Fibroin Nanofibrous Scaffolds Research Articles

Optimization and evaluation of oxygen-plasma-modified, aligned, poly (Є-caprolactone) and silk fibroin nanofibrous scaffold for corneal stromal regeneration

The shortage of human donor corneas for transplantation necessitates the exploration of tissue engineering approaches to develop corneal substitutes. However, these substitutes must possess the necessary strength, transparency, and ability to regulate cell behaviour before they can be used in patients. In this study, we investigated the effectiveness of an oxygen plasma surface-modified poly-ε-caprolactone (PCL) combined with silk fibroin (SF) nanofibrous scaffold for corneal stromal regeneration. To fabricate the electrospun scaffolds, PCL and SF blends were used on a rotating mandrel. The optimization of the blend aimed to replicate the structural and functional properties of the human cornea, focusing on nanofibre alignment, mechanical characteristics, and in vitro cytocompatibility with human corneal stromal keratocytes. Surface modification of the scaffold resulted in improved transparency and enhanced cell interaction. Based on the evaluation, a composite nanofibrous scaffold with a 1:1 blend of PCL and SF was selected for a more comprehensive analysis. The biological response of keratocytes to the scaffold was assessed through cellular adhesion, proliferation, cytoskeletal organization, gene expression, and immunocytochemical staining. The scaffold facilitated the adhesion of corneal stromal cells, supporting cell proliferation, maintaining normal cytoskeletal organization, and promoting increased expression of genes associated with healthy corneal stromal keratocytes. These findings highlight the potential of a surface-modified PCL/SF blend (1:1) as a promising scaffolding material for corneal stromal regeneration. The developed scaffold not only demonstrated favourable biological interactions with corneal stromal cells but also exhibited characteristics aligned with the requirements for successful corneal tissue engineering. Further research and refinement of these constructs could lead to significant advancements in addressing the shortage of corneas for transplantation, ultimately improving the treatment outcomes for patients in need.

Preparation and characterisation of polycaprolactone-fibroin nanofibrous scaffolds containing allicin.

Polycaprolactone (PCL) and silk fibroin are used to make nanofiber wound dressings, and then allicin is added to PCL and silk fibroin to expand antibacterial properties. The polymer solutions are subjected to various electrospinning parameters, and allicin‐containing and non‐allicin fibres are prepared. Fibres are examined by scanning electron microscopy (SEM), Fourier‐transform infrared spectroscopy (FTIR), contact angle analysis, mechanical testing, bacterial culture, and 3‐(4 5‐dimethylthiazol‐2‐yl)‐2 5‐diphenyltetrazolium bromide (MTT). The SEM results show that the addition of fibroin and allicin at a constant voltage provides a direct relationship between the distance and the diameter of the fibres. Also, the total variation algorithm is used for denoising the signal of FTIR that the results confirm the functional groups present in the fibres. Furthermore, the contact angle test for allicin‐free fibres shows that the contact angle of these fibres is 133.3° that decreases to 85.5° by adding allicin to the structure. Moreover, the tensile test of allicin‐free fibres shows that Young's modulus of these fibres is 2.06 MPa, while the value increases to 5.12 MPa with the addition of allicin to the structure and at the end of the bacterial culture test, a growth inhibition zone is seen after 17 and 24 h. According to the obtained results, these fibres have the potential to be used in burn applications.

The Study of 3D Printing-Assisted Electrospinning Technology in Producing Tissue Regeneration Polymer-Fibroin Scaffold for Ureter Repair.

Long segment ureteral lesion with obstruction is a clinically difficult issue for recovering and maintaining organ or tissue function. Regeneration medicine using various biomaterials as a scaffold in supporting tissue regrowth is emerging. We developed this customized scaffold using electrospinning and 3-dimensional assistance and expected that it may provide an alternative biomaterial for ureter defect repair. Our study synthesized polycaprolactone and silk fibroin combination as biomaterial scaffolds. The differences in physicochemical properties and biocompatibility of polycaprolactone-silk fibroin bio-scaffolds prepared by electrospinning alone and 3-dimensional printing combined with electrospinning in proper ratios were compared and characterized. SV-HUC-1 uroepithelial cells cultured in polycaprolactone-silk fibroin (4 : 6) scaffolds were observed under a scanning electron microscope and using calcein-acetomethoxy and propidium iodide stain. The ex vivo resected healthy human ureteral segment tissue was anastomosed with the polycaprolactone-silk fibroin scaffolds and cultured in an ex vivo bath for 2 weeks. The cellular growth on the polycaprolactone-silk fibroin scaffold was observed microscopically. In the New Zealand white rabbit model, we performed a 1/5 ratio (2 cm out of 10 cm) defect replacement of the unilateral ureter. After 7 weeks, the rabbits were sacrificed and the implanted ureter scaffolds were resected for tissue sectioning and the cellular growth was observed by hematoxylin and eosin and Masson staining. When the proportion of silk fibroin was increased and the 3-dimensional electrospinning method was used, both the size and diameter of nanofiber holes were increased in the polycaprolactone-silk fibroin scaffold. Scanning electron microscope and fluorescent stain revealed that cultured 3T3 and SV-HUC-1 uroepithelial cells could electively penetrate inside the polycaprolactone-silk fibroin (4 : 6) nanofibrous scaffolds in 3 days. The polycaprolactone-silk fibroin scaffold anastomosis in an ex vivo bath showed cellular growth stably along the scaffold for 2 weeks, and most of the cells grow along with the outboard of the scaffold in layers. In an animal model, different layered cells can be observed to grow along with the outboard of the scaffold with mucosa, submucosa, muscular layer, and the serosa layer order after 7 weeks. Mucosa and muscular layer growth along the scaffold inner wall were seen simultaneously. 3-dimensional electrospinning synthesized 4 : 6 polycaprolactone-silk fibroin nanofiber scaffolds that are feasible for tissue growth and achieve the purpose of ureteral reconstruction in animal experiments. This new form of 3-dimensional electrospinning constructed polycaprolactone-silk fibroin nanofiber scaffold may be considered as a clinical urinary tract tissue reconstruction alternative in the future.

Silk fibroin nanofibrous scaffolds incorporated with microRNA-222 loaded chitosan nanoparticles for enhanced neuronal differentiation of neural stem cells

Neural stem cells (NSCs) transplantation therapy is a promising method for neural tissue regeneration. How to enhance the neuronal differentiation of NSCs has been the most challenging aspect of NSCs application. Herein, the microRNA-222 loaded chitosan nanoparticles (miR-222/CS NPs) were incorporated with silk fibroin (SF) nanofibrous scaffolds to enhance neuronal differentiation of NSCs. The encapsulation efficiency of miR-222 in the miR-222/CS NPs was (96.4 ± 0.3) %. The results of the electrophoretic assay and cellular uptake assay confirmed that miR-222 was stable in the miR-222/CS NPs and can be effectively delivered into NSCs. The water contact angle decreased from (89 ± 3.05)° for the SF scaffolds to (14 ± 1.00)° for the composite scaffolds. The Western blot and RT-PCR results confirmed that the composite scaffolds could enhance neuronal differentiation of NSCs. In conclusion, the SF nanofibrous scaffolds in combination with miR-222/CS NPs are a promising approach for neural tissue regeneration.

Supercritical carbon dioxide assisted fabrication of biomimetic sodium alginate/silk fibroin nanofibrous scaffolds

AbstractIn this study, biomimetic sodium alginate (SA)/silk fibroin (SF) scaffolds were successfully fabricated by supercritical CO2technology. The SA/SF scaffolds exhibited an interconnected porous and extracellular matrix (ECM)‐like nanofibrous structures. Moreover, the SA microparticles were embedded in the SF scaffolds. Increasing the content of SA microparticles could improve tensile strength and compressive strength of the SF scaffolds and reduce the porosity of the SF scaffolds. The addition of the SA microparticles could also regulate the degradation rate of the SA/SF scaffolds. Furthermore, the results of in vitro biocompatibility evaluation, indicated that the SA/SF scaffolds exhibited no obvious cytotoxicity and higher cell adhesion ability and were more favorable for L929 fibroblasts proliferation than pure SF scaffolds. Therefore, the SA/SF scaffolds with ECM‐like nanofibrous and interconnected porous structure have potential application in skin tissue engineering.

Wnt pathway activator delivery by poly (lactide-co-glycolide)/silk fibroin composite nanofibers promotes dental pulp stem cell osteogenesis

The high regenerative ability of damaged bone tissue in Oral and maxillofacial area has made it an optimal target for tissue engineering. Introducing scaffold that has high biocompatibility and good degradability and can also deliver biological factors well is the most important goal of tissue engineering. In the present study, poly(lactide-co-glycolide) (PLGA)/silk fibroin (SF) nanofibrous scaffolds with and without inorganic polyphosphate (polyP) as a Wnt pathway activator was fabricated via electrospinning. The potential application of fabricated scaffolds in oral and maxillofacial tissue engineering was investigated with the culture of isolated and characterized dental pulp stem cells (DPSCs) in vitro. The obtained results demonstrated that the highest viability of the DPSCs was detected when grown on the PLGA/SF/polyP nanofibers compared to the PLGA/SF nanofibers. Furthermore, DPSCs cultured on PLGA/SF/polyP nanofibers exhibited a strong osteogenic differentiation potential compared to when cultured on the PLGA/SF nanofibers or standard culture plate. Therefore, according to the results obtained in this study, the PLGA/SF/polyP nanofibrous scaffold in combination with DPSCs or alone has a great potential to use for bone reconstruction in oral and maxillofacial tissue engineering applications.

Gradient Biomineralized Silk Fibroin Nanofibrous Scaffold with Osteochondral Inductivity for Integration of Tendon to Bone.

Enthesis injury repair remains a huge challenge because of the unique biomolecular composition, microstructure, and mechanics in the interfacial region. Surgical reconstruction often creates new bone-scaffold interfaces with mismatched properties, resulting in poor osseointegration. To mimic the natural interface tissue structures and properties, we fabricated a nanofibrous scaffold with gradient mineral coating based on 10 × simulated body fluid (SBF) and silk fibroin (SF). We then characterized the physicochemical properties of the scaffold and evaluated its biological functions both in vitro and in vivo. The results showed that different areas of SF nanofibrous scaffold had varying levels of mineralization with disparate mechanical properties and had different effects on bone marrow mesenchymal stem cell growth and differentiation. Furthermore, the gradient scaffolds exhibited an enhancement of integration in the tendon-to-bone interface with a higher ultimate load and more fibrocartilage-like tissue formation. These findings demonstrate that the silk-based nanofibrous scaffold with gradient mineral coating can regulate the formation of interfacial tissue and has the potential to be applied in interface tissue engineering.

Soy protein isolate supplemented silk fibroin nanofibers for skin tissue regeneration: Fabrication and characterization

Biocompatible soy protein isolate/silk fibroin (SPI/SF) nanofibrous scaffolds were successfully fabricated through electrospinning a novel protein blend SPI/SF. Prepared nanofibers were treated with ethanol vapor to obtain an improved water-stable structure. Fabricated scaffolds were characterized through scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), UV–VIS spectrophotometry and image analysis. The mean diameters of SPI/SF electrospun fibers were observed ranging between 71 and 160 nm. The scaffolds were found significantly stable for a prolong duration at the room temperature as well as at 37 °C, when placed in phosphate buffered saline, nutrient medium, and lysozyme-containing solution. The potential of fabricated scaffolds for skin tissue regeneration was evaluated by in vitro culturing of standard cell lines i.e., fibroblast cells (L929-RFP (red fluorescent protein) and NIH-3T3) and melanocytes (B16F10). The outcomes revealed that all the fabricated nanofibrous scaffolds were non-toxic towards normal mammalian cells. In addition, healing of full-thickness wound in rats within 14 days after treatment with a nanofibrous scaffold demonstrated its suitability as a potential wound dressing material. Interestingly, we found that nanofibers induced a noticeable reduction in the proliferation rate of B16F10 melanoma cells.

Electrospun polycaprolactone/silk fibroin nanofibrous bioactive scaffolds for tissue engineering applications

Degumming of Bombyx mori silk cocoons by a novel and mild process using aqueous ammonia and fabrication of electrospun polycaprolactone/silk fibroin (PCL/SF) nanofibrous scaffolds is reported. Cocoons were degummed in 0.3% w/w solutions of boiling ammonia (28–30%) for 45 min. Degummed SF fibers were dissolved in phosphoric and formic acid (7/3 v/v) mixture, coagulated in methanol, filtered and dried. PCL solutions containing different amounts of SF were electrospun in formic acid, a green solvent. Scaffolds were characterized to confirm the successful incorporation of SF and to demonstrate formation of nanofibrous webs with good biomechanical properties. Cell viability assay was performed by seeding Human BJ fibroblast cells on scaffolds. In vitro analysis showed that the scaffolds produced were non-toxic and incorporation of SF resulted in enhanced cell proliferation. Nanofibrous PCL/SF scaffolds with good biomechanical properties developed through dialysis free processing of silk fibroin can be promising substrates for tissue engineering applications.

Osteogenic potential of Rosuvastatin immobilized on silk fibroin nanofibers using argon plasma treatment

To begin developing a silk fibroin (SF) nanofibrous scaffolds that could promote osteogenesis, whilst enabling to deliver an active amount of Rosuvastatin (RSV) to the cells in long-time period, the present study aims to immobilize RSV onto the SF nanofibers through the argon radio frequency. Thus, the effect of plasma exposure times (0, 1, 3, and 5 min) was investigated on the morphology, loading efficiency, release profile, and osteogenesis activity. The successful loading of RSV on the SF nanofibers was proved by Fourier transformed infrared spectroscopy, Differential scanning calorimetry, and energy dispersive spectroscopy. In vitro drug release studies demonstrated that the RSV release was prolonged over a period of 21 d for plasma treated mats, while the non-plasma treated samples released the whole drug after 72 h. Moreover, the dose of RSV was controlled by the plasma exposure times, in which the highest amount of the released RSV was achieved after 3 min exposing to plasma. As suggested by MTT assay, the released amounts of RSV had no toxicity on the seeded human adipose tissue-derived stem cells and enhanced their proliferation. Moreover, using real-time reverse transcriptase-polymerase chain reaction and alizarin red staining proved that RSV-immobilized SF mats stimulate both early and late osteogenic gene differentiation in comparison with pure SF nanofibers. However, the highest differentiation was observed on the SF nanofibers treated with argon plasma for 3 min. The results support the potential of plasma treatment on sustained release of the RSV from SF nanofibers for osteogenesis enhancement.

Ramification of zinc oxide doped hydroxyapatite biocomposites for the mineralization of osteoblasts

Far-flung evolution in tissue engineering enabled the development of bioactive and biodegradable materials to generate biocomposite nanofibrous scaffolds for bone repair and replacement therapies. Polymeric bioactive nanofibers are to biomimic the native extracellular matrix (ECM), delivering tremendous regenerative potentials for drug delivery and tissue engineering applications. It's been known from few decades that Zinc oxide (ZnO) nanoparticles are enhancing bone growth and providing proliferation of osteoblasts when incorporated with hydroxyapatite (HAp). We attempted to investigate the interaction between the human foetal osteoblasts (hFOB) with ZnO doped HAp incorporated biocomposite poly(L-lactic acid)-co-poly(ε-caprolactone) and silk fibroin (PLACL/SF) nanofibrous scaffolds for osteoblasts mineralization in bone tissue regeneration. The present study, we doped ZnO with HAp (ZnO(HAp) using the sol-gel ethanol condensation technique. The properties of PLACL/SF/ZnO(HAp) biocomposite nanofibrous scaffolds enhanced with doped and blended ZnO/HAp were characterized using Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Contact angle and Tensile studies to determine the morphology, functionality, wettability and stability. The in vitro study results showed that the addition of ZnO and HAp enhances the secretion of bone mineral matrix (98%) with smaller fiber diameter (139.4 ± 27 nm) due to the presence of silk fibroin showing potential tensile properties (322.4%), and increased the proliferation of osteoblasts for bone tissue regeneration.

Melanin incorporated electroactive and antioxidant silk fibroin nanofibrous scaffolds for nerve tissue engineering

Nerve restoration and repair in the central nervous system is complicated and requires several factors to be considered while designing the scaffolds like being bioactive as well as having neuroinductive, neuroconductive and antioxidant properties. Aligned electrospun nanofibers provide necessary guidance and topographical cues required for directing the axonal and neurite outgrowth during regeneration. Conduction of nerve impulses is a mandatory feature of a typical nerve. The neuro-conductive property can be imparted by blending the biodegradable, bioactive polymers with conductive polymers. This will provide additional features, i.e., electrical cues to the already existing topographical and bioactive cues in order to make it a more multifaceted neuroregenerative approach. Hence in the present study, we used a combination of silk fibroin and melanin for the fabrication of random and aligned electrospun nanofibrous composite scaffolds. We performed the physico-chemical characterization and also assessed their antioxidant properties. We also evaluated their neurogenic potential using human neuroblastoma cells (SH-SY5Y) for their cellular viability, proliferation, adhesion and differentiation levels. Designed nanofibrous scaffolds had adequate physical properties suitable as neural substrates to promote neuronal growth and regeneration. They stimulated the neuroblastoma cell attachment and viability indicating their biocompatible nature. Silk/melanin composite scaffolds have specifically exhibited high antioxidant nature proven by the radical scavenging activity. Additionally, the melanin incorporated aligned silk fibroin scaffolds promoted the cell differentiation into neurons and orientation along their axis. Our results confirmed the potential of melanin incorporated aligned silk fibroin scaffolds as the promising candidates for effective nerve regeneration and recovery.

Fabrication and characterization of aligned graphene/silk fibroin nanofibrous scaffolds for nerve tissue regeneration

Fabrication and characterization of aligned graphene/silk fibroin nanofibrous scaffolds for nerve tissue regeneration

Random lasing from structurally-modulated silk fibroin nanofibers

Structural arrangement and dimension play vital roles in wave transport and amplification as they can restrict the volume explored by the waves. However, it is challenging to systematically investigate the interplay among structural, optical, and mechanical properties, in part because of limited experimental platforms that modulate the structural arrangement in a continuous manner. We present light amplification action in Rhodamine B doped silk fibroin (SF) nanofibrous scaffolds and its modulation via the control of the alignment or directionality of SF nanofibers through an electrospinning procedure. Random lasing features of such scaffolds are examined as a function of structural arrangement of the SF nanofibers, and optical-structural-mechanical relationships of the SF-based structures are examined. As SF nanofibers are aligned parallel undergoing a transition from three to quasi-two dimension, light amplification features (e.g., lasing threshold and output power) enhanced, which also strongly correlated with mechanical characteristics (i.e., Young’s moduli) of the scaffolds. We confirm such optical characteristics using quasi-mode analyses based on the finite element method. We further demonstrate non-contact, in situ measurement of alternations in lasing features of the scaffolds while the specimens are under tensile loads. These results may highlight potential utility of the scaffolds as a flexible and biocompatible sensor.

Electrospun Silk Fibroin Nanofibrous Scaffolds with Two-Stage Hydroxyapatite Functionalization for Enhancing the Osteogenic Differentiation of Human Adipose-Derived Mesenchymal Stem Cells.

The development of functional scaffolds with improved osteogenic potential is important for successful bone formation and mineralization in bone tissue engineering. In this study, we developed a functional electrospun silk fibroin (SF) nanofibrous scaffold functionalized with two-stage hydroxyapatite (HAp) particles, using mussel adhesive-inspired polydopamine (PDA) chemistry. HAp particles were first incorporated into SF scaffolds during the electrospinning process, and then immobilized onto the electrospun SF nanofibrous scaffolds containing HAp via PDA-mediated adhesive chemistry. We obtained two-stage HAp-functionalized SF nanofibrous scaffolds with improved mechanical properties and capable of providing a bone-specific physiological microenvironment. The developed scaffolds were tested for their ability to enhance the osteogenic differentiation of human adipose-derived mesenchymal stem cells (hADMSCs) in vitro and repair bone defect in vivo. To boost their ability for bone repair, we genetically modified hADMSCs with the transcriptional coactivator with PDZ-binding motif (TAZ) via polymer nanoparticle-mediated gene delivery. TAZ is a well-known transcriptional modulator that activates the osteogenic differentiation of mesenchymal stem cells (MSCs). Two-stage HAp-functionalized SF scaffolds significantly promoted the osteogenic differentiation of TAZ-transfected hADMSCs in vitro and enhanced mineralized bone formation in a critical-sized calvarial bone defect model. Our study shows the potential utility of SF scaffolds with nanofibrous structures and enriched inorganic components in bone tissue engineering.

Fenugreek Incorporated Silk Fibroin Nanofibers-A Potential Antioxidant Scaffold for Enhanced Wound Healing.

Free radicals are generated by various biochemical pathways in the living system, causing severe oxidative damage to the biomolecules leading to adverse disease conditions. Hence, there is an increasing interest in antioxidant studies for preventing the effects of these free radicals. Herein, we propose a novel electrospun scaffold with antioxidant properties that can be used as wound healing material. Fenugreek, a natural antioxidant incorporated silk fibroin nanofiber, was prepared in four different ratios by the co-electrospinning method. The biocompatibility of the nanofibers and its antioxidant activity were evaluated through 3-(4, 5-dimethylthiazol-2-yl)-diphenyltetrazolium bromide (MTT) assay and 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging assay, respectively. The experimental observations indicate that the incorporation of fenugreek increases the thermal and mechanical properties of silk fibroin nanofibers. DPPH assay proves that the antioxidant property is enhanced with increasing concentration of fenugreek in nanofiber mats, and the Swiss albino 3T6 fibroblasts show better proliferation on the nanofibrous scaffolds. Further, the wound healing efficiency of fenugreek incorporated silk fibroin nanofibrous scaffolds was evaluated using full thickness excisional wounds in rat model. Wound healing was accelerated in silk fibroin-fenugreek nanofibers treated wounds with complete re-epithelialization and enhanced collagen deposition. The present study validates the use of fenugreek incorporated silk fibroin nanofiber mats as antioxidant scaffolds in wound healing applications.

Silk-PVA Hybrid Nanofibrous Scaffolds for Enhanced Primary Human Meniscal Cell Proliferation.

In this study, silk fibroin nanofibrous scaffolds were developed to investigate the attachment and proliferation of primary human meniscal cells. Silk fibroin (SF)-polyvinyl alcohol (PVA) blended electrospun nanofibrous scaffolds with different blend ratios (2:1, 3:1, and 4:1) were prepared. Morphology of the scaffolds was characterized using atomic force microscopy (AFM). The hybrid nanofibrous mats were crosslinked using 25% (v/v) glutaraldehyde vapor. In degradation study, the crosslinked nanofiber showed slow degradation of 20% on weight after 35days of incubation in simulated body fluid (SBF). The scaffolds were characterized with suitable techniques for its functional groups, porosity, and swelling ratio. Among the nanofibers, 3:1 SF:PVA blend showed uniform morphology and fiber diameter. The blended scaffolds had fluid uptake and swelling ratio of 80% and 458±21%, respectively. Primary meniscal cells isolated from surgical debris after meniscectomy were subcultured and seeded onto these hybrid nanofibrous scaffolds. Meniscal cell attachment studies confirmed that 3:1 SF:PVA nanofibrous scaffolds supported better cell attachment and growth. The DNA and collagen content increased significantly with 3:1 SF:PVA. These results clearly indicate that a blend of SF:PVA at 3:1 ratio is suitable for meniscus cell proliferation when compared to pure SF-PVA nanofibers.

How direct electrospinning in methanol bath affects the physico‐chemical and biological properties of silk fibroin nanofibrous scaffolds

Developing a rapid and easy approach to fabricate crystalline silk fibroin nanofibres without any needs for post-processing stage is focused. Thus, methanol bath was chosen as the collector and then the effect of soaking time on the properties of fibroin fibres was investigated. The results indicated that the wet-electrospun mats had higher fibre diameter than mats made by conventional electrospinning system. With prolonging the electrospinning time in methanol bath, a slight increase in the average fibre diameter and crystallinity were observed. In addition, the stiffness of the wet-electrospun mats increased with increasing soaking time, while the breaking stress decreased. The cellular viability of the osteoblast-like cells (MG63) on fibroin mats improved during wet-electrospinning process, while no significant difference was observed for cell attachment. Accordingly, it seems that wet electrospinning in methanol for 30 min is optimal for bone regeneration on account of viability and mechanical property.

Shear stress with appropriate time-step and amplification enhances endothelial cell retention on vascular grafts.

Endothelial cells (ECs) are sensitive to changes in shear stress. The application of shear stress to ECs has been well documented to improve cell retention when placed into a haemodynamically active environment. However, the relationship between the time-step and amplification of shear stress on EC functions remains elusive. In the present study, human umbilical cord veins endothelial cells (HUVECs) were seeded on silk fibroin nanofibrous scaffolds and were preconditioned by shear stress at different time-steps and amplifications. It is shown that gradually increasing shear stress with appropriate time-steps and amplification could improve EC retention, yielding a complete endothelial-like monolayer both in vitro and in vivo. The mechanism of this improvement is mediated, at least in part, by an upregulation of integrin β1 and focal adhesion kinase (FAK) expression, which contributed to fibronectin (FN) assembly enhancement in ECs in response to the shear stress. A modest gradual increase in shear stress was essential to allow additional time for ECs to gradually acclimatize to the changing environment, with the goal of withstanding the physiological levels of shear stress. This study recognized that the time-steps and amplifications of shear stress could regulate EC tolerance to shear stress and the anti-thrombogenicity function of engineered vascular grafts via an extracellular cell matrix-specific, mechanosensitive signalling pathway and might prevent thrombus formation in vivo. Copyright © 2016 John Wiley & Sons, Ltd.

Fabrication of nanofibrous silkworm gland three-dimensional scaffold containing micro/nanoscale pores and study of its effects on adipose tissue-derived stem cell growth

An ideal tissue engineering scaffold requires a structure similar to that of the natural extracellular matrix. The structure of a scaffold is the most important parameter for determining the behavior and functions of cells. Therefore, the importance of designing a suitable scaffold has been greatly emphasized. Electrospinning has been extensively used to fabricate scaffolds for tissue engineering. In this study, we developed a nanofibrous scaffold made from silkworm gland (SG), which contains the silk protein fibroin and other proteins that have functions including antigenotoxicity and the promotion of cell growth. To investigate the physical and biological functions of SG nanofibrous (SGN) scaffold, we fabricated silk fibroin nanofibrous (SFN) scaffold as a control lacking the SG functional proteins. Field emission scanning electron microscope images revealed that the SGN three-dimensional scaffold had a homogenous pore distribution with a high porosity and interconnected pore walls. In biological tests, the SGN scaffold supported excellent cell viability and had a stronger antioxidant property compared to the SFN scaffold. In addition, the SGN scaffold efficiently supported the growth of adipose tissue-derived stem cells and their osteogenic and fibrocartilage differentiation. Therefore, this novel SGN three-dimensional scaffold shows high promise for use in tissue engineering.