as the involved percentage of Nano-CUR had been increased from 5 to 15%. It is considerable that the tensile strength can be increased by heightening the existing Nano-CUR from 5% towards 15%. The resultant NFs of zein/Nano-CUR 15% have exhibited higher in vitro release and lower encapsulation efficiency than the other evaluated zein/Nano-CUR NFs. It has been confirmed through the performed viability and antioxidant studies that zein/Nano-CUR 10% NFs are capable of providing the best conditions for cell proliferation. Considering the mentioned facts, this work has suggested that Nano-CUR can be successfully woven in zein NFs and maintain their biological properties.

Solution Blow Spinning of Polyvinylidene Fluoride Based Fibers for Energy Harvesting Applications: A Review

Polyvinylidene fluoride (PVDF)-based piezoelectric materials (PEMs) have found extensive applications in energy harvesting which are being extended consistently to diverse fields requiring strenuous service conditions. Hence, there is a pressing need to mass produce PVDF-based PEMs with the highest possible energy harvesting ability under a given set of conditions. To achieve high yield and efficiency, solution blow spinning (SBS) technique is attracting a lot of interest due to its operational simplicity and high throughput. SBS is arguably still in its infancy when the objective is to mass produce high efficiency PVDF-based PEMs. Therefore, a deeper understanding of the critical parameters regarding design and processing of SBS is essential. The key objective of this review is to critically analyze the key aspects of SBS to produce high efficiency PVDF-based PEMs. As piezoelectric properties of neat PVDF are not intrinsically much significant, various additives are commonly incorporated to enhance its piezoelectricity. Therefore, PVDF-based copolymers and nanocomposites are also included in this review. We discuss both theoretical and experimental results regarding SBS process parameters such as solvents, dissolution methods, feed rate, viscosity, air pressure and velocity, and nozzle design. Morphological features and mechanical properties of PVDF-based nanofibers were also discussed and important applications have been presented. For completeness, key findings from electrospinning were also included. At the end, some insights are given to better direct the efforts in the field of PVDF-based PEMs using SBS technique.

Electrospun Polymers in Cartilage Engineering-State of Play

Articular cartilage defects remain a clinical challenge. Articular cartilage defects progress to osteoarthritis, which negatively (e.g., remarkable pain, decreased mobility, distress) affects millions of people worldwide and is associated with excessive healthcare costs. Surgical procedures and cell-based therapies have failed to deliver a functional therapy. To this end, tissue engineering therapies provide a promise to deliver a functional cartilage substitute. Among the various scaffold fabrication technologies available, electrospinning is continuously gaining pace, as it can produce nano- to micro- fibrous scaffolds that imitate architectural features of native extracellular matrix supramolecular assemblies and can deliver variable cell populations and bioactive molecules. Herein, we comprehensively review advancements and shortfalls of various electrospun scaffolds in cartilage engineering.

Fabrication and characterization of PVA/CS-PCL/gel multi-scale electrospun scaffold: simulating extracellular matrix for enhanced cellular infiltration and proliferation

A new bi-component poly(vinylalcohol)(PVA)/chitosan(CS)-poly(e-caprolactone)(PCL)/gelatin(Gel) multiscale electrospun scaffold was developed and analyzed in comparison with several other single scale systems. To mimic the native extracellular matrix in composition and structure and promote the migration of cells inside the scaffold, PVA/CS composite nanofibers (102 ± 52 nm) and PCL/Gelcomposite microfiber (2.5 ± 1.0 µm) were simultaneously electrospun from the two opposite syringes and mixed on a rotating mandrel to generate a bi-component multi-scale membrane. The bi-component membrane was crosslinked by glutaraldehyde vapor to maintain its fiber morphology in the wet stage. Morphology, shrinkage and spectroscopic of the electrospun membranes were characterized. To test the newly developed multiscale membrane, we seeded mesenchymal stem cells (MSCs) derived from rabbit onto five different fiber scaffolds (PVA, PVA/CS, PCL, PCL/Gel and PVA/CS-PCL/Gel) and compared cell adhesion and proliferation between different groups for 3 days using scanning electron microscopy, inverted microscope observations assay and MTT colorimetric. Cell culture results suggest that the incorporation of chitosan and gelatin could enhance cell adhesion and cell spreading in comparison to the performance of single component scaffolds of PVA and PCL. The multiscale PVA/CS-PCL/Gel membrane scaffolds provide a better environment to increase the growth, adhesion, and proliferation of cells. Scanning electron microscopy (SEM) observations showed that the cells were not only adhered well and proliferated on the surface of the scaffolds, but were also able to infiltrate inside the scaffold within 3 days of culture. MTT assay and inverted microscope observations also showed that the PVA/CS-PCL/Gel complex fibrous membrane exhibited better activity than other single component/scale systems scaffolds. Our results provide the underlying insights needed to guide the design of the native extracellular matrix.

The Role of Relative Humidity on Physical Characteristics of Poly Vinyl Alcohol-Aloe vera Fiber Membrane by Using Electrospinning Methods

Electrospinning is a method to fabricate nanofiber scaffold for tissue engineering. One of the parameters that affects the fiber size and morphology and the other physical characteristics is relative humidity of the room in which the electrospinning process is undertaken. The synthesis of electrospun Poly Vinyl Alcohol (PVA)-Aloe vera was performed with a variation of relative humidity (52%, 55%, 58%, and 64%). The physical characteristics of the fiber was tested by using functional group test, morphology test, thermal analysis test, and degradation test. The result of functional group test by using Fourier Transform Infrared (FTIR) showed that there was a crosslinking bond when the Aloe vera was introduced to the PVA. The morphology test result by using Scanning Electron Microscope (SEM) indicated that the addition of Aloe vera could increase the average of fiber diameter and the increase of relative humidity reduced the fiber diameter. The thermal analysis test result by using Differential Scanning Calorimetry (DSC) showed that the increase in the relative humidity could increase the temperature of glass transition (Tg) and decrease the temperature of melting (Tm). The degradation test implied that all the fibers could be degraded in 12 minutes.

Electrospinning of pyrazole-isothiazole derivatives: nanofibers from small molecules

We investigate the electrospinning of small molecules, specifically designed peptide derivatives of the pyrazole-isothiazole scaffold. Such non-natural peptides enhance the spectrum of fundamental materials used for electrospinning. Unlike standard electrospun materials, our peptides are not polymeric, but able to aggregate in solution and especially during processing. They contain donor/acceptor groups that can form hydrogen bonds, and groups that are able to generate π-stacking interactions, which are known as important requirements for assembly processes. The pyrazole-isothiazole derivatives were synthesized by means of a 1,3-dipolar cycloaddition reaction, which is completely regioselective, affording only one isomer. We demonstrate that our compounds can be electrospun from fluoroalcohol solution into solid, quasi-endless micro- and nanofibers. The electrospinnability varies substantially, depending on the amino acids linked to the scaffold. Some compounds provide only short fibers, while Fmoc-glycyl-(N-benzyl)-pyrazole-isothiazole-tert-butyl carboxylate-1,1-dioxide forms continuous, homogenous, and bead-free fibers (droplet-like beads are a common problem in electrospinning). We analyzed the compounds and the fibers with various spectroscopic techniques (MS, IR and Raman). Electrospinning does not change chemical composition and configuration, suggesting the monomeric form of the compounds even in the fibers. Interestingly, we found that the stereochemistry of the scaffold can affect the ability of the peptide to be electrospun.

Computationally optimizing the compliance of multilayered biomimetic tissue engineered vascular grafts

Coronary artery bypass grafts used to treat coronary artery disease often fail due to compliance mismatch. In this study, we have developed an experimental/computational approach to fabricate an acellular biomimetic hybrid tissue engineered vascular graft composed of alternating layers of electrospun porcine gelatin/polycaprolactone (PCL) and human tropoelastin/PCL blends with the goal of compliance-matching to rat abdominal aorta, while maintaining specific geometrical constraints. Polymeric blends at three different gelatin:PCL (G:PCL) and tropoelastin:PCL (T:PCL) ratios (80:20, 50:50 and 20:80) were mechanically characterized. The stress-strain data was used to develop predictive models, which were used as part of an optimization scheme that was implemented to determine the ratios of G:PCL and T:PCL and the thickness of the individual layers within a tissue engineered vascular graft that would compliance match a target compliance value. The hypocompliant, isocompliant, and hypercompliant grafts had target compliance values of 0.000256, 0.000568 and 0.000880 mmHg-1, respectively. Experimental validation of the optimization demonstrated that the hypercompliant and isocompliant grafts were not statistically significant from their respective target compliance values (p-value=0.37 and 0.89, respectively). The experimental compliance value of the hypocompliant graft was statistically significant than their target compliance value (p-value=0.047). We have successfully demonstrated a design optimization scheme that can be used to fabricate multilayered and biomimetic vascular grafts with targeted geometry and compliance.

Electrospun PCL, gold nanoparticles, and soy lecithin composite material for tissue engineering applications

Soy lecithin has been shown to play a critical role in cell signaling and cellular membrane structure. In addition, it has been shown to increase biocompatibility, hydrophilicity, and decrease cytotoxicity. Gold nanoparticles have also shown to improve cellularity. Lecithin, gold nanoparticles, and polycaprolactone (PCL) solutions were electrospun in order to develop unique mesh materials for the treatment of osteoarthritis. The electrospinning parameters were optimized to achieve different solution ratios for fiber optimization. The amount of lecithin mixed with PCL varied from 30 wt.% to 50 wt.% . Gold nanoparticles (1% to 10% concentrations) were also added to lecithin-PCL mixture. The mechanical and chemical properties of the fiber mesh were analyzed via contact angle test, tensile mechanical tests, Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). Cell viability was measured using a WST-1 Assay. Scanning electron microscopy confirmed the successful formation of fiber mesh. The compositions of 40% soy lecithin with PCL in 40% solvent (40:40) resulted in the most well-formed fiber mesh. DSC melt temperatures were statically insignificant; uniaxial stresses and the moduli resulted in no significant difference between the test composition and pristine PCL compositions. WST-1 assay revealed all compositions were non-cytotoxic. Overall, the addition of lecithin increased hydrophilicity while maintaining cell viability and the mechanical and chemical properties of PCL. This study demonstrated that it is possible to successfully electrospin a lecithin, gold nanoparticle, and polycaprolactone scaffold for tissue engineering applications.