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We demonstrate the utility of block polyelectrolyte (bPE) additives to enhance viscosity and resolve longstanding challenges with the three-dimensional printability of extrusion-based biopolymer inks. The addition of oppositely charged bPEs into solutions of photocurable gelatin methacryloyl (GelMA) results in complexation-driven self- assembly of the bPEs, leading to GelMA/bPE inks that are printable at physiological temperatures, representing stark improvements over GelMA inks that suffer from low viscosity at 37 °C leading to low printability and poor structural stability. The hierarchical microstructure of the self-assemblies (either jammed micelles or three-dimensional networks) formed by the oppositely charged bPEs, as confirmed by small angle X-ray scattering, is attributed to the enhancements in the shear strength and printability of the GelMA/bPE inks. Varying bPE concentration in the inks is shown to enable tunability of the rheological properties to meet the criteria of pre- and post-extrusion flow characteristics for 3D bioprinting, including prominent yield stress behavior, strong shear thinning, and rapid recovery upon flow cessation. Moreover, the bPE self-assemblies also contribute to the robustness of the photocrosslinked hydrogels – photocrosslinked GelMA/bPE hydrogels are shown to exhibit higher shear strength than photocrosslinked GelMA hydrogels. We envision this study to serve as a practical guide for the bioprinting of bespoke extrusion inks where bPE are used as scaffolds and viscosity enhancers that can be emulated in a range of biopolymers and photocurable precursors.

We generate self-assembled biocompatible scaffolds with excellent structural integrity based on complex-forming block polyelectrolytes that enable extrusion-based 3D bioprinting of large constructs from low-viscosity bioinks. Despite remarkable progress of biofabrication techniques in tissue engineering, the development of extrudable bioinks that perform optimally at physiological temperatures remains a major challenge. Most biopolymer and photocurable precursor solutions exhibit low viscosities at 37 °C, resulting in undesirable flows and loss of form prior to chemical crosslinking. Temperature-sensitive bioinks, such as gelatin methacryloyl (GelMA), can be deposited near their gelling point, but suffer from suboptimal temperature-induced pre-gelation, poor cell viability emerging from long holding times in the cooled cartridges, inefficient temperature transfer from the print bed, and discontinuous layer-by-layer fabrication. Here, we demonstrate that block polyelectrolyte additives serve as effective viscosity enhancers when added to non-extrudable precursor solutions. Rapid, electrostatic self-assembly of block polyelectrolytes into either jammed micelles or interconnected networks provides hydrogel scaffoldings that form nearly instantly, lend initial structural robustness upon deposition, and enhance shear and tensile strength of the cured bioinks. Moreover, our approach enables continuous extrusion without the need of chemical crosslinking between individual layers, paving the way for fast biomanufacturing of human-scale tissue constructs with improved inter-layer bonding.

Seit nunmehr vierzehn Jahren sind Rumänien und Bulgarien Mitgliedstaaten der Europäischen Union und seit 2014 besteht die volle Arbeitnehmerfreizügigkeit für Staatsbürger*innen beider Länder. Nicht zuletzt durch die Freizügigkeitsregelungen, von denen auch Deutschland profitiert, kommen von Armut bedrohte Rom*nja aus beiden Staaten nach Deutschland, die in ihrer Heimat massiv diskriminiert werden und unter Perspektivlosigkeit leiden. Die vier in der vorliegenden Publikation zusammengetragenen Teilstudien wurden im bulgarischen Plovdiv-Stolipinovo durchgeführt, dem größten mehrheitlich von Rom*nja bewohnten Stadtteil in Bulgarien. Ziel dieser Veröffentlichung ist es, die transnationale Lebenswelt in Plovdiv-Stolipinovo aus verschiedenen thematischen Blickwickeln zu analysieren und besser zu verstehen, um Wissen für die praktische Soziale Arbeit in Ankunftsgebieten Deutschlands zu generieren. Es fußt auf studentischen Projektarbeiten und Exkursionen, die am Fachbereich Sozialwesen der Fachhochschule Münster durchgeführt wurden sowie auf Ergebnissen des von der DFG geförderten Projekts „Gewaltbezogene Normen junger Männer in hochriskanten urbanen Stadtteilen“, das unter Leitung von Prof. Dr. Wilhelm Heitmeyer am Institut für interdisziplinäre Konflikt- und Gewaltforschung der Universität Bielefeld angesiedelt war.