An increasing number of studies demonstrate phenotypic and genetic changes in natural populations that are subject to climate change, and there is hope that some of these changes will contribute to ...avoiding species extinctions (‘evolutionary rescue’). Here, we review theoretical models of rapid evolution in quantitative traits that can shed light on the potential for adaptation to a changing climate. Our focus is on quantitative‐genetic models with selection for a moving phenotypic optimum. We point out that there is no one‐to‐one relationship between the rate of adaptation and population survival, because the former depends on relative fitness and the latter on absolute fitness. Nevertheless, previous estimates that sustainable rates of genetically based change usually do not exceed 0.1 haldanes (i.e., phenotypic standard deviations per generation) are probably correct. Survival can be greatly facilitated by phenotypic plasticity, and heritable variation in plasticity can further speed up genetic evolution. Multivariate selection and genetic correlations are frequently assumed to constrain adaptation, but this is not necessarily the case and depends on the geometric relationship between the fitness landscape and the structure of genetic variation. Similar conclusions hold for adaptation to shifting spatial gradients. Recent models of adaptation in multispecies communities indicate that the potential for rapid evolution is strongly influenced by interspecific competition.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Major challenges in biofabrication revolve around capturing the complex, hierarchical composition of native tissues. However, individual 3D printing techniques have limited capacity to produce ...composite biomaterials with multi‐scale resolution. Volumetric bioprinting recently emerged as a paradigm‐shift in biofabrication. This ultrafast, light‐based technique sculpts cell‐laden hydrogel bioresins into 3D structures in a layerless fashion, providing enhanced design freedom over conventional bioprinting. However, it yields prints with low mechanical stability, since soft, cell‐friendly hydrogels are used. Herein, the possibility to converge volumetric bioprinting with melt electrowriting, which excels at patterning microfibers, is shown for the fabrication of tubular hydrogel‐based composites with enhanced mechanical behavior. Despite including non‐transparent melt electrowritten scaffolds in the volumetric printing process, high‐resolution bioprinted structures are successfully achieved. Tensile, burst, and bending mechanical properties of printed tubes are tuned altering the electrowritten mesh design, resulting in complex, multi‐material tubular constructs with customizable, anisotropic geometries that better mimic intricate biological tubular structures. As a proof‐of‐concept, engineered tubular structures are obtained by building trilayered cell‐laden vessels, and features (valves, branches, fenestrations) that can be rapidly printed using this hybrid approach. This multi‐technology convergence offers a new toolbox for manufacturing hierarchical and mechanically tunable multi‐material living structures.
The combination of melt electrowriting and volumetric bioprinting (VolMEW) improves the mechanical performance of the structures while maintaining high printing resolution, design freedom, and choice of material. VolMEW enables the fabrication of multi‐material and multi‐cell, functional scaffolds with physiological relevance in seconds.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Melt Electrowriting (MEW) is a continuously growing manufacturing platform. Its advantage is the consistent production of micro‐ to nanometer fibers, that stack intricately, forming complex ...geometrical shapes. MEW allows tuning of the mechanical properties of constructs via the geometry of deposited fibers. Due to this, MEW can create complex mechanics only seen in multi‐material compounds and serve as guiding structures for cellular alignment. The advantage of MEW is also shown in combination with other biotechnological manufacturing methods to create multilayered constructs that increase mechanical approximation to native tissues, biocompatibility, and cellular response. These features make MEW constructs a perfect candidate for small‐diameter vascular graft structures. Recently, studies have presented fascinating results in this regard, but is this truly the direction that tubular MEW will follow or are there also other options on the horizon? This perspective will explore the origins and developments of tubular MEW and present its growing importance in the field of artificial small‐diameter vascular grafts with mechanical modulation and improved biomimicry and the impact of it in convergence with other manufacturing methods and how future technologies like AI may influence its progress.
This perspective covers the advancements in the field of tubular, melt electrowritten constructs for use as small‐diameter vascular grafts. It presents how this technology can recreate the mechanical properties of native vessels as well as providing a hierarchical scaffold to mimic the blood vessel physiology by converging with other manufacturing technologies, and how novel fields like artificial intelligence can contribute.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Adaptation lies at the heart of Darwinian evolution. Accordingly, numerous studies have tried to provide a formal framework for the description of the adaptive process. Of these, two complementary ...modeling approaches have emerged: While so-called adaptive-walk models consider adaptation from the successive fixation of de novo mutations only, quantitative genetic models assume that adaptation proceeds exclusively from preexisting standing genetic variation. The latter approach, however, has focused on short-term evolution of population means and variances rather than on the statistical properties of adaptive substitutions. Our aim is to combine these two approaches by describing the ecological and genetic factors that determine the genetic basis of adaptation from standing genetic variation in terms of the effect-size distribution of individual alleles. Specifically, we consider the evolution of a quantitative trait to a gradually changing environment. By means of analytical approximations, we derive the distribution of adaptive substitutions from standing genetic variation, that is, the distribution of the phenotypic effects of those alleles from the standing variation that become fixed during adaptation. Our results are checked against individual-based simulations. We find that, compared to adaptation from de novo mutations, (i) adaptation from standing variation proceeds by the fixation of more alleles of small effect and (ii) populations that adapt from standing genetic variation can traverse larger distances in phenotype space and, thus, have a higher potential for adaptation if the rate of environmental change is fast rather than slow.
The current barrier to clinical translation of small‐caliber tissue‐engineered vascular grafts (TEVGs) is the long‐term patency upon implantation in vivo. Key contributors are thrombosis and ...stenosis caused by inadequate mechanical graft properties and mismatch of hemodynamic conditions. Herein, the authors report on an approach for the fabrication of a mechanically tunable bilayered composite TEVGs. Using a combination of solution electrospinning (SES) and melt electrowriting (MEW), it is shown that the mechanical properties can be tailored and the natural J‐shape of the stress–strain relationship can be recapitulated. Upon cell seeding, the luminal surface of the composite SES layers permits the formation of a confluent mature endothelium. MEW fibers provide structural support to promote stacking and orientation of MSCs in a near‐circumferential native vessel like direction. By adjusting the ratios of poly(ε‐caprolactone) and poly(ester‐urethane) during the SES process, TEVGs with a range of tunable mechanical properties can be manufactured. Notably, this hybrid approach permits modulation of the radial tensile properties of TEVGs to approximate different native vessels. Overall, a strategy for the fabrication of TEVGs with mechanical properties resembling those of native vessels which can help to accommodate long‐term patency of TEVGs at various treatment sites in future applications is demonstrated.
A barrier for clinical translation of small‐caliber tissue‐engineered vascular grafts (TEVGs) is long‐term patency. An important limiting factor is inadequate graft mechanics. This manuscript reports the fabrication of mechanically tunable TEVGs using a combination of solution electrospinning and melt electrowriting. The radial tensile properties of the TEVGs approximate human vessels and will accommodate long‐term patency of such TEVGs in future.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In 3D bioprinting, bioinks with high concentrations of polymeric materials are frequently used to enable fabrication of 3D cell‐hydrogel constructs with sufficient stability. However, this is often ...associated with restricted cell bioactivity and an inhomogeneous distribution of newly produced extracellular matrix (ECM). Therefore, this study investigates bioink compositions based on hyaluronic acid (HA), an attractive material for cartilage regeneration, which allow for reduction of polymer content. Thiolated HA and allyl‐modified poly(glycidol) in varying concentrations are UV‐crosslinked. To adapt bioinks to poly(ε‐caprolactone) (PCL)‐supported 3D bioprinting, the gels are further supplemented with 1 wt% unmodified high molecular weight HA (hmHA) and chondrogenic differentiation of incorporated human mesenchymal stromal cells is assessed. Strikingly, addition of hmHA to gels with a low polymer content (3 wt%) results in distinct increase of construct quality with a homogeneous ECM distribution throughout the constructs, independent of the printing process. Improved ECM distribution in those constructs is associated with increased construct stiffness after chondrogenic differentiation, as compared to higher concentrated constructs (10 wt%), which only show pericellular matrix deposition. The study contributes to effective bioink development, demonstrating dual function of a supplement enabling PCL‐supported bioprinting and at the same time improving biological properties of the resulting constructs.
3D printable constructs for cartilage biofabrication combining sufficient construct stability with a cell‐supportive environment still represent a major challenge. Here, hyaluronic acid‐based bioinks are used to modulate biological properties of 3D constructs after bioprinting and chondrogenic differentiation of mesenchymal stromal cells, focusing on extracellular matrix distribution. The study contributes to effective bioink development and presents a perspective for cartilage regeneration.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Melt electrowriting (MEW) is an additive manufacturing process that produces highly defined constructs with elements in the micrometer range. A specific configuration of MEW enables printing tubular ...constructs to create small‐diameter tubular structures. The small pool of processable materials poses a bottleneck for wider application in biomedicine. To alleviate this obstacle, an acrylate‐endcapped urethane‐based polymer (AUP), using a poly(ε‐caprolactone) (PCL) (molar mass: 20 000 g mol−1) (AUP PCL20k) as backbone material, is synthesized and utilized for MEW. Spectroscopic analysis confirms the successful modification of the PCL backbone with photo‐crosslinkable acrylate endgroups. Printing experiments of AUP PCL20k reveal limited printability but the photo‐crosslinking ability is preserved post‐printing. To improve printability and to tune the mechanical properties of printed constructs, the AUP‐material is blended with commercially available PCL (AUP PCL20k:PCL in ratios 80:20, 60:40, 50:50). Print fidelity improves for 60:40 and 50:50 blends. Blending enables modification of the constructs' mechanical properties to approximate the range of blood vessels for transplantation surgeries. The crosslinking‐ability of the material allows pure AUP to be manipulated post‐printing and illustrates significant differences in mechanical properties of 80:20 blends after crosslinking. An in vitro cell compatibility assay using human umbilical vein endothelial cells also demonstrates the material's non‐cytotoxicity.
An acrylate‐endcapped urethane‐based polymer (AUP) with a poly(ε‐caprolactone) (PCL) backbone is tested as novel material for melt electrowriting (MEW). AUP is compatible with MEW and enables postprocessing via UV‐crosslinking. Blending AUP and PCL improves printability and enables tuning mechanical properties of the constructs. The tubular samples are evaluated regarding physicochemical characteristics and reveal mechanical properties comparable to human blood vessels.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The objective of this study aims at using the Matlab-Simulink environment and the LabVIEW software environment to build computer models of a six-dimensional (6D) chaotic dynamic system. For the fixed ...system’s parameters, the spectrum of Lyapunov exponents and the Kaplan-York dimension are calculated. The presence of two positive Lyapunov exponents demonstrates the hyperchaotic behavior of the system. The fractional Kaplan-York dimension indicates the fractal structure of strange attractors. An active control method is extended to achieve global chaotic synchronization of two identical novel 6D chaotic systems with unknown system parameters. Based on the results obtained in Matlab-Simulink and LabVIEW models, a chaotic signal generator for the 6D chaotic system is implemented in the MultiSim environment. The experimental results show that the chaotic behavior simulation in the MultiSim environment is similar to those in the Matlab-Simulink and LabVIEW models. The simulation results demonstrate that the Pecora-Carroll method is a simple way of chaotic masking and signal decoding.
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FFLJ, NUK, ODKLJ, UL, UM, UPUK
Zum Erwerb von OER-Kompetenzen braucht es zertifizierte Weiterbildungsangebote, deren didaktisches Konzept sowohl die selbstständige Wissensaneignung als auch betreute Kursphasen und eine hohe ...Praxisorientierung umfasst. Die Evaluationsergebnisse zeigen, dass neben Lernvideos insbesondere die kollaborative Bearbeitung von Arbeitsaufträgen und der diskursive Austausch in synchronen Kurseinheiten die Erreichung klar formulierter Lernziele unterstützen. Aus der Evaluation geht zudem hervor, dass ein Abschlusszertifikat motivierend wirkt, aber auch, dass die mit der Weiterbildung verbundene Workload als belastend empfunden wird.
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