@article{BakirciFrankGumbeletal.2021, author = {Bakirci, Ezgi and Frank, Andreas and Gumbel, Simon and Otto, Paul F. and F{\"u}rsattel, Eva and Tessmer, Ingrid and Schmidt, Hans-Werner and Dalton, Paul D.}, title = {Melt Electrowriting of Amphiphilic Physically Crosslinked Segmented Copolymers}, series = {Macromolecular Chemistry and Physics}, volume = {222}, journal = {Macromolecular Chemistry and Physics}, number = {22}, doi = {10.1002/macp.202100259}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257572}, year = {2021}, abstract = {Various (AB)\(_{n}\) and (ABAC)\(_{n}\) segmented copolymers with hydrophilic and hydrophobic segments are processed via melt electrowriting (MEW). Two different (AB)\(_{n}\) segmented copolymers composed of bisurea segments and hydrophobic poly(dimethyl siloxane) (PDMS) or hydrophilic poly(propylene oxide)-poly(ethylene oxide)-poly(propylene oxide) (PPO-PEG-PPO) segments, while the amphiphilic (ABAC)\(_{n}\) segmented copolymers consist of bisurea segments in the combination of hydrophobic PDMS segments and hydrophilic PPO-PEG-PPO segments with different ratios, are explored. All copolymer compositions are processed using the same conditions, including nozzle temperature, applied voltage, and collector distance, while changes in applied pressure and collector speed altered the fiber diameter in the range of 7 and 60 µm. All copolymers showed excellent processability with MEW, well-controlled fiber stacking, and inter-layer bonding. Notably, the surfaces of all four copolymer fibers are very smooth when visualized using scanning electron microscopy. However, the fibers show different roughness demonstrated with atomic force microscopy. The non-cytotoxic copolymers increased L929 fibroblast attachment with increasing PDMS content while the different copolymer compositions result in a spectrum of physical properties.}, language = {en} } @article{KadeOttoLuxenhoferetal.2021, author = {Kade, Juliane C. and Otto, Paul F. and Luxenhofer, Robert and Dalton, Paul D.}, title = {Melt electrowriting of poly(vinylidene difluoride) using a heated collector}, series = {Polymers for Advanced Technologies}, volume = {32}, journal = {Polymers for Advanced Technologies}, number = {12}, issn = {1042-7147}, doi = {10.1002/pat.5463}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318493}, pages = {4951 -- 4955}, year = {2021}, abstract = {Previous research on the melt electrowriting (MEW) of poly(vinylidene difluoride) (PVDF) resulted in electroactive fibers, however, printing more than five layers is challenging. Here, we investigate the influence of a heated collector to adjust the solidification rate of the PVDF jet so that it adheres sufficiently to each layer. A collector temperature of 110°C is required to improve fiber processing, resulting in a total of 20 fiber layers. For higher temperatures and higher layers, an interesting phenomenon occurred, where the intersection points of the fibers coalesced into periodic spheres of diameter 206 ± 52 μm (26G, 150°C collector temperature, 2000 mm/min, 10 layers in x- and y-direction).The heated collector is an important component of a MEW printer that allows polymers with a high melting point to be processable with increased layers.}, language = {en} } @article{ThibaudeauTaubenbergerHolzapfeletal.2014, author = {Thibaudeau, Laure and Taubenberger, Anna V. and Holzapfel, Boris M. and Quent, Verena M. and Fuehrmann, Tobias and Hesami, Parisa and Brown, Toby D. and Dalton, Paul D. and Power, Carl A. and Hollier, Brett G. and Hutmacher, Dietmar W.}, title = {A tissue-engineered humanized xenograft model of human breast cancer metastasis to bone}, series = {Disease Models \& Mechanisms}, volume = {7}, journal = {Disease Models \& Mechanisms}, number = {2}, doi = {10.1242/dmm.014076}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-117466}, pages = {299-309}, year = {2014}, abstract = {The skeleton is a preferred homing site for breast cancer metastasis. To date, treatment options for patients with bone metastases are mostly palliative and the disease is still incurable. Indeed, key mechanisms involved in breast cancer osteotropism are still only partially understood due to the lack of suitable animal models to mimic metastasis of human tumor cells to a human bone microenvironment. In the presented study, we investigate the use of a human tissue-engineered bone construct to develop a humanized xenograft model of breast cancer-induced bone metastasis in a murine host. Primary human osteoblastic cell-seeded melt electrospun scaffolds in combination with recombinant human bone morphogenetic protein 7 were implanted subcutaneously in non-obese diabetic/severe combined immunodeficient mice. The tissue-engineered constructs led to the formation of a morphologically intact 'organ' bone incorporating a high amount of mineralized tissue, live osteocytes and bone marrow spaces. The newly formed bone was largely humanized, as indicated by the incorporation of human bone cells and human-derived matrix proteins. After intracardiac injection, the dissemination of luciferase-expressing human breast cancer cell lines to the humanized bone ossicles was detected by bioluminescent imaging. Histological analysis revealed the presence of metastases with clear osteolysis in the newly formed bone. Thus, human tissue-engineered bone constructs can be applied efficiently as a target tissue for human breast cancer cells injected into the blood circulation and replicate the osteolytic phenotype associated with breast cancer-induced bone lesions. In conclusion, we have developed an appropriate model for investigation of species-specific mechanisms of human breast cancer-related bone metastasis in vivo.}, language = {en} } @unpublished{SchaeferJanzenBakircietal.2019, author = {Schaefer, Natascha and Janzen, Dieter and Bakirci, Ezgi and Hrynevich, Andrei and Dalton, Paul D. and Villmann, Carmen}, title = {3D Electrophysiological Measurements on Cells Embedded within Fiber-Reinforced Matrigel}, series = {Advanced Healthcare Materials}, journal = {Advanced Healthcare Materials}, doi = {10.1002/adhm.201801226}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-244194}, year = {2019}, abstract = {2D electrophysiology is often used to determine the electrical properties of neurons, while in the brain, neurons form extensive 3D networks. Thus, performing electrophysiology in a 3D environment provides a closer situation to the physiological condition and serves as a useful tool for various applications in the field of neuroscience. In this study, we established 3D electrophysiology within a fiber-reinforced matrix to enable fast readouts from transfected cells, which are often used as model systems for 2D electrophysiology. Using melt electrowriting (MEW) of scaffolds to reinforce Matrigel, we performed 3D electrophysiology on a glycine receptor-transfected Ltk-11 mouse fibroblast cell line. The glycine receptor is an inhibitory ion channel associated when mutated with impaired neuromotor behaviour. The average thickness of the MEW scaffold was 141.4 ± 5.7µm, using 9.7 ± 0.2µm diameter fibers, and square pore spacings of 100 µm, 200 µm and 400 µm. We demonstrate, for the first time, the electrophysiological characterization of glycine receptor-transfected cells with respect to agonist efficacy and potency in a 3D matrix. With the MEW scaffold reinforcement not interfering with the electrophysiology measurement, this approach can now be further adapted and developed for different kinds of neuronal cultures to study and understand pathological mechanisms under disease conditions.}, language = {en} } @article{HochleitnerJuengstBrownetal.2015, author = {Hochleitner, Gernot and J{\"u}ngst, Tomasz and Brown, Toby D and Hahn, Kathrin and Moseke, Claus and Jakob, Franz and Dalton, Paul D and Groll, J{\"u}rgen}, title = {Additive manufacturing of scaffolds with sub-micron filaments via melt electrospinning writing}, series = {Biofabrication}, volume = {7}, journal = {Biofabrication}, number = {3}, doi = {10.1088/1758-5090/7/3/035002}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-254053}, year = {2015}, abstract = {The aim of this study was to explore the lower resolution limits of an electrohydrodynamic process combined with direct writing technology of polymer melts. Termed melt electrospinning writing, filaments are deposited layer-by-layer to produce discrete three-dimensional scaffolds for in vitro research. Through optimization of the parameters (flow rate, spinneret diameter, voltage, collector distance) for poly-ϵ-caprolactone, we could direct-write coherent scaffolds with ultrafine filaments, the smallest being 817 ± 165 nm. These low diameter filaments were deposited to form box-structures with a periodicity of 100.6 ± 5.1 μm and a height of 80 μm (50 stacked filaments; 100 overlap at intersections). We also observed oriented crystalline regions within such ultrafine filaments after annealing at 55 °C. The scaffolds were printed upon NCO-sP(EO-stat-PO)-coated glass slide surfaces and withstood frequent liquid exchanges with negligible scaffold detachment for at least 10 days in vitro.}, language = {en} } @article{JanzenBakirciFaberetal.2022, author = {Janzen, Dieter and Bakirci, Ezgi and Faber, Jessica and Andrade Mier, Mateo and Hauptstein, Julia and Pal, Arindam and Forster, Leonard and Hazur, Jonas and Boccaccini, Aldo R. and Detsch, Rainer and Teßmar, J{\"o}rg and Budday, Silvia and Blunk, Torsten and Dalton, Paul D. and Villmann, Carmen}, title = {Reinforced Hyaluronic Acid-Based Matrices Promote 3D Neuronal Network Formation}, series = {Advanced Healthcare Materials}, volume = {11}, journal = {Advanced Healthcare Materials}, number = {21}, doi = {10.1002/adhm.202201826}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318682}, year = {2022}, abstract = {3D neuronal cultures attempt to better replicate the in vivo environment to study neurological/neurodegenerative diseases compared to 2D models. A challenge to establish 3D neuron culture models is the low elastic modulus (30-500 Pa) of the native brain. Here, an ultra-soft matrix based on thiolated hyaluronic acid (HA-SH) reinforced with a microfiber frame is formulated and used. Hyaluronic acid represents an essential component of the brain extracellular matrix (ECM). Box-shaped frames with a microfiber spacing of 200 µm composed of 10-layers of poly(ɛ-caprolactone) (PCL) microfibers (9.7 ± 0.2 µm) made via melt electrowriting (MEW) are used to reinforce the HA-SH matrix which has an elastic modulus of 95 Pa. The neuronal viability is low in pure HA-SH matrix, however, when astrocytes are pre-seeded below this reinforced construct, they significantly support neuronal survival, network formation quantified by neurite length, and neuronal firing shown by Ca\(^{2+}\) imaging. The astrocyte-seeded HA-SH matrix is able to match the neuronal viability to the level of Matrigel, a gold standard matrix for neuronal culture for over two decades. Thus, this 3D MEW frame reinforced HA-SH composite with neurons and astrocytes constitutes a reliable and reproducible system to further study brain diseases.}, language = {en} } @article{WielandStrisselSchorleetal.2021, author = {Wieland, Annalena and Strissel, Pamela L. and Schorle, Hannah and Bakirci, Ezgi and Janzen, Dieter and Beckmann, Matthias W. and Eckstein, Markus and Dalton, Paul D. and Strick, Reiner}, title = {Brain and breast cancer cells with PTEN loss of function reveal enhanced durotaxis and RHOB dependent amoeboid migration utilizing 3D scaffolds and aligned microfiber tracts}, series = {Cancers}, volume = {13}, journal = {Cancers}, number = {20}, issn = {2072-6694}, doi = {10.3390/cancers13205144}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-248443}, year = {2021}, abstract = {Background: Glioblastoma multiforme (GBM) and metastatic triple-negative breast cancer (TNBC) with PTEN mutations often lead to brain dissemination with poor patient outcome, thus new therapeutic targets are needed. To understand signaling, controlling the dynamics and mechanics of brain tumor cell migration, we implemented GBM and TNBC cell lines and designed 3D aligned microfibers and scaffolds mimicking brain structures. Methods: 3D microfibers and scaffolds were printed using melt electrowriting. GBM and TNBC cell lines with opposing PTEN genotypes were analyzed with RHO-ROCK-PTEN inhibitors and PTEN rescue using live-cell imaging. RNA-sequencing and qPCR of tumor cells in 3D with microfibers were performed, while scanning electron microscopy and confocal microscopy addressed cell morphology. Results: In contrast to the PTEN wildtype, GBM and TNBC cells with PTEN loss of function yielded enhanced durotaxis, topotaxis, adhesion, amoeboid migration on 3D microfibers and significant high RHOB expression. Functional studies concerning RHOB-ROCK-PTEN signaling confirmed the essential role for the above cellular processes. Conclusions: This study demonstrates a significant role of the PTEN genotype and RHOB expression for durotaxis, adhesion and migration dependent on 3D. GBM and TNBC cells with PTEN loss of function have an affinity for stiff brain structures promoting metastasis. 3D microfibers represent an important tool to model brain metastasizing tumor cells, where RHO-inhibitors could play an essential role for improved therapy.}, language = {en} } @article{WeigandBoosTasbihietal.2016, author = {Weigand, Annika and Boos, Anja M. and Tasbihi, Kereshmeh and Beier, Justus P. and Dalton, Paul D. and Schrauder, Michael and Horch, Raymund E. and Beckmann, Matthias W. and Strissel, Pamela L. and Strick, Reiner}, title = {Selective isolation and characterization of primary cells from normal breast and tumors reveal plasticity of adipose derived stem cells}, series = {Breast Cancer Research}, volume = {18}, journal = {Breast Cancer Research}, number = {32}, doi = {10.1186/s13058-016-0688-2}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-164759}, year = {2016}, abstract = {Background There is a need to establish more cell lines from breast tumors in contrast to immortalized cell lines from metastatic effusions in order to represent the primary tumor and not principally metastatic biology of breast cancer. This investigation describes the simultaneous isolation, characterization, growth and function of primary mammary epithelial cells (MEC), mesenchymal cells (MES) and adipose derived stem cells (ADSC) from four normal breasts, one inflammatory and one triple-negative ductal breast tumors. Methods A total of 17 cell lines were established and gene expression was analyzed for MEC and MES (n = 42) and ADSC (n = 48) and MUC1, pan-KRT, CD90 and GATA-3 by immunofluorescence. DNA fingerprinting to track cell line identity was performed between original primary tissues and isolates. Functional studies included ADSC differentiation, tumor MES and MEC invasion co-cultured with ADSC-conditioned media (CM) and MES adhesion and growth on 3D-printed scaffolds. Results Comparative analysis showed higher gene expression of EPCAM, CD49f, CDH1 and KRTs for normal MEC lines; MES lines e.g. Vimentin, CD10, ACTA2 and MMP9; and ADSC lines e.g. CD105, CD90, CDH2 and CDH11. Compared to the mean of all four normal breast cell lines, both breast tumor cell lines demonstrated significantly lower ADSC marker gene expression, but higher expression of mesenchymal and invasion gene markers like SNAI1 and MMP2. When compared with four normal ADSC differentiated lineages, both tumor ADSC showed impaired osteogenic and chondrogenic but enhanced adipogenic differentiation and endothelial-like structures, possibly due to high PDGFRB and CD34. Addressing a functional role for overproduction of adipocytes, we initiated 3D-invasion studies including different cell types from the same patient. CM from ADSC differentiating into adipocytes induced tumor MEC 3D-invasion via EMT and amoeboid phenotypes. Normal MES breast cells adhered and proliferated on 3D-printed scaffolds containing 20 fibers, but not on 2.5D-printed scaffolds with single fiber layers, important for tissue engineering. Conclusion Expression analyses confirmed successful simultaneous cell isolations of three different phenotypes from normal and tumor primary breast tissues. Our cell culture studies support that breast-tumor environment differentially regulates tumor ADSC plasticity as well as cell invasion and demonstrates applications for regenerative medicine.}, language = {en} } @article{LiashenkoHrynevichDalton2020, author = {Liashenko, Ievgenii and Hrynevich, Andrei and Dalton, Paul D.}, title = {Designing Outside the Box: Unlocking the Geometric Freedom of Melt Electrowriting using Microscale Layer Shifting}, series = {Advanced Materials}, volume = {32}, journal = {Advanced Materials}, number = {28}, doi = {10.1002/adma.202001874}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-217974}, year = {2020}, abstract = {Melt electrowriting, a high-resolution additive manufacturing technology, has so far been developed with vertical stacking of fiber layers, with a printing trajectory that is constant for each layer. In this work, microscale layer shifting is introduced through deliberately offsetting the printing trajectory for each printed layer. Inaccuracies during the printing of sinusoidal walls are corrected via layer shifting, resulting in accurate control of their geometry and mechanical properties. Furthermore, more substantial layer shifting allows stacking of fiber layers in a horizontal manner, overcoming the electrostatic autofocusing effect that favors vertical layer stacking. Novel nonlinear geometries, such as overhangs, wall texturing and branching, and smooth and abrupt changes in printing trajectory are presented, demonstrating the flexibility of the layer shifting approach beyond the state-of-the-art. The practice of microscale layer shifting for melt electrowriting enables more complex geometries that promise to have a profound impact on the development of products in a broad range of applications.}, language = {en} } @article{MechauFrankBakircietal.2021, author = {Mechau, Jannik and Frank, Andreas and Bakirci, Ezgi and Gumbel, Simon and Jungst, Tomasz and Giesa, Reiner and Groll, J{\"u}rgen and Dalton, Paul D. and Schmidt, Hans-Werner}, title = {Hydrophilic (AB)\(_{n}\) Segmented Copolymers for Melt Extrusion-Based Additive Manufacturing}, series = {Macromolecular Chemistry and Physics}, volume = {222}, journal = {Macromolecular Chemistry and Physics}, number = {1}, doi = {10.1002/macp.202000265}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-224513}, year = {2021}, abstract = {Several manufacturing technologies beneficially involve processing from the melt, including extrusion-based printing, electrospinning, and electrohydrodynamic jetting. In this study, (AB)\(_{n}\) segmented copolymers are tailored for melt-processing to form physically crosslinked hydrogels after swelling. The copolymers are composed of hydrophilic poly(ethylene glycol)-based segments and hydrophobic bisurea segments, which form physical crosslinks via hydrogen bonds. The degree of polymerization was adjusted to match the melt viscosity to the different melt-processing techniques. Using extrusion-based printing, a width of approximately 260 µm is printed into 3D constructs, with excellent interlayer bonding at fiber junctions, due to hydrogen bonding between the layers. For melt electrospinning, much thinner fibers in the range of about 1-15 µm are obtained and produced in a typical nonwoven morphology. With melt electrowriting, fibers are deposited in a controlled way to well-defined 3D constructs. In this case, multiple fiber layers fuse together enabling constructs with line width in the range of 70 to 160 µm. If exposed to water the printed constructs swell and form physically crosslinked hydrogels that slowly disintegrate, which is a feature for soluble inks within biofabrication strategies. In this context, cytotoxicity tests confirm the viability of cells and thus demonstrating biocompatibility of this class of copolymers.}, language = {en} }