Entwicklung von Elastomeren geringer Dichte und hoher Verstärkung durch den Einsatz von faserigen Füllstoffen

Ein schonender Umgang mit Ressourcen und die Erforschung neuer regenerativer Füllstoffe sind wesentliche Bestandteile bei der Entwicklung neuer Elastomer-Materialien. Eine vollständige oder anteilige Substitution des am weitesten verbreiteten Füllstoffs Ruß kann in diesem Zusammenhang einen wichtigen Beitrag leisten. In dieser Arbeit wurde die Eignung und das Verstärkungspotential des am häufigsten vorkommenden Biopolymers Cellulose als Füllstoff untersucht, welche eine faserige Morphologie und eine geringe Dichte aufweist. Durch die Einarbeitung einer wässrigen Cellulose-Suspension in einen Kautschuk-Latex kann die hohe spezifische Oberfläche der nanofibrillierten Cellulose (NFC) aufrechterhalten werden und ermöglicht so die Herstellung von Elastomeren, die eine hohe Verstärkung und geringe Dichte aufweisen. Es wurden verschiedene Elastomermatrices ausgewählt und grundlegend charakterisiert. Dabei konnte gezeigt werden, dass die Einarbeitung von NFC, im Vergleich zu den hergestellten Referenz-Ruß-Systemen, in vielen Fällen zu vergleichbaren oder verbesserten Eigenschaften der Komposit-Materialien führt. Bei der Einarbeitung in eine Polychloropren-Matrix konnte gezeigt werden, dass die NFC-Materialien eine höhere Verstärkung bei niedrigeren Dehnungswerten aufweisen sowie mit steigendem Füllstoffgehalt eine deutliche Abnahme des Quellverhaltens einhergeht. Des Weiteren sind die Dichte-Werte die NFC-Materialien geringer als die der Ruß-Materialien. Die Permeabilität der Ruß- und NFC-Systeme ist ebenfalls vergleichbar. Außerdem wurde die etablierte Silica-Silan-Technologie auf Celluose übertragen, um eine Hydrophobierung und eine damit einhergehende bessere Verträglichkeit der polaren Cellulose gegenüber der unpolaren Polymermatrix zu erzielen. Zuvor musste jedoch ein zusätzlicher Verarbeitungsschritt durchgeführt werden, um die leichtflüchtigen Bestandteile, die durch das Sekundärlatexverfahren im Masterbatch zurückgeblieben sind, zu entfernen. Durch Plastifizierung der Masterbatch-Materialien konnten die leichtflüchtigen Komponenten entfernt und eine erfolgreiche Weiterverarbeitung gewährleistet werden. Die Einarbeitung verschieden modifizierter Cellulose-Varianten in eine Butylkautschuk-Matrix hat gezeigt, dass durch die Silanisierung der Cellulose die Polymer-Füllstoff-Wechselwirkungen erheblich verbessert werden konnte. Dies hat sich in einer Zunahme der Reißfestigkeit, einer Abnahme des Quellgrads und in einer deutlichen Reduktion der Permeabilität gezeigt. Die Auswirkungen des statischen und dynamischen Koagulationsverfahrens wurden ebenfalls untersucht. Dabei konnte gezeigt werden, dass das dynamische Koagulationsverfahren („Continuous Dynamic Latex Compounding“, CDLC) zu einer besseren Füllstoffdispersion beigetragen hat und dadurch Elastomere hergestellt werden konnten, die bessere Materialeigenschaften aufweisen. Dies wurde unter anderem an Mischungen untersucht, bei denen Acrylnitril-Butadien-Kautschuk als Polymermatrix eingesetzt wurde. Anhand der vorliegenden Ergebnisse und der breiten Untersuchungen in verschiedenen Polymeren konnte gezeigt werden, dass Cellulose eine nachhaltige Alternative zu den etablierten Füllstoffen darstellt und es möglich ist, Elastomere mit geringer Dichte und einer hohen Verstärkung herzustellen.The efficient handling of resources and research into new regenerative fillers are essential components of the development of new elastomer materials. A complete or partial substitution of the most common filler carbon black can make an important contribution in this context. In this paper, the suitability and the reinforcement potential of the most common biopolymer cellulose as a filler was investigated as it has a fibrous morphology and low density. By incorporating an aqueous cellulosic suspension into a rubber latex, the high specific surface area of nanofibrillated cellulose (NFC) can be maintained, enabling the production of elastomers that feature high reinforcement and low density. Various elastomer matrices were selected and fundamentally characterized. It could be shown that the incorporation of NFC, compared to the manufactured reference carbon black systems, led to comparable or improved properties of the composite materials in many cases. When incorporated into a polychloroprene matrix, it could be shown that the NFC materials have higher reinforcement at lower elongation values and that the swelling behavior decreases significantly with increasing filler content. Furthermore, the density values of the NFC materials are lower than those of the carbon black materials. The permeability of the carbon black and NFC systems is comparable. In addition, the established silica-silane technology was transferred to cellulose in order to make the polar cellulose hydrophobic and thus more compatible with the non-polar polymer matrix. Before that, however, an additional processing step had to be carried out in order to remove the volatile components that remained in the masterbatch as a result of the secondary latex process. By plasticizing the masterbatch materials, the volatile components could be removed and a successful further processing ensured. The incorporation of differently modified cellulose variants into a butyl rubber matrix has shown that the polymer-filler interactions can be significantly improved by silanizing the cellulose. This was reflected in an increase in tear strength, a decrease in the degree of swelling and a significant reduction in permeability. The effects of the static and dynamic coagulation procedure were also studied. It could be shown that the dynamic coagulation process (“Continuous Dynamic Latex Compounding”, CDLC) has contributed to better filler dispersion and, as a result, it has been possible to produce elastomers with better material properties. This was investigated, among other things, on mixtures in which acrylonitrile butadiene rubber was used as the polymer matrix. Based on the present results and the broad investigations in different polymers, it could be shown that cellulose represents a sustainable alternative to the established fillers and that it is possible to produce elastomers with low density and high reinforcement

Etablierung eines in vitro-Modells zur Untersuchung der Regeneration spinaler Motorneurone und ihrer Axone nach Axotomie und Neurodegeneration

Magdeburg, Univ., Fak. für Naturwiss., Diss., 2015von Josephine Pinkernell

Magnetic nanoparticles in primary neural cell cultures are mainly taken up by microglia

<p>Abstract</p> <p>Background</p> <p>Magnetic nanoparticles (MNPs) offer a large range of applications in life sciences. Applications in neurosciences are one focus of interest. Unfortunately, not all groups have access to nanoparticles or the possibility to develop and produce them for their applications. Hence, they have to focus on commercially available particles. Little is known about the uptake of nanoparticles in primary cells. Previously studies mostly reported cellular uptake in cell lines. Here we present a systematic study on the uptake of magnetic nanoparticles (MNPs) by primary cells of the nervous system.</p> <p>Results</p> <p>We assessed the internalization in different cell types with confocal and electron microscopy. The analysis confirmed the uptake of MNPs in the cells, probably with endocytotic mechanisms. Furthermore, we compared the uptake in PC12 cells, a rat pheochromocytoma cell line, which is often used as a neuronal cell model, with primary neuronal cells. It was found that the percentage of PC12 cells loaded with MNPs was significantly higher than for neurons. Uptake studies in primary mixed neuronal/glial cultures revealed predominant uptake of MNPs by microglia and an increase in their number. The number of astroglia and oligodendroglia which incorporated MNPs was lower and stable. Primary mixed Schwann cell/fibroblast cultures showed similar MNP uptake of both cell types, but the Schwann cell number decreased after MNP incubation. Organotypic co-cultures of spinal cord slices and peripheral nerve grafts resembled the results of the dispersed primary cell cultures.</p> <p>Conclusions</p> <p>The commercial MNPs used activated microglial phagocytosis in both disperse and organotypic culture systems. It can be assumed that <it>in vivo </it>application would induce immune system reactivity, too. Because of this, their usefulness for <it>in vivo </it>neuroscientific implementations can be questioned. Future studies will need to overcome this issue with the use of cell-specific targeting strategies. Additionally, we found that PC12 cells took up significantly more MNPs than primary neurons. This difference indicates that PC12 cells are not a suitable model for natural neuronal uptake of nanoparticles and qualify previous results in PC12 cells.</p

Growth factor choice is critical for successful functionalization of nanoparticles

Nanoparticles (NPs) show new characteristics compared to the corresponding bulk material. These nanoscale properties make them interesting for various applications in biomedicine and life sciences. One field of application is the use of magnetic NPs to support regeneration in the nervous system. Drug delivery requires a functionalization of NPs with bio-functional molecules. In our study, we functionalized self-made PEI-coated iron oxide NPs with nerve growth factor (NGF) and glial cell-line derived neurotrophic factor (GDNF). Next, we tested the bio-functionality of NGF in a rat pheochromocytoma cell line (PC12) and the bio-functionality of GDNF in an organotypic spinal cord culture. Covalent binding of NGF to PEI-NPs impaired bio-functionality of NGF, but non-covalent approach differentiated PC12 cells reliably. Non-covalent binding of GDNF showed a satisfying bio-functionality of GDNF:PEI-NPs, but turned out to be unstable in conjugation to the PEI-NPs. Taken together, our study showed the importance of assessing bio-functionality and binding stability of functionalized growth factors using proper biological models. It also shows that successful functionalization of magnetic NPs with growth factors is dependent on the used binding chemistry and that it is hardly predictable. For use as therapeutics, functionalization strategies have to be reproducible and future studies are needed

Micro-computed tomography of pulmonary fibrosis in mice induced by adenoviral gene transfer of biologically active transforming growth factor-β1

<p>Abstract</p> <p>Background</p> <p>Micro-computed tomography (micro-CT) is a novel tool for monitoring acute and chronic disease states in small laboratory animals. Its value for assessing progressive lung fibrosis in mice has not been reported so far. Here we examined the importance of in vivo micro-CT as non-invasive tool to assess progression of pulmonary fibrosis in mice over time.</p> <p>Methods</p> <p>Pulmonary fibrosis was induced in mice by intratracheal delivery of an adenoviral gene vector encoding biologically active TGF-ß1 (AdTGF-ß1). Respiratory gated and ungated micro-CT scans were performed at 1, 2, 3, and 4 weeks post pulmonary adenoviral gene or control vector delivery, and were then correlated with respective histopathology-based Ashcroft scoring of pulmonary fibrosis in mice. Visual assessment of image quality and consolidation was performed by 3 observers and a semi-automated quantification algorithm was applied to quantify aerated pulmonary volume as an inverse surrogate marker for pulmonary fibrosis.</p> <p>Results</p> <p>We found a significant correlation between classical Ashcroft scoring and micro-CT assessment using both visual assessment and the semi-automated quantification algorithm. Pulmonary fibrosis could be clearly detected in micro-CT, image quality values were higher for respiratory gated exams, although differences were not significant. For assessment of fibrosis no significant difference between respiratory gated and ungated exams was observed.</p> <p>Conclusions</p> <p>Together, we show that micro-CT is a powerful tool to assess pulmonary fibrosis in mice, using both visual assessment and semi-automated quantification algorithms. These data may be important in view of pre-clinical pharmacologic interventions for the treatment of lung fibrosis in small laboratory animals.</p

CARS microscopy for the visualization of micrometer-sized iron oxide MRI contrast agents in living cells

Micrometer-sized iron oxide particles (MPIOs) attract increasing interest as contrast agents for cellular tracking by clinical Magnetic Resonance Imaging (MRI). Despite the great potential of MPIOs for in vivo imaging of labeled cells, little is known on the intracellular localization of these particles following uptake due to the lack of techniques with the ability to monitor the particle uptake in vivo at single-cell level. Here, we show that coherent anti-Stokes Raman scattering (CARS) microscopy enables non-invasive, label-free imaging of MPIOs in living cells with sub-micron resolution in three dimensions. CARS allows simultaneous visualization of the cell framework and the MPIOs, where the particles can be readily distinguished from other cellular components of comparable dimensions, and localized inside the cell

In vivo imaging of pancreatic tumours and liver metastases using 7 Tesla MRI in a murine orthotopic pancreatic cancer model and a liver metastases model

<p>Abstract</p> <p>Background</p> <p>Pancreatic cancer is the fourth leading cause of tumour death in the western world. However, appropriate tumour models are scarce. Here we present a syngeneic murine pancreatic cancer model using 7 Tesla MRI and evaluate its clinical relevance and applicability.</p> <p>Methods</p> <p>6606PDA murine pancreatic cancer cells were orthotopically injected into the pancreatic head. Liver metastases were induced through splenic injection. Animals were analyzed by MRI three and five weeks following injection. Tumours were detected using T2-weighted high resolution sequences. Tumour volumes were determined by callipers and MRI. Liver metastases were analyzed using gadolinium-EOB-DTPA and T1-weighted 3D-Flash sequences. Tumour blood flow was measured using low molecular gadobutrol and high molecular gadolinium-DTPA.</p> <p>Results</p> <p>MRI handling and applicability was similar to human systems, resolution as low as 0.1 mm. After 5 weeks tumour volumes differed significantly (p < 0.01) when comparing calliper measurments (n = 5, mean 1065 mm³+/-243 mm³) with MRI (mean 918 mm³+/-193 mm³) with MRI being more precise. Histology (n = 5) confirmed MRI tumour measurements (mean size MRI 38.5 mm²+/-22.8 mm²versus 32.6 mm²+/-22.6 mm²(histology), p < 0,0004) with differences due to fixation and processing of specimens. After splenic injection all mice developed liver metastases with a mean of 8 metastases and a mean volume of 173.8 mm³+/-56.7 mm³after 5 weeks. Lymphnodes were also easily identified. Tumour accumulation of gadobutrol was significantly (p < 0.05) higher than gadolinium-DTPA. All imaging experiments could be done repeatedly to comply with the 3R-principle thus reducing the number of experimental animals.</p> <p>Conclusions</p> <p>This model permits monitoring of tumour growth and metastasis formation in longitudinal non-invasive high-resolution MR studies including using contrast agents comparable to human pancreatic cancer. This multidisciplinary environment enables radiologists, surgeons and physicians to further improve translational research and therapies of pancreatic cancer.</p

Enduring Effects of Paternal Deprivation in California Mice (Peromyscus californicus): Behavioral Dysfunction and Sex-Dependent Alterations in Hippocampal New Cell Survival

Partial funding for Open Access provided by the UMD Libraries' Open Access Publishing Fund.Early-life experiences with caregivers can significantly affect offspring development in human and non-human animals. While much of our knowledge of parent-offspring relationships stem from mother-offspring interactions, increasing evidence suggests interactions with the father are equally as important and can prevent social, behavioral, and neurological impairments that may appear early in life and have enduring consequences in adulthood. In the present study, we utilized the monogamous and biparental California mouse (Peromyscus californicus). California mouse fathers provide extensive offspring care and are essential for offspring survival. Non-sibling virgin male and female mice were randomly assigned to one of two experimental groups following the birth of their first litter: (1) biparental care: mate pairs remained with their offspring until weaning; or (2) paternal deprivation (PD): paternal males were permanently removed from their home cage on postnatal day (PND) 1. We assessed neonatal mortality rates, body weight, survival of adult born cells in the dentate gyrus of the hippocampus, and anxiety-like and passive stress-coping behaviors in male and female young adult offspring. While all biparentally-reared mice survived to weaning, PD resulted in a ~35% reduction in survival of offspring. Despite this reduction in survival to weaning, biparentally-reared and PD mice did not differ in body weight at weaning or into young adulthood. A sex-dependent effect of PD was observed on new cell survival in the dentate gyrus of the hippocampus, such that PD reduced cell survival in female, but not male, mice. While PD did not alter classic measures of anxiety-like behavior during the elevated plus maze task, exploratory behavior was reduced in PD mice. This observation was irrespective of sex. Additionally, PD increased some passive stresscoping behaviors (i.e., percent time spent immobile) during the forced swim task—an effect that was also not sex-dependent. Together, these findings demonstrate that, in a species where paternal care is not only important for offspring survival, PD can also contribute to altered structural and functional neuroplasticity of the hippocampus. The mechanisms contributing to the observed sex-dependent alterations in new cell survival in the dentate gyrus should be further investigated

Einsatz der mobilen Computertomographie in der Intensivmedizin

Thema: Ziel der Studie war die Evaluierung der mobilen CT im intensivmedizinischen Einsatz Methodik: Es wurde eine Prozessanalyse der mobilen CT in einem Interventionsraum auf der Intensivstation sowie der ortsfesten CT in der radiologischen Abteilung vorgenommen. Der klinische Teil richtete sich auf die Evaluierung des intensivmedizinischen Personals bezüglich der Bewertung der mobilen CT. Weiterhin wurden die mit der mobilen CT untersuchten Patienten hinsichtlich ihrer Transportfähigkeit anhand intensivmedizinischer Bewertungssysteme bewertet. Ergebnisse: Die CT-Untersuchungen mit der mobilen CT im Interventionsraum haben einen leichten zeitlichen Vorteil gegenüber denen in der radiologischen Abteilung (55 vs 65 Minuten). Die mobile CT wurde von der Mehrheit des intensivmedizinischen Personals positiv bewertet, z.B. empfanden sie 81 % der Ärzte sowie mehr als 50 % der Pflegekräfte als Arbeitserleichterung. Bei vier der 24 untersuchten Patienten hätte es keine Alternative zur mobilen CT gegeben. Schlussfolgerung: Die mobile CT hat sich im klinischen Einsatz bewährt. Sie gewährleistet eine kontinuierliche intensivmedizinische Umgebung bei der CT-Untersuchung. Darüber hinaus ermöglicht sie bei nicht transportfähigen Patienten eine adäquate radiologische Diagnostik.Purpose: To evaluate portable CT in ICU settings. Methods: Assessment of workflow of portable and stationary CT. Evaluation of ICU staff by questionnaire. Risk of transportation Assessment of examined patients by ICU-scores). Results: Examination by portable CT is little less time consuming compared to CT-examination in the radiology department (55 vs. 65 minutes). There was a great acceptance of portable CT by ICU staff. 81 % of ICU physicians and more than 50 % of nurses assessed portable CT as a reduction of work load. Portable CT could not have been missed in four of 24 examined patients for examination by computed tomography. Conclusions: Portable CT enables ICU-care to be continued during CT-examination. By Bedside CT patients can be examined who otherwise would have to abandon advanced radiologic diagnostic