Electrospun PET Research Articles

Effects of the electric field distribution on electrospun PET fibers properties

Electric field plays a key role in producing required nanofibers in electrospinning. The applied voltage and working distance are the two main factors affects the electric field distribution during the electrospinning process. This work discussed the effects of these two parameters on the fiber fineness and performance in the electrospinning process, and also verified the results of numerical simulation through a series of experiments. The results showed that the larger the voltage applied to the spinneret is, the greater the electric force acting on the fibers is, which leads to a smaller fiber fineness and a preferable hydrophobic performance and strength. On the other hand, as the spinning distance increases, the smaller the force exerted on the fiber is, the larger the diameter is and the weaker hydrophobic performance is.

Effect of the flame-retardant 3-hydroxyphenylphosphinyl-propanoic acid on the mechanical, thermal, and flammability properties of poly(ethylene terephthalate) nanofiber mats

The structure, thermal stability, and mechanical properties of electrospun nanofiber mats obtained from poly(ethylene terephthalate) (PET) solutions in trifluoroacetic acid/dichloromethane were evaluated. The electrospun PET nanofibers were characterized by means of attenuated total reflection Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, limiting oxygen index, and tensile testing. PET-3-hydroxyphenylphosphinyl-propanoic acid (HPP) copolymer was used as the flame-retardant (FR) agent to improve the thermal stability and flammability of the nanofiber mats. HPP is a commercial FR for polyesters which was studied from the viewpoint of chemical reactivity and reaction mechanism. To enhance the tensile strength of the nanofiber mats, the nanofibers were collected on high-speed rotating drum. The results showed that the nanofibers were oriented, and their strength was enhanced by increasing the velocity of the collector. The average diameter of electrospun nanofibers was in the range of 110–240 nm, decreasing with the increasing drum speed. Also the mean pore size of the mats decreased significantly with increasing orientation of the nanofibers. The results showed that HPP improved the flame retardancy of PET.

Abstract 132: Application of a Cryogel-Coated Prosthetic Vascular Graft Material for Delivery of Targeted Gene Therapies in a Rabbit Model

Objectives: Long-term success of prosthetic grafts (PG) in peripheral arterial disease is limited by development of anastomotic neointimal hyperplasia. We have constructed a bioactive prosthetic graft material (BPGM) capable of delivering biologic agents in vitro, and evaluate our BPGM in vivo with a rabbit carotid interposition bypass model. Methods: We synthesized our BPGM by cryopolymerization of RGD with methacrylated alginate and heparin, coating 1.5cm by 2mm electrospun PET (ePET) grafts, and dipcoating in fluorescent siRNA for 3 hours. Three rabbits received bare ePET and 3 received cryogel-coated ePET for a carotid interposition bypass (Figure 1). After 24 hours, bypass patency was assessed, and cell toxicity of the proximal anastomosis, mid-graft, and distal anastomosis examined with H&E staining. Confocal microscopy was used to visualize fluorescence, correlating with ability to deliver siRNA in vivo. Results: Graft patency was equal between groups, with no increased cell toxicity in rabbits receiving cryogel-coated ePET. Confocal microscopy demonstrated no difference in retained fluorescence between rabbits receiving cryogel-coated or bare ePET, and no increased transfection of cells at 24 hours (Figure 2). Conclusion: Creation of the optimal PG demands a material that is biocompatible, responsive, and nonthrombogenic. We have constructed a modified PG capable of in vitro delivery of targeted gene therapies, with comparable patency and biocompatibility in our large animal model. Additional optimization to achieve predictable and sustained release is needed to validate this as an effective and practical method to deliver biologic agents in vivo.

Biomimetic coating of cross-linked gelatin to improve mechanical and biological properties of electrospun PET: A promising approach for small caliber vascular graft applications.

Electrospun PET (ePET) is a promising material for small caliber vascular graft applications owing to its tunable mechanical properties, biocompatibility, and nanofibrous structure that mimic the morphology of natural extracellular matrix. However, the inherent inertness of PET impairs the adhesion and proliferation of endothelial cells on the inner surface of ePET tubular grafts, hindering the formation of a functional endothelium. Gelatin coatings, owing to their ability to promote endothelialization, are a valuable approach to overcome the limitations of ePET. Herein, a novel process for the deposition of stable biomimetic coatings of gelatin on ePET tubular grafts is proposed. Electrospun PET was first aminated by plasma treatment and then coated with a gelatin hydrogel cross-linked in situ by a Michael-type addition reaction. Amination provided a superhydrophilic behavior to the ePET surface, allowing easy gelatin interpenetration along the wall thickness of the tubular structure, and the obtainment of thin coatings that maintained the morphology of ePET fibers. Gelatin coating was stable at long term in a physiological-like environment, noncytotoxic and promoted in vitro cell adhesion and proliferation. Noteworthy, the mechanical properties of gelatin-coated ePET tubular grafts were improved in terms of elastic modulus, compliance, and elastic recoil, finally better matching the characteristics of native blood vessels. Altogether, the proposed coating technique successfully combines the advantages of ePET nanofibrous structure with cross-linked gelatin biological cues and mechanical reinforcement, and emerges as a promising strategy for the development of biocompatible small caliber vascular grafts with superior biomimetic and mechanical properties. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2405-2415, 2017.

Electrospun recycled PET-based mats: Tuning the properties by addition of cellulose and/or lignin

The aim of this study was to evaluate the influence of cellulose and/or lignin on the properties of mats prepared from dissolution (for 48 h or 72 h, solvent: trifluoroacetic acid) of recycled poly (ethylene terephthalate) (PET). Briefly, the presence of cellulose led to a tendency of higher average fiber diameter and average pore area as well as lower average porosity compared to the neat mat (PETref, 242 ± 59 nm, 9.6 ± 1.1 104 nm2 and 19.0 ± 1.1%, respectively). The Tg values for electrospun PET combined with cellulose and/or lignin were higher than that of PETref (92.5 ± 0.1 °C), and the tensile strength increased with the cellulose and/or lignin loading. In addition, the presence of lignin (72 h of dissolution) led to a mat with an elongation at break of 149 ± 9% compared to 14 ± 2% for PETref. The results indicated that the properties of mats based on PET can be tuned by adding cellulose and/or lignin to solutions posteriorly electrospun as well as by varying the dissolution time.

Assessing the Suitability of Electrospun Poly(Ethylene Terephthalate) and Polystyrene as Cell Carrier Substrates for Potential Subsequent Implantation as a Synthetic Bruch's Membrane

Electrospun poly(ethylene terephthalate) (PET) and polystyrene (PS) were tested for suitability as cell carrier substrates. Membranes were UV/ozone treated, which improved protein adsorption, with aminolysis observed on PET. PET demonstrated greater handling and durability compared to PS. Treated and untreated PET supported cell proliferation, with cells exhibiting the desired monolayer morphology. Untreated PS did not support cell proliferation and although treated PS did, the resultant RPE cell morphology was undesirable. Preliminary tests investigating thickness of mats were also undertaken, with PET exhibiting better results. Electrospun PET exhibited cytocompatibility, and could prove to be a suitable candidate for potential subsequent implantation.

Gene silencing in human aortic smooth muscle cells induced by PEI–siRNA complexes released from dip-coated electrospun poly(ethylene terephthalate) grafts

An excessive tissue response to prosthetic arterial graft material leads to intimal hyperplasia (IH), the leading cause of late graft failure. Seroma and abnormal capsule formation may also occur after prosthetic material implantation. The matricellular protein Thrombospondin-2 (TSP-2) has shown to be upregulated in response to biomaterial implantation. This study evaluates the uptake and release of small interfering RNA (siRNA) from unmodified and surface functionalized electrospun PET graft materials. ePET graft materials were synthesized using electrospinning technology. Subsets of the ePET materials were then chemically modified to create surface functional groups. Unmodified and surface-modified ePET grafts were dip-coated in siRNAs alone or siRNAs complexed with transfection reagents polyethyleneimine (PEI) or Lipofectamine RNAiMax. Further, control and TSP-2 siRNA–PEI complex treated ePET samples were placed onto a confluent layer of human aortic smooth muscle cells (AoSMCs).Complexation of all siRNAs with PEI led to a significant increase in adsorption to unmodified ePET. TSP-2 siRNA-PEI released from unmodified-ePET silenced TSP-2 in AoSMC. Regardless of the siRNA–PEI complex evaluated, AoSMC migrated into the ePET. siRNA–PEI complexes delivered to AoSMC from dip-coated ePET can result in gene knockdown. This methodology for siRNA delivery may improve the tissue response to vascular and other prosthetics.

SiRNA Transfection With Cholesterol Modification From Electrospun PET Facilitates Gene Silencing in Human Aortic Smooth Muscle Cells

Anastomotic intimal hyperplasia (AIH) remains the leading cause for prosthetic arterial graft failure. RNAi is a promising tool to silence genes such as Thrombospondin-2 (TSP-2), previously shown by our group to be upregulated in AIH. The present study is aimed at delivering modified TSP-2 siRNA (3’cholesterol tagged TSP-2 siRNA) from electrospun polyethylene terephthalate (ePET) and therefore knocking down TSP-2 gene and ultimately inhibiting AIH.

SiRNA Transfection with Cholesterol Modification from Electrospun PET Facilitates Gene Silencing in Human Aortic Smooth Muscle Cells

SiRNA Transfection with Cholesterol Modification from Electrospun PET Facilitates Gene Silencing in Human Aortic Smooth Muscle Cells

Solution-Electrospun Poly(ethylene terephthalate) Fibers: Processing and Characterization

Electrospun poly(ethylene terephthalate) (PET) fibers were prepared from a trifluoroacetic acid (TFA)-based solvent. Rheological studies revealed the concentration (ϕ) dependence of the specific viscosity (ηsp) to be ηsp ∼ ϕ3.7 for PET/TFA solutions in the entangled regime. The determined entanglement concentration (ϕe) was higher using a lower-molecular-weight PET. To obtain bead-free fibers, the minimum concentration for the electrospinning was 0.8–1.0ϕe owing to the high volatility of TFA solvent, which significantly enhanced the chain network strength during jet whipping. The double-logarithmic plots of the jet (dj) and fiber (df) diameters versus the zero-shear viscosity (η0) revealed that two scaling laws existed for the present solutions, i.e., dj ∼ η00.06 and df ∼ η00.77. The microstructural evolution of the electrospun PET fibers from stepwise annealing to crystal melting was investigated by simultaneous small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) measurements using synchrotron radiation sources. The conformer transformation from gauche to trans was monitored by in-situ Fourier transform infrared spectral measurement. In the absence of any WAXD reflection, the as-spun PET fibers possessed a SAXS scattering peak, indicating the presence of a mesomorphic phase with an interdomain distance of 6.8 nm. At annealing temperatures (Ta) higher than 100 °C, the mesomorphic phase gradually transformed into imperfect triclinic crystals and reached its saturation at 130 °C. Further increased Ta perfected the triclinic structure without altering fiber crystallinity until the initial crystal melting at 218 °C, at which a significantly increased long period was detected. When the electrospun PET fibers were embedded in an isotactic polypropylene (iPP) matrix, surface-induced crystallization occurred to develop a transcrsytalline layer of iPP monoclinic crystals at the interface.

Responsive PET Nano/Microfibers via Surface-Initiated Polymerization

Poly(ethylene terephthalate) (PET) is one of the most important thermoplastics in ubiquitous use today because of its mechanical properties, clarity, solvent resistance, and recyclability. In this work, we functionalize the surface of electrospun PET microfibers by growing poly(N-isopropylacrylamide) (PNIPAAm) brushes through a chemical sequence that avoids PET degradation to generate thermoresponsive microfibers that remain mechanically robust. Amidation of deposited 3-aminopropyltriethoxysilane, followed by hydrolysis, yields silanol groups that permit surface attachment of initiator molecules, which can be used to grow PNIPAAm via "grafting from" atom-transfer radical polymerization. Spectroscopic analyses performed after each step confirm the expected reaction and the ultimate growth of PNIPAAm brushes. Water contact-angle measurements conducted at temperatures below and above the lower critical solution temperature of PNIPAAm, coupled with adsorption of Au nanoparticles from aqueous suspension, demonstrate that the brushes retain their reversible thermoresponsive nature, thereby making PNIPAAm-functionalized PET microfibers suitable for filtration media, tissue scaffolds, delivery vehicles, and sensors requiring robust microfibers.

SiRna Transfection and Gene Silencing in Human Aortic Smooth Muscle Cells from Electrospun PET

SiRna Transfection and Gene Silencing in Human Aortic Smooth Muscle Cells from Electrospun PET

Generation of functional PET microfibers through surface-initiated polymerization

In this study, we report on a facile and robust method by which poly(ethylene terephthalate) (PET) surfaces can be chemically modified with functional polymer brushes while avoiding chemical degradation. The surface of electrospun PET microfibers has been functionalized by growing poly(2-dimethylaminoethyl methacrylate) (PDMAEMA) and poly(2-hydroxyethyl methacrylate) (PHEMA) brushes through a multi-step chemical sequence that ensures retention of mechanically robust microfibers. Polymer brushes are grown via “grafting from” atom-transfer radical polymerization after activation of the PET surface with 3-aminopropyltriethoxysilane. Spectroscopic analyses confirm the expected reactions at each reaction step, as well as the ultimate growth of brushes on the PET microfibers. Post-polymerization modification reactions have likewise been conducted to further functionalize the brushes and impart surface properties of biomedical interest on the PET microfibers. Antibacterial activity and protein resistance of PET microfibers functionalized with PDMAEMA and PHEMA brushes, respectively, are demonstrated, thereby making these surface-modified PET microfibers suitable for filtration media, tissue scaffolds, delivery vehicles, and sensors requiring mechanically robust support media.

Effect of dispersion of nanofibers on the properties of LDPE FILMS

Nanofiber reinforced composites based on dispersion of electrospun PET nanofibers and LDPE were prepared by melt extrusion. The nanofibers were dispersed in 0.1, 0.5 and 1 wt%. Test specimens were prepared in a blown film extruder. Samples of each stage of nano fibers reinforced composites’ processing were characterized by means of scanning electron microscopy (SEM), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), gas permeability, mechanical testing, dart impact strength and heat seal strength. It was observed that the nanofiber dispersed films show exceptionally good resistance to gas permeability along with an improvement in mechanical, dart impact and sealing properties.

Application of electrospun poly(ethylene terephthalate) nanofiber mat to apple juice clarification

Electrospinning was used to produce self-supporting nanofibrous poly(ethylene terephthalate) membranes with good mechanical properties and straightforward handling. The application of this type of membranes in apple juice clarification process was investigated. Processing characteristics and quality parameters of apple juice were analyzed in order to compare the proposed method to traditional clarification techniques. In general, the apple juice obtained from electrospun nanofiber membrane filtration revealed physico-chemical characteristics comparable to those from juice clarified by ultrafiltration or by conventional clarification using filtering aids. Nevertheless, the new process showed a high flux performance and revealed to be much faster, simple and more economical than the traditional processes. This work demonstrated the filtration potential of an electrospun PET membrane thus introducing a new concept of clarification and opening new approaches for the juice processing industry or even for other food industry fields.

Study of charge storage in the nanofibrous poly(ethylene terephthalate) electrets prepared by electrospinning or by corona discharge method

In this paper, the charge storage performance of electrospun poly(ethylene terephthalate) (PET) mats with high specific surface area was evaluated in comparison to that of PET film electrets. Corona discharge method was used to charge the electrospun PET mats and PET films. The surface potential decay measurements revealed that the corona charged РЕТ mats had higher initial values for the normalized surface potential compared to the РЕТ electret films. A tendency for stabilization of the electret charge to one and the same value for all charged samples (mats and films) after the 50th day was observed. The peaks at 90 °C in the thermally stimulated current (TSC) spectra of uncharged and charged in corona discharge electrospun PET mats were observed and attributed to a relaxation of the separated space charges, the dipole disorientation or injected charges within the bulk. It was found that the value of the storage charge in a corona charged electrospun PET mats was higher than that in PET mats prepared by electrospinning.

Ultra-Fine Fibers Produced by Laser-Electrospinning

We used a CO2 laser as a heat source to avoid thermodegradation in the melt-electrospinning process (termed “laser electrospinning” (LES)). Nylon 6, polypropylene, poly (ethylene terephthalate) and poly (L-lactide-co-e-caprolactone) fiber webs were prepared by the LES. For Nylon 6 and poly (L-lactide-co-e-caprolactone), fibers having average diameters of approximately 1 μm and a coefficient of variation (CV) of no more than 20% were obtained. The effects of the applied voltage and laser power on the diameter of the PET fibers were investigated. The average diameter of the electrospun PET fibers decreased with a decrease in the applied voltage; however, using an applied voltage that was too low caused thermodegradation. The average diameter decreased with an increase in laser power. Above a certain laser power, however, shot particles and large deviations in the fiber diameter were observed.

Melt‐electrospinning of poly(ethylene terephthalate) and polyalirate

AbstractRodlike polymer samples were made from three kinds of poly(ethylene terephthalate) (PET) pellets with different intrinsic viscosities (IV), and from polyalirate (Vectra) pellets. PET and Vectra fibers were produced using a melt‐electrospinning system equipped with a CO2‐laser melting device from these rodlike samples. The effects of IV value and laser output power on the fiber diameter of PET were investigated. Furthermore, the effect of the laser output power on the fiber diameter of Vectra was investigated. The crystal orientation of these produced fibers was also investigated by X‐ray photographs. The following conclusions were reached: (i) the diameter of PET fiber decreases with increasing laser output power; (ii) the minimum average diameter of PET fibers is scarcely influenced by the value of IV; (iii) the electrospun PET fibers show isotropic crystal orientation; (iv) fibers having an average fiber diameter smaller than 1 μm cannot be obtained from PET and Vectra using the system developed; and (v) preferred liquid crystal orientation can be seen in electrospun Vectra fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

The effect of molecular weight and the linear velocity of drum surface on the properties of electrospun poly(ethylene terephthalate) nonwovens

In this study, we evaluated the effect of the molecular weight of the polymer on electrospun poly(ethylene terephthalate) (PET) nonwovens, and their mechanical properties as a function of the linear velocity of drum surface. Polymer solutions and electrospun PET nonwovens were characterized by means of viscometer, tensiometer, scanning electron microscope (SEM), wide angle X-ray diffraction measurement (WAXD) and universal testing machine (UTM). By keeping the uniform solution viscosity, regardless of molecular weight differences, electrospun PET nonwovens with similar average diameter could be obtained. In addition, the mechanical properties of the electrospun PET nonwovens were strongly dependent on the linear velocity of drum surface. From the results of the WAXD scan, it was found that the polymer took on a particular molecular orientation when the linear velocity of drum surface was increased. The peaks became more definite and apparent, evolving from an amorphous pattern at 0 m/min to peaks and signifying the presence of crystallinity at 45 m/min.