Farshad Kheiri

In vitro and in vivo assays on egg white/polyvinyl alcohol/clay nanocomposite hydrogel wound dressings

Abstract Novel nanocomposite hydrogel wound dressings on the basis of egg white and polyvinyl alcohol, as matrix, and natural Na-montmorillonite clay, as reinforcing agent, were prepared and their performances on wound healing investigated in vitro and in vivo. In vitro cytotoxicity assay revealed non-cytotoxic activity and excellent biocompatibility level of prepared nanocomposite hydrogel wound dressings. The bacterial penetration assay showed the prepared nanocomposite hydrogel wound dressings are excellent barriers against microorganisms and could protect the wound from infection during the wound healing. In vivo animal study showed that the wound healing process was considerably faster in wounds covered with nanocomposite hydrogel wound dressings compared to the conventional wound dressing, i.e. sterile gauze, due to creation of a moist environment on the wound surface and faster migration rate of the epidermal cells. The mechanical properties of healed wounds with nanocomposite hydrogel wound dressings were better than those control wounds covered with sterile gauze due to their better collagen formation ability as a result of created moist healing condition as well as the presence of egg white, as a source of proteins, in their structures.

Egg white/poly (vinyl alcohol)/MMT nanocomposite hydrogels for wound dressing

Abstract Nanocomposite hydrogels on the basis of egg white and poly (vinyl alcohol) (PVA) containing 0, 5, and 10 wt.% of montmorillonite (MMT) nanoclay were prepared by a facile cyclic freezing–thawing technique and their properties investigated for wound dressing application. The morphological, structural, thermal, physical, and in vitro cytotoxic properties of the prepared nanocomposite hydrogel wound dressings (NHWDs) were experimentally studied. The NHWDs had an exfoliated morphology with a porous structure having pores sizes in the nanometric scale. It was shown that MMT acted as cross-linker in the network of NHWDs and improved their thermal stabilities. The prepared wound dressings were transparent and their equilibrium water contents and water vapor transmission rates, as two important factors of wound dressings, were very close to the properties of human skin which means that the prepared wound dressings could interact appropriately with the damaged tissues of wounds and protect them like an artificial skin during the wound healing process. The in vitro cytotoxicity assay also confirmed the non-cytotoxic nature of the prepared NHWDs. It was finally concluded that the prepared egg white/PVA/MMT nanocomposite hydrogels are promising materials to be used as novel wound dressings in wound and burn care.

Nanoclay and Cu Nanoparticles Loaded Polyethylene Nanocomposites for Natural Gas Transfer Applications

ABSTRACT High density polyethylene nanocomposites loaded with a reinforcing filler (Cloisite 20A as a modified nanoclay) and an electrically conductive filler (Cu nanoparticles) were prepared by a melt blending method. The morphological, mechanical, thermal, and electrical properties of the prepared nanocomposites were investigated to evaluate their performances as appropriate materials for production of reinforced conductive polymeric pipes to be used in natural gas distribution and transportation pipelines. A random and uniform dispersion of both nanoparticles in the polyethylene matrix, with a nanoclay intercalated morphology, was observed by scanning electron microscopy and X-ray diffraction techniques. The results revealed ca. 117, 13 and 21% increases in the Young’s modulus, tensile strength and yield stress of the polyethylene matrix by adding 3 wt.% of Cloisite 20A into it. For the similar conditions, however, more than a 71% decrease was observed for the elongation at break. Thermal analysis demonstrated that the melting points of the nanocomposites were increased by incorporating both fillers and the crystallinity of polyethylene chains was decreased by incorporating Cloisite 20A and then slightly increased by adding Cu nanoparticles. Moreover, the results revealed the creation of conductivity inside the non-conductive polyethylene matrix due to the presence of the conductive Cu nanoparticles.

Synthetic-Natural Bionanocomposite Hydrogels on the Basis of Polyvinyl Alcohol and Egg White

ABSTRACT A series of bionanocomposite hydrogels composed of polyvinyl alcohol, a synthetic polymer, and egg white, a natural protein containing material, were prepared by the freezing- thawing cyclic method. Na-montmorillonite nanoclay (Na-MMT), as a crosslinker and reinforcing agent, with 0, 5, 10, and 15 wt% loadings (based on the dried mass of the bionanocomposite hydrogel) was incorporated in the polyvinyl alcohol and egg white hydrogel matrix. The microstructural characteristics of the prepared bionanocomposite hydrogels were characterized by the X-ray diffractometry, transmission electron microscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and gel fraction measurements. Thermal and mechanical properties of the samples were also studied using differential scanning calorimetry and dynamic mechanical-thermal analysis. The swelling and drying kinetics and mechanisms of the bionanocomposite hydrogels were also studied. The bionanocomposite hydrogels had an exfoliated Na-MMT morphology with an appropriate dispersion of nanoclay layers in the hydrogel matrix. The results showed that the Na-MMT platelets acted as crosslinkers and created a hydrogel network with a smaller pore size in the bio-nanocomposite hydrogels, compared with the clay-free hydrogel. The obtained thermal and mechanical properties confirmed the reinforcing effect of the nanoclay in the bionanocomposite hydrogels. The swelling and drying rates of the bionanocomposite hydrogels exhibited an inverse dependency on the nanoclay loading. In general, it was concluded that the prepared bionanocomposite hydrogels could be used as appropriate biomaterials in biomedical applications, especially in drug delivery, tissue engineering and wound care.