Institute of Fundamental Technological Research

This piece of research explores porous nanocomposite polyurethane (PU) foam synthesis, containing nanolignin (NL), coated with natural antimicrobial propolis for wound dressing. PU foam was synthesized using polyethylene glycol, glycerol, NL, and 1, 6-diisocyanato-hexane (NCO/OH ratio: 1.2) and water as blowing agent. The resultant foam was immersed in ethanolic extract of propolis (EEP). PU, NL-PU, and PU-NL/EEP foams were characterized from mechanical, morphological, and chemical perspectives. NL Incorporation into PU increased mechanical strength, while EEP coating showed lower strength than PU-NL/EEP. Morphological investigations confirmed an open-celled structure with a pore diameter of 150–200 μm, a density of nearly 0.2 g/cm3,, and porosity greater than 85%, which led to significantly high water absorption (267% for PU-NL/EEP). The hydrophilic nature of foams, measured by the contact angle, proved to be increased by NL addition and EEP coating. PU and PU-NL did not show important antibacterial features, while EEP coating resulted in a significant antibacterial efficiency. All foams revealed high biocompatibility toward L929 fibroblasts, with the highest cell viability and cell attachment for PU-NL/EEP. In vivo wound healing using Wistar rats’ full-thickness skin wound model confirmed that PU-NL/EEP exhibited an essentially higher wound healing efficacy compared with other foams. Hence, PU-NL/EEP foam could be a promising wound dressing candidate.

polyurethane foam, nanolignin, propolis, wound dressing

Since the introduction of tissue engineering as an encouraging method for the repair and regeneration of injured tissue, there have been many attempts by researchers to construct bio-mimetic scaffolds which mimic the native extracellular matrix, with the aim of promoting cell growth, cell proliferation, and restoration of the tissue's native functionality. Among the different materials and methods of scaffold fabrication, one particularly promising class of materials, hydrogels, has been extensively studied, with the inclusion of nano-scaled materials into hydrogels leading to the creation of an exciting new generation of nanocomposites, known as nanocomposite hydrogels. To closely mimic the native tissue behavior, scientists have recently focused on the functionalization of incorporated nanomaterials via chiral biomolecules, with reported results showing great potential. The current article aims to introduce a perspective of nano-scaled cellulose as a promising nanomaterial which can be multi-functionalized for the fabrication of nanocomposite hydrogels with applications in tissue engineering and drug delivery systems. This article also briefly reviews the recently reported literature on nanocomposite hydrogels incorporated with chiral functionalized nanomaterials. Such knowledge paves the path for the development of tailored hydrogels toward practical applications.

scaffold, nanocomposite hydrogels, biodegradable hydrogels, chiral biomolecules, self-healing

The current work studies the electrospun poly (vinyl alcohol) (PVA) nanofibers and its nanocomposites including nanohydroxy apatite (nHAp) and nHAp/cellulose nanofibers (CNFs), emphasizing the impact of nanofillers on the toughness of nanofibers. PVA nanofibers were incorporated with 10 wt% of nHAp and then various amounts of CNF were added to subsequent PVA/nHAp fibrous nanocomposites. The morphology of nonwoven mats was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). While neat PVA nanofibers were smooth and uniform in thickness, the nanofiller loading resulted in thinner fibers with less uniformity. Furthermore, the thermal properties of the nonwoven network of fibers were characterized employing thermogravimetric analysis (TGA). Although the maximum loss mass temperature of PVA was partially reduced upon addition of nanofillers, the onset of decomposition was not altered. The mechanical characterizations were performed using static tensile and dynamic mechanical analysis (DMA). Compared to neat PVA mats, the tensile test of nanocomposites mats demonstrated the significant increase in Young's modulus; however, strain at break was dramatically reduced. In addition, the fracture work was assessed from the area under the stress-strain curve, which showed brittleness of fibrous nanocomposites due to the nanofiller incorporation. Field emission SEM (FE-SEM) was employed to scan the fracture surface of stretched fibers. The increase in modulus of electrospun mats was also shown by DMA in frequency mode. In parallel, both tensile test and DMA confirmed the change in fracture of PVA fibers from a tough to brittle mode, due to the nanofiller addition.

electrospun nanocomposites, nanofillers, toughness, mechanical properties