Stable Jet Electrospinning Research Articles

Highly aligned electroactive ultrafine fibers promote the differentiation of mesenchymal stem cells into Schwann-like cells for nerve regeneration

This study investigates the efficacy of a novel tissue-engineered scaffold for nerve repair and functional reconstruction following injury. Utilizing stable jet electrospinning, we fabricated aligned ultrafine fibers from dopamine and poly(L-lactic acid) (PLLA), further developing a biomimetic, oriented, and electroactive scaffold comprising poly(pyrrole) (PPy), polydopamine (PDA), and PLLA through dual in situ polymerizations. The scaffold demonstrated enhanced cell adhesion and reactive oxygen species (ROS) scavenging capabilities and promoted the differentiation of mesenchymal stem cells (MSCs) into Schwann-like cells, essential for nerve regeneration. In vivo assessments revealed significant peripheral nerve regeneration in 10 mm sciatic nerve defects in rats, with observations made 12 weeks post-transplantation. This included facilitated myelination and increased muscle density on the injured side, leading to improved motor function recovery. Our results suggest that the aligned PPy/PDA/PLLA fibrous scaffold offers a promising approach for promoting the differentiation of MSCs into Schwann-like cells conducive to nerve regeneration and represents a significant advancement in nerve repair technologies. This study provides a foundational basis for future research into tissue-engineered solutions for nerve damage, potentially impacting clinical strategies for nerve reconstruction.

Dual-bioactive molecules loaded aligned core-shell microfibers for tendon tissue engineering

Development of a controlled delivery ultrafine fibrous system with two bioactive molecules is required to stimulate tendon healing in different phase. In this study, we used emulsion stable jet electrospinning to fabricate aligned poly(L-lactic acid) (PLLA) based ultrafine fibers with two small bioactive molecules of L-Arginine (Arg) and low molecular weight hyaluronic acid (HA). The results demonstrated that the aligned Arg/HA/PLLA microfibrous scaffold showed core-shell structure and allowed sequential release of Arg and HA due to their different electric charge. The scaffold also showed enhanced hydrophilicity, cell migration, spread and proliferation. Using an Achilles tendon repair model in rats, we demonstrated that this novel fibrous scaffold can prevent adhesion and promote tendon regeneration. Additionally, two p53 and ER-α-mediated signalling pathways were described as the probable main path of synergistic effects of the novel scaffold on tendon generation. Thus, this study may provide an important strategy for developing biofunctional and biomimetic tendon scaffolds.

Production of highly aligned microfiber bundles from polymethyl methacrylate via stable jet electrospinning for organic solid‐state lasers

AbstractThe fabrication of micron‐sized poly(methyl methacrylate) (PMMA) polymer optical fibers doped with rhodamine B as an organic dye is demonstrated. Highly aligned and defect‐free fibers are fabricated by using the stable jet electrospinning (SJES) method and systematically varying critical parameters such as solvent type and polymer concentration. At optimal conditions, for example, a polymer concentration of 35 wt% of PMMA in butanone, ribbon‐shaped fibers with a smooth surface and diameter of about 20 μm could be spun using SJES mode and deposited on a rotating drum as target in a highly aligned manner. Photoluminescence spectra of the doped fibers excited longitudinally and transversely with a laser show an excitation peak with full‐width‐at‐half‐maximum of only 5.05 nm and a low lasing threshold at a pump energy of 0.55 μJ, indicating that SJES could become a new source of amplified optics components or organic solid‐state fiber lasers.

Aligned Electrospun PLLA/Graphene Microfibers with Nanotopographical Surface Modulate the Mitochondrial Responses of Vascular Smooth Muscle Cells

AbstractAlthough electrospun polymer fibers with unique (bio)physicochemical features have been demonstrated to regulate cellular phenotype, their specific effect on organelles has not been examined closely. Herein, this work investigates the impact of aligned electrospun poly(L‐lactic acid) (PLLA)/graphene (Gr) microfibers with the nanoporous surface on the mitochondrial responses of human aorta smooth muscle cells. Highly aligned PLLA/Gr microfibers with an average fiber diameter of ≈1.3 µm are prepared via a novel stable jet electrospinning strategy. Nanoporous topography is formed onto individual fiber surfaces using highly volatile solvent dichloromethane and suitable ambient humidity. Further, it is found that the addition of Gr in PLLA fibers significantly facilitates the formation of mitochondrial reactive oxygen species (mROS) and adenosine triphosphate (ATP) as well as mitochondrial autophagy and division by upregulating the protein expression of microtubule‐associated protein light chain 3, mitochondrial fission 1 protein, and dynamin‐related protein 1. In contrast, the introduction of the nanoporous structure greatly inhibits the generation of mROS and ATP as well as mitochondrial autophagy and division. The work thus indicates that the incorporation of nanotopography and Gr in/on the PLLA fibers can offer additional physicochemical stimuli to regulate the mitochondrial responses of cells.

Well-aligned Polycaprolactone Fiber by Stable Jet Electrospinning

In this work, polycaprolactone (PCL) fiber membrane with random, partially aligned and well-aligned morphology by conventional electrospinning, high speed drum electrospinning and stable jet electrospinning, respectively. By adjusting PCL polymer solution (solution viscosity and conductivity) and electrospinning parameter (voltage, temperature, humidity et al.), well-aligned PCL membrane with fibers arranged in one direction under SEM observation. The mechanical behaviour were also studied. The stable jet electrospinning offers a possibility of producing well-aligned fiber membranes for future potential applications.

Tailoring Nano-Porous Surface of Aligned Electrospun Poly (L-Lactic Acid) Fibers for Nerve Tissue Engineering.

Despite the existence of many attempts at nerve tissue engineering, there is no ideal strategy to date for effectively treating defective peripheral nerve tissue. In the present study, well-aligned poly (L-lactic acid) (PLLA) nanofibers with varied nano-porous surface structures were designed within different ambient humidity levels using the stable jet electrospinning (SJES) technique. Nanofibers have the capacity to inhibit bacterial adhesion, especially with respect to Staphylococcus aureus (S. aureus). It was noteworthy to find that the large nano-porous fibers were less detrimentally affected by S. aureus than smaller fibers. Large nano-pores furthermore proved more conducive to the proliferation and differentiation of neural stem cells (NSCs), while small nano-pores were more beneficial to NSC migration. Thus, this study concluded that well-aligned fibers with varied nano-porous surface structures could reduce bacterial colonization and enhance cellular responses, which could be used as promising material in tissue engineering, especially for neuro-regeneration.

Collagen and chondroitin sulfate functionalized bioinspired fibers for tendon tissue engineering application

Functional tendon tissue engineering depends on harnessing the biochemical and biophysical cues of the native tendon extracellular matrix. In this study, we fabricated highly-aligned poly(L-lactic acid) (PLLA) fibers with surfaces decorated by two of the crucial tendon ECM components, type 1 collagen (COL1) and chondroitin sulfate (CS), through a coaxial stable jet electrospinning approach. Effects of the biomimetic COL1-CS (shell)/PLLA (core) fibers on the tenogenic differentiation of human mesenchymal stem cells (hMSCs) in vitro were investigated. Higher rates of cell spreading and proliferation are observed on the aligned COL1-CS/PLLA fibers compared to that on the plain PLLA fibers. Expression of the tendon-associated genes scleraxis (SCX) and COL1 as well as protein tenomodulin (TNMD) are significantly increased. Introduction of mechanical stimulation gives rise to synergistic effect on tenogenic differentiation of hMSCs. Higher expression of TGF-β2, TGFβR-II, and Smad3 by the cells on the COL1-CS/PLLA fiber substrates are observed, which indicates that COL1-CS/PLLA ultrafine fibers dictate the hMSC tenogenic differentiation through activating the TGF-β signaling pathway. Animal study in rat Achilles tendon repair model corroborated the promoting role of COL1-CS/PLLA in regenerating a tendon-like tissue. Thus, our highly aligned biomimicking fibers may serve as an efficient scaffolding system for functional tendon regeneration.

Effects of GO and rGO incorporated nanofibrous scaffolds on the proliferation of Schwann cells

Graphene oxide (GO) and reduced graphene oxide (rGO) are two of the most representative graphene derivatives that can be employed to engineer bioactive and/or electroactive scaffolds for neural tissue engineering (NTE). However, a comparison with regard to their chemical structural impact on cytocompatibility has yet to be performed. In this study, GO was prepared using a modified Hummers’ method followed by thermal treatment to obtain the rGO. Thereafter, a stable jet electrospinning approach was used to electrospin a viscous mixed solution of polycaprolactone (PCL)/poly(ethylene oxide) (PEO) (mass ratio 4:1) containing a tiny amount of GO and rGO (1% w/w), for the generation of highly-aligned nanoscale fibers of PCL-PEO-GO and PCL-PEO-rGO, respectively. Structural characteristics and physicochemical properties of the GO and/or rGO incorporated PCL-PEO nanofibers were characterized by various analytical techniques including Raman, FTIR, SEM, water drop contact angle, cyclic voltammetry and tensile testing. Finally, biological study in vitro by culturing the fibrous scaffolds with murine Schwann cells for cytocompatibility evaluation demonstrated that comparatively PCL-PEO-GO scaffold could more favorably promote the proliferation of the Schwann cells. However, considering the noted higher electroconductivity, the fibrous PCL-PEO-rGO may be applied to induce stem cell differentiation towards neural lineage. This research could provide a guidance for judicious selection of the GO and rGO incorporated nanofibers to construct electroactive scaffolds for engineering functional neural tissues.

Fabrication of high performance silk fibroin fibers via stable jet electrospinning for potential use in anisotropic tissue regeneration.

Regenerated silk fibroin (SF) from Bombyx mori silkworm cocoons is a highly regarded natural protein-biomaterial suitable for engineering a variety of biological tissues. Electrospinning offers a unique approach to fiber formation that can readily produce micro- and nano-scale fibers recapitulating the ultrastructure of a native extracellular matrix. However, SF fibers from conventional electrospinning suffer from the problem of poor mechanical properties for load-bearing relevant tissue regeneration applications. In this study, highly aligned high-strength SF fibers were fabricated by a recently emerged stable jet electrospinning (SJES) approach, with the aid of high molecular weight poly(ethylene oxide) (PEO) acting as a fiber-forming ingredient to increase control over the jetting instability during electrospinning. The results showed that 90% of the collected SF/PEO (mass ratio 88 : 12) fiber assembly via SJES oriented unidirectionally with an angle variation of <1° and displayed obvious anisotropic wettability. Mechanically, the as-electrospun highly aligned SF/PEO fibers exhibited a 22.0-fold increase in ultimate tensile strength (50.85 ± 1.13 MPa) and a 49.3-fold increase in Young's modulus (1185.99 ± 164.56 MPa) compared with the randomly oriented SF fibers. A subsequent methanol treatment further remarkably boosted the tensile strength to 73.91 ± 5.15 MPa and Young's modulus to 2426.13 ± 86.67 MPa. The mechanical performance of the SF fibers via SJES was also impressive, even when tested in the wet state. The substantial improvement in the mechanical properties of the electrospun SF fibers is attributed to the SJES-enabled higher molecular orientation and contents of the secondary structure (α-helix and β-pleated sheet), as well as the high degree of fiber alignment. Moreover, biological tests verified that these SF-based fibrous scaffolds supported the induced pluripotent stem cell derived mesenchymal stem cells to adhere, migrate and grow in a manner of orienting along the fiber axis. We speculate that these high-performance biomimicking SF fibers might give rise to improved efficacy while being utilized to architecturally regenerate anisotropic load-bearing tissues (e.g., tendon, ligament, and blood vessel).

An epigenetic bioactive composite scaffold with well-aligned nanofibers for functional tendon tissue engineering.

Electrospun aligned fibers, resembling the ultrastructure of tendon, have been previously reported to promote tenogenesis. However, the underlying mechanism is unclear and the aligned fibers alone are not capable enough to commit teno-differentiation of stem cells. The uniqueness of our studies are as follows, based on our observation of reduced expression of histone deacetylases (HDACs) in tendon stem/progenitor cells (TSPCs) cultured on aligned fibers, we proposed a strategy to enhance the tenogenesis effect of aligned fibers by using a small molecule Trichostatin A (TSA), a HDAC inhibitor. Such a TSA-laden poly (l-lactic acid) (PLLA) aligned fiber (A-TSA) scaffold was successfully fabricated by a stable jet electrospinning method, and demonstrated its sustained capability in releasing TSA. The incorporation and subsequent release of bioactive small molecule TSA into electrospun aligned fibers allows a controllable manner for both biochemical and physical regulation of tenogenesis of stem cells both in vitro and in vivo. Collectively, the present study provides a model of "translating the biological knowledge learned from cell-material interaction into optimizing biomaterials (from Biomat-to-Biomat)".

Continuous aligned poly(meta‐phenylene isophthalamide) fibers via stable jet electrospinning

ABSTRACTContinuous aligned poly(meta‐phenylene isophthalamide) (PMIA) fibers are first fabricated by Stable Jet Electrospinning (SJES) with a collection distance of 15 cm. The unfolded length of every single fiber is calculated to be several hundred to several thousand meters. Morphology analysis by field emission scanning electron microscopy (FE‐SEM) shows that these fibers are well arranged and uniformly distributed and their average fiber diameters decrease gradually with increasing collection speed. The effects of ambient temperature and humidity on the duration of stable jet are also discussed. Moderate temperatures and humidity are preferred for fabricating PMIA fibers with ultra‐long size. Besides, the changes of the thermal and crystalline properties of PMIA fibers are also investigated. The significant decline in crystallinity should be responsible for its decreased thermal property. Further improvements to its thermal and crystalline performance must be given consideration in future applications. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43690.

Fabrication of high performance ultrafine fibers of silk fibroin for tissue scaffolding

Event Abstract Back to Event Fabrication of high performance ultrafine fibers of silk fibroin for tissue scaffolding Bingcheng Yi1, Huilan Zhang1, Zhepao Yu1, Xiangxin Lou1 and Yanzhong Zhang1 1 Donghua University, College of Chemistry, Chemical Engineering & Biotechnology, China Introduction: Silk fibroin (SF) in the form of fibers is a kind of well-liked biomaterial for engineering load-bearing biological tissues. Electrospinning has been known to produce ultrafine SF fibers in nano/micro-scale fineness that highly mimics the ultrastructure of extracellular matrix in many tissues. However, ultrafine SF fibers from conventional electrospinning usually are of low mechanical strength and poor degree of orientation. To address the noted problems, this study attempts to fabricate highly aligned ultrafine SF fibers through a novel stable jet electrospinning (SJES) approach[1]-[3], from which their physicochemical and biological properties can be evaluated for potential tissue scaffolding applications. Materials and Methods: Poly(ethylene oxide) (PEO, 0-14 wt%) was employed to formulate the spinning dope of SF so as to generate a long stable jet during the SJES. The as-electrospun SF fibers were subsequently treated in a methanol solution (90%) for 10 min (termed as M-SF/PEO). Thereafter, PEO in the M-SF/PEO fibers were extracted by being immersed in distilled water for 2 days (termed as W-M-SF/PEO). These SF fibers were thoroughly characterized by different techniques. Finally, cytocompatibility of these ultrafine SF fibers was evaluated using murine iPSC-derived MSCs (i.e., iPSC-MSCs) by Cell Counting Kit-8 (CCK-8) assay. Results and Discussion: Introduction of PEO into SF is beneficial to eliminate the occurrence of jet bending instability so that a very long linear jet can be obtained (Fig. 1A). The formulation SF/PEO (SF:PEO = 88:12) appeared to be the optimal solution system that gave rise to highly aligned ultrafine SF fibers: more than 90% of fibers with an averaged diameter of ~1200 nm oriented unidirectionally (angle variation < 1°) (Fig. 1B,C). XRD patterns of the SF fibers suggest configuration transformation from amorphous to beta-sheet after methanol treatment (Fig. 1D). The disappearance of absorption peak of PEO at 1101 cm-1 (C-O-C) in W-M-SF/PEO fibers confirmed the effectiveness in extracting PEO by soaking in water (Fig. 1E). Compared to random SF fibers, the M-SF/PEO fibers showed higher breaking tenacity (53.3 ± 14.0 MPa, increased by 53.9-fold) and Young's modulus (2803.1 ± 435.0 MPa, increased by 52.85-fold) (Fig. 1F), whereas the W-M-SF/PEO fibers became mechanically weaker but more hydrophilic after water treatment (Fig. 1G). These SF fibers supported the iPSC-MSCs to adhere and grow in a manner of orienting along the fiber axis (images not shown) and the cell proliferation was ameliorated on the W-M-SF/PEO fibers (Fig. 1H). Fig.1. (A) Actual process of SJES in collecting aligned SF fibers. (B) SEM images and (C) angular histograms of the aligned SF fibers prepared with the following variables: applied voltage 8 kV, feed rate 0.2 mL/h, rotating speed 600 rpm and collecting distance 22 cm. (D) XRD patterns and (E) IR spectra of the aligned SF/PEO, M-SF/PEO and W-M-SF/PEO fibers and raw components of SF and PEO. (F) Typical tensile stress-strain curves of SF-based fibers; inset shows the Young's modulus data. (G) Anisotropic wettability by measuring water contact angles of the different fibers in alignment. (H) Cell proliferation of the iPSC-MSCs on TCP, M-SF/PEO and W-M-SF/PEO fibers after culturing for 1, 4 and 7days. **p < 0.01. Conclusions: This study demonstrated that ultrafine SF fibers could be successfully produced via the SJES method. With the high degree of fiber orientation, impressive mechanical properties, and good cytocompatibility, our electrospun SF fibers may be considered as high performance fibers for engineering load-bearing tissues (e.g., tendon, ligament, and blood vessel) in future. This work was partially supported by the National Natural Science Foundation of China (51073032, 31570969), the Natural Science Foundation of Shanghai (15ZR1400500), the Key Basic Research Foundation of Shanghai Committee of Science and Technology (14JC1490100), and the Fundamental Research Funds for the Central Universities by the Ministry of Education of China (2232013D3-13, 15D110538).

Highly aligned core-shell structured nanofibers for promoting phenotypic expression of vSMCs for vascular regeneration.

This study was designed to assess the efficacy of hyaluronan (HA) functionalized well-aligned nanofibers of poly-l-lactic acid (PLLA) in modulating the phenotypic expression of vascular smooth muscle cells (vSMCs) for blood vessel regeneration. Highly aligned HA/PLLA nanofibers in core-shell structure were prepared using a novel stable jet electrospinning approach. Formation of a thin HA-coating layer atop each PLLA nanofiber surface endowed the uni-directionally oriented fibrous mats with increased anisotropic wettability and mechanical compliance. The HA/PLLA nanofibers significantly promoted vSMC to elongation, orientation, and proliferation, and also up-regulated the expression of contractile genes/proteins (e.g., α-SMA, SM-MHC) as well as the synthesis of elastin. Six weeks of in vivo scaffold replacement of rabbit carotid arteries showed that vascular conduits made of circumferentially aligned HA/PLLA nanofibers could maintain patency and promoted oriented vSMC regeneration, lumen endothelialization, and capillary formation. This study demonstrated the synergistic effects of nanotopographical and biochemical cues in one biomimetic scaffold design for efficacious vascular regeneration.

Direct printing of patterned three-dimensional ultrafine fibrous scaffolds by stable jet electrospinning for cellular ingrowth

Electrospinning has been widely used to produce ultrafine fibers in microscale and nanoscale; however, traditional electrospinning processes are currently beset by troublesome limitations in fabrication of 3D periodic porous structures because of the chaotic nature of the electrospinning jet. Here we report a novel strategy to print 3D poly(L-lactic acid) (PLLA) ultrafine fibrous scaffolds with the fiber diameter of approximately 2 μm by combining a stable jet electrospinning method and an X-Y stage technique. Our approach allows linearly deposited electrospun ultrafine fibers to assemble into 3D structures with tunable pore sizes and desired patterns. Process conditions (e.g., plotting speed, feeding rate, and collecting distance) were investigated in order to achieve stable jet printing of ultrafine PLLA fibers. The proposed 3D scaffold was successfully used for cell penetration and growth, demonstrating great potential for tissue engineering applications.

Well-aligned chitosan-based ultrafine fibers committed teno-lineage differentiation of human induced pluripotent stem cells for Achilles tendon regeneration

Physical property of substrates such as stiffness and topography have been reported to induce mesenchymal stem cells differentiation into bone, muscle and neuron lineages. Human-induced pluripotent stem cells (hiPSCs) are a highly promising cell source for regenerative medicine. However, physical properties have not yet been reported to successfully induce pluripotent stem cells into specific lineages. This study aimed to develop a robust, stepwise topographic strategy to induce hiPSCs differentiate into teno-lineage. A novel spinning approach termed stable jet electrospinning (SJES), is utilized to fabricate continuous well-aligned ultrafine fibers (891 ± 71 nm), which mimic the native tendon's microstructure and mechanical properties. hiPSCs are first differentiated into MSCs on smooth plastic surface as confirmed by the differentiations into three mesenchymal lineages and expression of characteristic MSC surface markers through an EMT (Epithelial–Mesenchymal Transition) process. Subsequently, the hiPSC derived MSCs are seeded onto well-aligned fibers to differentiate into tenocyte-like cells through activating mechanic-signal pathway. The in situ tendon repair study further confirms that aligned fiber scaffold with hiPSC-MSCs had significant effect on improving the structural and mechanical properties of tendon injury repair. These findings indicate that the stepwise physical substrate change strategy can be adopted to induce hiPSCs differentiation for tendon tissue regeneration.

Engineering aligned electrospun PLLA microfibers with nano-porous surface nanotopography for modulating the responses of vascular smooth muscle cells.

In tissue engineering research, aligned electrospun ultrafine fibers have been shown to regulate cellular alignment and relevant functional expression, but the imposed effect of individual fiber surface nanotopography on cell behaviour has not been examined closely. This work investigates the impact of superimposing a nano-pore feature atop individual fiber surfaces on the responsive behaviour of human vascular smooth muscle cells (vSMCs) for blood vessel tissue engineering. Well-aligned ultrafine poly(l-lactic acid) (PLLA) microfibers with an average fiber diameter of ca. 1.6 μm were fabricated by using a novel stable jet electrospinning (SJES) method. Ellipse-shaped nano-pores with varied aspect ratios (defined as long-to-short axis ratio) of 2.7-3.9, corresponding to a surface nano-roughness in the range of 54.8-110.0 nm, were in situ generated onto individual fiber surfaces by varying ambient humidity from 45% to 75% during the SJES process. The presence of elliptical nano-pores on fiber surfaces affected the characteristic anisotropic wettability of the aligned PLLA fibers and contributed to greater protein adsorption (up to 17.59 μg mg-1). A 7 day in vitro assessment of human umbilical arterial SMCs cultured on these aligned nano-porous fiber substrates indicated that cellular responses were in close correlation with the elliptical nano-pore feature. A pronounced fiber surface nanotopography was superior in soliciting favorable cellular responses, leading to enhanced cell attachment, proliferation, alignment, expression of the vascular matrix proteins and maintenance of a contractile phenotype. This study thus suggests that introduction of an elliptical nano-pore feature to the aligned microfiber surfaces could provide additional dimensionality of topographical cues to modulate the vSMC responses when using the aligned electrospun ultrafine fibers for engineering vascular constructs.

Stable jet electrospinning for easy fabrication of aligned ultrafine fibers

Electrospinning has emerged as an attractive technique for the fabrication of ultrafine fibers in micro-/nano-scale fineness. However, it is still a huge technological challenge in achieving aligned fibers and arrays due to the inherent chaotic motion of an electrospinning jet. We report herein a novel spinning approach termed stable jet electrospinning to offer a facile solution to the noted issue. It involves judiciously using an ultrahigh molecular weight poly(ethylene oxide) to formulate the viscoelasticity of a spinning dope such that a very long and stable jet can be formed during electrospinning. This consequently allows for readily collecting and fabricating individual fibers, multi-filament yarns, well-aligned unidirectional fiber arrays in a large area, and ordered fiber patterns by controlling fiber placement. Our approach could thus open up the possibility of achieving continuous aligned ultrafine fibers and structures in a straightforward and scalable fashion, suitable for a variety of practical applications.