Encapsulation of Phytoncide in Nanofibers by Emulsion Electrospinning and their Antimicrobial Assessment

This study aimed to fabricate core/sheath-structured composite nanofibers containing cinnamon oil by emulsion electrospinning and to investigate their acaricidal effect on house dust mites as well as their antibacterial and antifungal properties in relation to cinnamon oil concentration in the nanofibers. An oil-in-water emulsion, which comprised cinnamon oil and poly(vinyl alcohol) solution as oil and water phases, respectively, was used to prepare core/sheath-structured nanofibers. The morphology and the inner structure of the electrospun nanofibers were observed by scanning electron microscopy and confocal laser scanning microscopy. Core/sheath-structured nanofibers containing cinnamon oil were successfully prepared by emulsion electrospinning. The composite nanofibers prepared from an emulsion containing 20 wt% of cinnamon oil exhibited a strong acaricidal effect against house dust mites (Dermatophagoides farinae). The composite nanofibers fabricated from an emulsion containing 4.29 wt% of cinnamon oil showed excellent antimicrobial effects against Staphylococcus aureus and a series of fungi that can trigger respiratory- and skin-related diseases. The release profile of cinnamon oil from the core/sheath-structured nanofibers showed a continuous release of functional ingredients over 28 days. Our findings demonstrate that the use of such fibrous structures could be a promising approach for delivering naturally derived bioactive agents in a controlled way.

To develop bioactive and interactive wound-dressing materials based on natural products, poly(vinyl alcohol) (PVA) nanofibrous membranes containing plant-derived essential oils were fabricated and their potential applications for wound dressing were examined. Since essential oils, particularly palmarosa oil and phytoncide oil, possess natural antimicrobial and anti-inflammatory properties and are ecofriendly, they were chosen as bioactive agents to be incorporated into the nanofiber matrix. Antimicrobial efficacy, air/moisture vapor transport, and water uptake properties of the composite membranes were assessed to find suitable processing conditions for effective wound care. Palmarosa oil or phytoncide oil was incorporated into the core of PVA nanofibers via emulsion electrospinning. The PVA-based composite nanofibrous membranes were heat-treated to increase their stability in aqueous environments. Qualitative and quantitative antimicrobial assessments showed that the membranes containing palmarosa oil possessed superior antimicrobial effects against Staphylococcus aureus and Candida albicans over the membranes containing phytoncide oil. Air/moisture vapor transport and water uptake properties were assessed for the PVA-based composite membranes having two levels of web area density to find suitable conditions for creating an optimal wound-healing environment. The composite nanofibrous membranes, which had a web area density of 3 g/m2, provided reasonable levels of gas and moisture vapor permeability for effective wound care and possessed water uptake ability to allow exudate absorption. These results demonstrate that the electrospun core/sheath structured PVA nanofibrous membranes containing palmarosa oil have high potential as bioactive wound-dressing materials.

ABSTRACTThis article reports on the encapsulation of a phase change material (PCM) into a hydrophilic polymer, poly(vinyl alcohol) (PVOH), by means of electrospinning. Different strategies were carried out to improve the thermal buffering capacity and the stability of the developed structures when they were exposed to different relative humidity (RH) conditions. On the one hand, the thermal energy storage capacity of PVOH/PCM structures obtained through emulsion electrospinning was optimized by using different amounts of polyoxyethylene sorbitan monolaureate (Tween 20). Surfactant addition successfully increased the heat storage capacity of the developed structures, reaching an optimum performance at a concentration of 0.32% in weight with respect to the total emulsion weight. However, the hydrophilic nature of the developed structures made them extremely difficult to handle due to swelling with increasing RH. To avoid this issue an additional shell layer of poly(caprolactone) (PCL), was applied by coaxial electrospinning. In this case, the PVOH/PCM ratio (core) was optimized to reach the highest heat storage capacity per gram of sample and, then, a PCL solution was used as a shell material to hydrophobize the structures. The optimized coaxial electrospun structures were able to encapsulate about 82% of PCM. The use of both emulsion and coaxial electrospinning strategies are introduced here for the first time as advanced strategies to overcome application issues such as unintended migration and performance drop in the previously developed monophase materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43903.

Basic fibroblast growth factor-encapsulated PCL nano/microfibrous composite scaffolds for bone regeneration

Emulsion electrospinning is an advanced technique to fabricate core-shell structured nanofibrous scaffolds, with great potential for drug encapsulation. Incorporation of dual factors hydroxyapatite (HA) and laminin, respectively, within the shell and core of nanofibers through emulsion electrospinning might be of advantageous in supporting the adhesion, proliferation, and maturation of cells instead of single factor-encapsulated nanofibers. We fabricated poly(L-lactic acid-co-ϵ-caprolactone) (PLCL)/hydroxyapaptite (PLCL/HA), PLCL/laminin (PLCL/Lam), and PLCL/hydroxyapatite/laminin (PLCL/HA/Lam) scaffolds with fiber diameter of 388 ± 35, 388 ± 81, and 379 ± 57 nm, respectively, by emulsion electrospinning. The elastic modulus of the prepared scaffolds ranged from 22.7–37.0 MPa. The osteoblast proliferation on PLCL/HA/Lam scaffolds, determined on day 21, was found 10.4% and 12.0% higher than the cell proliferation on PLCL/Lam or PLCL/HA scaffold, respectively. Cell maturation determined on day 14, by alkaline phosphatase (ALP) activity, was significantly higher on PLCL/HA/Lam scaffolds than the ALP activity on PLCL/HA and PLCL/Lam scaffolds (p ⩽ 0.05). Results of the energy dispersive X-ray studies carried out on day 28 also showed higher calcium deposition by cells seeded on PLCL/HA/Lam scaffolds. Osteoblasts were found to adhere, proliferate, and mature actively on PLCL/HA/Lam nanofibers with enhanced cell proliferation, ALP activity, bone protein expression, and mineral deposition. Based on the results, we can conclude that laminin and HA individually played roles in osteoblast proliferation and maturation, and the synergistic function of both factors within the novel emulsion electrospun PLCL/HA/Lam nanofibers enhanced the functionality of osteoblasts, confirming their potential application in bone tissue regeneration.

Cephalexin loaded electrospun nanofibers with core-shell structures were prepared from poly(vinyl alcohol) (PVA) blended with various biopolymers such as chitosan (CH), carboxymethyl cellulose (CMC), carboxymethyl starch (CMS), and hydroxyproyl cellulose (HPC) in PVA:biopolymer ratio of 90:10. The electrospun nanofiber mats were cross-linked by heat treatment to avoid disintegration in water. Molecular interactions between the polymeric chains and the drug were analyzed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The morphology of nanofiber mats was studied by field emission scanning electron microscope (FE-SEM), and the core-shell structure formation through emulsion electrospinning was confirmed by transmission electron microscope (TEM) and confocal laser scanning microscope (CLSM). The in vitro drug release profile was studied and the mechanism was determined through kinetic models using non-linear regression methods. Drug release was gradual within the first 8 h. Furthermore, release predominantly occurred by a diffusion mechanism which makes this system suitable for wound healing treatment.

Fabrication and characterization of oleic acid/sesame protein isolate/ poly (vinyl) alcohol core-shell nanofibers: Mitigating lipid oxidation by emulsion electrospinning

The viscoelastic interaction between dispersed and continuous phase of PCL/HA-PVA oil-in-water emulsion uncovers the theoretical and experimental basis for fiber formation during emulsion electrospinning

We have been investigating the preparation of macroporous gel particles of poly(vinyl alcohol) [1-3]. These particles are obtained by the saponification of particles of poly(vinyl acetate) formed in the polymerization of vinyl acetate in a suspension process. The poly(vinyl alcohol) gel particles have been used as a column packing for aqueous separations. However, the gels have a disadvantage in pressure-resistant property because of poor mechanical strength. We expected that a gel having excellent mechanical stability might be obtained by reinforcing poly(vinyl alcohol) with an inorganic component. We report here that reinforcement using silica as an inorganic component is useful for the improvement of performance of poly(vinyl alcohol) gel particles used as a column packing for gel permeation chromatography in aqueous media. Tetraethoxy silane (TEOS) was used as the inorganic component of the hybrid gels throughout this study. The sol-gel method was applied to the preparation of hybrid gel [4-6]. The process is divided into two steps: hydrolysis of metal alkoxides to produce metal hydroxides, followed by polycondensation of hydroxyl groups. By carrying out this reaction in a poly(vinyl alcohol) gel matrix containing many hydroxyl groups, it is possible to copolymerize metal alcoxide with poly(vinyl alcohol). Thus a silica network may be incorporated into the poly (vinyl alcohol) gel matrix. The gel particles of poly(vinyl acetate) (DP = 1000) obtained by suspension polymerization were classified to give a particle size distribution with particle diameters in the range 350-400 #m. The saponification of poly(vinyl acetate) to poly(vinyl alcohol) was carried out at 30 ~ for 1 month by immersing the gel particles in a solution containing sodium hydroxide and methanol in an aqueous saturated sodium sulfate solution [7]. The gel particles of poty(vinyl alcohol) obtained above have sufficient mechanical stability in water below 55 ~ without crosslinking treatment. The gel particles (1 g) obtained above were immersed in 10 ml of ethanol for 24 h and then tetraethoxy silane and hydrochloric acid as catalyst were added to the particles. The reaction was carried out at 30 ~ For the purpose of removal of TEOS homopolymer the reaction product was then subjected to a Soxhlet extraction using tetrahydrofuran. Swelling behaviour and gel permeation chromatographic properties of the hybrid gel particles obtained above were investigated. The ratio of the volume of the particles in ethanol to that on swelling with water (swelling ratio) was evaluated from observations by optical microscopy. As shown in Fig. 1, swelling ratio decreases with increase of reaction time and levels off at about 2 h. This is due to the formation of the silica network in the poly(vinyl alcohol) gel matrix. The swelling behaviour is mainly controlled by the amount of TEOS added. The slurry of hybrid gel particles was packed into a 150 x 4 mm stainless column at a pressure of about 5 MPa. High-performance gel permeation chromatography (HP-GPC) separations were performed with a Shimazu LC-6AD, employing distilled water as eluent. Solutions (40 #1) of individual solutes were injected with an off-column syringe-septum arrangement. Detection of solutes was performed with a Shimazu Refracto Monitor Model RID-6A (cell volume = 10 ~tl, aqueous reference). The samples of poly(ethylene glycol) are designated PEG with a number which is the molecular weight provided by the suppliers (Kanto Chemicals, Tokyo). The calibration curve was established at a flow rate of 0.4cm3/min with a PEG concentration of 2.0% (w/v). The calibration curve of the hybrid gel particles established with PEG samples is shown in Fig. 2, in comparison with the poly(vinyl alcohol) gel particles. The value of the excluded molecular weight is almost the same for the hybrid gel particles and the poly(vinyl alcohol) gel particles. However, the calibration curve for the column packing containing the hybrid gel particles shifts to higher elution volumes. Since separation power is inversely proportional to the slope of the plot of molecular weight versus elution volume, it is clear that the column containing the hybrid gel particles shows better resolution separations. The shape of the slope

Assessment of antibacterial properties of electrospun fish collagen/poly (vinyl) alcohol nanofibers with biosurfactant rhamnolipid

Highly aligned graphene oxide/poly(vinyl alcohol) nanocomposite fibers with high-strength, antiultraviolet and antibacterial properties

Controlling drug release using a nanocomposite method is crucial; however, burst release must be avoided in order to obtain effective controllable drug release. In this study, poly(vinyl) alcohol/polyoxalate/Span-80 (PVA/ POX/ Span-80) composite nanofibers loaded with Rhodamine B were produced using emulsion electrospinning. The objective of this work was to evaluate the cooperative roles of POX and Span-80 on nanofibrous scaffold stability and drug release regulation by monitoring Rhodamine B release performance from electrospun composite nanofibers. The microstructure and hydrophilic properties of the emulsion electrospun nanofibers were studied using scanning electron microscopy (SEM), water contact angle, and swelling tests. According to the results, increasing the POX content had a significant effect on the size of nanofibers. The water contact angles increased as the POX content increased. The release of Rhodamine B was governed by a two-stage diffusion mechanism that was greatly influenced by PVA/POX ratios and Span-80. To compare release behavior, non-emulsion electrospun nanofibers without Span-80 were prepared as control samples. Emulsion nanofibers were found to release at a slower rate than non-emulsion nanofibers. The in vitro release profiles revealed that Rhodamine B was released from emulsion electrospun fibers in a sustainable manner and that no initial burst release was observed. These findings imply that emulsion electrospun nanofibers can potentially be used to deliver drugs, nutraceuticals, and fragrances in a prolonged manner

Conducive 3D porous mesh of poly(ε-caprolactone) made via emulsion electrospinning

We report the mechanical property and electromagnetic interference shielding effectiveness (EMI SE) of poly(vinyl alcohol) (PVA)/graphene and PVA/multi-walled carbon nanotube (MWCNT) composite nanofibers prepared by electrospinning. The metal (Cu) was deposited on the resultant PVA composite nanofibers using metal deposition technique in order to improve the mechanical properties and EMI shielding properties. The resulting PVA composite nanofibers and Cu-deposited corresponding nanofibers were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and wide angle X-ray diffraction (WAXD). Tensile tests were performed on the PVA/graphene and PVA/MWCNT composite nanofibers. The tensile strength of the PVA/graphene and PVA/MWCNT composite nanofibers was found to be 19.2 +/- 0.3 MPa at graphene content - 6.0 wt% and 12.2 +/- 0.2 MPa at MWCNT content - 3.0 wt%, respectively. The EMI SE of the Cu-deposited PVA/graphene composite nanofibers was significantly improved compared to pure PVA/graphene composite nanofibers, and also depended on the thickness of Cu metal layer deposited on the PVA composite nanofibers.

Nanoweb fabricated by electrospinning has a large specific area and a small pore size which can be controlled through a spinning process to enable a strong adsorption and selective permeability. It is required to produce nanofiber of different polymer mixture with a limited miscibility for improvement of physical, chemical, or biological properties. In this study, poly (vinyl alcohol) (PVA)/polyurethane (PU) nanofibers were produced by coaxial electrospinning. PVA (core)/PU (shell) nanofibers were defect-free and had a uniform thickness. The pseudo core/shell structure of PVA/PU nanofibers was confirmed by transmission electron microscopy. The presence of PVA and PU in the nanofibers was identified by 13C solid state nuclear magnetic resonance spectroscopy, fourier transform infrared spectroscopy, and X-ray diffraction analysis. Water contact angle was reduced by incorporation of PVA in a core of PU nanofiber. For variety of biomedical applications, bioactive substances such as antibiotics and proteins can be incorporated in a core of hydrophobic PU nanofiber by coaxial electrospinning of water-soluble polymer/bioactive substance mixture.