Electrospun Materials Based on Cellulose Acetate Loaded with Rosmarinic Acid with Antioxidant and Antifungal Properties

Fibrous cellulose acetate (CA) materials loaded with rosmarinic acid (RA) were successfully created by one-pot electrospinning. In order to improve the water solubility of the polyphenolic acid and to facilitate its release from the fibrous materials, the non-ionic water-soluble polyethylene glycol (PEG) was added. Detailed characterization of the fabricated fibrous CA/RA and CA/PEG/RA materials was performed using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), UV-Vis spectroscopy and water contact angle analysis. The optimal ratio between CA, RA and PEG for preparation of defect-free and uniform fibers was accomplished by varying their concentrations. Furthermore, the incorporation of the PEG improved the hydrophilicity and wettability of the fibrous CA materials. Moreover, PEG facilitated the RA release and over 360 min, the amount released from fibrous CA/PEG/RA fibers was 91%, while that released from CA/RA materials was 53%. Both of the RA-containing fibrous materials, with and without PEG, manifested high antioxidant activity as determined by the DPPH free radical-scavenging method. In addition, the electrospun CA/PEG/RA materials displayed good antifungal activity against C. albicans. These features make the fibrous CA/PEG/RA materials promising candidates for treatment of wound infections.

Fabrication of Electrospun Cellulose Acetate/Nanoclay Composites for Pollutant Removal

The creation of eco-friendly clay-based composites for pollutant removal by adsorption still remains a challenge. This problem might be successfully solved by the development of electrospun polymer-clay composites. For the first time in this study, a one-step fabrication of cellulose acetate (CA) fibers filled with commercially available nanoclays (NCs) was described. The optimal ratio at which CA/NCs dispersions remained stable was accomplished by varying the nanoclay concentration with respect to CA. Furthermore, the selected solvent system and the electrospinning conditions allowed for the successful fabrication of electrospun CA/NC composites. It was found that the composites' surface morphology was not affected by the incorporated nanoclays and was the same as that of the electrospun CA fibers. The performed analyses clearly showed that CA and nanoclays did not react during the electrospinning process. It was found that the distribution of nanoclay layers probably was a mixture of intercalated and exfoliated structures. Notably, the type of the nanoclay strongly influenced the adsorption ability of CA/NC composites toward Cr(VI) ions and MB dye. These results suggested that the fabricated CA/NC composites are suitable for pollutant removal due to their specific structure.

Electrospun Poly(methyl methacrylate)/TiO2 Composites for Photocatalytic Water Treatment

Electrospinning was successfully used for the one-step fabrication of poly(methyl methacrylate) (PMMA) fibers loaded with an inorganic photocatalyst—titanium oxide (TiO₂). By tuning the PMMA/TiO₂ ratio and the electrospinning conditions (applied voltage, needle tip-to-collector distance, and flow rates), PMMA/TiO₂ composites with selected organic/inorganic ratios, tailored designs, and targeted properties were obtained. The morphology of the electrospun composites was affected by the amount of TiO₂ incorporated into the PMMA fibers. In addition, the inorganic photocatalyst had an impact on the wettability, thermal stability, and optical properties of the electrospun composites. In particular, the surface wettability of the composites was strongly influenced by UV light irradiation and from hydrophobic became superhydrophilic. Moreover, PMMA/TiO₂ composites had enhanced tensile strength in comparison with those of bare PMMA mats. The electrospun PMMA/TiO₂ composites showed excellent photocatalytic efficiency against the model organic pollutant—methylene blue—which is very promising for the future development of membranes that are highly efficacious for photocatalytic water treatment.

Electrospun Eco-Friendly Materials Based on Poly(3-hydroxybutyrate) (PHB) and TiO2 with Antifungal Activity Prospective for Esca Treatment

Esca is a type of grapevine trunk disease that severely affects vine yield and longevity. Phaeomoniella chlamydospora (P. chlamydospora) is one of the main fungi associated with esca. The aim of the present study was to obtain eco-friendly materials with potential antifungal activity against P. chlamydospora based on biodegradable and biocompatible poly(3-hydroxybutyrate) (PHB), nanosized TiO₂-anatase (nanoTiO₂), and chitosan oligomers (COS) by conjunction of electrospinning and electrospraying. One-pot electrospinning of a suspension of nanosized TiO₂ nanoparticles in PHB solution resulted in materials in which TiO₂ was incorporated within the fibers (design type “in”). Simultaneous electrospinning of PHB solution and electrospraying of the dispersion of nanosized TiO₂ in COS solution enabled the preparation of materials consisting of PHB fibers on which TiO₂ was deposited on the fibers’ surface (design type “on”). Several methods including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD), thermogravimetric analyses (TGA) and water contact angle were utilized to characterize the obtained materials. The incorporation of nanoTiO₂ in the PHB fibers, as well as nanoTiO₂ deposition onto the surface of the PHB fibers resulted in increased roughness and hydrophobicity of the obtained composite fibrous materials. Moreover, TiO₂-on-PHB fibrous material exhibited complete inhibition of fungal growth of P. chlamydospora. Therefore, the obtained eco-friendly fibrous materials based on PHB and nanoTiO₂ are promising candidates for protection against esca in agriculture.

Modulating the Mechanical Properties of Electrospun PHB/PCL Materials by Using Different Types of Collectors and Heat Sealing

Two-component fibrous materials based on poly(3-hydroxybutyrate) (PHB, T_m = 160 °C) and poly(ε-caprolactone) (PCL, T_m = 60 °C) were successfully fabricated by dual-jet electrospinning of their separate spinning solutions. The desired alignment of the fibers that compose PHB/PCL mats was achieved by using three types of rotating collectors-drum (smooth), blade and grid. Additional fiber alignment in the direction of collector rotation was achieved by rotating at 2200 rpm. Moreover, the selected concentration of PCL spinning solution resulted in fibers with spindle-like defects along their length. Thus, "segment" sealing of the PHB (high-melting) fibers by the molten PCL (low-melting) fibers/defects sites was achieved after heating the PHB/PCL mats above the melting temperature (T_m) of PCL. The surface morphology, thermal behavior and mechanical properties of the PHB/PCL mats before and after thermal treatment were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, differential scanning calorimetry (DSC) and mechanical tests. The results indicated that regardless of the cutting direction of the specimens (0° or 90°), thermal treated PHB/PCL mats reveal enhanced mechanical properties. Therefore, this work provides an easily feasible route for the fabrication of electrospun PHB/PCL mats with tunable mechanical properties and improved performance.

Hydrolysis of Chitosan, Chitosan-Polyoxyethylene and Chitosan-Poly(2-acryloylamido-2-methylpropanesulfonic acid) by a Crude Enzyme Complex from Trichoderma viride

The degradation of chitosan using a crude enzyme complex from the soil fungus Trichoderma viride was examined in terms of temperature, pH, enzyme activity and the presence of a polymer partner. It was found that chitosan hydrolysis is not suppressed by combining it with polyoxyethylene or poly(2-acryloylamido-2-methylpropanesulfonic acid). The results on Trichoderma viride immobilized on beads imply that chitosan, as well as its polymer complexes are appropriate carriers for development of ecologically safe phytosanitary preparations.

Preparation of PLLA/PEG Nanofibers by Electrospinning and Potential Applications

Poly(L-lactide) (PLLA)/polyethylene glycol (PEG) mixed solutions were successfully electrospun into micro-or nanofibrous polymer mats. The fiber diameter was in the range 100nm-6μm. The effect of the concentration of the spinning solutions and the ratio of PLLA/PEG on the fiber diameter and morphology was investigated. The hydrophilicity was tuned by varying the PLLA/PEG ratio. The tissue compatibility of the electrospun nanofibrous scaffolds was screened using two different cell models of human dermal fibroblasts and the osteoblast-like cell line MG-63. Both types of cells attached uniformly and approximately equally to all PLLA/PEG nanofibers. In long-term cultures osteoblast-like cells tend to spatially organize in tissue-like structure, particularly within the scaffold with the highest PEG content (PLLA/PEG at weight ratio 70/30). These results indicate that PLLA mixed with hydrophilic PEG produces a promising new biocompatible material for engineering scaffolds.

From design of bio-based biocomposite electrospun scaffolds to osteogenic differentiation of human mesenchymal stromal cells

Electrospinning coupled with electrospraying provides a straightforward and robust route toward promising electrospun biocomposite scaffolds for bone tissue engineering. In this comparative investigation, four types of poly(3-hydroxybutyrate) (PHB)-based nanofibrous scaffolds were produced by electrospinning a PHB solution, a PHB/gelatin (GEL) mixture or a PHB/GEL/nHAs (hydroxyapatite nanoparticles) mixed solution, and by electrospinning a PHB/GEL solution and electrospraying a nHA dispersion simultaneously. SEM and TEM analyses demonstrated that the electrospun nHA-blended framework contained a majority of nHAs trapped within the constitutive fibers, whereas the electrospinning-electrospraying combination afforded fibers with a rough surface largely covered by the bioceramic. Structural and morphological characterizations were completed by FTIR, mercury intrusion porosimetry, and contact angle measurements. Furthermore, an in vitro investigation of human mesenchymal stromal cell (hMSC) adhesion and proliferation properties showed a faster cell development on gelatin-containing scaffolds. More interestingly, a long-term investigation of hMSC osteoblastic differentiation over 21 days indicate that hMSCs seeded onto the nHA-sprayed scaffold developed a significantly higher level of alkaline phosphatase activity, as well as a higher matrix biomineralization rate through the staining of the generated calcium deposits: the fiber surface deposition of nHAs by electrospraying enabled their direct exposure to hMSCs for an efficient transmission of the bioceramic osteoinductive and osteoconductive properties, producing a suitable biocomposite scaffold for bone tissue regeneration.

Electrospun Polyacrylonitrile Nanofibrous Membranes Tailored for Acetylcholinesterase Immobilization

Nanofibrous polyacrylonitrile membranes (PANNFM) were obtained by electrospinning and then prepared for immobilizing acetylcholinesterase (AChE). Initially, the chemical modification of PANNFM with ethylenediamine produced reactive groups to overcome their inertness and hydrophobicity. The natural polymer, chitosan, was then tethered on the nanofibrous membranes to improve their biocompatibility. Scanning electron microscopy (SEM) and cross-section SEM were used to determine morphological and porosity changes of the membranes. The immobilized AChE had greater relative activity as well as thermal and storage stability compared to the free enzyme. The bound AChE showed excellent reusability. Chitosan-modified PANNFM was shown to be a suitable strategy for facile immobilization of AChE to produce a promising system that effectively supports biocatalysts.

Poly(acrylonitrile)chitosan composite membranes for urease immobilization

(Poly)acrylonitrile/chitosan (PANCHI) composite membranes were prepared. The chitosan layer was deposited on the surface as well as on the pore walls of the base membrane. This resulted in the reduction of the pore size of the membrane and in an increase of their hydrophilicity. The pore structure of PAN and PANCHI membranes were determined by TEM and SEM analyses. It was found that the average size of the pore under a selective layer base PAN membrane is 7 microm, while the membrane coated with 0.25% chitosan shows a reduced pore size--small or equal to 5 microm and with 0.35% chitosan--about 4 microm. The amounts of the functional groups, the degree of hydrophilicity and transport characteristics of PAN/Chitosan composite membranes were determined. Urease was covalently immobilized onto all kinds of PAN/chitosan composite membranes using glutaraldehyde. Both the amount of bound protein and relative activity of immobilized urease were measured. The highest activity (94%) was measured for urease bound to PANCHI2 membranes (0.25% chitosan). The basic characteristics (pH(opt), pH(stability), T(opt), T(stability), heat inactivation and storage stability) of immobilized urease were determined. The obtained results show that the poly(acrylonitrile)chitosan composite membranes are suitable for enzyme immobilization.

Magnetic hydrogel beads based on chitosan

A novel effective route for incorporating magnetic material in chitosan beads by capillary extrusion is proposed. Magnetic material (Fe3O4) with particle size 2 μm and 10 nm was used. The weight ratio chitosan : Fe3O4 was varied in the range from 4:1 to 1:1. The obtained magnetic beads were modified by physical crosslinking with CuSO4, chemical crosslinking with epichlorohydrin, or were coated with a polyelectrolyte complex chitosan/poly(2-acryloylamido-2-methylpropanesulfonic acid). The morphology and the magnetic properties of the beads were studied by optical and scanning electron microscopy, and magnetometry. The magnetisation values of the beads increased on increasing the proportion of Fe3O4. A magnetic field intensity of 6 kOe was completely enough to reach orientation of all dipole moments of the incorporated Fe3O4. The magnetic beads completely sorbed a model dye - reactive red - from its aqueous solution, thus implying that such materials might be used for wastewater treatment in textile industry.

Novel polyelectrolyte complex between chitosan and poly(2-acryloylamido-2-methylpropanesulfonic acid-coacrylic acid)

A novel polyelectrolyte complex between chitosan and copolymers of 2- acryloylamido-2-methylpropanesulfonic acid (AMPS) and acrylic acid (AA) has been prepared. The formation of the complex has been studied viscometrically, gravimetrically and turbidimetrically in the pH range from 1.2 to 5.8. The stoichiometry and the yield of the complex depend on the copolymer composition and on the pH value of the medium. In the case of copolymers with low content of AMPS units the complexes are enriched in copolymer when formed in the pH range from 1.2 to 4.8. In this pH region mainly AMPS units take part in complex formation. A stoichiometric complex forms only at higher pH values due to the increased number of complexable carboxylate ions of AA units. The stoichiometry of the complexes prepared from copolymers with higher content of AMPS units is close to equimolar and is less sensitive to pH. The obtained complexes are stable up to pH 8. It has been shown that chitosan once included in the complexes remains degradable under the action of a crude enzyme complex produced by the soil fungus Trichoderma viride. The rate of the enzymatic hydrolysis decreases in the order chitosan/PAA > chitosan/P(AMPS-co-AA) > chitosan/PAMPS. Tests on the proliferation of T. viride embedded in chitosan beads have shown that coating the beads with chitosan/P(AMPS-co-AA) complex does not hamper the development of the microorganisms.