Electrospun Chitosan Nanofibers Research Articles

Coating cortical bone allografts with periosteum-mimetic scaffolds made of chitosan, trimethyl chitosan, and heparin

Bone allografts have very limited healing leading to high rates of failure from non-union, fracture, and infection. The limited healing of bone allografts is due in large part to devitalization and removal of the periosteum, which removes osteogenic cells and osteoinductive signals. Here we report techniques for directly coating cortical bone with tissue scaffolds, and evaluate the scaffolds’ capacity to support osteoprogenitor cells. Three types of coatings are investigated: N,N,N-trimethyl chitosan–heparin polyelectrolyte multilayers, freeze-dried porous chitosan foam coatings, and electrospun chitosan nanofibers. The freeze-dried and electrospun scaffolds are also further modified with polyelectrolyte multilayers. All of the scaffolds are durable to subsequent aqueous processing, and are cytocompatible with adipose-derived stem cells. Alkaline phosphatase and receptor activator of nuclear factor kappa-B ligand expression at days 7 and 21 suggest that these scaffolds support an osteoprogenitor phenotype. These scaffolds could serve as periosteum mimics, deliver osteoprogenitor cells, and improve bone allograft healing.

High concentration honey chitosan electrospun nanofibers: Biocompatibility and antibacterial effects

Honey nanofibers represent an attractive formulation with unique medicinal and wound healing advantages. Nanofibers with honey concentrations of <10% were prepared, however, there is a need to prepare nanofibers with higher honey concentrations to increase the antibacterial and wound healing effects. In this work, chitosan and honey (H) were cospun with polyvinyl alcohol (P) allowing the fabrication of nanofibers with high honey concentrations up to 40% and high chitosan concentrations up to 5.5% of the total weight of the fibers using biocompatible solvents (1% acetic acid). The fabricated nanofibers were further chemically crosslinked, by exposure to glutaraldehyde vapor, and physically crosslinked by heating and freezing/thawing. The new HP–chitosan nanofibers showed pronounced antibacterial activity against Staphylococcus aureus but weak antibacterial activity against Escherichia coli. The developed HP–chitosan nanofibers revealed no cytotoxicity effects on cultured fibroblasts. In conclusion, biocompatible, antimicrobial crosslinked honey/polyvinyl alcohol/chitosan nanofibers were developed which hold potential as effective wound dressing.

Antimicrobial and sustainable food packaging based on poly(butylene adipate-co-terephthalate) and electrospun chitosan nanofibers

PBAT/CS-NF bionanocomposites show an optimal combination of flexibility, strength, barrier, migration, and antibacterial properties, therefore are suitable for food packaging applications.

Wet chemical process to enhance osteoconductivity of electrospun chitosan nanofibers

In this study, chitosan/hydroxyapatite (CS/HA) nanofibers were prepared using a wet chemical method. First, CS nanofibers with uniform diameters were fabricated using electrospinning. Then, a wet chemical process was used to mineralize nanofiber surfaces to form a homogeneous HA deposit. Reactions with three cycles were found to optimize biomimetic properties of the HA. The mineralization process required only approximately 3 h, which corresponded to a saving of 98 % in preparation time compared with that needed by the process using a simulated body fluid (SBF). According to the attachment and spreading of UMR (rat osteosarcoma) cells on the CS/HA composite fibers, the deposited mineralization layer significantly enhanced cell affinity of the CS nanofibers and the HA created by the wet chemical method was as effective as that created by the SBF. The composite nanofibrous scaffolds produced by the wet chemical process also promoted osteogenic differentiation by inducing ossification. Thus, expressions of collagen type I, alkaline phosphatase, osteocalcin, bone sialoprotein, and osterix were all enhanced. These results demonstrated that composite electrospun fibers can be efficiently prepared using wet chemical method and the resulting nanofibrous scaffolds have considerable potential in future bone tissue engineering applications.

Chitosan/polyurethane blended fiber sheets containing silver sulfadiazine for use as an antimicrobial wound dressing.

Electrospun chitosan (CTS) nanofibers have been well known for use as a wound dressing in the biomedical field. Nevertheless, fatal bacterial infections are still a serious problem when CTS nanofibers are used for wound treatment. In this study, we designed a novel wound dressing based on blending the chitosan with polyurethane (CTS/PU) containing silver sulfadiazine (AgSD) in order to enhance both antibacterial activity and mechanical strength. This fiber sheet was produced using the electrospinning (ELSP) technique. The CTS/PU containing AgSD fiber sheet was characterized by energy-dispersive X-ray spectroscopy (EDX). The physicochemical properties of the CTS/PU/AgSD fiber sheets were also characterized by thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR). The electrospun fibers were morphologically characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For an in vitro evaluation, the CTS/PU/AgSD fiber sheets were tested for their antibacterial activity against gram-negative Pseudomonas aeruginosa (P. aeruginosa), gram-positive Staphylococcus aureus (S. aureus) and Methicillin-resistant Staphylococcus aureus (MRSA). The results indicate that CTS/PU/AgSD fiber sheets have strong antimicrobial activity as displayed by inhibition of bacterial growth and prevention of infection during the healing process. These results indicate that this material would be good for use as a wound dressing material.

The stabilization of electrospun chitosan nanofibers by reversible acylation

Chitosan nanofibers fabricated by electrospinning are contaminated by acidic anions from the acid spinning solution, leading to instability of the nanofibers in aqueous solutions, and the traditional fiber treatment method will also lead to the deterioration of the nanostructure. Here we demonstrate a novel approach to removing the acidic anions with full preservation of the nanofibrous structure. The as-spun nanofibers are first protected (stabilized) by reversible acylation. Second, contaminants are then eliminated by hydrolysis; finally, acylation is reversed. Chemical analysis showed the removal of the acidic anions and the graft and removal of acyl groups. Morphological analysis showed that the reversibly acylated fibers had diameters <150 nm and nanofiber structure was maintained after immersion in aqueous solution. The membranes also were compatible with bone cells in culture. The resultant pure chitosan nanofibers show excellent stability in aqueous solution and exhibit broad potential in biomedical applications.

The adsorptive extraction of oxidized sulfur-containing compounds from fuels by using molecularly imprinted chitosan materials

An innovative approach for desulfurisation of fuels is proposed. It relies on the formation of recognition sites, complementary to oxidized sulfur-containing compounds, on cross-linked chitosan microspheres and electrospun chitosan nanofibers using the molecularly imprinted polymer technique. Benzothiophene sulfone (BTO2), dibenzothiophene sulfone (DBTO2) and 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO2) were used as templates for the preparation of molecularly imprinted polymers (MIPs). The possible molecular interactions between imprinted chitosan adsorbent and oxidized sulfur-containing compounds were investigated by molecular modeling using density functional theory (DFT) and results indicated that interactions took place via hydrogen bonding. The molecularly imprinted polymer adsorbents (cross-linked microspheres and electrospun nanofibers) gave better selectivity for the target sulfonated compounds and the adsorption isothermal studies followed the Freundlich model. Maximum adsorption capacities of 8.5±0.6mg/g, 7.0±0.5mg/g and 6.6±0.7mg/g were observed for model BTO2, DBTO2 and 4,6-DMDBTO2 respectively at 1mL/h when imprinted nanofibers were employed, and the imprinted microspheres gave maximum adsorption capacity of 4.9±0.5mg/g, 4.2±0.7mg/g and 3.9±0.6mg/g for BTO2, DBTO2 and 4,6-DMDBTO2 respectively. Application of the nanofibers to oxidized hydro-treated fuel under continuous flow adsorption system at 1mL/h indicated that 84% of sulfur was adsorbed, with adsorption capacity of 2.2±0.2mg/g.

Electrospun chitosan nanofibers with controlled levels of silver nanoparticles. Preparation, characterization and antibacterial activity

The ideal wound dressing would have properties that allow for absorption of exudates, and inhibition of microorganism for wound protection. In this study, we utilized an electrospinning (ELSP) technique to design a novel wound dressing. Chitosan (CTS) nanofibers containing various ratios of silver nanoparticles (AgNPs) were obtained. AgNPs were generated directly in the CTS solution by using a chemical reduction method. The formation and presence of AgNPs in the CTS/AgNPs composite was confirmed by x-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV) and thermogravimetric analysis (TGA). The electrospun CTS/AgNPs nanofibers were characterized morphologically by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These nanofibers were subsequently tested to evaluate their antibacterial activity against gram-negative Pseudomonas aeruginosa (P. aeruginosa) and gram-positive Methicillin-resistant Staphylococcus aureus (MRSA). Results of this antibacterial testing suggest that CTS/AgNPs nanofibers may be effective in topical antibacterial treatment in wound care.

A smart methodology to fabricate electrospun chitosan nanofiber matrices for regenerative engineering applications

The electrospinning of chitosan remains challenging due to its rigid crystalline structure, insufficient viscosity, and limited solubility in common organic solvents. This work presents a “smart” chitosan modification that allows electrospinning irrespective of molecular weight or deacetylation value and without blending with synthetic polymers. A novel derivative, namely 2‐nitrobenzyl‐chitosan (NB), at various molar compositions of chitosan:2‐nitrobenzaldehyde (1:1 (NB‐1), 1:0.5 (NB‐2), 1:0.25 (NB‐3)) was synthesized by the reaction between amino groups of chitosan and aldehyde groups of 2‐nitrobenzaldehyde. In this Schiff base, 2‐nitrobenzaldehyde protects the amine functionalities of chitosan and improves its solubility in trifluoroacetic acid. 2‐nitrobenzaldehyde is a photoactivatable‐caged compound that cleaves off from iminochitosan on ultraviolet exposure yielding neat chitosan. Derivatives showed improved solubility in trifluoroacetic acid and dynamic viscosities in the range of 1.34 ± 0.7 to 12 ± 0.5 Pa·s based on the degree of substitution and concentration. Electrospinning conditions were optimized to produce bead free nanofibers in the range of 100–600 nm, and concentrations beyond 12% (wt/v) for NB‐1 and NB‐2, and 15% (wt/v) for NB‐3 were suitable. Photolysis did not alter fiber morphology; however, regenerated chitosan matrices were soluble in culture media presumably due to the presence of 2‐nitrosobenzoic acid in trace amounts. Human skin fibroblasts exhibited excellent (&gt;90%) cytocompatibility on treatment with polymer extractions from cross‐linked regenerated chitosan matrices prepared to the ISO standard. Newly synthesized iminochitosan derivatives were very effective against microorganisms including bacteria (Gram‐positive and Gram‐negative), fungi, and yeast. These fiber matrices may serve as scaffolds for a variety of tissue healing and factor delivery applications. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Size Also Matters in Biodegradable Composite Microfiber Reinforced by Chitosan Nanofibers

ABSTRACTPioneer works on nanocomposites were focused in carbon nanofibers or nanotubes dispersed in epoxy matrix, a viscous liquid facilitating the compounding stage. The interest in developing new composites aimed for biomedical applications led us to design new nanocomposites based in biodegradable polymers with demonstrated biological performance.We report herein the development of micro-nano composites by extruding poly(butylene succinate) (PBS) microfibers with two different diameters, 200 and 500 µm, reinforced with electrospun chitosan nanofibers. Analysis of the microfibers showed high levels of alignment of the reinforcing phase and excellent distribution of the nanofibers in the composite. Its geometry facilitates the development of orthotropy, maximizing the reinforcement in the axial fiber main axis.The biodegradable microfiber composites show an outstanding improvement of mechanical properties and of the kinetics of biodegradation, with very small fractions (0.05 and 0.1 wt.%) of electrospun chitosan nanofibers reinforcement. The high surface area-to-volume ratio of electrospun nanofibers combined with the increased water uptake capability of chitosan justify the accelerated kinetics of biodegradation of the composite as compared with the unfilled synthetic polymer.

Antibacterial activity of polyacrylonitrile–chitosan electrospun nanofibers

Polyacrylonitrile (PAN)–chitosan double-face films and nanofibers were manufactured. PAN and a chitosan salt were dissolved in dimethyl sulfoxide, and then thin-layered on a glass plate or electro-spun followed by coagulation in sodium hydroxide solution. The morphology of the PAN–chitosan double-face films and nanofibers was analyzed by scanning electron microscopy. The thermal behavior and the glass transition temperature of PAN–chitosan blends were assessed by differential scanning calorimetry and dynamic mechanical analysis, respectively. The antibacterial efficacy was measured by a swatch test with bacterial suspensions. The PAN–chitosan nanofibers produced a 5-log reduction against Escherichia coli, Staphylococcus aureus, and Micrococcus luteus.

Preparation of lead-ion imprinted crosslinked electro-spun chitosan nanofiber mats and application in lead ions removal from aqueous solutions

Herein we report a novel and high efficient lead ion-imprinted adsorbent of chitosan nanofiber mats by electrospinning of chitosan solution with Pb(II) as template and glutaraldehyde as crosslinker. The structure of the resulting nanofiber mats was characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS) and Thermal Gravimetric analysis (TGA). The equilibrium adsorption capacity for Pb(II) ions of such chitosan nanofiber adsorbents can arrive at 577mg/g, which is two or five times higher than that of the common chitosan-based adsorbents. The kinetic study demonstrates that the adsorption of Pb(II) ions follows a pseudo-second-order model. Besides, the comparative adsorptions of Pb(II), Cu(II), Cd(II), Ni(II) and Zn(II) ions were also studied, which show the equilibrium adsorption capacity in the order of Pb(II)>Cu(II)>Cd(II)>Ni(II)>Zn(II). The nanofiber adsorbents can be regenerated under EDTA and still has equilibrium adsorption capacity of 359mg/g for the second Pb(II) ion adsorption.

Immobilization of lysozyme-CLEA onto electrospun chitosan nanofiber for effective antibacterial applications

Chitosan (CS) nanofibers with a diameter of 150–200nm were fabricated from a mixed chitosan/poly (vinyl alcohol) (PVA) solution by the electrospinning method. The nascent CS/PVA nanofibers were treated with 0.5M NaOH solution to make stable CS nanofibers by removing PVA under aqueous conditions. Hen egg-white lysozyme was immobilized on electrospun CS nanofibers via cross-linked enzyme aggregates (CLEAs) and used for effective and continuous antibacterial applications. The maximum amount of lysozyme immobilized on the CS nanofibers was determined to be 62.3mg/g of nanofibers under the optimum conditions. The immobilized lysozyme-CLEA retained more than 75.4% of its initial activity after 80 days of storage at room temperature, while the free lysozyme lost all of its activity under the same conditions. In addition, the immobilized lysozyme-CLEA retained more than 76% of its activity after 100 consecutive uses. Finally, the durability of the lysozyme-CLEA immobilized CS nanofibers showed bacteriostasis ratios of 82.4%, 79.8%, 83.4%, and 84.1% after 10 cycles against 4 pathogenic bacteria, viz. Staphylococcus aureus, Bacillus subtilis, Shigella flexneri, and Psedomonas aeruginosa, respectively. These results demonstrated that lysozyme-CLEA immobilized CS nanofibers could be used as a promising material for enhanced and continuous antibacterial applications.

In vitro characterization of magnetic electrospun IDA-grafted chitosan nanofiber composite for hyperthermic tumor cell treatment

Magnetic nanoparticles were the thermoseeds under an alternating magnetic field and can be used to produce highly localized hyperthermia effect on deep-seated tumor. Nevertheless, effective and precisive delivery of nanoparticles to the treatment-intended site remains a challenge. In this study, Fe3O4 nanoparticles were incorporated onto the crosslinked electrospun chitosan nanofibers using chemical co-precipitation from the Fe ions adsorbed. Such magnetic nanoparticle–nanofiber composites could be delivered to the treatment site precisely by surgical or endoscopic method. Iminodiacetic acid (IDA) functionality was grafted onto the chitosan with an aim to increase the amount of magnetic nanoparticles formed in the electrospun magnetic nanofiber composite. The morphology, crystalline phase as well as the magnetism characteristic of the magnetic electrospun nanofiber matrixes, was analyzed. Results have indicated that, with the incorporation of IDA functionality, more magnetic nanoparticles were formed in the electrospun chitosan nanofiber matrix. In addition, the magnetic IDA-grafted chitosan nanofiber composite can effectively reduced the tumor cell proliferation under the application of magnetic field. This finding suggested the magnetic electrospun chitosan nanofiber composite can be of potential for hyperthermia treatment.

In vitro feasibility study of the use of a magnetic electrospun chitosan nanofiber composite for hyperthermia treatment of tumor cells

Hyperthermia has been reported to be an effective cancer treatment modality, as tumor cells are more temperature-sensitive than their normal counterparts. Since the ambient temperature can be increased by placing magnetic nanoparticles in an alternating magnetic field it has become of interest to incorporate these magnetic nanoparticles into biodegradable nanofibers for possible endoscopic hyperthermia treatment of malignant tumors. In this preliminary investigation we have explored various characteristics of biodegradable electrospun chitosan nanofibers containing magnetic nanoparticles prepared by different methods. These methods included: (1) E-CHS-Fe3O4, with electrospun chitosan nanofibers directly immersed in a magnetic nanoparticle solution; (2) E-CHS-Fe2+, with the electrospun chitosan nanofibers initially immersed in Fe+2/Fe+3 solution, followed by chemical co-precipitation of the magnetic nanoparticles. The morphology and crystalline phase of the magnetic electrospun nanofiber matrices were determined by scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and X-ray diffraction spectroscopy. The magnetic characteristics were measured using a superconducting quantum interference device. The heating properties of these magnetic electrospun nanofiber matrices in an alternating magnetic field were investigated at a frequency of 750kHz and magnetic intensity of 6.4kW. In vitro cell incubation experiments indicated that these magnetic electrospun nanofiber matrices are non-cytotoxic and can effectively reduce tumor cell proliferation upon application of a magnetic field.

Preparation of Chitosan-Thiamine Pyrophosphate/Polyvinyl Alcohol Blend Electrospun Nanofibers

Electrospinning of chitosan (CS) has been interested due to the excellent properties of CS such as biocompatibility, biodegradability, antibacterial and non toxic. In this study, chitosan-thiamine pyrophosphate (CS-TPP)/polyvinyl alcohol (PVA) blend nanofibers were prepared using electrospinning techniques without acidic and organic solvent. CS was dissolved with TPP aqueous solution and then blended with PVA solution at various weight ratios. Physicochemical properties of CS-TPP/PVA solution such as viscosity, conductivity and surface tension were evaluated. The morphology and diameter of the electrospun fiber mats were investigated by using scanning electron microscopy (SEM). The chemical structure was characterized by Fourier Transform Infrared (FT-IR) spectroscopy and Differential Scanning Calorimetry (DSC). The morphology and diameter of the nanofibers were mainly affected by the weight ratio of the blend polymers. Nanofibers were obtained when the CS-TPP content was less than 50 % wt. The average diameter of the nanofibers was 99.91-216.42 nm, and the fiber diameter decreased with increasing CS-TPP content. Cytotoxicity tests in human fibroblast cells showed that the fibers had low toxic to the cells. In conclusion, these CS electrospun nanofiber mats can be applied for the wound dressing or transdermal drug delivery systems.

Nitrate removal from liquid effluents using microalgae immobilized on chitosan nanofiber mats

Mats of electrospun chitosan nanofibers were found effective in immobilizing microalgal cells. These immobilized microalgal cells were also used as a durable model system for wastewater treatment which has been demonstrated by the removal of around 87% nitrate from liquid effluents ([NO3−-N]initial 30 mg L−1). Virtuous nitrate removal rates were derived by superimposing physicochemical adsorption and biological nutrient consumption phenomena for chitosan and microalgae, respectively.

Biomedical Exploitation of Chitin and Chitosan via Mechano-Chemical Disassembly, Electrospinning, Dissolution in Imidazolium Ionic Liquids, and Supercritical Drying

Recently developed technology permits to optimize simultaneously surface area, porosity, density, rigidity and surface morphology of chitin-derived materials of biomedical interest. Safe and ecofriendly disassembly of chitin has superseded the dangerous acid hydrolysis and provides higher yields and scaling-up possibilities: the chitosan nanofibrils are finding applications in reinforced bone scaffolds and composite dressings for dermal wounds. Electrospun chitosan nanofibers, in the form of biocompatible thin mats and non-wovens, are being actively studied: composites of gelatin + chitosan + polyurethane have been proposed for cardiac valves and for nerve conduits; fibers are also manufactured from electrospun particles that self-assemble during subsequent freeze-drying. Ionic liquids (salts of alkylated imidazolium) are suitable as non-aqueous solvents that permit desirable reactions to occur for drug delivery purposes. Gel drying with supercritical CO2 leads to structures most similar to the extracellular matrix, even when the chitosan is crosslinked, or in combination with metal oxides of interest in orthopedics.

Preparation and characterizations of anisotropic chitosan nanofibers via electrospinning

We report the preparation of anisotropic chitosan nanofibers prepared using an electrospinning technique. The effect of electrospinning on the formation of nanofibers was examined from results of bulk chitosan. The morphological, structural characterizations and thermal properties of the chitosan bulk and electrospun nanofibers were analyzed by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TGA), Fourier transform infrared (FTIR), and Raman spectroscopy. Matrixassisted laser desorption ionization time-of-flight (MALDI-TOF) was performed to accurately characterize the high aspect ratio nanofiber structure by the direct identification of mass resolved chains. FE-SEM showed that the electrospun chitosan nanofibers had diameters ranging from 10 to 1,200 nm with an anisotropic nature. MALDI-TOF revealed the presence of lower mass group protonated amino groups, which was the main constituent for the formation of the ultrafine nanofibers in chitosan.

Coating Electrospun Chitosan Nanofibers with Polyelectrolyte Multilayers Using the Polysaccharides Heparin and N,N,N‐Trimethyl Chitosan

A new method is presented for functionalizing electrospun nanofibers with GAGs and growth factors by PEM deposition. Electrospun chitosan nanofibers, spun from trifluoroacetic acid and dichloromethane, were coated with PEMs, using the polysaccharides heparin and N,N,N-trimethyl chitosan. FGF-2 was adsorbed on the PEM-coated nanofibers. Nanofiber neutralization, PEM construction, and FGF-2 adsorption were monitored using FT-IR spectroscopy and X-ray photoelectron spectroscopy. Alcian blue staining was used to confirm the presence of heparin. SEM was used to study nanofiber morphology.