Polyacrylonitrile nanofibers coated with silver nanoparticles using a modified coaxial electrospinning process

Optimization of process parameters for fabrication of electrospun nanofibers containing neomycin sulfate and Malva sylvestris extract for a better diabetic wound healing

Diabetes mellitus is one of the most concerning conditions, and its chronic consequences are almost always accompanied by infection, oxidative stress, and inflammation. Reducing excessive reactive oxygen species and the wound's inflammatory response is a necessary treatment during the acute inflammatory phase of diabetic wound healing. Malva sylvestris extract (MS) containing nanofibers containing neomycin sulfate (NS) were synthesized for this investigation, and their impact on the healing process of diabetic wounds was assessed. Using Design Expert, the electrospinning process for the fabrication of NS nanofibers (NS-NF) was adjusted for applied voltage (X₁), the distance between the needle's tip and the collector (X₂), and the feed rate (X₃) for attaining desired entrapment efficacy [EE] and average nanofiber diameter (ND). The optimal formulation can be prepared with 19.11 kV of voltage, 20 cm of distance, and a flow rate of 0.502 mL/h utilizing the desirability approach. All the selected parameters and responses have their impact on drug delivery from nanofibers. In addition, M. sylvestris extracts have been added into the optimal formulation [MS-NS-NF] and assessed for their surface morphology, tensile strength, water absorption potential, and in vitro drug release studies. The NS and MS delivery from MS-NS-NF has been extended for more than 60 h. M. sylvestris-loaded nanofibers demonstrated superior antibacterial activity compared to plain NS nanofibers. The scaffolds featured a broad aspect and a highly linked porous fibrous network structure. Histomorphometry study and the in vitro scratch assay demonstrate the formulation's efficacy in treating diabetic wound healing. The cells treated with MS-NS-NF in vivo demonstrated that wound dressings successfully reduced both acute and chronic inflammations. To improve the healing of diabetic wounds, MS-NS-NF may be regarded as an appropriate candidate for wound dressing.

Synthesis of Electrospun PAN/TiO2/Ag Nanofibers Membrane As Potential Air Filtration Media with Photocatalytic Activity

The PAN/TiO₂/Ag nanofibers membrane for air filtration media was successfully synthesized with electrospinning method. The morphology, size, and element percentage of the nanofiber were characterized by a scanning electron microscopy-energy dispersive spectroscopy, while X-ray fluorescence and FTIR were used to observe the chemical composition. The water contact angle and UV-vis absorption were measured for physical properties. Performance for air filtration media was measured by pressure drop, efficiency, and quality factor test. TiO₂ and Ag have been successfully deposited in nonuniform 570 nm PAN/TiO₂/Ag nanofibers. The nanofiber membrane had hydrophilic surface after TiO₂ and Ag addition with a water contact angle of 34.58°. UV-vis data showed the shifting of absorbance and band gap energy of nanofibers membrane to visible light from 3.8 to 1.8 eV. The 60 min spun PAN/TiO₂/Ag nanofibers membrane had a 96.9% efficiency of PM_2.5, comparable to results reported in previous studies. These properties were suitable to be applied on air filtration media with photocatalytic activity for self-cleaning performance.

Multifunctional Membranes-A Versatile Approach for Emerging Pollutants Removal

This paper presents a comprehensive literature review surveying the most important polymer materials used for electrospinning processes and applied as membranes for the removal of emerging pollutants. Two types of processes integrate these membrane types: separation processes, where electrospun polymers act as a support for thin film composites (TFC), and adsorption as single or coupled processes (photo-catalysis, advanced oxidation, electrochemical), where a functionalization step is essential for the electrospun polymer to improve its properties. Emerging pollutants (EPs) released in the environment can be efficiently removed from water systems using electrospun membranes. The relevant results regarding removal efficiency, adsorption capacity, and the size and porosity of the membranes and fibers used for different EPs are described in detail.

Covalently Bound S-Nitroso-N-Acetylpenicillamine to Electrospun Polyacrylonitrile Nanofibers for Multifunctional Tissue Engineering Applications

Attachment of a nitric oxide (NO) donor to an electrospun polymer has the potential to improve its proliferative and antimicrobial capabilities. This study presents the novel, covalent attachment of S-nitroso-N-acetylpenicillamine (SNAP) to polyacrylonitrile (PAN) fibers. By attaching the NO donor to the polymer, rather than blending it, leaching is reduced to maintain a NO flux within the physiologically relevant range for a longer duration, while limiting any cytotoxic effects. The synthesized fibers were characterized using a variety of techniques such as scanning electron microscopy, ¹H NMR, and drop shape analysis. Due to the antimicrobial activity of NO, the SNAP-PAN fibers demonstrated a 2-log reduction of S. aureus adhesion. Furthermore, the extended zone of inhibition of S. aureus by SNAP-PAN demonstrates the ability of NO to impact the environment surrounding the material, in addition to the environment in direct contact with it. The combination of NO release, hydrophilicity of PAN, and the fibrous network led to increased fibroblast proliferation and attachment, potentially expanding the fibers as an improved cell scaffolding platform. The results from this study demonstrate a novel preparation and design of NO-releasing fibers to provide multiple benefits for a variety of biomedical applications.

Electrospun Functional Nanofiber Membrane for Antibiotic Removal in Water: Review

As a new kind of water pollutant, antibiotics have encouraged researchers to develop new treatment technologies. Electrospun fiber membrane shows excellent benefits in antibiotic removal in water due to its advantages of large specific surface area, high porosity, good connectivity, easy surface modification and new functions. This review introduces the four aspects of electrospinning technology, namely, initial development history, working principle, influencing factors and process types. The preparation technologies of electrospun functional fiber membranes are then summarized. Finally, recent studies about antibiotic removal by electrospun functional fiber membrane are reviewed from three aspects, namely, adsorption, photocatalysis and biodegradation. Future research demand is also recommended.

Protein encapsulation by electrospinning and electrospraying

Given the increasing interest in the use of peptide- and protein-based agents in therapeutic strategies, it is fundamental to develop delivery systems capable of preserving the biological activity of these molecules upon administration, and which can provide tuneable release profiles. Electrohydrodynamic (EHD) techniques, encompassing electrospinning and electrospraying, allow the generation of fibres and particles with high surface area-to-volume ratios, versatile architectures, and highly controllable release profiles. This review is focused on exploring the potential of different EHD methods (including blend, emulsion, and co-/multi-axial electrospinning and electrospraying) for the development of peptide and protein delivery systems. An overview of the principles of each technique is first presented, followed by a survey of the literature on the encapsulation of enzymes, growth factors, antibodies, hormones, and vaccine antigens using EHD approaches. The possibility for localised delivery using stimuli-responsive systems is also explored. Finally, the advantages and challenges with each EHD method are summarised, and the necessary steps for clinical translation and scaled-up production of electrospun and electrosprayed protein delivery systems are discussed.

Polyurethane/carboxymethylcellulose nanofibers containing Malva sylvestris extract for healing diabetic wounds: Preparation, characterization, in vitro and in vivo studies

In this study, new polyurethane (PU)-based nanofibers wound dressings containing Malva sylvestris extract were prepared and their effect on diabetic wound healing process was evaluated. Different amounts of carboxymethyl cellulose (CMC) were used to improve the absorption ability of wound exudates. The result showed that the usage of 20% w/w CMC in the polymer blend; and producing of nanofibers with an average diameter of 386.5 nm, led to the gradual release of the herbal compound in 85 h and bead-free morphology. Due to the antibacterial activity of wound dressing and wound healing process, the amount of 15% w/w herbal extract was selected as the optimum. For this sample, the fluid absorption was 412.31%. The extract loaded wound dressing samples showed satisfactory effects on Staphylococcus aureus and Escherichia coli bacteria. In vivo wound-healing and histological performance observations indicated that the use of the herbal extract in wound dressing improved wound healing significantly. On day 14, the average healing rate for gauze bandage, PU/CMC, and different amounts of 5, 10, 15 and 20% w/w extract containing wound dressings was 32.1 ± 0.2%, 51.4 ± 0.4%, 71 ± 0.14%, 87.64 ± 1.02%, 95.05 ± 0.24% and 95.11 ± 0.2%, respectively. Compared to the control groups, treatments with extract loaded wound dressings were effective in lowering acute and chronic inflammations. In diabetic rat wounds, collagen deposition and neovascularization were higher in wounds treated with an herbal extract containing wound dressing compared to the wounds treated with a gauze bandage and PU/CMC treated wounds. It can be suggested that this product may be considered as a good dual anti-inflammatory-antimicrobial wound dressing candidate for improving the diabetic wound healing.

Nanodecoration of electrospun polymeric fibers with nanostructured silver coatings by ionized jet deposition for antibacterial tissues

Silver-based nanomaterials are used as antibacterial agents in a number of applications, including wound dressing, where electrospun materials can effectively promote wound healing and tissue regeneration thanks to their biomimicry, flexibility and breathability. Incorporation of such nanomaterials in electrospun nonwovens is highly challenging if aiming at maximizing stability and antibacterial efficacy and minimizing silver detachment, without neglecting process straightforwardness and scalability. In this work nanostructured silver coatings were deposited by Ionized Jet Deposition (IJD) on Polylactic acid, a medical grade polyester-urethane and Polyamide 6,6 nanofibers. The resulting materials were thoroughly characterized to gain an in-depth view of coating morphology and substrate resistance to the low-temperature deposition process used. Morphology of silver coatings with well-cohesive grains having dimensions from a few tens to a few hundreds of nanometers was analyzed by SEM, TEM and AFM. TGA, DSC, FTIR and GPC showed that the polymers well withstand the deposition process with negligible effects on their properties, the only exception being the polylactic acid that resulted more susceptible to degradation. Finally, the efficacy against S. aureus and E. coli bacterial strains was demonstrated, indicating that electrospun fibers decorated with nanostructured silver by IJD represent a breakthrough solution in the field of antibacterial devices.

Electrospun Environment Remediation Nanofibers Using Unspinnable Liquids as the Sheath Fluids: A Review

Electrospinning, as a promising platform in multidisciplinary engineering over the past two decades, has overcome major challenges and has achieved remarkable breakthroughs in a wide variety of fields such as energy, environmental, and pharmaceutics. However, as a facile and cost-effective approach, its capability of creating nanofibers is still strongly limited by the numbers of treatable fluids. Most recently, more and more efforts have been spent on the treatments of liquids without electrospinnability using multifluid working processes. These unspinnable liquids, although have no electrospinnability themselves, can be converted into nanofibers when they are electrospun with an electrospinnable fluid. Among all sorts of multifluid electrospinning methods, coaxial electrospinning is the most fundamental one. In this review, the principle of modified coaxial electrospinning, in which unspinnable liquids are explored as the sheath working fluids, is introduced. Meanwhile, several typical examples are summarized, in which electrospun nanofibers aimed for the environment remediation were prepared using the modified coaxial electrospinning. Based on the exploration of unspinnable liquids, the present review opens a way for generating complex functional nanostructures from other kinds of multifluid electrospinning methods.

Synthesis of photo-excited Chlorin e6 conjugated silica nanoparticles for enhanced anti-bacterial efficiency to overcome methicillin-resistant Staphylococcus aureus

Nano photodynamic therapy to overcome multidrug resistant bacteria.

Recent Progress in Coaxial Electrospinning: New Parameters, Various Structures, and Wide Applications

Electrospinning, a common method for synthesizing 1D nanostructures, has contributed to developments in the electrical, electrochemical, biomedical, and environmental fields. Recently, a coaxial electrospinning process has been used to fabricate new nanostructures with advanced performance, but intricate and delicate process conditions hinder reproducibility and mass production. Herein, recent progress in new emerging parameters for successful coaxial electrospinning, and the various nanostructures and critical application areas resulting from these activities. Relationships between the new parameters and final product characteristics are described, new possibilities for nanostructures achievable via coaxial electrospinning are identified, and new research directions with a view to future applications are suggested.

Electrospun Silver Coated Polyacrylonitrile Membranes for Water Filtration Applications

The scarcity of drinking water and the contamination of water sources in underdeveloped countries are serious problems that require immediate low-tech and low-cost solutions. In this study, we fabricated polyacrylonitrile (PAN) porous membranes coated with silver nanoparticles (AgNP) and demonstrated their use for water filtration and water treatment applications. The membranes were prepared by electrospinning a PAN solution and treating in a hydroxylamine (NH₂OH) aqueous solution to form –C(NH₂)N–OH groups that were used for functionalization (Ag⁺ ions) of the membrane. The coordinated silver ions were then converted to silver nanoparticles. The microstructure of the membrane, water permeability, antimicrobial effect (using Escherichia coli), and particulate filtration capabilities were studied. This study verified that the membrane demonstrated a 100% reduction for Gram-negative bacteria with an effective filtration rate of 8.0 mL/cm² min. Furthermore, the membrane was able to eliminate 60% of latex beads as small as 50 nm and over 80% of the 2 µm beads via gravity filtration. This study demonstrated that PAN–AgNP membranes can be employed as antimicrobial membranes for the filtration of water in underdeveloped countries.

Recent developments in polymeric electrospun nanofibrous membranes for seawater desalination

Seawater desalination is a promising strategy that offers an abundant and reliable source of clean fresh water. Nanotechnology, in terms of nanoparticles or electrospun nanofibrous membranes, for water-treatment or desalination applications, is a new concept that has rapidly grown in interest as a method for improving performance by enhancing the surface properties of membranes. Here, we report a critical review on recent developments in membrane-fabrication methods for seawater desalination technologies, focusing mainly on the electrospinning technique. High-performance membranes that address ongoing permeability concerns, while maintaining membrane selectivity, need further study and development. Considering that the world today is faced with energy-shortage crises, these membranes also need to be energy efficient. As electrospinning is considered to be a feasible method for the production of desalination membranes, this technique requires appropriate optimization and the structural properties of the membranes produced need to be controlled in order to tailor their properties to those desired for well-known desalination technologies, such as reverse osmosis and membrane distillation. Moreover, there is a need to understand the influence of membrane structure on performance, and the latest trends in their use as high-performance desalination membranes.

Seawater desalination is a promising strategy that offers an abundant and reliable source of clean fresh water.

Electrospun polymeric micro/nanofibrous scaffolds for long-term drug release and their biomedical applications

Electrospun polymeric micro/nanofibrous scaffolds have been investigated extensively as drug delivery platforms capable of controlled and sustained release of therapeutic agents in situ. Such scaffolds exhibit excellent physicochemical and biological properties and can encapsulate and release various drugs in a controlled fashion. This article reviews recent advances in the design and manufacture of electrospun scaffolds for long-term drug release, placing particular emphasis on polymer selection, types of incorporated drugs and the latest drug-loading techniques. Finally, applications of such devices in traumatic or disease states requiring effective and sustained drug action are discussed and critically appraised in their biomedical context.

The potential applications of fibrin-coated electrospun polylactide nanofibers in skin tissue engineering

Fibrin plays an important role during wound healing and skin regeneration. It is often applied in clinical practice for treatment of skin injuries or as a component of skin substitutes. We prepared electrospun nanofibrous membranes made from poly(l-lactide) modified with a thin fibrin nanocoating. Fibrin surrounded the individual fibers in the membrane and also formed a thin fibrous mesh on several places on the membrane surface. The cell-free fibrin nanocoating remained stable in the cell culture medium for 14 days and did not change its morphology. On membranes populated with human dermal fibroblasts, the rate of fibrin degradation correlated with the degree of cell proliferation. The cell spreading, mitochondrial activity, and cell population density were significantly higher on membranes coated with fibrin than on nonmodified membranes, and this cell performance was further improved by the addition of ascorbic acid in the cell culture medium. Similarly, fibrin stimulated the expression and synthesis of collagen I in human dermal fibroblasts, and this effect was further enhanced by ascorbic acid. The expression of beta₁-integrins was also improved by fibrin, and on pure polylactide membranes, it was slightly enhanced by ascorbic acid. In addition, ascorbic acid promoted deposition of collagen I in the form of a fibrous extracellular matrix. Thus, the combination of nanofibrous membranes with a fibrin nanocoating and ascorbic acid seems to be particularly advantageous for skin tissue engineering.

Fabrication of electrospun poly(ethylene oxide)–poly(capro lactone) composite nanofibers for co-delivery of niclosamide and silver nanoparticles exhibits enhanced anti-cancer effects in vitro

An intrinsic property of many anticancer drugs including niclosamide is poor water solubility, which hindered their translation from laboratory to clinics.

A polymer/metal core–shell nanofiber membrane by electrospinning with an electric field, and its application for catalyst support

PVP/Ag core–shell nanofibers are prepared via electrospinning; electric field induces phase separation, and leads Ag migrate; the nanofiber exhibits a great potential in the field of catalysis.

Highly Efficient Phosphate Scavenger Based on Well-Dispersed La(OH)3 Nanorods in Polyacrylonitrile Nanofibers for Nutrient-Starvation Antibacteria

La(OH)3 nanorods immobilized in polyacrylonitrile (PAN) nanofibers (PLNFs) were fabricated for the first time by electrospinning and a subsequent in situ surfactant-free precipitation method and then applied as a highly efficient phosphate scavenger to realize nutrient-starvation antibacteria for drinking water security. The immobilization by PAN nanofibers effectively facilitated the in situ formation of the aeolotropic and well-dispersed La(OH)3 nanostructures and, thus, rendered higher phosphate removal efficiency due to more exposed active sites for binding phosphate. The maximum phosphate capture capacity of La(OH)3 nanorods in PAN nanofibers was around 8 times that of the La(OH)3 nanocrystal fabricated by precipitation without PAN protection. Moreover, remarkably fast adsorption kinetics and high removal rate were observed toward low concentration phosphate due to the high activity of our materials, which can result in a stringent phosphate-deficient condition to kill microorganisms in water effectively. The present material is also capable of preventing sanitized water from recontamination by bacteria and keeping water biologically stable for drinking. Impressively, stabilized by PAN nanofibers, the La(OH)3 nanorods can be easily separated out after reactions and avoid leaking into water. The present development has great potential as a promising antimicrobial solution for practical drinking water security and treatment with a negligible environmental footprint.

Silver/polysaccharide-based nanofibrous materials synthesized from green chemistry approach

In this contribution a novel green chemistry approach for the synthesis of nanofibrous materials based on blends of carboxymethyl-cellulose (CMC)-silver nanoparticles (AgNPs) composite and polyvinyl-alcohol (PVA) is proposed. These nanofibrous materials were obtained from the electrospinning of blends of aqueous solutions of CMC-AgNPs composite and PVA, which were prepared at different CMC/PVA weight ratios in order to electrospin nanofibers applying a constant tension of 15kV. The synthesized materials were characterized by means of transmission electron microscopy, scanning electron microscopy; as well as Fourier-transform infrared, ultraviolet and Raman spectroscopic techniques. Experimental evidence suggests that the diameter of the nanofibers is thinner than any other reported in the literature regarding the electrospinning of CMC. This feature is related to the interactions of AgNPs with carboxyl functional groups of the CMC, which diminish those between the later and acetyl groups of PVA.

Sustained release of bactericidal concentrations of penicillin in the pleural space via an antibiotic-eluting pigtail catheter coated with electrospun nanofibers: results from in vivo and in vitro studies

BACKGROUND

Inadequate intrapleural drug concentrations caused by poor penetration of systemic antibiotics into the pleural cavity is a major cause of treatment failure in empyema. Herein, we describe a novel antibiotic-eluting pigtail catheter coated with electrospun nanofibers used for the sustained release of bactericidal concentrations of penicillin in the pleural space.

METHODS

Electrospun nanofibers prepared using polylactide-polyglycolide copolymer and penicillin G sodium dissolved in 1,1,1,3,3,3-hexafluoro-2-propanol were used to coat the surface of an Fr6 pigtail catheter. The in vitro patterns of drug release were tested by placing the catheter in phosphate-buffered saline. In vivo studies were performed using rabbits treated with penicillin either intrapleurally (Group 1, 20 mg delivered through the catheter) or systemically (Group 2, intramuscular injection, 10 mg/kg). Penicillin concentrations in the serum and pleural fluid were then measured and compared.

RESULTS

In vitro studies revealed a burst release of penicillin (10% of the total dose) occurring in the first 24 hours, followed by a sustained release in the subsequent 30 days. Intrapleural drug levels were significantly higher in Group 1 than in Group 2 (P<0.001). In the former, penicillin concentrations remained above the minimum inhibitory concentration breakpoint throughout the entire study period. In contrast, serum penicillin levels were significantly higher in Group 2 than in Group 1 (P<0.001). Notably, all Group 2 rabbits showed signs of systemic toxicity (paralytic ileus and weight loss).

CONCLUSION

We conclude that our antibiotic-eluting catheter may serve as a novel therapeutic option to treat empyema.

CD44(+)/CD24(-) breast cancer cells exhibit phenotypic reversion in three-dimensional self-assembling peptide RADA16 nanofiber scaffold

Background

Self-assembling peptide nanofiber scaffolds have been shown to be a permissive biological material for tissue repair, cell proliferation, differentiation, etc. Recently, a subpopulation (CD44⁺/CD24⁻) of breast cancer cells has been reported to have stem/progenitor cell properties. The aim of this study was to investigate whether this subpopulation of cancer cells have different phenotypes in self-assembling COCH₃-RADARADARADARADA-CONH₂ (RADA16) peptide nanofiber scaffold compared with Matrigel^® (BD Biosciences, Two Oak Park, Bedford, MA, USA) and collagen I.

Methods

CD44 and CD24 expression was determined by flow cytometry. Cell proliferation was measured by 5-bromo-2′-deoxyuridine assay and DNA content measurement. Immunostaining was used to indicate the morphologies of cells in three-dimensional (3D) cultures of different scaffolds and the localization of β-catenin in the colonies. Western blot was used to determine the expression of signaling proteins. In vitro migration assay and inoculation into nude mice were used to evaluate invasion and tumorigenesis in vivo.

Results

The breast cancer cell line MDA-MB-435S contained a high percentage (>99%) of CD44⁺/CD24⁻ cells, which exhibited phenotypic reversion in 3D RADA16 nanofiber scaffold compared with collagen I and Matrigel. The newly formed reverted acini-like colonies reassembled a basement membrane and reorganized their cytoskeletons. At the same time, cells cultured and embedded in RADA16 peptide scaffold exhibited growth arrest. Also, they exhibited different migration potential, which links their migration ability with their cellular morphology. Consistent with studies in vitro, the in vivo tumor formation assay further supported of the functional changes caused by the reversion in 3D RADA16 culture. Expression levels of intercellular surface adhesion molecule-1 were upregulated in cells cultured in RADA16 scaffolds, and the NF-kappa B inhibitor pyrrolidine dithiocarbamate could inhibit RADA16-induced upregulation of intercellular surface adhesion molecule-1 and the phenotype reversion of MDA-MB-453S cells.

Conclusion

Culturing a CD44⁺/CD24⁻-enriched breast cancer cell population in 3D RADA16 peptide nanofiber scaffold led to a significant phenotypic reversion compared with Matrigel and collagen I.

Tuning of ZnO 1D nanostructures by atomic layer deposition and electrospinning for optical gas sensor applications

We explored for the first time the ability of a three-dimensional polyacrylonitrile/ZnO material-prepared by a combination of electrospinning and atomic layer deposition (ALD) as a new material with a large surface area-to enhance the performance of optical sensors for volatile organic compound (VOC) detection. The photoluminescence (PL) peak intensity of these one-dimensional nanostructures has been enhanced by a factor of 2000 compared to a flat Si substrate. In addition, a phase transition of the ZnO ALD coating from amorphous to crystalline has been observed due to the properties of a polyacrylonitrile nanofiber template: surface strain, roughness, and an increased number of nucleation sites in comparison with a flat Si substrate. The greatly improved PL performance of these nanostructured surfaces could produce exciting materials for implantation in VOC optical sensor applications.

Sustained release of vancomycin from novel biodegradable nanofiber-loaded vascular prosthetic grafts: in vitro and in vivo study

This study describes novel biodegradable, drug-eluting nanofiber-loaded vascular prosthetic grafts that provide local and sustained delivery of vancomycin to surrounding tissues. Biodegradable nanofibers were prepared by first dissolving poly(D,L)-lactide-co-glycolide and vancomycin in 1,1,1,3,3,3-hexafluoro-2-propanol. The solution was then electrospun into nanofibers onto the surface of vascular prostheses. The in vitro release rates of the pharmaceutical from the nanofiber-loaded prostheses was characterized using an elution method and a high-performance liquid chromatography assay. Experimental results indicated that the drug-eluting prosthetic grafts released high concentrations of vancomycin in vitro (well above the minimum inhibitory concentration) for more than 30 days. In addition, the in vivo release behavior of the drug-eluting grafts implanted in the subcutaneous pocket of rabbits was also documented. The drug-eluting grafts developed in this work have potential applications in assisting the treatment of vascular prosthesis infection and resisting reinfection when an infected graft is to be exchanged.

Effect of silk fibroin nanofibers containing silver sulfadiazine on wound healing

BACKGROUND

One of the promising applications of silk fibroin (SF) in biomedical engineering is its use as a scaffolding material for skin regeneration. The purpose of this study was to determine the wound healing effect of SF nanofibrous matrices containing silver sulfadiazine (SSD) wound dressings.

METHODS

An SF nanofibrous matrix containing SSD was prepared by electrospinning. The cell attachment and spreading of normal human epidermal keratinocytes (NHEK) and normal human epidermal fibroblasts (NHEF) to SF nanofibers containing three different concentrations of SSD contents (0.1, 0.5, and 1.0 wt%) were determined. In addition, a rat wound model was used in this study to determine the wound healing effect of SF nanofibers containing SSD compared with that of Acticoat™, a commercially available wound dressing.

RESULTS

The number of NHEK and NHEF attached to SF nanofibers containing SSD decreased when the concentration of SSD increased. The number of attached NHEF cells was lower than that of attached NHEK cells. The SF matrix with 1.0 wt% SSD produced faster wound healing than Acticoat, although 1.0 wt% SSD inhibited the attachment of epidermal cells to SF nanofibers in vitro.

CONCLUSION

The cytotoxic effects of SF nanofibers with SSD should be considered in the development of silver-release dressings for wound healing through its antimicrobial activity. It is challenging to design wound dressings that maximize antimicrobial activity and minimize cellular toxicity.

Antibacterial continuous nanofibrous hybrid yarn through in situ synthesis of silver nanoparticles: preparation and characterization

Nanofibrous hybrid yarns of polyvinyl alcohol (PVA) and poly-l-lactide acid (PLLA) with the antibacterial activity were prepared that contains 0, 5, 10, 20, and 30 wt.% of silver nanoparticles according to the PVA polymer content. This was performed by electrospinning using distilled water and 2, 2, 2-trifluoroethanol as a solvent for PVA and PLLA respectively, and sodium borohydride was used as a reducing agent. The scanning electron microscope observation confirmed the formation of AgNPs into the PVA nanofiber structure, and they were uniform, bead free, cylindrical and smooth. The diameter of hybrid yarns and their nanofiber component was decreased as the silver nitrate concentration in electrospinning solutions was increased. The differential scanning calorimetry results indicated that the silver nanoparticles can form interactions with polymer chains and decrease the melting enthalpy. The mechanical analysis showed a lower stress and strain at break of the AgNP-loaded nanofibrous hybrid yarns than the unloaded hybrid yarn. However, there wasn't a statistically significant difference between the strain at break of electrospun nanofibrous hybrid yarns. Moreover, the bactericidal efficiency of all loaded samples was over 99.99%.

Fabrication and characterization of anisotropic nanofiber scaffolds for advanced drug delivery systems

Stimuli-responsive, polymer-based nanostructures with anisotropic compartments are of great interest as advanced materials because they are capable of switching their shape via environmentally-triggered conformational changes, while maintaining discrete compartments. In this study, a new class of stimuli-responsive, anisotropic nanofiber scaffolds with physically and chemically distinct compartments was prepared via electrohydrodynamic cojetting with side-by-side needle geometry. These nanofibers have a thermally responsive, physically-crosslinked compartment, and a chemically-crosslinked compartment at the nanoscale. The thermally responsive compartment is composed of physically crosslinkable poly(N-isopropylacrylamide) poly(NIPAM) copolymers, and poly(NIPAM-co-stearyl acrylate) poly(NIPAM-co-SA), while the thermally-unresponsive compartment is composed of polyethylene glycol dimethacrylates. The two distinct compartments were physically crosslinked by the hydrophobic interaction of the stearyl chains of poly(NIPAM-co-SA) or chemically stabilized via ultraviolet irradiation, and were swollen in physiologically relevant buffers due to their hydrophilic polymer networks. Bicompartmental nanofibers with the physically-crosslinked network of the poly(NIPAM-co-SA) compartment showed a thermally-triggered shape change due to thermally-induced aggregation of poly(NIPAM-co-SA). Furthermore, when bovine serum albumin and dexamethasone phosphate were separately loaded into each compartment, the bicompartmental nanofibers with anisotropic actuation exhibited decoupled, controlled release profiles of both drugs in response to a temperature. A new class of multicompartmental nanofibers could be useful for advanced nanofiber scaffolds with two or more drugs released with different kinetics in response to environmental stimuli.

Silver nanoparticle/chitosan oligosaccharide/poly(vinyl alcohol) nanofibers as wound dressings: a preclinical study

In this study, a mixture of poly(vinyl alcohol) (PVA) and chitosan oligosaccharides (COS) was electrospun with silver nanoparticles (AgNPs) to produce fibrous mats for use in wound healing. The AgNPs were reduced by COS prior to electrospinning or Ag⁺ was reduced via ultraviolet irradiation in nanofibers. The morphologies of the PVA/COS/AgNO₃ and PVA/COS-AgNP nanofibers were analyzed by scanning electron microscopy. Formation of the AgNPs was investigated by field emission transmission electron microscopy, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. We also evaluated the biocompatibility of the nanofibers, particularly their cytotoxicity to human skin fibroblasts and potential to cause primary skin irritation. The in vitro antibacterial activity and in vivo wound healing capacity of the nanofibers were also investigated. The nanofibers had a smooth surface with an average diameter of 130–192 nm. The diameters of the AgNPs were in the range of 15–22 nm. The nanofibers significantly inhibited growth of Escherichia coli and Staphylococcus aureus bacteria. PVA/COS-AgNP nanofibers accelerated the rate of wound healing over that of the control (gauze). The results of our in vitro and in vivo animal experiments suggest that PVA/COS-AgNP nanofibers should be of greater interest than PVA/COS/AgNO₃ nanofibers for clinical use as a bioactive wound dressing.