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Wondraczek H.,Abo Akademi University | Petzold-Welcke K.,Friedrich - Schiller University of Jena | Petzold-Welcke K.,Jenpolymer Materials Ltd and Co. KG | Fardim P.,Abo Akademi University | And 2 more authors.
Cellulose | Year: 2013

Nano-scaled particles were obtained from two different cellulose acetates, cellulose acetate propionate, and cellulose acetate butyrate using the emulsification solvent evaporation procedure and the low energy methods of solvent displacement (dialysis and controlled precipitation). The relationship between the formulation parameters and the particle properties were evaluated in case of the emulsification-evaporation technique. For the solvent displacement procedures, the influence of the formulation parameters, and the intrinsic polymer properties like the hydrophilic-hydrophobic balance was evaluated. Comparing the methods, it could be shown that large amounts of small and uniform nanoparticles can be obtained by the emulsification solvent evaporation procedure. The solvent displacement techniques turned out to be very easy to use and to yield narrowly distributed particles as well. © 2013 Springer Science+Business Media Dordrecht. Source


Biank H.C.,TU Ilmenau | Shokhovets S.,TU Ilmenau | Gobsch G.,TU Ilmenau | Runge E.,TU Ilmenau | And 3 more authors.
Thin Solid Films | Year: 2014

We report on the optical characterization of a low-bandgap thieno[3,4-b]pyrazine phenylenevinylene copolymer. Individual layers on quartz and Si substrates as well as layered structures on indium tin oxide covered glass with and without a PEDOT:PSS (poly(3,4-ethylenedioxythiophene)- poly(styrenesulfonate)) layer were examined using spectroscopic ellipsometry, transmission, reflectance, electroreflectance and external quantum efficiency measurements. For comparison, current-voltage and capacitance-voltage characteristics were also measured. Changes in optical spectra of the pristine polymer due to an applied external voltage are analyzed quantitatively in terms of the Stark effect which allows the determination of the exciton radius, binding energy and ionization field strength. For structures with an inserted PEDOT:PSS layer, a significant charge trapping in the polymer layer is observed that considerably modifies both optical and electrical properties. © 2013 Elsevier B.V. All rights reserved. Source


Renz J.A.,TU Ilmenau | Ashraf R.S.,Imperial College London | Erb T.,TU Ilmenau | Shokhovets S.,TU Ilmenau | And 3 more authors.
Macromolecular Chemistry and Physics | Year: 2010

Polymer/fullerene bulk heterojunction solar cells consisting of PDDTP:PCBM blends have been investigated and optimized. The structural properties of the photoactive layers were studied by GID-XRD, which revealed a pronounced response of photovoltaic parameters on the polymer crystallinity. In addition to P3HT, another donor polymer was found that develops crystalline domains upon annealing. We found a clear correlation between annealing time, power conversion efficiency, and polymer crystallinity. The PDDTP crystallization ability is a promising property. This is a first step toward the synthesis of lowbandgap polymers, which likewise show the ability to form crystalline domains and may therefore lead to a substantial increase in efficiency. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Ahrem H.,Jenpolymer Materials Ltd and Co. KG | Ahrem H.,Friedrich - Schiller University of Jena | Pretzel D.,Jena University Hospital | Pretzel D.,Friedrich - Schiller University of Jena | And 8 more authors.
Acta Biomaterialia | Year: 2014

The small size and heterogeneity of the pores in bacterial nanocellulose (BNC) hydrogels limit the ingrowth of cells and their use as tissue-engineered implant materials. The use of placeholders during BNC biosynthesis or post-processing steps such as (touch-free) laser perforation can overcome this limitation. Since three-dimensionally arranged channels may be required for homogeneous and functional seeding, three-dimensional (3-D) laser perforation of never-dried BNC hydrogels was performed. Never-dried BNC hydrogels were produced in different shapes by: (i) the cultivation of Gluconacetobacter xylinus (DSM 14666; synonym Komagataeibacter xylinus) in nutrient medium; (ii) the removal of bacterial residues/media components (0.1 M NaOH; 30 min; 100 C) and repeated washing (deionized water; pH 5.8); (iii) the unidirectional or 3-D laser perforation and cutting (pulsed CO2 Rofin SC ×10 laser; 220 μm channel diameter); and (iv) the final autoclaving (2 M NaOH; 121 C; 20 min) and washing (pyrogen-free water). In comparison to unmodified BNC, unidirectionally perforated - and particularly 3-D-perforated - BNC allowed ingrowth into and movement of vital bovine/human chondrocytes throughout the BNC nanofiber network. Laser perforation caused limited structural modifications (i.e. fiber or globular aggregates), but no chemical modifications, as indicated by Fourier transform infrared spectroscopy, X-ray photoelectron scattering and viability tests. Pre-cultured human chondrocytes seeding the surface/channels of laser-perforated BNC expressed cartilage-specific matrix products, indicating chondrocyte differentiation. 3-D-perforated BNC showed compressive strength comparable to that of unmodified samples. Unidirectionally or 3-D-perforated BNC shows high biocompatibility and provides short diffusion distances for nutrients and extracellular matrix components. Also, the resulting channels support migration into the BNC, matrix production and phenotypic stabilization of chondrocytes. It may thus be suitable for in vivo application, e.g. as a cartilage replacement material. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source


Pretzel D.,Friedrich - Schiller University of Jena | Linss S.,Friedrich - Schiller University of Jena | Ahrem H.,Jenpolymer Materials Ltd and Co. KG | Ahrem H.,Friedrich - Schiller University of Jena | And 4 more authors.
Arthritis Research and Therapy | Year: 2013

Introduction: Current therapies for articular cartilage defects fail to achieve qualitatively sufficient tissue regeneration, possibly because of a mismatch between the speed of cartilage rebuilding and the resorption of degradable implant polymers. The present study focused on the self-healing capacity of resident cartilage cells in conjunction with cell-free and biocompatible (but non-resorbable) bacterial nanocellulose (BNC). This was tested in a novel in vitro bovine cartilage punch model. Methods: Standardized bovine cartilage discs with a central defect filled with BNC were cultured for up to eight weeks with/without stimulation with transforming growth factor-β1 (TGF-β1. Cartilage formation and integrity were analyzed by histology, immunohistochemistry and electron microscopy. Content, release and neosynthesis of the matrix molecules proteoglycan/aggrecan, collagen II and collagen I were also quantified. Finally, gene expression of these molecules was profiled in resident chondrocytes and chondrocytes migrated onto the cartilage surface or the implant material. Results: Non-stimulated and especially TGF-β1-stimulated cartilage discs displayed a preserved structural and functional integrity of the chondrocytes and surrounding matrix, remained vital in long-term culture (eight weeks) without signs of degeneration and showed substantial synthesis of cartilage-specific molecules at the protein and mRNA level. Whereas mobilization of chondrocytes from the matrix onto the surface of cartilage and implant was pivotal for successful seeding of cell-free BNC, chondrocytes did not immigrate into the central BNC area, possibly due to the relatively small diameter of its pores (2 to 5 μm). Chondrocytes on the BNC surface showed signs of successful redifferentiation over time, including increase of aggrecan/collagen type II mRNA, decrease of collagen type I mRNA and initial deposition of proteoglycan and collagen type II in long-term high-density pellet cultures. Although TGF-β1 stimulation showed protective effects on matrix integrity, effects on other parameters were limited. Conclusions: The present bovine cartilage punch model represents a robust, reproducible and highly suitable tool for the long-term culture of cartilage, maintaining matrix integrity and homoeostasis. As an alternative to animal studies, this model may closely reflect early stages of cartilage regeneration, allowing the evaluation of promising biomaterials with/without chondrogenic factors. © 2013 Pretzel et al.; licensee BioMed Central Ltd. Source

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