Toxicity assessment of organomodified clays used in food contact materials on human target cell lines
Houtman, J. ; Maisanaba, S. ; Puerto, M. ; Gutierrez-Praena, D. ; Jorda, M. ; Aucejo, S. ; Jos, A. - \ 2014
Applied Clay Science 90 (2014). - ISSN 0169-1317 - p. 150 - 158.
packaging applications - in-vitro - nanocomposites - montmorillonite - nanomaterials - genotoxicity
Nowadays, the incorporation of organomodified clays based on montmorillonite into polymers intended for packaging industry is a reality. The final result is a polymer nanocomposite with enhanced barrier properties. Different organomodified clays are already commercially available and others new ones are being developed; however little is known about their safety. In the present work, the cytotoxic effects (a tetrazolium salt reduction and protein content) of three organomodified clays, Cloisite (R) 20A, a commercial clay, and Clay 1 and Clay 2, two novel modified clays developed by the Packaging, Transport, & Logistics Research Institute, were evaluated in Caco-2 and HepG2 cells after 24 and 48 h of exposure. Our results showed that only Clay 2 induced toxic effects in both cell lines. The mean effective concentration was calculated for each case, showing Caco-2 to be more sensitive than HepG2. Moreover, in order to elucidate the toxicity mechanisms of Clay 2, different mechanistic biomarkers were investigated. Interleukin leakage and generation of intracellular reactive oxygen species were not observed, whereas glutathione content decreased in HepG2. DNA damage (comet assay) was induced in both cell lines at the highest concentration tested. Overall, results show that the type of day, the concentrations range and the type of cell line play an important role in the toxicity observed. (C) 2014 Elsevier B.V. All rights reserved.
A physical cross-linking process of cellulose nanofibril gels with shear-controlled fibril orientation
Fall, A.B. ; Lindstrom, S.B. ; Sprakel, J.H.B. ; Wagberg, L. - \ 2013
Soft Matter 9 (2013)6. - ISSN 1744-683X - p. 1852 - 1863.
dynamic light-scattering - microfibrillated cellulose - nanocomposites - polyelectrolyte - mechanism - networks - modulus
Cellulose nanofibrils constitute the smallest fibrous components of wood, with a width of approximately 4 nm and a length in the micrometer range. They consist of aligned linear cellulose chains with crystallinity exceeding 60%, rendering stiff, high-aspect-ratio rods. These properties are advantageous in the reinforcement components of composites. Cross-linked networks of fibrils can be used as templates into which a polymer enters. In the semi-concentrated regime (i.e. slightly above the overlap concentration), carboxy methylated fibrils dispersed in water have been physically cross-linked to form a volume-spanning network (a gel) by reducing the pH or adding salt, which diminishes the electrostatic repulsion between fibrils. By applying shear during or after this gelation process, we can orient the fibrils in a preferred direction within the gel, for the purpose of fully utilizing the high stiffness and strength of the fibrils as reinforcement components. Using these gels as templates enables precise control of the spatial distribution and orientation of the dispersed phase of the composites, optimizing the potentially very large reinforcement capacity of the nanofibrils.
Direct access to mesoporous crystalline TiO2/carbon composites with large and uniform pores for use as anode materials in lithium ion batteries
Lee, J. ; Jung, Y.S. ; Warren, S.C. ; Kamperman, M.M.G. ; Oh, S.M. ; DiSalvo, F.J. ; Wiesner, U. - \ 2011
Macromolecular Chemistry and Physics 212 (2011)4. - ISSN 1022-1352 - p. 383 - 390.
metal-oxides - electrode material - cathode materials - carbon nanotubes - anatase tio2 - performance - intercalation - frameworks - nanocomposites - nanoparticles
Mesoporous and highly crystalline TiO2 (anatase)/carbon composites with large (>5¿nm) and uniform pores were synthesized using PI-b-PEO block copolymers as structure directing agents. Pore sizes could be tuned by utilizing block copolymers with different molecular weights. The resulting mesoporous TiO2/carbon was successfully used as an anode material for Li ion batteries. Without addition of conducting aid (Super P), the electrode showed high capacity during the first insertion/desertion cycle due to carbon wiring inside the walls of mesoporous TiO2/carbon. The electrode further showed stable cycle performance up to 50 cycles and the specific charge capacity at 30¿C was 38¿mA h (g of TiO2)-1, which indicates CCM-TiO2/carbon can be used as a material for high rate use.
Nanomanufacturing of continuous composite nanofibers with confiment-induced morphologies
Kamperman, M.M.G. ; Korley, L.T.J. ; Yau, B. ; Johansen, K.M. ; Joo, Y.L. ; Wiesner, U. - \ 2010
Polymer Chemistry 1 (2010)7. - ISSN 1759-9954 - p. 1001 - 1004.
block-copolymer nanofibers - styrene triblock copolymer - high-temperature ceramics - lamellar morphology - electrospun fibers - diblock copolymers - diameter fibers - nanocomposites - mesostructures - microphase
Continuous core-shell nanofibers with poly(isoprene-block-dimethylaminoethyl methacrylate) (PI-b-PDMAEMA) block copolymer/polymer derived ceramic (PDC) precursor nanocomposites as cores enveloped in rigid polyacrylonitrile (PAN) shells were nanomanufactured using coaxial electrospinning. The cylindrical confinement imposed by the rigid shell led to ordered morphologies in the core not observed in bulk block copolymer nanocomposites.