@article{BlumTaskinShanetal.2021,
  author    = {Blum, Carina and Taskin, Mehmet Berat and Shan, Junwen and Schilling, Tatjana and Schlegelmilch, Katrin and Teßmar, J{\"o}rg and Groll, J{\"u}rgen},
  title     = {Appreciating the First Line of the Human Innate Immune Defense: A Strategy to Model and Alleviate the Neutrophil Elastase-Mediated Attack toward Bioactivated Biomaterials},
  series = {Small},
  volume    = {17},
  journal   = {Small},
  number    = {13},
  doi       = {10.1002/smll.202007551},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257691},
  year      = {2021},
  abstract  = {Biointerface engineering is a wide-spread strategy to improve the healing process and subsequent tissue integration of biomaterials. Especially the integration of specific peptides is one promising strategy to promote the regenerative capacity of implants and 3D scaffolds. In vivo, these tailored interfaces are, however, first confronted with the innate immune response. Neutrophils are cells with pronounced proteolytic potential and the first recruited immune cells at the implant site; nonetheless, they have so far been underappreciated in the design of biomaterial interfaces. Herein, an in vitro approach is introduced to model and analyze the neutrophil interaction with bioactivated materials at the example of nano-bioinspired electrospun surfaces that reveals the vulnerability of a given biointerface design to the contact with neutrophils. A sacrificial, transient hydrogel coating that demonstrates optimal protection for peptide-modified surfaces and thus alleviates the immediate cleavage by neutrophil elastase is further introduced.},
  language  = {en}
}
@article{BotheDeubelHesseetal.2019,
  author    = {Bothe, Friederike and Deubel, Anne-Kathrin and Hesse, Eliane and Lotz, Benedict and Groll, J{\"u}rgen and Werner, Carsten and Richter, Wiltrud and Hagmann, Sebastien},
  title     = {Treatment of focal cartilage defects in minipigs with zonal chondrocyte/mesenchymal progenitor cell constructs},
  series = {International Journal of Molecular Sciences},
  volume    = {20},
  journal   = {International Journal of Molecular Sciences},
  number    = {3},
  issn      = {1422-0067},
  doi       = {10.3390/ijms20030653},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-285118},
  year      = {2019},
  abstract  = {Despite advances in cartilage repair strategies, treatment of focal chondral lesions remains an important challenge to prevent osteoarthritis. Articular cartilage is organized into several layers and lack of zonal organization of current grafts is held responsible for insufficient biomechanical and biochemical quality of repair-tissue. The aim was to develop a zonal approach for cartilage regeneration to determine whether the outcome can be improved compared to a non-zonal strategy. Hydrogel-filled polycaprolactone (PCL)-constructs with a chondrocyte-seeded upper-layer deemed to induce hyaline cartilage and a mesenchymal stromal cell (MSC)-containing bottom-layer deemed to induce calcified cartilage were compared to chondrocyte-based non-zonal grafts in a minipig model. Grafts showed comparable hardness at implantation and did not cause visible signs of inflammation. After 6 months, X-ray microtomography (µCT)-analysis revealed significant bone-loss in both treatment groups compared to empty controls. PCL-enforcement and some hydrogel-remnants were retained in all defects, but most implants were pressed into the subchondral bone. Despite important heterogeneities, both treatments reached a significantly lower modified O'Driscoll-score compared to empty controls. Thus, PCL may have induced bone-erosion during joint loading and misplacement of grafts in vivo precluding adequate permanent orientation of zones compared to surrounding native cartilage.},
  language  = {en}
}
@article{BrandForsterBoecketal.2022,
  author    = {Brand, Jessica S. and Forster, Leonard and B{\"o}ck, Thomas and Stahlhut, Philipp and Teßmar, J{\"o}rg and Groll, J{\"u}rgen and Albrecht, Krystyna},
  title     = {Covalently Cross-Linked Pig Gastric Mucin Hydrogels Prepared by Radical-Based Chain-Growth and Thiol-ene Mechanisms},
  series = {Macromolecular Bioscience},
  volume    = {22},
  journal   = {Macromolecular Bioscience},
  number    = {4},
  doi       = {10.1002/mabi.202100274},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318453},
  year      = {2022},
  abstract  = {Mucin, a high molecular mass hydrophilic glycoprotein, is the main component of mucus that coats every wet epithelium in animals. It is thus intrinsically biocompatible, and with its protein backbone and the o-glycosidic bound oligosaccharides, it contains a plethora of functional groups which can be used for further chemical modifications. Here, chain-growth and step-growth (thiol-ene) free-radical cross-linked hydrogels prepared from commercially available pig gastric mucin (PGM) are introduced and compared as cost-efficient and easily accessible alternative to the more broadly applied bovine submaxillary gland mucin. For this, PGM is functionalized with photoreactive acrylate groups or allyl ether moieties, respectively. Whereas homopolymerization of acrylate-functionalized polymers is performed, for thiol-ene cross-linking, the allyl-ether-functionalized PGM is cross-linked with thiol-functionalized hyaluronic acid. Morphology, mechanical properties, and cell compatibility of both kinds of PGM hydrogels are characterized and compared. Furthermore, the biocompatibility of these hydrogels can be evaluated in cell culture experiments.},
  language  = {en}
}
@article{BruecknerMeiningerGrolletal.2019,
  author    = {Br{\"u}ckner, Theresa and Meininger, Markus and Groll, J{\"u}rgen and K{\"u}bler, Alexander C. and Gbureck, Uwe},
  title     = {Magnesium Phosphate Cement as Mineral Bone Adhesive},
  series = {Materials},
  volume    = {12},
  journal   = {Materials},
  number    = {23},
  issn      = {1996-1944},
  doi       = {10.3390/ma12233819},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-193052},
  year      = {2019},
  abstract  = {Mineral bone cements were actually not developed for their application as bone-bonding agents, but as bone void fillers. In particular, calcium phosphate cements (CPC) are considered to be unsuitable for that application, particularly under moist conditions. Here, we showed the ex vivo ability of different magnesium phosphate cements (MPC) to adhere on bovine cortical bone substrates. The cements were obtained from a mixture of farringtonite (Mg\(_3\)(PO\(_4\))\(_2\)) with different amounts of phytic acid (C\(_6\)H\(_{18}\)O\(_{24}\)P\(_6\), inositol hexaphosphate, IP6), whereas cement setting occurred by a chelation reaction between Mg\(^{2+}\) ions and IP6. We were able to show that cements with 25\% IP6 and a powder-to-liquid ratio (PLR) of 2.0 g/mL resulted in shear strengths of 0.81 ± 0.12 MPa on bone even after 7 d storage in aqueous conditions. The samples showed a mixed adhesive-cohesive failure with cement residues on the bone surface as indicated by scanning electron microscopy and energy-dispersive X-ray analysis. The presented material demonstrated appropriate bonding characteristics, which could enable a broadening of the mineral bone cements' application field to bone adhesives},
  language  = {en}
}
@article{CastilhoHochleitnerWilsonetal.2018,
  author    = {Castilho, Miguel and Hochleitner, Gernot and Wilson, Wouter and van Rietbergen, Bert and Dalton, Paul D. and Groll, J{\"u}rgen and Malda, Jos and Ito, Keita},
  title     = {Mechanical behavior of a soft hydrogel reinforced with three-dimensional printed microfibre scaffolds},
  series = {Scientific Reports},
  volume    = {8},
  journal   = {Scientific Reports},
  doi       = {10.1038/s41598-018-19502-y},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-222280},
  year      = {2018},
  abstract  = {Reinforcing hydrogels with micro-fibre scaffolds obtained by a Melt-Electrospinning Writing (MEW) process has demonstrated great promise for developing tissue engineered (TE) constructs with mechanical properties compatible to native tissues. However, the mechanical performance and reinforcement mechanism of the micro-fibre reinforced hydrogels is not yet fully understood. In this study, FE models, implementing material properties measured experimentally, were used to explore the reinforcement mechanism of fibre-hydrogel composites. First, a continuum FE model based on idealized scaffold geometry was used to capture reinforcement effects related to the suppression of lateral gel expansion by the scaffold, while a second micro-FE model based on micro-CT images of the real construct geometry during compaction captured the effects of load transfer through the scaffold interconnections. Results demonstrate that the reinforcement mechanism at higher scaffold volume fractions was dominated by the load carrying-ability of the fibre scaffold interconnections, which was much higher than expected based on testing scaffolds alone because the hydrogel provides resistance against buckling of the scaffold. We propose that the theoretical understanding presented in this work will assist the design of more effective composite constructs with potential applications in a wide range of TE conditions.},
  language  = {en}
}
@article{DoganScheuringWagneretal.2021,
  author    = {Dogan, Leyla and Scheuring, Ruben and Wagner, Nicole and Ueda, Yuichiro and Schmidt, Sven and W{\"o}rsd{\"o}rfer, Philipp and Groll, J{\"u}rgen and Erg{\"u}n, S{\"u}leyman},
  title     = {Human iPSC-derived mesodermal progenitor cells preserve their vasculogenesis potential after extrusion and form hierarchically organized blood vessels},
  series = {Biofabrication},
  volume    = {13},
  journal   = {Biofabrication},
  number    = {4},
  doi       = {10.1088/1758-5090/ac26ac},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-254046},
  year      = {2021},
  abstract  = {Post-fabrication formation of a proper vasculature remains an unresolved challenge in bioprinting. Established strategies focus on the supply of the fabricated structure with nutrients and oxygen and either rely on the mere formation of a channel system using fugitive inks or additionally use mature endothelial cells and/or peri-endothelial cells such as smooth muscle cells for the formation of blood vessels in vitro. Functional vessels, however, exhibit a hierarchical organization and multilayered wall structure that is important for their function. Human induced pluripotent stem cell-derived mesodermal progenitor cells (hiMPCs) have been shown to possess the capacity to form blood vessels in vitro, but have so far not been assessed for their applicability in bioprinting processes. Here, we demonstrate that hiMPCs, after formulation into an alginate/collagen type I bioink and subsequent extrusion, retain their ability to give rise to the formation of complex vessels that display a hierarchical network in a process that mimics the embryonic steps of vessel formation during vasculogenesis. Histological evaluations at different time points of extrusion revealed the initial formation of spheres, followed by lumen formation and further structural maturation as evidenced by building a multilayered vessel wall and a vascular network. These findings are supported by immunostainings for endothelial and peri-endothelial cell markers as well as electron microscopic analyses at the ultrastructural level. Moreover, endothelial cells in capillary-like vessel structures deposited a basement membrane-like matrix at the basal side between the vessel wall and the alginate-collagen matrix. After transplantation of the printed constructs into the chicken chorioallantoic membrane (CAM) the printed vessels connected to the CAM blood vessels and get perfused in vivo. These results evidence the applicability and great potential of hiMPCs for the bioprinting of vascular structures mimicking the basic morphogenetic steps of de novo vessel formation during embryogenesis.},
  language  = {en}
}
@article{DoryabTaskinStahlhutetal.2021,
  author    = {Doryab, Ali and Taskin, Mehmet Berat and Stahlhut, Philipp and Schr{\"o}ppel, Andreas and Orak, Sezer and Voss, Carola and Ahluwalia, Arti and Rehberg, Markus and Hilgendorff, Anne and St{\"o}ger, Tobias and Groll, J{\"u}rgen and Schmid, Otmar},
  title     = {A Bioinspired in vitro Lung Model to Study Particokinetics of Nano-/Microparticles Under Cyclic Stretch and Air-Liquid Interface Conditions},
  series = {Frontiers in Bioengineering and Biotechnology},
  volume    = {9},
  journal   = {Frontiers in Bioengineering and Biotechnology},
  issn      = {2296-4185},
  doi       = {10.3389/fbioe.2021.616830},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-223830},
  year      = {2021},
  abstract  = {Evolution has endowed the lung with exceptional design providing a large surface area for gas exchange area (ca. 100 m\(^{2}\)) in a relatively small tissue volume (ca. 6 L). This is possible due to a complex tissue architecture that has resulted in one of the most challenging organs to be recreated in the lab. The need for realistic and robust in vitro lung models becomes even more evident as causal therapies, especially for chronic respiratory diseases, are lacking. Here, we describe the Cyclic In VItro Cell-stretch (CIVIC) "breathing" lung bioreactor for pulmonary epithelial cells at the air-liquid interface (ALI) experiencing cyclic stretch while monitoring stretch-related parameters (amplitude, frequency, and membrane elastic modulus) under real-time conditions. The previously described biomimetic copolymeric BETA membrane (5 μm thick, bioactive, porous, and elastic) was attempted to be improved for even more biomimetic permeability, elasticity (elastic modulus and stretchability), and bioactivity by changing its chemical composition. This biphasic membrane supports both the initial formation of a tight monolayer of pulmonary epithelial cells (A549 and 16HBE14o\(^{-}\)) under submerged conditions and the subsequent cell-stretch experiments at the ALI without preconditioning of the membrane. The newly manufactured versions of the BETA membrane did not improve the characteristics of the previously determined optimum BETA membrane (9.35\% PCL and 6.34\% gelatin [w/v solvent]). Hence, the optimum BETA membrane was used to investigate quantitatively the role of physiologic cyclic mechanical stretch (10\% linear stretch; 0.33 Hz: light exercise conditions) on size-dependent cellular uptake and transepithelial transport of nanoparticles (100 nm) and microparticles (1,000 nm) for alveolar epithelial cells (A549) under ALI conditions. Our results show that physiologic stretch enhances cellular uptake of 100 nm nanoparticles across the epithelial cell barrier, but the barrier becomes permeable for both nano- and micron-sized particles (100 and 1,000 nm). This suggests that currently used static in vitro assays may underestimate cellular uptake and transbarrier transport of nanoparticles in the lung.},
  language  = {en}
}
@article{DoryabTaskinStahlhutetal.2021,
  author    = {Doryab, Ali and Taskin, Mehmet Berat and Stahlhut, Philipp and Schr{\"o}ppel, Andreas and Wagner, Darcy E. and Groll, J{\"u}rgen and Schmid, Otmar},
  title     = {A Biomimetic, Copolymeric Membrane for Cell-Stretch Experiments with Pulmonary Epithelial Cells at the Air-Liquid Interface},
  series = {Advanced Functional Materials},
  volume    = {31},
  journal   = {Advanced Functional Materials},
  number    = {10},
  doi       = {10.1002/adfm.202004707},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-225645},
  year      = {2021},
  abstract  = {Chronic respiratory diseases are among the leading causes of death worldwide, but only symptomatic therapies are available for terminal illness. This in part reflects a lack of biomimetic in vitro models that can imitate the complex environment and physiology of the lung. Here, a copolymeric membrane consisting of poly(ε-)caprolactone and gelatin with tunable properties, resembling the main characteristics of the alveolar basement membrane is introduced. The thin bioinspired membrane (≤5 μm) is stretchable (up to 25\% linear strain) with appropriate surface wettability and porosity for culturing lung epithelial cells under air-liquid interface conditions. The unique biphasic concept of this membrane provides optimum characteristics for initial cell growth (phase I) and then switch to biomimetic properties for cyclic cell-stretch experiments (phase II). It is showed that physiologic cyclic mechanical stretch improves formation of F-actin cytoskeleton filaments and tight junctions while non-physiologic over-stretch induces cell apoptosis, activates inflammatory response (IL-8), and impairs epithelial barrier integrity. It is also demonstrated that cyclic physiologic stretch can enhance the cellular uptake of nanoparticles. Since this membrane offers considerable advantages over currently used membranes, it may lead the way to more biomimetic in vitro models of the lung for translation of in vitro response studies into clinical outcome.},
  language  = {en}
}
@article{GaritanoTrojaolaSanchoGoetzetal.2021,
  author    = {Garitano-Trojaola, Andoni and Sancho, Ana and G{\"o}tz, Ralph and Eiring, Patrick and Walz, Susanne and Jetani, Hardikkumar and Gil-Pulido, Jesus and Da Via, Matteo Claudio and Teufel, Eva and Rhodes, Nadine and Haertle, Larissa and Arellano-Viera, Estibaliz and Tibes, Raoul and Rosenwald, Andreas and Rasche, Leo and Hudecek, Michael and Sauer, Markus and Groll, J{\"u}rgen and Einsele, Hermann and Kraus, Sabrina and Kort{\"u}m, Martin K.},
  title     = {Actin cytoskeleton deregulation confers midostaurin resistance in FLT3-mutant acute myeloid leukemia},
  series = {Communications Biology},
  volume    = {4},
  journal   = {Communications Biology},
  number    = {1},
  doi       = {10.1038/s42003-021-02215-w},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-260709},
  year      = {2021},
  abstract  = {The presence of FMS-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD) is one of the most frequent mutations in acute myeloid leukemia (AML) and is associated with an unfavorable prognosis. FLT3 inhibitors, such as midostaurin, are used clinically but fail to entirely eradicate FLT3-ITD+AML. This study introduces a new perspective and highlights the impact of RAC1-dependent actin cytoskeleton remodeling on resistance to midostaurin in AML. RAC1 hyperactivation leads resistance via hyperphosphorylation of the positive regulator of actin polymerization N-WASP and antiapoptotic BCL-2. RAC1/N-WASP, through ARP2/3 complex activation, increases the number of actin filaments, cell stiffness and adhesion forces to mesenchymal stromal cells (MSCs) being identified as a biomarker of resistance. Midostaurin resistance can be overcome by a combination of midostaruin, the BCL-2 inhibitor venetoclax and the RAC1 inhibitor Eht1864 in midostaurin-resistant AML cell lines and primary samples, providing the first evidence of a potential new treatment approach to eradicate FLT3-ITD+AML. Garitano-Trojaola et al. used a combination of human acute myeloid leukemia (AML) cell lines and primary samples to show that RAC1-dependent actin cytoskeleton remodeling through BCL2 family plays a key role in resistance to the FLT3 inhibitor, Midostaurin in AML. They showed that by targeting RAC1 and BCL2, Midostaurin resistance was diminished, which potentially paves the way for an innovate treatment approach for FLT3 mutant AML.},
  language  = {en}
}
@article{GeffersGrollGbureck2015,
  author    = {Geffers, Martha and Groll, J{\"u}rgen and Gbureck, Uwe},
  title     = {Reinforcement strategies for load-bearing calcium phosphate biocements},
  series = {Materials},
  volume    = {8},
  journal   = {Materials},
  doi       = {10.3390/ma8052700},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-148636},
  pages     = {2700-2717},
  year      = {2015},
  abstract  = {Calcium phosphate biocements based on calcium phosphate chemistry are well-established biomaterials for the repair of non-load bearing bone defects due to the brittle nature and low flexural strength of such cements. This article features reinforcement strategies of biocements based on various intrinsic or extrinsic material modifications to improve their strength and toughness. Altering particle size distribution in conjunction with using liquefiers reduces the amount of cement liquid necessary for cement paste preparation. This in turn decreases cement porosity and increases the mechanical performance, but does not change the brittle nature of the cements. The use of fibers may lead to a reinforcement of the matrix with a toughness increase of up to two orders of magnitude, but restricts at the same time cement injection for minimal invasive application techniques. A novel promising approach is the concept of dual-setting cements, in which a second hydrogel phase is simultaneously formed during setting, leading to more ductile cement-hydrogel composites with largely unaffected application properties.},
  language  = {en}
}