All issues / Volume 12 (2018) / Issue 8 (August)
This is an editorial article. It has no abstract.
Abdominal hernia is a purely surgical disorder where due to a defect in the abdominal wall, tissues or organs can extrude out of the abdominal cavity. The only conclusive treatment is surgical making a mesh implantation indispensable. Tissue engineering is now a promising method for creating scaffolds that provide an adequate support for tissue ingrowth. Our purpose was to develop a non-adhesive hernia mesh, which could be used in the repair of abdominal wall hernias but concurrently a scaffold for abdominal tissue regeneration. Poly(vinyl alcohol) bulk hydrogels are promising materials in wound dressing hence, interest in electrospun poly(vinyl alcohol) meshes has emerged in the past few years for different biomedical applications. In the present paper, preparation of electrospun poly(vinyl alcohol) fiber membranes and their in vitro and in vivo behaviors were followed to study the adhesion, biocompatibility, and biodegradability of the meshes. Our results showed that the surface of PVA meshes does not favor cell adhesion in vitro. During the animal experiments, PVA meshes demonstrated good integration into the surrounding tissue with minimal inflammatory reaction and minimal adhesions to intra abdominal structures.
A novel pH and redox responsive system of sub-100 nm nanogels was prepared by arm-first approach via Diels-Alder click reaction. First, well-defined poly(ethylene glycol)-block-poly(styrene-alt-maleic anhydride) (PEG-b-PSM) was synthesized and subsequently functionalized with furfuryl amine, leading to the formation of the dual-functional block copolymer of PEG-b-PSMf. The furfuryl groups in the PSMf block were employed to incorporate a redox-responsive linkage and the carboxylic acid moieties generated through functionalization acted as a pH-responsive part. The Diels-Alder click reaction between a bismaleimide crosslinker and PEG-b-PSMf was conducted at 60 °C, affording star-like nanogel structures. Doxorubicin, a model anticancer drug, was loaded into to the core of the nanogels primarily by the ionic interaction with carboxylates of core blocks and a highest drug loading capacity of 38.1% was obtained. Furthermore, the in vitro profile showed a low release percentage (11.2%) of DOX at PBS pH 7.4, whereas a burst release (62%) at pH 5.0 in the presence of 10 mM glutathione, indicating the effective pH and redox responsive characteristic of the PEG-b-PSMf nanogels.
Surface patterns with controllable features are constructed via the evaporation of an acetone solution of poly(methyl methacrylate) under the confinement of a copper tube. The effects of the dimensions of copper tube and the substrate temperature on the surface patterns are systematically studied. For the substrate temperature in the range of 30 to 50 °C, the surface patterns are concentric rings consisting of waved rings and/or linked beads. The wavelength of the concentric rings decreases with the increase of the height of copper tube, and is dependent on the substrate temperature. At the substrate temperature of 20 °C, surface patterns are presented in wrinkling-like shape. At the substrate temperature of 10 °C, ‘breath figure’phenomenon occurs, and ‘hole network’ patterns are formed. A summary of the geometrical characteristics of the surface patterns is given, which can be used to better design and control evaporation-induced surface patterns.
This work provides a comprehensive investigation of the anisotropic mechanical and electrical properties of elastomeric nanocomposites based on natural rubber and sp2 carbon allotropes. They can be either nanometric and with high shape anisotropy like Carbon Nanotubes (CNT) and lamellar nanographite, or nanostructured and nearly isometric like carbon black. Studies were performed on calendered and compression molded plates. A complete mechanical characterization along all main directions could be performed by a non-standard testing approach. Composites with nanometric, high aspect ratio fillers gave rise to remarkable mechanical anisotropy, revealing an orthotropic and transversally isotropic response: modulus values were very similar in the sheet plane and much larger (almost twice as much) in the orthogonal direction. The electrical anisotropy achieved its maximum at lower CNT content. Composites with carbon black did not reveal mechanical anisotropy, while, quite strikingly, a very large electrical anisotropy was observed for carbon black content close to the percolation threshold. These results provide insights into the anisotropic behavior of nanofilled elastomers, and could pave the way to their exploitation in advanced engineering design and biomimicking biomedical applications.
For the first time since its formulation in 1986, the theoretical approach proposed by Helmis, Heinrich and Straube (HHS model), which considers the contribution of topological restrictions from entanglements to the swelling of polymer networks, is applied to experimental data. The main aspects and key equations are reviewed and their application is illustrated for unfilled rubber compounds. The HHS model is based on real networks and gives new perspectives to the interpretation of experimental swelling data for which the entanglement contributions are usually neglected by considering phantom network models. This investigation applies a reliable constrained-chain approach through a deformation-dependent tube model for defining the elastic contribution of swollen networks, which is one of the main limitations on the applicability of classical (affine) Flory-Rehner and (non-affine) phantom models. This short communication intends to provide a baseline for the application and validation of this modern approach for a broader class of rubber materials.
This work presents a new approach to synthesize the colloidal ODA-MMT-poly(maleic anhydride-alt-1-dodecene)-g-α,ω-methoxyhydroxyl-PEO/silver nanoparticles (AgNPs) nanohybrid composites (NHC) using the following synthetic pathways: (1) complex-radical alternating copolymerization of maleic anhydride with 1-dodecene α-olefin comonomer, (2) grafting of PEO onto alternating copolymer through esterification, (3) intercalating a copolymer-g-PEO between organoclay layers via complex formation of maleate carboxyl with octadecyl amine, and (4) in situ generation of AgNPs in polymer nanocomposite by annealing method under vacuum. The obtained multifunctional NHCs with different contents of AgNPs were characterized by UV spectroscopy, ζ-potential and size analysis methods. It was demonstrated that annealing of the colloidal NHC is accompanied with in situ generation of stable and partially protonated AgNPs due to specific reducing and stabilizing effects of multifunctional matrix polymer contained positively charged reactive and bioactive sites. Antibacterial and antifungal activities against Gram-negative and Gram-positive bacteria and fungal microorganism were investigated. The cytotoxic, apoptotic and necrotic effects in NHC/L929 fibroblast cells systems were evaluated. The synthesized watersoluble, biocompatible, and bioactive colloidal NHCs are promising candidate for a wide-range of applications in air filtration, food packaging systems, bioengineering, especially in tissue regeneration and nanomedicine.
We report on unique enhancement of fracture resistance of poly(methyl methacrylate) (PMMA) using short and low bending modulus poly(p-phenylene-2,6-benzobisoxazole) (PBO) fibers. While no significant effect of the PBO fibers on stiffness and strength was observed, the strain at break and fracture energy were enhanced substantially. The in situ observations of damage development during the tensile tests showed that the additional extrinsic toughening mechanisms consists of homogenous distribution of micro-cracking and delocalization of the deformation sites to the whole volume of the sample with micro-cracks bridged by the entangled PBO fiber mesh. Employing unique toughening mechanisms of PBO fiber network in hybrid PMMA/CF/PBO composites containing both carbon (CF) and PBO fibers lead to simultaneous enhancement of stiffness, strength and toughness suitable for wide range of engineering applications.