Electrospinning of chitosan–poly(ethylene oxide) blend nanofibers in the presence of micellar surfactant solutions

Nanofibrous chitosan-polyethylene oxide engineered scaffolds: a comparative study between simulated structural characteristics and cells viability

3D nanofibrous chitosan-polyethylene oxide (PEO) scaffolds were fabricated by electrospinning at different processing parameters. The structural characteristics, such as pore size, overall porosity, pore interconnectivity, and scaffold percolative efficiency (SPE), were simulated by a robust image analysis. Mouse fibroblast cells (L929) were cultured in RPMI for 2 days in the presence of various samples of nanofibrous chitosan/PEO scaffolds. Cell attachments and corresponding mean viability were enhanced from 50% to 110% compared to that belonging to a control even at packed morphologies of scaffolds constituted from pores with nanoscale diameter. To elucidate the correlation between structural characteristics within the depth of the scaffolds' profile and cell viability, a comparative analysis was proposed. This analysis revealed that larger fiber diameters and pore sizes can enhance cell viability. On the contrary, increasing the other structural elements such as overall porosity and interconnectivity due to a simultaneous reduction in fiber diameter and pore size through the electrospinning process can reduce the viability of cells. In addition, it was found that manipulation of the processing parameters in electrospinning can compensate for the effects of packed morphologies of nanofibrous scaffolds and can thus potentially improve the infiltration and viability of cells.

Electrospun chitosan/sericin composite nanofibers with antibacterial property as potential wound dressings

Chitosan and sericin are natural and low cost biomaterials. Both biomaterials displayed good compatibility to human tissues and antibacterial properties for biomedical application. In this study, we have successfully fabricated chitosan/sericin composite nanofibers by electrospinning. The obtained composite nanofibers were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FT-IR), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) studies. The composite nanofibers had good morphology with diameter between 240nm and 380nm. In vitro methyl thiazolyl tetrazolium (MTT) assays demonstrated that the chitosan/sericin composite nanofibers were biocompatible and could promote the cell proliferation. Furthermore, the composite nanofibers showed good bactericidal activity against both of Gram-positive and Gram-negative bacteria. Thus, the chitosan/sericin composite nanofibers are promising for wound dressing applications.

Fabrication of Electrospun Chitosan and Chitosan/Poly(ethylene oxide) Nanofiber Webs and Assessment of Their Antimicrobial Activity

In recent years, production of nano-sized wound dressing materials from biopolymers by electrospinning method has attracted great attention. In this study, chitosan that is an inherently antimicrobial polymer and chitosan (CS)/poly(ethylene oxide) (PEO) blend solutions were electrospun to obtain nanofiber webs for wound-dressing applications. Although electrospinning of chitosan with PEO was previously studied, this study emphasized the effect of molecular weight of polymer used, total polymer concentration and electrical conductivity of polymer solution on fiber formation. Results show that selection of suitable solvent and determination of optimum process parameters were key factors for obtaining uniform nanofibers. Antimicrobial activities of these nanofiber webs against S.aureus, E.coli, and C.albicans were tested according to AATCC 100–2004. Over 99% reduction in the number of microorganisms with pure chitosan nanofibers and over 50% reduction with CS/PEO blend nanofibers were obtained.

Fabrication, gastromucoadhesivity, swelling, and degradation of zein-chitosan composite ultrafine fibers

Fabrication, via electrospinning, and characterization of an ultrafine structure architected from a blend of hydrophobic zein and hydrophilic chitosan (CS) were conducted. Poly(ethylene oxide) (PEO) and nonionic surfactant, namely, Tween 40, were employed to improve the electrospinnability of the blend, while ethanol was used as a solvent for zein. The effects of ethanol (EtOH) concentration (85% and 90%) and ratio of zein/PEO/CS (95/2.5/2.5 and 87.5/10/2.5) on the fiber morphology as well as gastromucoadhesivity against porcine stomach mucosa were then investigated; polymer-mucosa adhesion was also investigated via Fourier-transform infrared spectroscopy. Swelling and degradation of the composite ultrafine fibers were investigated under 2 simulated gastric conditions, namely, at pH 2 without pepsin and at pH 1.2 with pepsin. Using 85% EtOH as a solvent for zein resulted in a spider-web-like morphology; the maximum detachment force (MDF), which is an indirect indicator of the gastromucoadhesivity was nevertheless higher. Zein-based ultrafine fibers exhibited higher MDF than the zein-PEO-CS composite; however, the cohesiveness of the composite fibers was higher. FTIR spectroscopic results indicated molecular interactions between the composite fibers and mucin functional groups. Swelling of the composite ultrafine fibers in simulated gastric fluid (SGF) at pH 2 without pepsin was not different from that in SGF at pH 1.2 with pepsin. Nevertheless, degradation of the composite fibers in SGF at pH 2 without pepsin was much less than that in SGF at pH 1.2 with pepsin; only 20% degradation was noted in the former case.

Core-shell structured PEO-chitosan nanofibers by coaxial electrospinning

Core-shell structured PEO-chitosan nanofibers have been produced using a coaxial electrospinning setup. PEO and chitosan solutions, both in an aqueous acetic acid solvent, were used as the inner (core) and outer (shell) layer, respectively. Uniform-sized defect-free nanofibers of 150-190 nm diameter were produced. In addition, hollow nanofibers could be obtained subsequent to PEO washing of the membranes. The core-shell nanostructure and existence of chitosan on the shell layer were confirmed by TEM images obtained before and after washing the PEO content with water. The presence of chitosan on the surface of the composite nanofibers was further supported by XPS studies. The chitosan and PEO compositions in the nanofibrous mats were determined by TGA analysis, which were similar to their ratio in the feed solutions. The local compositional homogeneity of the membranes and the efficiency of the washing step to remove PEO were also verified by FTIR. In addition, DSC and XRD were used to characterize the crystalline structure and morphology of the co-electrospun nonwoven mats. The prepared coaxial nanofibers (hollow and solid) have several potential applications due to the presence of chitosan on their outer surfaces.

Electrospun polyethylene oxide/cellulose nanocrystal composite nanofibrous mats with homogeneous and heterogeneous microstructures

An electrospinning process was successfully used to fabricate polyethylene oxide/cellulose nanocrystal (PEO/CNC) composite nanofibrous mats. Transition of homogeneous to heterogeneous microstructures was achieved by tailoring the concentration of PEO/CNC mixture in the solution from 5 to 7 wt %. Morphology investigation of the obtained nanofibers demonstrated that rod-shaped CNCs were well-dispersed in the as-spun nanofibers and highly aligned along the nanofiber long-axis. PEO/CNC nanofibers became more uniform and smaller in diameter with increased CNC-loading level. The heterogeneous composite mats were composed of rigid-flexible bimodal nanofibers. Results of structure characterization indicated that the incorporated CNCs interacted strongly with the PEO matrix through hydrogen bonding. Mechanical properties of both types of mats were effectively improved by using CNCs, with heterogeneous mats being stronger than their homogeneous counterparts for all compositions (0-20 wt % CNC contents). When a smaller diameter needle was used to form homogeneous mats, enhanced thermal and mechanical properties were obtained.

Nanofibers as carrier systems for antimicrobial microemulsions. Part I: fabrication and characterization

Antimicrobial nanofibers were prepared by solubilizing an antimicrobial essential oil (eugenol; 0.75-1.5 wt %) in surfactant micelles (Surfynol 465; 5-10 wt %) to form eugenol-containing microemulsions. Microemulsions were mixed with a nonionic synthetic polymer (poly(vinyl alcohol), PVA; M(w) = 130 kDa, degree of hydrolysis approximately 87%) and solutions subjected to electrospinning to induce nanofiber formation. Solution properties, fiber morphology, and composition of nanofibers were determined. The surface conductivity and viscosity of the polymer solutions increased, while surface tension decreased as both surfactant and eugenol concentration increased. Material deposited on the collector plate consisted primarily of nanofibers with a circular cross section with some surface roughness, although some bead defects were observed. The mean fiber diameters ranged from 57 to 126 nm with fibers having a broad diameter distribution (10-280 nm). The mean diameter of the nanofibers decreased with increasing surfactant concentration and decreasing eugenol concentration. Transmission electron microscopy indicated that microemulsion droplets were homogenously dispersed throughout the nanofibers. Results suggest that electrospun nanofibers may serve as carrier vehicles for microemulsions containing solubilized lipophilic functional compounds such as bioactives, antimicrobials, antioxidants, flavors, and pharmaceuticals.

Solubilization of Oleic Acid by Myrj 59 Surfactant

Palm oil mill effluent (POME) is one of the sources of contamination in effluent that leads to problems such asclogging in drainpipes and sewer lines. POME discharge consists of high content of free fatty acids (FFAs) aswell as high concentration of biochemical oxygen demand (BOD), chemical oxygen demand and suspendedsolids. FFAs in effluent are not favorable due to low water solubility and resistant to biodegradation whenprecipitated from effluent and binds to soil limiting their bioavailability to microorganisms for biodegradation.Nonionic surfactants are favorable as hydrocarbon or oil solubilizer because they can perform at lowtemperatures, has low-foaming characteristics and relatively stable at high temperatures and under harshchemical conditions. Therefore, there is a need for the usage of surfactant that is biodegradable and at the sametime effective at solubilizing FFAs in POME before being released to streams. Thus, FFAs will be keptmobilized and readily available for biodegradation by microorganisms. Oleic acid is a long chain free fatty acidpresents as the major fatty acid component (40-52 %w/w) in palm oil. Oleic acid was selected for solubilizationby biodegradable nonionic surfactant polyoxyethylene (100) stearate with the commercial name Myrj 59. Thesolubilizations were conducted with various concentrations of Myrj 59; below, at and above the critical micelleconcentration (CMC). The amount solubilized was determined by gas chromatography (GC) using flameionization detector (FID) technique. The solubilization process was confirmed by characterizing the solubilizedoil using Fourier Transform infrared (FTIR) to observe changes in chemical bonds. Highest solubilization wasachieved with Myrj 59 solution at above its CMC, solubilizing 516.31 ppm oleic acid. The FTIR spectra showedstrong peak at 2927 cm-1 with high intensity suggesting intermolecular hydrogen bonding between oleic acid andethylene oxide (EO) groups of surfactant.