Optimization of cell-laden bioinks for 3D bioprinting and efficient infection with influenza A virus

Bioprinting is a new technology, which arranges cells with high spatial resolution, but its potential to create models for viral infection studies has not yet been fully realized. The present study describes the optimization of a bioink composition for extrusion printing. The bioinks were biophysically characterized by rheological and electron micrographic measurements. Hydrogels consisting of alginate, gelatin and Matrigel were used to provide a scaffold for a 3D arrangement of human alveolar A549 cells. A blend containing 20% Matrigel provided the optimal conditions for spatial distribution and viability of the printed cells. Infection of the 3D model with a seasonal influenza A strain resulted in widespread distribution of the virus and a clustered infection pattern that is also observed in the natural lung but not in two-dimensional (2D) cell culture, which demonstrates the advantage of 3D printed constructs over conventional culture conditions. The bioink supported viral replication and proinflammatory interferon release of the infected cells. We consider our strategy to be paradigmatic for the generation of humanized 3D tissue models by bioprinting to study infections and develop new antiviral strategies.DFG, 325093850, Open Access Publizieren 2017 - 2018 / Technische Universität Berli

An observational study of ballooning in large spiders: Nanoscale multifibers enable large spiders' soaring flight.

The physical mechanism of aerial dispersal of spiders, "ballooning behavior," is still unclear because of the lack of serious scientific observations and experiments. Therefore, as a first step in clarifying the phenomenon, we studied the ballooning behavior of relatively large spiders (heavier than 5 mg) in nature. Additional wind tunnel tests to identify ballooning silks were implemented in the laboratory. From our observation, it seems obvious that spiders actively evaluate the condition of the wind with their front leg (leg I) and wait for the preferable wind condition for their ballooning takeoff. In the wind tunnel tests, as-yet-unknown physical properties of ballooning fibers (length, thickness, and number of fibers) were identified. Large spiders, 16-20 mg Xysticus spp., spun 50-60 nanoscale fibers, with a diameter of 121-323 nm. The length of these threads was 3.22 ± 1.31 m (N = 22). These physical properties of ballooning fibers can explain the ballooning of large spiders with relatively light updrafts, 0.1-0.5 m s-1, which exist in a light breeze of 1.5-3.3 m s-1. Additionally, in line with previous research on turbulence in atmospheric boundary layers and from our wind measurements, it is hypothesized that spiders use the ascending air current for their aerial dispersal, the "ejection" regime, which is induced by hairpin vortices in the atmospheric boundary layer turbulence. This regime is highly correlated with lower wind speeds. This coincides well with the fact that spiders usually balloon when the wind speed is lower than 3 m s-1

Microstructural Stability of Extruded Mg-Mn-Ce Hollow Profiles with Weld Seams

Despite aluminum profiles, magnesium profiles have not been well developed due to the low formability. Furthermore, extruded magnesium profiles show a strong dependence on the mechanical properties, according to the loading direction. This is caused by a strong basal texture, which is directly dependent on the process parameters during the extrusion and the subsequent aging. Thus, the present paper focuses on the analysis of the microstructure and its evolution of extruded magnesium hollow profiles, which were subjected to a series of heat treatments at 475 °C up to one hour. The hollow profiles were extruded through a porthole die, thus, containing longitudinal weld seams. These were formed by material that underwent heavy shearing along the tool surface based on the friction conditions in the porthole die. Three extrusion ratios (ER = 8:1, ER = 16:1, ER = 30:1) were applied, resulting in three different wall thicknesses of the profiles. The microstructure of the profiles was analyzed using light-optical microscopy (LOM) and scanning electron microscopy (SEM) coupled with electron backscatter diffraction (EBSD). The analysis revealed no change of the microstructure of the profiles extruded at the two higher extrusion ratios within the time frame of the heat treatment. In contrast, the microstructure and, thus, the micro-texture of the profile with the lowest extrusion ratio (ER = 8:1) has been affected to a great extent. While only small changes in microstructure in the weld-free area were observed, the initial microstructure in the weld seam was transformed from fine recrystallized grains into a significantly bimodal microstructure mainly due to an abnormal grain growth (AGG). These changes were accompanied by a promotion of the rare-earth (RE) texture component for the weld-free material and a change of the overall texture from RE to a typical non-RE double fiber texture for the weld seam due to the intense AGG within the short-time heat treatments. In addition, the influence of the extrusion ratio on particle size and distribution as well as the character of the microstructure governing the behavior during heat treatments was analyzed and discussed.DFG, 414044773, Open Access Publizieren 2021 - 2022 / Technische Universität Berli

Microstructural Stability of Extruded Mg-Mn-Ce Hollow Profiles with Weld Seams

Despite aluminum profiles, magnesium profiles have not been well developed due to the low formability. Furthermore, extruded magnesium profiles show a strong dependence on the mechanical properties, according to the loading direction. This is caused by a strong basal texture, which is directly dependent on the process parameters during the extrusion and the subsequent aging. Thus, the present paper focuses on the analysis of the microstructure and its evolution of extruded magnesium hollow profiles, which were subjected to a series of heat treatments at 475 °C up to one hour. The hollow profiles were extruded through a porthole die, thus, containing longitudinal weld seams. These were formed by material that underwent heavy shearing along the tool surface based on the friction conditions in the porthole die. Three extrusion ratios (ER = 8:1, ER = 16:1, ER = 30:1) were applied, resulting in three different wall thicknesses of the profiles. The microstructure of the profiles was analyzed using light-optical microscopy (LOM) and scanning electron microscopy (SEM) coupled with electron backscatter diffraction (EBSD). The analysis revealed no change of the microstructure of the profiles extruded at the two higher extrusion ratios within the time frame of the heat treatment. In contrast, the microstructure and, thus, the micro-texture of the profile with the lowest extrusion ratio (ER = 8:1) has been affected to a great extent. While only small changes in microstructure in the weld-free area were observed, the initial microstructure in the weld seam was transformed from fine recrystallized grains into a significantly bimodal microstructure mainly due to an abnormal grain growth (AGG). These changes were accompanied by a promotion of the rare-earth (RE) texture component for the weld-free material and a change of the overall texture from RE to a typical non-RE double fiber texture for the weld seam due to the intense AGG within the short-time heat treatments. In addition, the influence of the extrusion ratio on particle size and distribution as well as the character of the microstructure governing the behavior during heat treatments was analyzed and discussed

Sequential relations between behaviors for ballooning.

<p>(A) The percentage frequency of the behavior transition (the total number of transitions: <i>N</i> = 141). (B) The transition matrix between behaviors (the total numbers of categorized behaviors: <i>N</i>_<i>I</i> = 25, <i>N</i>_<i>S</i> = 65, <i>N</i>_<i>T</i> = 41, <i>N</i>_<i>D</i> = 8, <i>N</i>_<i>H</i> = 2). The corresponding underlying data can be found in <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2004405#pbio.2004405.s012" target="_blank">S1 Data</a>. B, takeoff; D, dropping and hanging behavior; E, escape; H, hiding motion; I, initial state; N, not flown; S, sensing motion; T, tiptoe behavior.</p

Sketches of ballooning structures (body + ballooning threads).

<p>These structures were observed above the water surface, at heights of 1–8 m. Wind was blowing from left to right. Therefore, these structures were transported in the same direction as the wind. Black, thick points represent the spider’s body. Black lines represent ballooning threads.</p

Ballooning behaviors on the artificial platform.

<p>Ballooning behaviors on the artificial platform.</p

A crab spider’s ballooning process (images were converted to negative images to visualize ballooning lines).

<p>(A, B) Initial phase of spinning ballooning lines; (C, D, E, F) Fluttering of a bundle of ballooning lines. Because of turbulent flows in wind, the ballooning threads fluttered unsteadily. (G) Takeoff moment. (H) Airborne state of a ballooning spider. (Original video: see <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2004405#pbio.2004405.s011" target="_blank">S3 Video</a>).</p

Scanning electron microscopic images of ballooning lines and drag lines.

<p>(A) Ballooning fibers of <i>X</i>. <i>cristatus</i> (1,300×). (B) Ballooning fibers of <i>X</i>. <i>audax</i> (10,000×). (C) Middle part of ballooning fibers of <i>X</i>. <i>audax</i> (20,000×). (D) Ballooning fibers of <i>X</i>. <i>cristatus</i> (30,000×). (E) One pair of drag fibers of <i>X</i>. <i>cristatus</i> (a weight of 18 mg) (20,000×). (F) Two pairs of drag fibers of <i>Xysticus</i> spp. (a weight of 15.6 mg), which attached together (20,000×).</p