Electrospun nanostructured chitosan–poly(vinyl alcohol) scaffolds: a biomimetic extracellular matrix as dermal substitute

Innovative spiral nerve conduits: Addressing nutrient transport and cellular activity for critical-sized nerve defects

Large-gap nerve defects require nerve guide conduits (NGCs) for complete regeneration and muscle innervation. Many NGCs have been developed using various scaffold designs and tissue engineering strategies to promote axon regeneration. Still, most are tubular with inadequate pore sizes and lack surface cues for nutrient transport, cell attachment, and tissue infiltration. This study developed a porous spiral NGC to address these issues using a 3D-printed thermoplastic polyurethane (TPU) fiber lattice. The lattice was functionalized with poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) electrospun aligned (aPHBV) and randomly (rPHBV) oriented nanofibers to enhance cellular activity. TPU lattices were made with 25 %, 35 %, and 50 % infill densities to create scaffolds with varied mechanical compliance. The fabricated TPU/PHBV spiral conduits had significantly higher surface areas (25 % TPU/PHBV: 698.97 mm2, 35 % TPU/PHBV: 500.06 mm2, 50 % TPU/PHBV: 327.61 mm2) compared to commercially available nerve conduits like Neurolac™ (205.26 mm2). Aligned PHBV nanofibers showed excellent Schwann cell (RSC96) adhesion, proliferation, and neurogenic gene expression for all infill densities. Spiral TPU/PHBV conduits with 25 % and 35 % infill densities exhibited Young's modulus values comparable to Neurotube® and ultimate tensile strength like acellular cadaveric human nerves. A 10 mm sciatic nerve defect in Wistar rats treated with TPU/aPHBV NGCs demonstrated muscle innervation and axon healing comparable to autografts over 4 months, as evaluated by gait analysis, functional recovery, and histology. The TPU/PHBV NGC developed in this study shows promise as a treatment for large-gap nerve defects.

Therapeutic effects of electrospun chitosan nanofibers on animal skin wounds: A systematic review and meta-analysis

Electrospun chitosan nanofibers (QSNFs) enhance the healing process by mimicking skin structure and function. The aim of this study was to analyze the therapeutic effects of QSNFs application on animal skin wounds to identify a potential direction for translational research in dermatology. The PRISMA methodology and the PICO scheme were used. A random effects model and mean difference analysis were applied for the meta-analysis. A meta-regression model was constructed, risk of bias was determined, and methodological quality assessment was performed. Of the 2370 articles collected, 54 studies were selected based on the inclusion and exclusion criteria. The wound healing area was used for building models on the 3rd, 7th, and 14th days of follow-up; the results were - 10.4% (95% CI, -18.2% to -2.6%, p = 0.001), -21.0% (95% CI, -27.3% to -14.7%, p = 0.001), and - 14.0% (95% CI, -19.1 to -8.8%, p = 0.001), respectively. Antioxidants and synthetic polymers combined with QSNFs further reduced skin wound areas (p < 0.05). The results show a more efficient reduction in wound area percentages in experimental groups than in control groups, so QSNFs could potentially be applied in translational human medicine research.

A novel transdermal delivery route for energy supplements: Electrospun chitosan/polyvinyl alcohol nanofiber patches loaded with vitamin B12

Nanofibrous patches have attracted much attention as a solution to resolve drug delivery challenges. In this study, vitamin B₁₂- loaded polyvinyl alcohol (PVA)/chitosan (Cs) nanofiber patch (NFP) was electrospun and cross-linked by glutaraldehyde (GA). The physicochemical properties of the nanofiber patches were assessed by morphological studies, FTIR analysis, hydrophilicity test, mechanical tests, and in-vitro evaluations including biodegradability, MTT assay, and cumulative release test of vitamin. In-vivo studies were also carried out by measuring vitamin B₁₂ levels in the bloodstream and conducting histopathology studies on the animal models. The results showed that the mean diameter of Cs/PVA/B₁₂ and cross-linked patch were approximately 207 and 256 nm, respectively. Cross-linking of NFP led to the lower, slower, and more continuous release of the vitamin with a slight decrease in biodegradability, and an increase in the mechanical properties of the nanofiber patches. Furthermore, the cytocompatibility assay, MTT, and in vivo results revealed no cytotoxicity of Cs/PVA/B₁₂ NFP towards L929 cell line. No lesion or tissue damage was observed in the skin tissue of the animal models wearing these skin patches. Therefore, B₁₂-loaded NFP can be introduced as a potential candidate for commercial transdermal routes.

ECM Mimicking Biodegradable Nanofibrous Scaffold Enriched with Curcumin/ZnO to Accelerate Diabetic Wound Healing via Multifunctional Bioactivity

Introduction

Foot ulceration is one of the most severe and debilitating complications of diabetes, which leads to the cause of non-traumatic lower-extremity amputation in 15-24% of affected individuals. The healing of diabetic foot (DF) is a significant therapeutic problem due to complications from the multifactorial healing process. Electrospun nanofibrous scaffold loaded with various wound dressing materials has excellent wound healing properties due to its multifunctional action.

Purpose

This work aimed to develop and characterize chitosan (CS)-polyvinyl alcohol (PVA) blended electrospun multifunctional nanofiber loaded with curcumin (CUR) and zinc oxide (ZnO) to accelerate diabetic wound healing in STZ-induced diabetic rats.

Results

In-vitro characterization results revealed that nanofiber was fabricated successfully using the electrospinning technique. SEM results confirmed the smooth surface with web-like fiber nanostructure diameter ranging from 200 - 250 nm. An in-vitro release study confirmed the sustained release of CUR and ZnO for a prolonged time. In-vitro cell-line studies demonstrated significantly low cytotoxicity of nanofiber in HaCaT cells. Anti-bacterial studies demonstrated good anti-bacterial and anti-biofilm activities of nanofiber. In-vivo animal studies demonstrated an excellent wound-healing efficiency of the nanofibers in STZ-induced diabetic rats. Furthermore, the ELISA assay revealed that the optimized nanofiber membrane terminated the inflammatory phases successfully by downregulating the pro-inflammatory cytokines (TNF-α, MMP-2, and MMP-9) in wound healing. In-vitro and in-vivo studies conclude that the developed nanofiber loaded with bioactive material can promote diabetic wound healing efficiently via multifunction action such as the sustained release of bioactive molecules for a prolonged time of duration, proving anti-bacterial/anti-biofilm properties and acceleration of cell migration and proliferation process during the wound healing.

Discussion

CUR-ZnO electrospun nanofibers could be a promising drug delivery platform with the potential to be scaled up to treat diabetic foot ulcers effectively.

Matricellular proteins in cutaneous wound healing

Cutaneous wound healing is a complex process that encompasses alterations in all aspects of the skin including the extracellular matrix (ECM). ECM consist of large structural proteins such as collagens and elastin as well as smaller proteins with mainly regulative properties called matricellular proteins. Matricellular proteins bind to structural proteins and their functions include but are not limited to interaction with cell surface receptors, cytokines, or protease and evoking a cellular response. The signaling initiated by matricellular proteins modulates differentiation and proliferation of cells having an impact on the tissue regeneration. In this review we give an overview of the matricellular proteins that have been found to be involved in cutaneous wound healing and summarize the information known to date about their functions in this process.

Advanced Nanofiber-Based Scaffolds for Achilles Tendon Regenerative Engineering

The Achilles tendon (AT) is responsible for running, jumping, and standing. The AT injuries are very common in the population. In the adult population (21–60 years), the incidence of AT injuries is approximately 2.35 per 1,000 people. It negatively impacts people’s quality of life and increases the medical burden. Due to its low cellularity and vascular deficiency, AT has a poor healing ability. Therefore, AT injury healing has attracted a lot of attention from researchers. Current AT injury treatment options cannot effectively restore the mechanical structure and function of AT, which promotes the development of AT regenerative tissue engineering. Various nanofiber-based scaffolds are currently being explored due to their structural similarity to natural tendon and their ability to promote tissue regeneration. This review discusses current methods of AT regeneration, recent advances in the fabrication and enhancement of nanofiber-based scaffolds, and the development and use of multiscale nanofiber-based scaffolds for AT regeneration.

The Effect of Strontium-Substituted Hydroxyapatite Nanofibrous Matrix on Osteoblast Proliferation and Differentiation

Natural bone tissue consists primarily of bioapatite and collagen. Synthetic hydroxyapatite (HA) possesses good biocompatibility, bioactivity, and osteoconductivity due to its chemical and biological similarity to bioapatite. Hence, HA has been widely used as a bone graft, cell carrier and drug/gene delivery carrier. Moreover, strontium-substituted hydroxyapatite (SrHA) can enhance osteogenic differentiation and inhibit adipogenic differentiation of mesenchymal stem cells. Hence, SrHA has the potential to be used as a bone graft for bone regeneration. It is widely accepted that cell adhesion and most cellular activities are sensitive to the topography and molecular composition of the matrix. Electrospun polymer or polymer-bioceramic composite nanofibers have been demonstrated to enhance osteoblast differentiation. However, to date, no studies have investigated the effect of nanofibrous bioceramic matrices on osteoblasts. In this study, hydroxyapatite nanofiber (HANF) and strontium-substituted hydroxyapatite nanofiber (SrHANF) matrices were fabricated by electrospinning. The effect of the HANF components on MG63 osteoblast-like cells was evaluated by cell morphology, proliferation, alkaline phosphatase activity (ALP) and gene expression levels of RUNX2, COLI, OCN and BSP. The results showed that MG63 osteoblast-like cells exhibited higher ALP and gene expression levels of RUNX2, COLI, BSP and OCN on the SrHANF matrix than the HANF matrix. Hence, SrHANFs could enhance the differentiation of MG63 osteoblast-like cells.

Fabrication of Hybrid Nanofibers from Biopolymers and Poly (Vinyl Alcohol)/Poly (ε-Caprolactone) for Wound Dressing Applications

The management of chronic wounds is challenging. The factors that impede wound healing include malnutrition, diseases (such as diabetes, cancer), and bacterial infection. Most of the presently utilized wound dressing materials suffer from severe limitations, including poor antibacterial and mechanical properties. Wound dressings formulated from the combination of biopolymers and synthetic polymers (i.e., poly (vinyl alcohol) or poly (ε-caprolactone) display interesting properties, including good biocompatibility, improved biodegradation, good mechanical properties and antimicrobial effects, promote tissue regeneration, etc. Formulation of these wound dressings via electrospinning technique is cost-effective, useful for uniform and continuous nanofibers with controllable pore structure, high porosity, excellent swelling capacity, good gaseous exchange, excellent cellular adhesion, and show a good capability to provide moisture and warmth environment for the accelerated wound healing process. Based on the above-mentioned outstanding properties of nanofibers and the unique properties of hybrid wound dressings prepared from poly (vinyl alcohol) and poly (ε-caprolactone), this review reports the in vitro and in vivo outcomes of the reported hybrid nanofibers.

Preparation of multilayer electrospun nanofibrous scaffolds containing soluble eggshell membrane as potential dermal substitute

Electrospinning of natural and synthetic polymers has shown to be a great candidate for the fabrication of tissue engineering scaffolds due to their similarity to the nanofibrous structure of natural extracellular matrix (ECM). Moreover, the addition of ECM-like proteins could enhance the biocompatibility of these scaffolds. In this study, soluble eggshell protein (SEP) was first extracted and synthesized from the raw eggshell membrane. The characteristics and biocompatibility of the extracted SEP were evaluated using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) analysis and 3-(4,5- dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide) (MTT) assay. For scaffolds fabrication, a three-layer nanofibrous composite structure was produced using the electrospinning technique. The outer layers composed of polyvinyl alcohol, chitosan, and extracted SEP while the middle layer composed of polyethylene oxide, gelatin, and zinc oxide nanoparticles (ZnO-NPs). For each layer, the electrospinning parameters were adjusted to form bead-free fibers. To improve fibers' stability against body fluids, the produced fibers were crosslinked using glutaraldehyde vapor. Several techniques such as scanning electron microscopy (SEM), energy dispersive X-ray, ATR-FTIR, swelling, tensile test, in vitro biodegradation, and MTT assay were implemented to evaluate the physical, chemical, and biological characterization of the fabricated fibers. The results showed that crosslinked fibers have adequate stability in water, suitable mechanical properties, and promising water uptake capacity. The MTT results also revealed that SEP and ZnO-NPs could increase scaffolds biocompatibility. Moreover, SEM photographs of cultured fibroblasts cells on the scaffolds showed that cells were well attached on the scaffolds and preserve their natural spindle shapes. Altogether, our findings demonstrated that the produced three-layer composite scaffolds are potential candidates for skin tissue engineering.

Design and evaluation of ciprofloxacin loaded collagen chitosan oxygenating scaffold for skin tissue engineering

Hypoxia and sepsis are key concerns towards modern regenerative medicine. Oxygen generating biomaterials having antibacterial property aims to answer these concerns. Hypoxia promotes reactive oxygen species at the implant site that delays wound healing. Sepsis in wound also contributes to delay in wound healing. Therefore, scaffold with antibacterial property and oxygen-producing capacities have shown ability to promote wound healing. In the present study oxygen releasing, ciprofloxacin loaded collagen chitosan scaffold was fabricated for sustained oxygen delivery. Calcium peroxide (CPO) acted as a chemical oxygen source. Oxygen release pattern exhibited a sustained release of oxygen with uniform deposition of CPO on the scaffold. The drug release study shows a prolonged, continuous, and sustained release of ciprofloxacin. Cell culture studies depict that scaffold has suitable cell attachment and migration properties for fibroblasts. In vivo studies performed in the skin flip model visually shows better wound healing and less necrosis. Histological studies show the maintenance of tissue architecture and the deposition of collagen. The results demonstrate that the proposed CPO coated ciprofloxacin loaded collagen-chitosan scaffold can be a promising candidate for skin tissue engineering.

Postoperative placement of an anti-fibrotic poly L-lactide electrospun fibrous membrane after sinus surgery

BACKGROUND

Endoscopic sinus surgery (ESS) is used to treat chronic rhinosinusitis. However, nasal adhesions often develop postoperatively, triggered by chronic inflammation and local fibrosis. A poly L-lactide (PLLA) electrospun microfibrous membrane is a functional biodegradable material that can be placed on the wound surface to protect the wound and prevent adhesions.

METHODS

We divided 24 rabbits randomly into 2 groups, a control operation group (group A) and an operation+PLLA placement group (group B). We investigated the anti-fibrotic effects of the topical biomaterial after sinus surgery. We placed PLLA fibrous membranes in the sinus cavity of group B rabbits after sinus surgery, and then evaluated changes in the mucosa and in the levels of collagen fibers, interleukin 4 (IL-4), IL-8, tumor necrosis factor α (TNF-α), transforming growth factor β1 (TGF-β1), α-smooth muscle actin (α-SMA), and collagen I (Col I), using morphological and molecular biological methods.

RESULTS

PLLA fibrous membranes did not inhibit the synthesis of messenger RNAs (mRNAs) encoding IL-4, IL-8, or TNF-α, or the protein levels, indicating that the membrane did not have an anti-inflammatory effect. However, the membrane inhibited the synthesis of mRNAs encoding TGF-β1, α-SMA, and Col I, and reduced collagen production. Thus, the nanostructured membrane inhibited fibroblast proliferation.

CONCLUSION

The PLLA membrane had anti-fibrotic effects, and may be used to prevent fibrosis and adhesions after ESS in human patients.

Biocompatible Crosslinked Nanofibers of Poly(Vinyl Alcohol)/Carboxymethyl-Kappa-Carrageenan Produced by a Green Process

This study presents a new type of biocompatible nanofiber based on poly(vinyl alcohol) (PVA) and carboxymethyl-kappa-carrageenan (CMKC) blends, produced with no generation of hazardous waste. The nanofibers are produced by electrospinning using PVA:CMKC blends with ratios of 1:0, 1:0.25, 1:0.4, 1:0.5, and 1:0.75 (w/w PVA:CMKC) in aqueous solution, followed by thermal crosslinking. The diameter of the fibers is in the nanometer scale and below 300 nm. Fourier transform infrared spectroscopy shows the presence of the carboxyl and sulfate groups in all the fibers with CMKC. The nanofibers from water-soluble polymers are stabilized by thermal crosslinking. The incorporation of CMKC improves cytocompatibility, biodegradability, cell growth, and cell adhesion, compared to PVA nanofibers. Furthermore, the incorporation of CMKC modulates phenotype of human adipose-derived stem cells (ADSCs). PVA/CMKC nanofibers enhance ADSC response to osteogenic differentiation signals and are therefore good candidates for application in tissue engineering to support stem cells.

Coaxial nanofiber scaffold with super-active platelet lysate to accelerate the repair of bone defects

To develop biocomposite materials with the local sustained-release function of biological factors to promote bone defect repair, coaxial electrospinning technology was performed to prepare a coaxial nanofiber scaffold with super-active platelet lysate (sPL), containing gelatin/PCL/PLLA. The nanofibers exhibited a uniform bead-free round morphology, observed by a scanning electron microscope (SEM), and the core/shell structure was confirmed by a transmission electron microscope (TEM). A mixture of polycaprolactone and sPL encapsulated by hydrophilic gelatin and hydrophobic l-polylactic acid can continuously release bioactive factors for up to 40 days. Encapsulation of sPL resulted in enhanced cell adhesion and proliferation, and sPL loading can increase the osteogenesis of osteoblasts. Besides, in vivo studies demonstrated that sPL-loaded biocomposites promoted the repair of skull defects in rats. Therefore, these results indicate that core-shell nanofibers loaded with sPL can add enormous potential to the clinical application of this scaffold in bone tissue engineering.

Chemisorption and sustained release of cefotaxime between a layered double hydroxide and polyvinyl alcohol nanofibers for enhanced efficacy against second degree burn wound infection

Zn–Al layered double hydroxides (LDHs) were synthesized by a chemical method, while polyvinyl alcohol (PVA) nanofibers were fabricated by an electrospinning approach; we also synthesized Zn–Al LDH/cefotaxime (cefotax), Zn–Al LDH@PVA, and Zn–Al LDH/cefotax@PVA (LCP). Characterizations were performed by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, Brunauer–Emmett–Teller analysis, thermogravimetric-differential thermal analysis techniques, dynamic light scattering, X ray-florescence, and carbon, hydrogen, and nitrogen (CHN) analyses. The adsorption isotherm of cefotax and its entrapment percentage, release, and kinetics were also investigated. The results confirmed the elemental constituents of the mentioned formulas, which exhibited different degrees of crystallinity and different morphologies. Besides, these formulas were tested in vitro as antimicrobial agents and applied in vivo against second-degree wound burns induced in rats' skin. The adsorption of cefotax occurred chemically, and the experimental data were fitted with different isotherm models, where the Freundlich and Toth models gave the best fits. The entrapment percentage in LDH/cefotax was 77.41% and in LDH/cefotax@PVA, it was 67.83%. The sustained release of cefotax from LDH and LCP was attainable; the release percentages were 89.31% and 81.55% in up to 12 h, respectively. The release kinetics of cefotax from LDH fitted well with first-order kinetics, while that for LCP was parabolic. The formulas showed uneven antimicrobial effects against Gram-positive and Gram-negative bacteria; the best effect was exhibited by Zn–Al LDH/cefotax@PVA due to its sustained release. Finally, investigating the possibility of using these formulas in the clinical setting should be considered.

This study succeeded to formulate, characterize, and investigate cefotax release and kinetics, and to compare cetofax with other known antibacterial agents.

Osteogenic differentiation of preconditioned bone marrow mesenchymal stem cells with lipopolysaccharide on modified poly-l-lactic-acid nanofibers

Tissue engineering is an interdisciplinary expertise that involves the use of nanoscaffolds for repairing, modifying, and removing tissue defects and formation of new tissues. Mesenchymal stem cells (MSCs) can differentiate into a variety of cell types, and they are attractive candidates for tissue engineering. In the current study, the electrospinning process was used for nanofiber preparation, based on a poly-l-lactic-acid (PLLA) polymer. The surface was treated with O ₂ plasma to enhance hydrophilicity, cell attachment, growth, and differentiation potential. The nanoscaffolds were preconditioned with lipopolysaccharide (LPS) to enhance induction of differentiation. The nanoscaffolds were categorized by contact angle measurements and scanning electron microscopy. The MTT assay was used to analyze the rate of growth and proliferation of cells. Osteogenic differentiation of cultured MSCs was evaluated on nanofibers using common osteogenic markers, such as alkaline phosphatase activity, calcium mineral deposition, quantitative real-time polymerase chain reaction, and immunocytochemical analysis. Based on the in vitro results, primed MSCs with LPS on the PLLA nanoscaffold significantly enhanced the proliferation and osteogenesis of MSCs. Also, the combination of LPS and electrospun nanofibers can provide a new and suitable matrix to support stem cells' differentiation for bone tissue engineering.

Electrospun polylactic acid-chitosan composite: a bio-based alternative for inorganic composites for advanced application

Fabricating novel materials for biomedical applications mostly require the use of biodegradable materials. In this work biodegradable materials like polylactic acid (PLA) and chitosan (CHS) were used for designing electrospun mats. This work reports the physical and chemical characterization of the PLA-CHS composite, prepared by the electrospinning technique using a mixed solvent system. The addition of chitosan into PLA, offered decrease in fiber diameter in the composites with uniformity in the distribution of fibers with an optimum at 0.4wt% CHS. The fiber formation and the reduction in fiber diameter were confirmed by the SEM micrograph. The inverse gas chromatography and contact angle measurements supported the increase of hydrophobicity of the composite membrane with increase of filler concentration. The weak interaction between PLA and chitosan was confirmed by Fourier transform infrared spectroscopy and thermal analysis. The stability of the composite was established by zeta potential measurements. Cytotoxicity studies of the membranes were also carried out and found that up to 0.6% CHS the composite material was noncytotoxic. The current findings are very important for the design and development of new materials based on polylactic acid-chitosan composites for environmental and biomedical applications.

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.

Functional electrospun fibers for the treatment of human skin wounds

Wounds are trauma induced defects of the human skin involving a multitude of endogenous biochemical events and cellular reactions of the immune system. The healing process is extremely complex and affected by the patient's physiological conditions, potential implications like infectious pathogens and inflammation as well as external factors. Due to increasing incidence of chronic wounds and proceeding resistance of infection pathogens, there is a strong need for effective therapeutic wound care. In this context, electrospun fibers with diameters in the nano- to micrometer range gain increasing interest. While resembling the structure of the native human extracellular matrix, such fiber mats provide physical and mechanical protection (including protection against bacterial invasion). At the same time, the fibers allow for gas exchange and prevent occlusion of the wound bed, thus facilitating wound healing. In addition, drugs can be incorporated within such fiber mats and their release can be adjusted by the material and dimensions of the individual fibers. The review gives a comprehensive overview about the current state of electrospun fibers for therapeutic application on skin wounds. Different materials as well as fabrication techniques are introduced including approaches for incorporation of drugs into or drug attachment onto the fiber surface. Against the background of wound pathophysiology and established therapy approaches, the therapeutic potential of electrospun fiber systems is discussed. A specific focus is set on interactions of fibers with skin cells/tissues as well as wound pathogens and strategies to modify and control them as key aspects for developing effective wound therapeutics. Further, advantages and limitations of controlled drug delivery from fiber mats to skin wounds are discussed and a future perspective is provided.

Novel bilayer wound dressing based on electrospun gelatin/keratin nanofibrous mats for skin wound repair

A bilayer membrane (GKU) with a commercial polyurethane wound dressing as an outer layer and electrospun gelatin/keratin nanofibrous mat as an inner layer was fabricated as a novel wound dressing. Scanning electron micrographs showed that gelatin/keratin nanofibers had a uniform morphology and bead-free structure with average fiber diameter of 160.4nm. 3-(4,5-Dimethylthiazolyl)-2,5-diphenyltetrazolium bromide assay using L929 fibroblast cells indicated that the residues released from the gelatin/keratin composite nanofibrous mat accelerated cell proliferation. Cell attachment experiments revealed that adhered cells spread better and migrated deeper into the gelatin/keratin nanofibrous mat than that into the gelatin nanofibrous mat. In animal studies, compared with the bilayer membrane without keratin, gauze and commercial wound dressing, Comfeel®, GKU membrane gave much more number of blood vessels and a greater reduction in wound area at 4days, and better wound repair at 14days with a thicker epidermis and larger number of newly formed hair follicles. GKU membrane, thus, could be a good candidate for wound dressing applications.

Versatility of Chitosan-Based Biomaterials and Their Use as Scaffolds for Tissue Regeneration

Chitosan is a naturally occurring polysaccharide obtained from chitin, present in abundance in the exoskeletons of crustaceans and insects. It has aroused great interest as a biomaterial for tissue engineering on account of its biocompatibility and biodegradation and its affinity for biomolecules. A significant number of research groups have investigated the application of chitosan as scaffolds for tissue regeneration. However, there is a wide variability in terms of physicochemical characteristics of chitosan used in some studies and its combinations with other biomaterials, making it difficult to compare results and standardize its properties. The current systematic review of literature on the use of chitosan for tissue regeneration consisted of a study of 478 articles in the PubMed database, which resulted, after applying inclusion criteria, in the selection of 61 catalogued, critically analysed works. The results demonstrated the effectiveness of chitosan-based biomaterials in 93.4% of the studies reviewed, whether or not combined with cells and growth factors, in the regeneration of various types of tissues in animals. However, the absence of clinical studies in humans, the inadequate experimental designs, and the lack of information concerning chitosan's characteristics limit the reproducibility and relevance of studies and the clinical applicability of chitosan.

Tetracycline hydrochloride-loaded electrospun nanofibers mats based on PVA and chitosan for wound dressing

Fibrous mats built from biopolymer have been extensively explored for tissue engineering due mainly to their mimic structure to the extracellular matrix. The incorporation of drug in such scaffolds represents a growing interest for control drug delivery system in order to promote the tissue repair. In the present work, we present an experimental investigation of morphological, thermal, mechanical, drug release, antibacterial and cytotoxicity properties of electrospun PVA/Chitosan and PVA/Chitosan/Tetracycline hydrochloride (TCH) mats for wound dressing. Fibrous mats with cross-linked three-dimensional nanofibers were formed from the polymer blends. A uniform incorporation of drug was achieved along the nanofibers with not significant change on the morphological and thermal properties of the mats. Furthermore, the TCH release profile with a burst delivery during the first 2h allows an effective antibacterial activity on the Gram-negative Escherichia coli as well as on the Gram-positive Staphylococci epidermidis and Staphylococcus aureus. In vitro indirect MTT assay also showed that the developed drug-loaded nanofibrous scaffolds have good cytocompatibility, which was confirmed by scratch assay, indicating that the investigated scaffold may be used as antibacterial wound dressing for healing promotion.

Skin Diseases Modeling using Combined Tissue Engineering and Microfluidic Technologies

In recent years, both tissue engineering and microfluidics have significantly contributed in engineering of in vitro skin substitutes to test the penetration of chemicals or to replace damaged skins. Organ-on-chip platforms have been recently inspired by the integration of microfluidics and biomaterials in order to develop physiologically relevant disease models. However, the application of organ-on-chip on the development of skin disease models is still limited and needs to be further developed. The impact of tissue engineering, biomaterials and microfluidic platforms on the development of skin grafts and biomimetic in vitro skin models is reviewed. The integration of tissue engineering and microfluidics for the development of biomimetic skin-on-chip platforms is further discussed, not only to improve the performance of present skin models, but also for the development of novel skin disease platforms for drug screening processes.

Fabrication and investigation of nanofibrous matrices as esophageal tissue scaffolds using human non-keratinized, stratified, squamous epithelial cells

Clinical conditions of the esophagus are conventionally treated by autologous grafts and are generally associated with complications such as leakage, infection and stenosis necessitating an alternative synthetic graft with superior outcomes.

Multidimensional nanofibrous scaffolds of poly(lactide-co-caprolactone) and poly(ethyl oxazoline) with improved features for cardiac tissue engineering

Aim: The aim of the study is to develop scaffolds that mimic native tissue properties for effective regeneration of the myocardium, which is affected by the gradual thinning of left ventricular tissue after an infarction. Materials & methods: Heterogenous nanofibrous scaffolds made of poly(lactide-co-caprolactone) and poly(ethyl oxazoline) were characterized for physico-chemical properties. The biocompatibility of the scaffolds was evaluated by studying the adhesion, proliferation and differentiation of H9c2 cells. Results: The scaffolds mimic the cardiac extracellular matrix and showed enhanced tensile strength, improved cell compatibility along with the expression of cardiac marker proteins. Conclusion: Our experimental data confirmed the importance of native tissue architecture and mechanical strength for improved cell response in cardiac tissue engineering.

Collagen nanofiber containing silver nanoparticles for improved wound-healing applications

Electrospun nanofibers showing great promise for fabricating nanostructured materials might help to improve the quality of wound care. The present study aimed to investigate the wound-healing potential of collagen nanofiber mats containing silver nanoparticles. Silver nanoparticles (AgNPs) synthesized by the chemical reduction method were incorporated in collagen nanofibers during the electrospinning process. Characterization of electrospun nanofiber mats revealed a mean fiber diameters in the range of 300-700 nm with a sustained release of silver ions shown to follow pseudo-order kinetics. MIC of AgNPs against Staphylococcus aureus and Pseudomonas aeruginosa were evaluated using micro-dilution assay and further antimicrobial activity of fabricated nanofibers was performed. Finally, in vivo studies were performed to demonstrate the wound-healing efficacy of composite nanofibers. In vitro results confirmed the potential antimicrobial efficacy provided by AgNPs and AgNPs composite nanofibers, essential to provide an aseptic environment at the wound site. In vivo study revealed that the rate of wound healing of the composite nanofiber mats was found to be accelerated compared with plain collagen nanofibers. Histology analysis revealed an accelerated re-epithelization, collagen production, and better wound contraction with AgNPs composite collagen nanofibers.

An update on clinical applications of electrospun nanofibers for skin bioengineering

Mimicking morphological similarities of the natural extra cellular matrix (ECM), described by ultrafine continuous fibers, high surface to volume ratio, and high porosity is valuable for effective regeneration of injured skin tissue. Electrospun nanofibers, being one of the most favorable and fast developing products of technology today, display a tremendous potential in wound healing and skin tissue engineering. Under the remarkable attention being given to electrospun nanofibrous scaffolds in promoting wound healing and skin regeneration, this review focuses on the potential of the electrospinning technique as a promising tool for constructing polymeric nanofibrous scaffolds with the favorable physicochemical properties needed for skin bioengineering. In addition, current applications of electrospun nanofibrous matrices for skin bioengineering are detailed in this review.

Use of Amniotic Microparticles Coated With Fibroblasts Overexpressing SDF-1α to Create an Environment Conducive to Neovascularization for Repair of Full-Thickness Skin Defects

As angiogenesis and vasculogenesis involve the complex network structures of various types of cells, extracellular matrix components, and cytokines, it is still difficult to exactly mimic the microenvironment of vascularization in vivo. In our study, we constructed a complex containing highly proliferative fibroblasts that can secrete extracellular matrix components and growth factors to chemotaxize endothelial progenitor cells (EPCs) in an attempt to create an ideal microenvironment for quick vascularization. Amniotic membrane microparticles (mAM) rich in type IV collagen (COL IV) and laminin (LN) were prepared, and human dermal fibroblasts (HDF) were infected with lentivirus (LV) of overexpression of SDF-1α to construct SDF-1α(ov)HDF. Using the rotary cell culture system (RCCS), mAM was loaded with HDF or SDF-1α(ov)HDF to construct HDF-mAM and SDF-1α(ov)HDF-mAM complexes. The complexes were able to secrete various types of active peptides (IL-6, IL-8, TGF-β, and bFGF) during in vitro culture. In addition, SDF-1α(ov)HDF-mAM complex highly expressed SDF-1α. Transwell assay showed SDF-1α(ov)HDF-mAM complex had an apparent chemotactic effect on EPCs. Transplantation of complexes onto full-thickness skin defects of C57BL mice further demonstrated that SDF-1α expression and the number of peripheral EPCs at days 3, 5, and 7 in the SDF-1α(ov)HDF-mAM group were significantly higher than that in other groups (p < 0.01). The local microvascular density at day 10 of transplantation showed that the microvascular density in the SDF-1α(ov)HDF-mAM group was significantly higher than that in HDF-mAM group (p < 0.01). In conclusion, HDF-mAM had a strong proliferative activity and could be used to create a sound microenvironment for quick vascularization by secreting multiple cytokines and extracellular matrix components. Overexpression of SDF-1α could chemotaxize EPCs to reach local wounds, thus further accelerating angiogenesis in the transplant site. The technique described may prove to be a new model for accelerating vascularization of tissue and organ transplants and chronic ischemic wounds.

Carboxyl-modified poly(vinyl alcohol)-crosslinked chitosan hydrogel films for potential wound dressing

The objective of this study was to develop a novel carboxyl-modified poly(vinyl alcohol)-crosslinked chitosan hydrogel films for potential wound dressing. To prepare the crosslinked hydrogels, poly(vinyl alcohol) (PVA) was grafted with succinate acid to yield carboxyl-modified poly(vinyl alcohol) (PVA-COOH). Hydrogel films based on PVA-COOH and chitosan (CS) at different concentrations were crosslinked through the formation of amide linkages. The mechanical properties of these crosslinked hydrogel films in dry and swollen state were greatly improved with high swelling ratio. Water vapor and oxygen permeability evaluations indicated that crosslinked hydrogel films could maintain a moist environment over wound bed. Biocompatibility test showed the crosslinked hydrogels had no cytotoxicity and hemolytic potential. Gentamicin sulfate-loaded crosslinked hydrogel films showed sustained drug release profile, and could effectively suppress bacterial proliferation and protect wound from infection.

Osteogenic differentiation of stem cells on mesoporous silica nanofibers

Mesoporous silica nanofibers promote osteogenic differentiation of bone marrow derived mesenchymal stem cells.