Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Electrospun Nanofibers Containing Natural Deep Eutectic Solvents Exhibiting a 3D Rugose Morphology and Charge Retention Properties.

In the present study, electrospun nanofibers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a biodegradable polyester, containing natural deep eutectic solvents (NADES) were obtained and reported for the first time, exhibiting an unreported 3D morphology and enhanced charge retention properties. Choline chloride (ChCl)/urea/water in a molar ratio of 1:2:1 was used as the NADES model system. Electrospun nanofibers were produced from a 10 wt % solution of PHBV containing 26 wt % NADES with respect to the polymer and were deposited on different substrates, that is, aluminum foil and non-woven spunbond polypropylene (PP). The morphology and charge retention ability were characterized under different conditions and on different substrates. The attained fiber morphology for the NADES-containing mats showed an average fiber diameter of around 300 nm, whereas the pure PHBV polymer under the same conditions produced electrospun fibers of around 880 nm. However, the deposition of PHBV/ChCl/urea/water fibers resulted in a surprising macroscopic rugose 3D surface morphology made of aligned nanofibers when processed at 50% relative humidity (RH). The nanofiber grammages above which this 3D morphology, associated with NADES-induced charge retention, formed was found to be dependent on the substrate used and RH. This morphology was not seen at 20% RH nor when pure PHBV was produced. Charge stability studies revealed that PHBV/ChCl/urea/water nanofibers exhibited lasting charge retention, especially when sandwiched between spunbond polypropylene textiles. Finally, such multilayer structures containing a very thin double layer of PHBV/ChCl/urea/water fibers after corona treatment exhibited improved paraffin aerosol penetration, which was ascribed to the combination of thinner fibers and their charge retention capacity. The here-developed electrospun PHBV fibers containing NADES demonstrated for the first time a new potential application as electret filter media.

Encapsulation of ß-Carotene by Emulsion Electrospraying Using Deep Eutectic Solvents.

The encapsulation ß-carotene in whey protein concentrate (WPC) capsules through the emulsion electrospraying technique was studied, using deep eutectic solvents (DES) as solvents. These novel solvents are characterized by negligible volatility, a liquid state far below 0 °C, a broad range of polarity, high solubilization power strength for a wide range of compounds, especially poorly water-soluble compounds, high extraction ability, and high stabilization ability for some natural products. Four DES formulations were used, based on mixtures of choline chloride with water, propanediol, glucose, glycerol, or butanediol. ß-Carotene was successfully encapsulated in a solubilized form within WPC capsules; as a DES formulation with choline chloride and butanediol, the formulation produced capsules with the highest carotenoid loading capacity. SEM micrographs demonstrated that round and smooth capsules with sizes around 2 µm were obtained. ATR-FTIR results showed the presence of DES in the WPC capsules, which indirectly anticipated the presence of ß-carotene in the WPC capsules. Stability against photo-oxidation studies confirmed the expected presence of the bioactive and revealed that solubilized ß-carotene loaded WPC capsules presented excellent photo-oxidation stability compared with free ß-carotene. The capsules developed here clearly show the significant potential of the combination of DES and electrospraying for the encapsulation and stabilization of highly insoluble bioactive compounds.

Preparation of electrospun PCL-based scaffolds by mono/multi-functionalized GO.

In the present study, sythetic biodegradable polymer poly(ε-caprolactone) (PCL) and graphene oxide (GO) were combined together to prepare 3D, composite tissue scaffolds (PCL/GO scaffolds) by using electrospinning technique. Also, the influence of Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) and/or thiophene (Th) modified GO on the composite PCL/GO mats (PCL/GO, PCL/GO-GRGDSP, PCL/GO-Th, PCL/GO-GRGDSP-Th) was further investigated. Characteristic examinations of the scaffolds were carried out by scanning electron microscope (SEM), contact angle (CA) measurements, x-ray photoelectron spectroscopy, TGA, electrical conductivity tests, phosphate buffer saline absorption and shrinkage tests and mechanical tests. All of the scaffolds were exhibited suitable bead-free and uniform morphology according to SEM images. With the addition of GO, better hydrophilicity and a slight CA decrease (∼5°) for the PCL/GO scaffolds were observed. Mechanical properties were reinforced drastically with the addition and well-dispersion of GO into PCL matrix. The incorporation of PCL and GO exhibited enhanced electrical conductivity and the highest value was found for PCL/GO-GRGDSP-Th (2%) as 15.06 µS cm-1. The MG-63 osteoblast cell culture studies (MTT assay, ALP activity, Alizarin-Red staining, fluorescence and SEM analyses) showed that PCL/GO-GRGDSP-Th (1%) scaffolds exhibited the highest biocompatibility performance (1.87 fold MTT absorbance value comparing with neat PCL) due to the advanced properties of GO and the biological interfaces.

Development of Antibacterial Composite Electrospun Chitosan-Coated Polypropylene Materials.

In this study, a natural antibacterial substance chitosan was coated with/without potassium sorbate (KS) (0.8% (w/w) of KS, 8% (w/v) chitosan) onto the polypropylene (PP) film by using electrospinning technique to obtain novel antibacterial composite materials for various applications such as wound dressing, tissue engineering, drug delivery and food packaging. Atmospheric pressure plasma surface treatment was applied onto polypropylene films in order to increase its wettability thus enhancing the adhesion capacity of the films and the optimum CA value was determined as 42.75 ± 0.80°. Scanning Electron Microscope (SEM) and X-ray Photoelectron Spectroscopy (XPS) analyses were realized to observe the morphological changes and chemical properties of the samples, respectively. Contact angle measurements, tensile testing, oxygen and water vapor transmission rate analyses were performed to obtain wettability values, mechanical properties and WVTRs, respectively. The WVTR was increased by plasma treatment and addition of KS (from 14.264 ± 0.214% to 21.020 ± 0.659%). The desired antibacterial performance of the samples was assessed with Staphylococcus aureus and Escherichia coli by inhibition ratio calculation and disc diffusion assay. The highest inhibition ratios were found as 64% for S. aureus and 92% for E. coli for plasma-treated CS-KS-PP films.