Biostable electrospun microfibrous scaffolds mitigate hypertrophic scar contraction in an immune-competent murine model

In vitro and in vivo evaluation of electrospun poly (ε-caprolactone)/collagen scaffolds and Wharton's jelly mesenchymal stromal cells (hWJ-MSCs) constructs as potential alternative for skin tissue engineering

Dermal substitutes bear a high clinical demand because of their ability to promote the healing process of cutaneous wounds by reducing the healing time the appearance and improving the functionality of the repaired tissue. Despite the increasing development of dermal substitutes, most of them are only composed of biological or biosynthetic matrices. This demonstrates the need for new developments focused on using scaffolds with cells (tissue construct) that promote the production of factors for biological signaling, wound coverage, and general support of the tissue repair process. Here, we fabricate by electrospinning two scaffolds: poly(ε-caprolactone) (PCL) as a control and poly(ε-caprolactone)/collagen type I (PCol) in a ratio lower collagen than previously reported, 19:1, respectively. Then, characterize their physicochemical and mechanical properties. As we bear in mind the creation of a biologically functional construct, we characterize and assess in vitro the implications of seeding human Wharton's jelly mesenchymal stromal cells (hWJ-MSCs) on both scaffolds. Finally, to determine the potential functionality of the constructs in vivo, their efficiency was evaluated in a porcine biomodel. Our findings demonstrated that collagen incorporation in the scaffolds produces fibers with similar diameters to those in the human native extracellular matrix, increases wettability, and enhances the presence of nitrogen on the scaffold surface, improving cell adhesion and proliferation. These synthetic scaffolds improved the secretion of factors by hWJ-MSCs involved in skin repair processes such as b-FGF and Angiopoietin I and induced its differentiation towards epithelial lineage, as shown by the increased expression of Involucrin and JUP. In vivo experiments confirmed that lesions treated with the PCol/hWJ-MSCs constructs might reproduce a morphological organization that seems relatively equivalent to normal skin. These results suggest that the PCol/hWJ-MSCs construct is a promising alternative for skin lesions repair in the clinic.

Synthesis and Characterization of PU/PLCL/CMCS Electrospun Scaffolds for Skin Tissue Engineering

As tissue regeneration material, electrospun fibers can mimic the microscale and nanoscale structure of the natural extracellular matrix (ECM), which provides a basis for cell growth and achieves organic integration with surrounding tissues. At present, the challenge for researchers is to develop a bionic scaffold for the regeneration of the wound area. In this paper, polyurethane (PU) is a working basis for the subsequent construction of tissue-engineered skin. poly(L-lactide-co-caprolactone) (PLCL)/carboxymethyl chitosan (CMCS) composite fibers were prepared via electrospinning and cross-linked by glutaraldehyde. The effect of CMCS content on the surface morphology, mechanical properties, hydrophilicity, swelling degree, and cytocompatibility were explored, aiming to assess the possibility of composite scaffolds for tissue engineering applications. The results showed that randomly arranged electrospun fibers presented a smooth surface. All scaffolds exhibited sufficient tensile strength (5.30-5.60 MPa), Young's modulus (2.62-4.29 MPa), and swelling degree for wound treatment. The addition of CMCS improved the hydrophilicity and cytocompatibility of the scaffolds.

A Systematic Review Comparing Animal and Human Scarring Models

Introduction

A reproducible, standardised model for cutaneous scar tissue to assess therapeutics is crucial to the progress of the field. A systematic review was performed to critically evaluate scarring models in both animal and human research.

Method

All studies in which cutaneous scars are modelling in animals or humans were included. Models that were focused on the wound healing process or those in humans with scars from an existing injury were excluded. Ovid Medline^® was searched on 25 February 2019 to perform two near identical searches; one aimed at animals and the other aimed at humans. Two reviewers independently screened the titles and abstracts for study selection. Full texts of potentially suitable studies were then obtained for analysis.

Results

The animal kingdom search yielded 818 results, of which 71 were included in the review. Animals utilised included rabbits, mice, pigs, dogs and primates. Methods used for creating scar tissue included sharp excision, dermatome injury, thermal injury and injection of fibrotic substances. The search for scar assessment in humans yielded 287 results, of which 9 met the inclusion criteria. In all human studies, sharp incision was used to create scar tissue. Some studies focused on patients before or after elective surgery, including bilateral breast reduction, knee replacement or midline sternotomy.

Discussion

The rabbit ear scar model was the most popular tool for scar research, although pigs produce scar tissue which most closely resembles that of humans. Immunodeficient mouse models allow for in vivo engraftment and study of human scar tissue, however, there are limitations relating to the systemic response to these xenografts. Factors that determine the use of animals include cost of housing requirements, genetic traceability, and ethical concerns. In humans, surgical patients are often studied for scarring responses and outcomes, but reproducibility and patient factors that impact healing can limit interpretation. Human tissue use in vitro may serve as a good basis to rapidly screen and assess treatments prior to clinical use, with the advantage of reduced cost and setup requirements.

Improved porosity of electrospun poly (Lactic-Co-Glycolic) scaffolds by sacrificial microparticles enhances cellular infiltration compared to sacrificial microfiber

Electrospinning is a technique used to fabricate nano-/microfiber scaffolds for tissue engineering applications. However, a major limitation of electrospun scaffolds is the high packing density of fibers that leads to poor cellular infiltration. Thus, incorporation of a water soluble sacrificial porogen, polyethylene oxide (PEO), was utilized to fine-tune the porous fraction of the scaffolds and decrease fiber packing density. Poly(lactic-co-glycolic) acid (PLGA) scaffolds were either co-electrospun with sacrificial PEO microfibers or co-electrosprayed with sacrificial PEO microparticles at three different extrusion rates to control the relative morphology and dose of PEO. A dose-dependent response in PLGA scaffold bulk porosity and pore area was noted as PEO content was increased. Notably, PLGA scaffolds after removal of sacrificial PEO microparticles significantly increased the porous fraction and pore area approximately 8, 10, and 14% and 46, 20, and 33 μm², respectively, relative to the analogous PEO microfiber scaffold. The tensile properties of the more porous PLGA scaffolds after PEO microparticle removal, remained stable for all extrusion rates of PEO tested, relative to the PLGA scaffolds after PEO microfiber removal. Histological analysis revealed that removal of PEO microparticles significantly increased the depth of cellular migration through the PLGA scaffolds, relative to PEO microfiber scaffolds, with maximum migratory depths of 1120 μm versus 150 μm over 28 days, respectively. Additionally, depth of cellular infiltration responded dose-dependently in the PEO microparticle scaffolds, whereas in the PEO microfiber scaffolds there was no correlation. Further analysis with Masson's Trichrome staining and electron microscopy revealed that collagen density and depth of deposition substantially increased in PLGA scaffolds after removal of PEO microparticles relative to PEO microfibers. Thus, this study demonstrates an effective strategy to control the porous fraction of electrospun scaffolds via the incorporation of sacrificial PEO microparticles, without significant decreases in mechanical properties, thereby enhancing cellular infiltration and subsequent extracellular matrix deposition.

Comparison of Thermal Burn-Induced and Excisional-Induced Scarring in Animal Models: A Review of the Literature

Significance: Scar formation is a natural result of mammalian wound healing. In humans and other mammals, however, deep dermal wounds and thermal injuries often result in formation of hypertrophic scars, leading to substantial morbidity and lending great importance to development of therapeutic modalities for burn scars. Clinical Issues: Thus, preclinical burn wound models that adequately simulate processes underlying human burn-induced wound healing, particularly those processes leading to chronic inflammation and development of hypertrophic scars, are critical to developing further treatment paradigms for clinical use. Approach: In this study, we review literature describing various burn models, focusing on their characteristics and the functional readouts that lead to generation of useful data. We also briefly discuss recent work using human ex vivo skin culture as an alternative to animal models, as well as our own development of rabbit ear wound models for burn scars, and assess the pros and cons of these models compared to other models. Future Direction: Understanding of the strengths and weaknesses of preclinical burn wound models will enable choice of the most appropriate wound model to answer particular clinically relevant questions, furthering research aimed at treating burn scars.

Nanomaterials for application in wound Healing: current state-of-the-art and future perspectives

Nanoparticles are the gateway to the new era in drug delivery of biocompatible agents. Several products have emerged from nanomaterials in quest of developing practical wound healing dressings that are nonantigenic, antishear stress, and gas-exchange permeable. Numerous studies have isolated and characterised various wound healing nanomaterials and nanoproducts. The electrospinning of natural and synthetic materials produces fine products that can be mixed with other wound healing medications and herbs. Various produced nanomaterials are highly influential in wound healing experimental models and can be used commercially as well. This article reviewed the current state-of-the-art and briefly specified the future concerns regarding the different systems of nanomaterials in wound healing (i.e., inorganic nanomaterials, organic and hybrid nanomaterials, and nanofibers). This review may be a comprehensive guidance to help health care professionals identify the proper wound healing materials to avoid the usual wound complications.

Recent Advances in Experimental Burn Models

Experimental burn models are essential tools for simulating human burn injuries and exploring the consequences of burns or new treatment strategies. Unlike clinical studies, experimental models allow a direct comparison of different aspects of burns under controlled conditions and thereby provide relevant information on the molecular mechanisms of tissue damage and wound healing, as well as potential therapeutic targets. While most comparative burn studies are performed in animal models, a few human or humanized models have been successfully employed to study local events at the injury site. However, the consensus between animal and human studies regarding the cellular and molecular nature of systemic inflammatory response syndrome (SIRS), scarring, and neovascularization is limited. The many interspecies differences prohibit the outcomes of animal model studies from being fully translated into the human system. Thus, the development of more targeted, individualized treatments for burn injuries remains a major challenge in this field. This review focuses on the latest progress in experimental burn models achieved since 2016, and summarizes the outcomes regarding potential methodological improvements, assessments of molecular responses to injury, and therapeutic advances.

Collagen based electrospun materials for skin wounds treatment

Materials used for wound care have evolved from simple covers to functional wound dressings with bioactive properties. Electrospun nanofibers show great similarity to the natural fibrillar structure of skin extracellular matrix (ECM); therefore, by mimic, the morphology of ECM, nanofibers show high potential for facilitating the healing of skin injuries. Besides morphology, scaffold composition is another important parameter in the production of bioactive wound dressings. Collagen type I is the main structural protein of skin ECM is biocompatible, biodegradable, and its extraction from animal sources is relatively simple. The fabrication of electrospun wound dressings based on collagen and its blends have been studied for skin tissue engineering applications. This review focus on the new advances of collagen electrospun materials for skin wound treatment. It summarizes the recent research on pristine collagen, collagen blends, and collagen surface modifications on nanofibers mats. Finally, the strategies for three-dimensional nanofibers production will also be discussed.

Petite miracles: insight into the nano-management of scarless wound healing

Scars affect millions of patients worldwide, yet their treatment efficacy and options clinically remain limited. In recent years, increased understanding of scar formation pathways leading to developments in nanotechnology have opened many opportunities for scar detection, prevention, and treatment due to the nanoscale features and therapeutic delivery capabilities of such technologies. Led by nanoparticles (NPs) and nanofibers, these novel strategies can aid in reducing scar contracture, improving wound-healing efficacy, and advancing progress towards scarless wound healing.

WITHDRAWN: Petite miracles: insight into the nano-management of scarless wound healing

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Prevention of excessive scar formation using nanofibrous meshes made of biodegradable elastomer poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

To reduce excessive scarring in wound healing, electrospun nanofibrous meshes, composed of haloarchaea-produced biodegradable elastomer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), are fabricated for use as a wound dressing. Three PHBV polymers with different 3HV content are used to prepare either solution-cast films or electrospun nanofibrous meshes. As 3HV content increases, the crystallinity decreases and the scaffolds become more elastic. The nanofibrous meshes exhibit greater elasticity and elongation at break than films. When used to culture human dermal fibroblasts in vitro, PHBV meshes give better cell attachment and proliferation, less differentiation to myofibroblasts, and less substrate contraction. In a full-thickness mouse wound model, treatment with films or meshes enables regeneration of pale thin tissues without scabs, dehydration, or tubercular scar formation. The epidermis of wounds treated with meshes develop small invaginations in the dermis within 2 weeks, indicating hair follicle and sweat gland regeneration. Consistent with the in vitro results, meshes reduce myofibroblast differentiation in vivo through downregulation of α-SMA and TGF-β1, and upregulation of TGF-β3. The regenerated wounds treated with meshes are softer and more elastic than those treated with films. These results demonstrate that electrospun nanofibrous PHBV meshes mitigate excessive scar formation by regulating myofibroblast formation, showing their promise for use as wound dressings.

Fabrication and characterization of high molecular keratin based nanofibrous membranes for wound healing

Keratin is widely used in the biomaterial application, but the keratin prepared by the physical or chemical approach has relatively low molecular weight and mechanical properties. Here we report the preparation of high molecular keratin (HMK) with molecular weight of 120 kDa via multi-enzyme cascade pathway and its application in wound healing. Briefly, we prepared the soluble keratin from wool by keratinase and improved the molecular weight of keratin by transglutaminase (TGase). The HMK was coelectrospun with poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) and the prepared nanofibrous mats demonstrated improved mechanical properties. Ag nanoparticles (AgNPs) were synthesized on the nanofibers via in situ bioreduction, using the above-mentioned keratinase as the reducing agent. It is demonstrated that the PHBV/HMK/AgNPs nanofibrous mats possess favorable antibacterial properties and good biocompatibility. Moreover, in vivo wound healing assessment, the PHBV/HMK/AgNPs membrane displayed better wound healing ability than the control group. These results indicate that PHBV/HMK/AgNPs mats exhibit significant potential in tissue engineering.

Modulating cationicity of chitosan hydrogel to prevent hypertrophic scar formation during wound healing

It is of great clinical significance to design wound dressing materials with combined excellent wound healing properties and superior capability to suppress hypertrophic scar formation. This study aimed to examine if and how the cationicity of chitosan would affect the hypertrophic scar-related outcomes, through preparing carboxymethyl chitosan hydrogels with different genipin concentrations (2.5%, 5%, 10% and 15%, respectively). An optimum window of chitosan cationicity (5% in our case) demonstrated potential to mitigate hypertrophic scar in wound healing by suppressing the expression of a-smooth muscle actin (a-SMA) and promoting secretion of type I matrix metalloproteinases (MMP-1). In vivo, the CMCS-5% hydrogel again showed smaller, thinner and smoother wound appearance. Moreover, the CMCS-5% sample with additional incorporation of 2% (V/V) Aloe vera gel exhibited further improved performance in scar inhibition. Overall, such findings might have important implications in chitosan-based wound dressing design for high-quality wound repair and effective scar inhibition.

Integration of an ultra-strong poly(lactic-co-glycolic acid) (PLGA) knitted mesh into a thermally induced phase separation (TIPS) PLGA porous structure to yield a thin biphasic scaffold suitable for dermal tissue engineering

We aimed to capture the outstanding mechanical properties of meshes, manufactured using textile technologies, in thin biodegradable biphasic tissue-engineered scaffolds through encapsulation of meshes into porous structures formed from the same polymer. Our novel manufacturing process used thermally induced phase separation (TIPS), with ethylene carbonate (EC) as the solvent, to encapsulate a poly(lactic-co-glycolic acid) (PLGA) mesh into a porous PLGA network. Biphasic scaffolds (1 cm × 4 cm × 300 μm) were manufactured by immersing strips of PLGA mesh in 40 °C solutions containing 5% PLGA in EC, supercooling at 4 °C for 4 min, triggering TIPS by manually agitating the supercooled solution, and lastly eluting EC into 4 °C Milli-Q water. EC processing was rapid and did not compromise mesh tensile properties. Biphasic scaffolds exhibited a tensile strength of 40.7 ± 2.2 MPa, porosity of 94%, pore size of 16.85 ± 3.78 μm, supported HaCaT cell proliferation, and degraded in vitro linearly over the first ∼3 weeks followed by rapid degradation over the following three weeks. The successful integration of textile-type meshes yielded scaffolds with exceptional mechanical properties. This thin, porous, high-strength scaffold is potentially suitable for use in dermal wound repair or repair of tubular organs.

Bionic Poly(γ-Glutamic Acid) Electrospun Fibrous Scaffolds for Preventing Hypertrophic Scars

Hypertrophic scarring (HS) remains a great challenge in wound dressing. Although various bionic extracellular matrix (ECM) biomaterials have been designed towards HS treatment, not all biomaterials can synergize biological functions and application functions in wound repair. Bionic scar-inhibiting scaffolds, loaded with biomolecules or drugs, become promising strategies for scarless skin regeneration. In this work, inspired by the physicochemical environment of ECM, a versatile fabrication of poly(γ-glutamic acid) based on electrospun photocrosslinkable hydrogel fibrous scaffolds incorporated with ginsenoside Rg3 (GS-Rg3) is developed for tissue repair and wound therapy. Decorated with adhesive peptide, bionic fibrous scaffolds can accelerate fibroblasts to sprout and grow, forming organized space-filling basement that gradually fills a depression before wound close up in the early stage. Additionally, by sustained release of GS-Rg3 in late stage, fibrous scaffolds promote scarless wound healing in vivo as evidenced by the promotion of cell communication and skin regeneration, as well as the subsequent decrease of angiogenesis and collagen accumulation. These ECM-inspired fibrous scaffolds, therefore, offer new perspectives on accelerated wound healing and tissue regeneration.

The Dynamics of the Skin's Immune System

The skin is a complex organ that has devised numerous strategies, such as physical, chemical, and microbiological barriers, to protect the host from external insults. In addition, the skin contains an intricate network of immune cells resident to the tissue, crucial for host defense as well as tissue homeostasis. In the event of an insult, the skin-resident immune cells are crucial not only for prevention of infection but also for tissue reconstruction. Deregulation of immune responses often leads to impaired healing and poor tissue restoration and function. In this review, we will discuss the defensive components of the skin and focus on the function of skin-resident immune cells in homeostasis and their role in wound healing.

Biomimetic Elastomeric Polypeptide-Based Nanofibrous Matrix for Overcoming Multidrug-Resistant Bacteria and Enhancing Full-Thickness Wound Healing/Skin Regeneration

Overcoming the multidrug-resistant (MDR) bacterial infection is a challenge and urgently needed in wound healing. Few wound dressings possess the capacity to treat MDR bacterial infections and enhance wound healing. Herein, we develop an elastomeric, photoluminescent, and antibacterial hybrid polypeptide-based nanofibrous matrix as a multifunctional platform to inhibit the MDR bacteria and enhance wound healing. The hybrid nanofibrous matrix was composed of poly(citrate)-ε-poly lysine (PCE) and poly caprolactone (PCL). The PCL-PCE hybrid nanofibrous matrix showed a biomimetic elastomeric behavior, robust antibacterial activity including killing MDR bacteria capacity, and excellent biocompatibility. PCL-PCE nanofibrous system can efficiently prevent the MDR bacteria-derived wound infection and significantly enhance the complete skin-thickness wound healing and skin regeneration in a mouse model. PCL-PCE hybrid nanofibrous matrix might become a competitive multifunctional dressing for bacteria-infected wound healing and skin regeneration.

Morphology-induced physico-mechanical and biological characteristics of TPU-PDMS blend scaffolds for skin tissue engineering applications

Composition and architecture of scaffolds are the most important factors determining the performance of skin substitutes. In this work, morphology induced unique physical and biological characteristics of compatibilized TPU-PDMS blend scaffolds at 90:10, 80:20, and 70:30 blend ratios of TPU and PDMS was studied. The fiber morphology, porosity, surface wettability, and mechanical properties of electrospun scaffolds were distinctly influenced by the presence of PDMS. Interestingly, the scaffold architecture varied from electrospun fibers to porous fibers and finally occurrence of unique porous beads noticed at 30% PDMS in the microstructure which was confirmed using FESEM. Micro-CT analysis revealed that the porosity of electrospun scaffolds was enhanced from 61% to 79% with 30 parts of PDMS addition. Moreover, MTT assay and cell proliferation were studied using human skin fibroblast cells and found to be significantly enhanced with the PDMS percentage. TPU-PDMS blends offer better overall performance at 70:30 blend ratio of TPU and PDMS (T70P30). Only 4% of hemolysis was observed for T70P30 blends, which establishes the hemocompatibility of the material. In comparison, the results reveal the potential of the cytocompatible T70P30 scaffold for the fabrication of skin substitutes for tissue engineering applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1634-1644, 2019.

Biomaterials for Skin Substitutes

Patients with extensive burns rely on the use of tissue engineered skin due to a lack of sufficient donor tissue, but it is a challenge to identify reliable and economical scaffold materials and donor cell sources for the generation of a functional skin substitute. The current review attempts to evaluate the performance of the wide range of biomaterials available for generating skin substitutes, including both natural biopolymers and synthetic polymers, in terms of tissue response and potential for use in the operating room. Natural biopolymers display an improved cell response, while synthetic polymers provide better control over chemical composition and mechanical properties. It is suggested that not one material meets all the requirements for a skin substitute. Rather, a composite scaffold fabricated from both natural and synthetic biomaterials may allow for the generation of skin substitutes that meet all clinical requirements including a tailored wound size and type, the degree of burn, the patient age, and the available preparation technique. This review aims to be a valuable directory for researchers in the field to find the optimal material or combination of materials based on their specific application.

Hierarchical Micro/Nanofibrous Bioscaffolds for Structural Tissue Regeneration

Various biomimetic scaffolds with hierarchical micro/nanostructures are designed to closely mimic native extracellular matrix network and to guide cell behavior to promote structural tissue generation. However, it remains a challenge to fabricate hierarchical micro/nanoscaled fibrous scaffolds with different functional components that endow the scaffolds with both biochemical and physical features to exert different biological roles during the process of tissue healing. In this study, a biomimetic designed micro/nanoscaled scaffold with integrated hierarchical dual fibrillar components is fabricated in order to repair dura mater and prevent the formation of epidural scars via collagen molecule self-assembly, electrospinning, and biological interface crosslinking strategies. The fabricated biomimetic scaffolds display micro/nanofibers staggered hierarchical architecture with good mechanical properties and biocompatibility, and it has a more profound effect on attachment, proliferation, and differentiation of fibroblasts. Using a rabbit duraplasty model in vivo, the authors find that dural defects repaired with hierarchical micro/nanoscaled scaffold form a continuous neodura tissue similar to native dura mater; furthermore, the number of scar tissues decreases significantly in the laminectomy sites compared with conventional electrospun microfibrous scaffold. Taken together, these data suggest that the hierarchical micro/nanoscaled fibrous scaffolds with dual fibrillar components may act as a "true" dural substitutes for dual repair.

Recent advances in electrospun nanofibers for wound healing

Electrospun nanofibers represent a novel class of materials that show great potential in many biomedical applications including biosensing, regenerative medicine, tissue engineering, drug delivery and wound healing. In this work, we review recent advances in electrospun nanofibers for wound healing. This article begins with a brief introduction on the wound, and then discusses the unique features of electrospun nanofibers critical for wound healing. It further highlights recent studies that have used electrospun nanofibers for wound healing applications and devices, including sutures, multifunctional dressings, dermal substitutes, engineered epidermis and full-thickness skin regeneration. Finally, we finish with conclusions and future perspective in this field.

Electrospinning of PVA/sericin nanofiber and the effect on epithelial-mesenchymal transition of A549 cells

This research aims to investigate the cell-nanomaterial interaction between epithelial-mesenchymal transition of A549 cell and electrospinning nanofibers composed of polyvinyl alcohol (PVA)/silk sericin (SS). The electrospinning of regenerated nanofiber was performed with water as a spinning solvent and glutaraldehyde as a chemical cross-linker. Solution concentration, applied voltage and spin distances as well as other parameters were optimized to generate fine nanofibers with smooth surface in good homogeneity. From the scanning electron microscopy (SEM) analysis, the nanofibers had an average diameter of 200nm. Epithelial-mesenchymal transition (EMT) is a process by which epithelial cells lose their cell polarity to become mesenchymal stem cells. This transition is affected by multiple biochemical and physical factors in cell metabolism cascade. Herein, we investigate the biophysical effect on A549 EMT by culturing cells on nanofibrous mats with different topography and composition. The cell viability was evaluated by biochemical assay and its morphology was observed with SEM. The results demonstrate that cells appropriately attached to the surface of the nanofibrous mats with extended morphology by their filopodia. Gene expression analysis was conducted by real-time PCR using multiple markers for detecting EMT: N-cadherin (NCad), Vimentin (Vim), Fibronectin (Fib) and Matrix metallopeptidase (MMP9). An increasing expression pattern was observed on NCad, Vim, Fib, with respect to a negative control as cell cultured on polystyrene dish. This result indicates the 200nm PVA/SS nanofibers may induce A549 cells to process epithelial-mesenchymal transition during the culturing.