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Item Open Access Acid catalyzed cross‐linking of polyvinyl alcohol for humidifier membranes(2021) Michele, Andre; Paschkowski, Patrick; Hänel, Christopher; Tovar, Günter E. M.; Schiestel, Thomas; Southan, AlexanderPolyvinyl alcohol (PVA) is a hydrophilic polymer well known for good film forming properties, high water vapor permeance JW, and low nitrogen permeance. However, depending on molar mass and temperature, PVA swells strongly in water until complete dissolution. This behavior affects the usability of PVA in aqueous environments and makes cross‐linking necessary if higher structural integrity is envisaged. In this work, PVA networks are formed by thermal cross‐linking in the presence of p‐toluenesulfonic acid (TSA) and investigated in a design of experiments approach. Experimental parameters are the cross‐linking period tc, temperature ϑ and the TSA mass fraction wTSA. Cross‐linking is found to proceed via ether bond formation at all reaction conditions. Degradation is promoted especially by a combination of high wTSA, tc and ϑ. Thermal stability of the networks after preparation is strongly improved by neutralizing residual TSA. Humidification membranes with a JW of 6423 ± 63.0 gas permeation units (GPU) are fabricated by coating PVA on polyvinyliden fluoride hollow fibers and cross‐linking with TSA. Summarizing, the present study contributes to a clearer insight into the cross‐linking of PVA in presence of TSA, the thermal stability of the resulting networks and the applicability as selective membrane layers for water vapor transfer.Item Open Access Nano-in-micro-particles consisting of PLGA nanoparticles embedded in chitosan microparticles via spray-drying enhances their uptake in the olfactory mucosa(2021) Spindler, Lena Marie; Feuerhake, Andreas; Ladel, Simone; Günday, Cemre; Flamm, Johannes; Günday-Türeli, Nazende; Türeli, Emre; Tovar, Günter E. M.; Schindowski, Katharina; Gruber-Traub, CarmenIntranasal delivery has gained prominence since 1990, when the olfactory mucosa was recognized as the window to the brain and the central nervous system (CNS); this has enabled the direct site specific targeting of neurological diseases for the first time. Intranasal delivery is a promising route because general limitations, such as the blood-brain barrier (BBB) are circumvented. In the treatment of multiple sclerosis (MS) or Alzheimer’s disease, for example, future treatment prospects include specialized particles as delivery vehicles. Poly(lactic-co-glycolic acid) (PLGA) nanoparticles are well known as promising delivery systems, especially in the area of nose-to-brain (N2B) delivery. Chitosan is also broadly known as a functional additive due to its ability to open tight junctions. In this study, we produced PLGA nanoparticles of different sizes and revealed for the first time their size-time-dependent uptake mechanism into the lamina propria of porcine olfactory mucosa. The intracellular uptake was observed for 80 and 175 nm within only 5 min after application to the epithelium. After 15 min, even 520 nm particles were detected, associated with nuclei. Especially the presence of only 520 nm particles in neuronal fibers is remarkable, implying transcellular and intracellular transport via the olfactory or the trigeminal nerve to the brain and the CNS. Additionally, we developed successfully specialized Nano-in-Micro particles (NiMPs) for the first time via spray drying, consisting of PLGA nanoparticles embedded into chitosan microparticles, characterized by high encapsulation efficiencies up to 51%, reproducible and uniform size distribution, as well as smooth surface. Application of NiMPs accelerated the uptake compared to purely applied PLGA nanoparticles. NiMPs were spread over the whole transverse section of the olfactory mucosa within 15 min. Faster uptake is attributed to additional paracellular transport, which was examined via tight-junction-opening. Furthermore, a separate chitosan penetration gradient of ∼150 µm caused by dissociation from PLGA nanoparticles was observed within 15 min in the lamina propria, which was demonstrated to be proportional to an immunoreactivity gradient of CD14. Due to the beneficial properties of the utilized chitosan-derivative, regarding molecular weight (150-300 kDa), degree of deacetylation (80%), and particle size (0.1-10 µm) we concluded that M2-macrophages herein initiated an anti-inflammatory reaction, which seems to already take place within 15 min following chitosan particle application. In conclusion, we demonstrated the possibility for PLGA nanoparticles, as well as for chitosan NiMPs, to take all three prominent intranasal delivery pathways to the brain and the CNS; namely transcellular, intracellular via neuronal cells, and paracellular transport.Item Open Access Oral bioavailability of omega-3 fatty acids and carotenoids from the microalgae Phaeodactylum tricornutum in healthy young adults(2021) Stiefvatter, Lena; Lehnert, Katja; Frick, Konstantin; Montoya-Arroyo, Alexander; Frank, Jan; Vetter, Walter; Schmid-Staiger, Ulrike; Bischoff, Stephan C.The microalgae Phaeodactylum tricornutum (PT) contains valuable nutrients such as proteins, polyunsaturated omega-3 fatty acids (n-3 PUFA), particularly eicosapentaenoic acid (EPA) and some docosahexaenoic acid (DHA), carotenoids such as fucoxanthin (FX), and beta-glucans, which may confer health benefits. In a randomized intervention trial involving 22 healthy individuals, we administered for two weeks in a crossover manner the whole biomass of PT (5.3 g/day), or fish oil (FO) containing equal amounts of EPA and DHA (together 300 mg/day). In an additional experiment, sea fish at 185 g/week resulting in a similar EPA and DHA intake was administered in nine individuals. We determined the bioavailability of fatty acids and carotenoids and assessed safety parameters. The intake of PT resulted in a similar increase in the n-3 PUFA and EPA content and a decrease in the PUFA n-6:n-3 ratio in plasma. PT intake caused an uptake of FX that is metabolized to fucoxanthinol (FXOH) and amarouciaxanthin A (AxA). No relevant adverse effects occurred following PT consumption. The study shows that PT is a safe and effective source of EPA and FX—and likely other nutrients—and therefore should be considered as a future sustainable food item.Item Open Access Differentiation of physical and chemical cross-linking in gelatin methacryloyl hydrogels(2021) Rebers, Lisa; Reichsöllner, Raffael; Regett, Sophia; Tovar, Günter E. M.; Borchers, Kirsten; Baudis, Stefan; Southan, AlexanderGelatin methacryloyl (GM) hydrogels have been investigated for almost 20 years, especially for biomedical applications. Recently, strengthening effects of a sequential cross-linking procedure, whereby GM hydrogel precursor solutions are cooled before chemical cross-linking, were reported. It was hypothesized that physical and enhanced chemical cross-linking of the GM hydrogels contribute to the observed strengthening effects. However, a detailed investigation is missing so far. In this contribution, we aimed to reveal the impact of physical and chemical cross-linking on strengthening of sequentially cross-linked GM and gelatin methacryloyl acetyl (GMA) hydrogels. We investigated physical and chemical cross-linking of three different GM(A) derivatives (GM10, GM2A8 and GM2), which provided systematically varied ratios of side-group modifications. GM10 contained the highest methacryloylation degree (DM), reducing its ability to cross-link physically. GM2 had the lowest DM and showed physical cross-linking. The total modification degree, determining the physical cross-linking ability, of GM2A8 was comparable to that of GM10, but the chemical cross-linking ability was comparable to GM2. At first, we measured the double bond conversion (DBC) kinetics during chemical GM(A) cross-linking quantitatively in real-time via near infrared spectroscopy-photorheology and showed that the DBC decreased due to sequential cross-linking. Furthermore, results of circular dichroism spectroscopy and differential scanning calorimetry indicated gelation and conformation changes, which increased storage moduli of all GM(A) hydrogels due to sequential cross-linking. The data suggested that the total cross-link density determines hydrogel stiffness, regardless of the physical or chemical nature of the cross-links.Item Open Access The HSV1 tail-anchored membrane protein pUL34 contains a basic motif that supports active transport to the inner nuclear membrane prior to formation of the nuclear egress complex(2021) Funk, Christina; Marques da Silveira e Santos, Débora; Ott, Melanie; Raschbichler, Verena; Bailer, Susanne M.Herpes simplex virus type 1 nucleocapsids are released from the host nucleus by a budding process through the nuclear envelope called nuclear egress. Two viral proteins, the integral membrane proteins pUL34 and pUL31, form the nuclear egress complex at the inner nuclear membrane, which is critical for this process. The nuclear import of both proteins ensues separately from each other: pUL31 is actively imported through the central pore channel, while pUL34 is transported along the peripheral pore membrane. With this study, we identified a functional bipartite NLS between residues 178 and 194 of pUL34. pUL34 lacking its NLS is mislocalized to the TGN but retargeted to the ER upon insertion of the authentic NLS or a mimic NLS, independent of the insertion site. If co-expressed with pUL31, either of the pUL34-NLS variants is efficiently, although not completely, targeted to the nuclear rim where co-localization with pUL31 and membrane budding seem to occur, comparable to the wild-type. The viral mutant HSV1(17+)Lox-UL34-NLS mt is modestly attenuated but viable and associated with localization of pUL34-NLS mt to both the nuclear periphery and cytoplasm. We propose that targeting of pUL34 to the INM is facilitated by, but not dependent on, the presence of an NLS, thereby supporting NEC formation and viral replication.Item Open Access Friction and wear behavior of deep drawing tools using volatile lubricants injected through laser-drilled micro-holes(2021) Reichardt, Gerd; Henn, Manuel; Reichle, Paul; Umlauf, Georg; Riedmüller, Kim; Weber, Rudolf; Barz, Jakob; Liewald, Mathias; Graf, Thomas; Tovar, Günter E. M.In deep drawing processes, the use of lubricants is mandatory in order to prevent wear on tools and surface damage to the formed sheet metal components. Here, frequently used lubricants are synthetic and mineral oils, emulsions, and waxes. However, these conventional lubricants have to be applied to the sheet material prior to the forming operation and removed afterwards by cleaning processes. Additionally, the lubricants often contain substances that are harmful to the environment and to human health. To counteract these economic and ecological disadvantages, research is currently being conducted on a novel tribological system. For this, volatile media such as liquid carbon dioxide and gaseous nitrogen are being used, and are introduced directly into the friction zones between the tool and the sheet metal material during deep drawing under high pressure through special laser-drilled micro-holes. This paper covers the latest investigations and findings regarding the design of flow-optimized micro-holes, the laser drilling process, the friction characterization on tool radii, and the tool wear to be expected when using the lubrication medium CO2.Item Open Access The influence of flow shear on drift-wave interactions in the stellarator TJ-K(2021) Ullmann, Til; Tovar, Günter (Prof. Dr.)The investigation of the interaction between shear flows and turbulence in magnetically confined fusion plasmas is motivated by the fact that shear flows can lead to a reduction or even suppression of the turbulent transport to the vessel wall. Thus they can significantly improve the performance of future nuclear fusion power plants. Therefore, in this thesis the influence of stationary background shear and time-dependent zonal flows on the wave interactions was investigated. The turbulence-generated zonal flows not only have the character of a shear flow, but in turn extract energy from the turbulence, while they themselves do not contribute to the transport of particles to the outside. Due to this special property, the dependence of this energy transfer on the background shearing rate was investigated experimentally. Because of its low-temperature plasmas, the stellarator experiment TJ-K offers the possibility of measuring the dynamics even within the confinement area by invasive diagnostics, such as Langmuir probes. This way, the tilting of turbulent eddy structures could be related to the background shear. The Reynolds stress, as a measure for the tilting, is linearly dependent on the shearing rate. Since the energy transfer between zonal flows and turbulence is composed of the product of the Reynolds stress and the background shear, a quadratic dependence of the energy transfer on the shearing rate was expected and here experimentally confirmed. In addition, the energy transfer between turbulence and zonal flows also led to a redistribution of the spectral power in favor of the zonal flows from ≈ 5% up to ≈ 40% of the total power for increasing shearing rate. In the picture of drift-wave turbulence, the non-linearity of the dynamics is reflected in three-wave interaction. The drift waves follow resonance conditions in the wavenumber and frequency space, which in turn are linked by the dispersion relation so that not all couplings are allowed. This defined coupling space is also called the resonant manifold. Theoretical considerations by Gürcan assumed that shear flows cause the coupling space of the nonlinear three-wave interaction to contract. Experimentally, this behavior could now be demonstrated on the basis of the shear-character of time-dependent zonal flows using the method of time-resolved wavenumber-frequency bicoherence. Here, it was shown that the effective coupling space actually shrinks with the occurrence of the shear flow and expands again with the decay of the zonal flow. The results in this thesis show that E×B background shear flows, as they occur during the transition from low to highly confined fusion plasmas, can trigger turbulence-driven zonal flows, whose Reynolds stress drive was initiated by a mean tilt of the vortex structure. At the same time, shear flows can restrict the coupling space of drift waves and thus increase the importance of large-scale structures, in particular e.g. zonal flows that do not contribute to turbulent transport, as possible energy sinks. If the shear flows are zonal flows themselves, self-amplification can become effective.Item Open Access Immune status and hepatic antioxidant capacity of gilthead seabream Sparus aurata juveniles fed yeast and microalga derived β-glucans(2021) Reis, Bruno; Gonçalves, Ana Teresa; Santos, Paulo; Sardinha, Manuel; Conceição, Luís E. C.; Serradeiro, Renata; Pérez-Sánchez, Jaume; Calduch-Giner, Josep; Schmid-Staiger, Ulrike; Frick, Konstantin; Dias, Jorge; Costas, BenjamínThis work aimed to evaluate the effects of dietary supplementation with β-glucans extracted from yeast (Saccharomyces cerevisiae) and microalga (Phaeodactylum tricornutum) on gene expression, oxidative stress biomarkers and plasma immune parameters in gilthead seabream (Sparus aurata) juveniles. A practical commercial diet was used as the control (CTRL), and three others based on CTRL were further supplemented with different β-glucan extracts. One was derived from S. cerevisiae (diet MG) and two different extracts of 21% and 37% P. tricornutum-derived β-glucans (defined as Phaeo21 and Phaeo37), to give a final 0.06% β-glucan dietary concentration. Quadruplicate groups of 95 gilthead seabream (initial body weight: 4.1 ± 0.1 g) were fed to satiation three times a day for 8 weeks in a pulse-feeding regimen, with experimental diets intercalated with the CTRL dietary treatment every 2 weeks. After 8 weeks of feeding, all groups showed equal growth performance and no changes were found in plasma innate immune status. Nonetheless, fish groups fed β-glucans supplemented diets showed an improved anti-oxidant status compared to those fed CTRL at both sampling points (i.e., 2 and 8 weeks). The intestinal gene expression analysis highlighted the immunomodulatory role of Phaeo37 diet after 8 weeks, inducing an immune tolerance effect in gilthead seabream intestine, and a general down-regulation of immune-related gene expression. In conclusion, the results suggest that the dietary pulse administration of a P. tricornutum 37% enriched-β-glucans extract might be used as a counter-measure in a context of gut inflammation, due to its immune-tolerant and anti-oxidative effects.Item Open Access Synthesis of bio- and synthetic-based functional nanoparticles via inverse miniemulsion for the adsorption and detection of pharmaceuticals in aqueous media(2021) Riegger, Benjamin R.; Tovar, Günter E. M. (Prof. Dr.)Item Open Access Physikalische und chemische Wechselwirkungen in Gelatine-Methacryloyl-Lösungen und deren Vernetzung zu Hydrogelen als Trägerstruktur für Gelenkknorpel-Äquivalente(2021) Rebers, Lisa; Tovar, Günter (Prof. Dr.)