@phdthesis{MathewSchmitt2024, author = {Mathew-Schmitt, Sanjana}, title = {Development of blood-brain barrier spheroid models based on human induced pluripotent stem cells (hiPSCs) and investigation of shear stress on hiPSC-derived brain capillary endothelial-like cells}, doi = {10.25972/OPUS-32247}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-322475}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2024}, abstract = {A highly regulated microenvironment is essential in maintaining normal functioning of the central nervous system (CNS). The existence of a biological barrier, termed as the blood-brain barrier (BBB), at the blood to brain interface effectively allows for selective passage of substances and pathogens into the brain (Kadry, Noorani et al. 2020). The BBB chiefly serves in protecting the brain from extrinsic toxin entry and pathogen invasions. The BBB is formed mainly by brain capillary endothelial cells (BCECs) which are responsible for excluding ∼ 100\% of large-molecule neurotherapeutics and more than 98\% of all small-molecule drugs from entry into the brain. Minimal BBB transport of major potential CNS drugs allows for attenuated effective treatments for majority of CNS disorders (Appelt-Menzel, Oerter et al. 2020). Animals are generally used as model systems to study neurotherapeutic delivery into the brain, however due to species based disparity, experimental animal models lead to several false positive or false negative drug efficacy predictions thereby being unable to fully predict effects in humans (Ruck, Bittner et al. 2015). An example being that over the last two decades, much of the studies involving animals lead to high failure rates in drug development with ~ 97\% failure in cancers and ~ 99\% failure for Alzheimer´s disease (Pound 2020). Widespead failures in clinical trials associated with neurological disorders have resulted in questions on whether existing preclinical animal models are genuinely reflective of the human condition (Bhalerao, Sivandzade et al. 2020). Apart from high failure rates in humans, the costs for animal testings is extremely high. According to the Organisation for Economic Co-operation and Development (OECD), responsible for determining animal testing guidelines and methodology for government, industry, and independent laboratories the average cost of a single two-generation reproductive animal toxicity study worldwide is 318,295 € and for Europe alone is ~ 285,842 € (Van Norman 2019). Due to these reasons two separate movements exist within the scientific world, one being to improve animal research and the other to promote new approach methodologies with the European government setting 2025 - 2035 as a deadline for gradually disposing the use of animals in pharmaceutical testing (Pound 2020). The discovery of human induced pluripotent stem cell (hiPSC) technology in 2006 (Takahashi and Yamanaka 2006, Takahashi, Tanabe et al. 2007) revolutionized the field of drug discovery in-vitro. HiPSCs can be differentiated into various tissue types that mimic disease phenotypes, thereby offering the possibility to deliver humanized in-vitro test systems. With respect to the BBB, several strategies to differentiate hiPSCs to BCECs (iBCECs) are reported over the years (Appelt-Menzel, Oerter et al. 2020). However, iBCECs are said to possess an epithelial or undifferentiated phenotype causing incongruity in BBB lineage specifications (Lippmann, 7 Azarin et al. 2020). Therefore, in order to identify a reliable differentiation strategy in deriving iBCECs possessing hallmark BBB characteristics, which can be used for downstream applications, the work in this thesis compared two methods, namely the co-differentiation (CD) and the directed differentiation (DD). Briefly, CD mimics a brain like niche environment for iBCEC specification (Lippmann, Al-Ahmad et al. 2014), while DD focuses on induction of the mesoderm followed by iBCEC specification (Qian, Maguire et al. 2017). The results obtained verified that while iBCECs derived via CD, in comparison to human BCEC cell line hCMEC/D3 showed the presence of epithelial transcripts such as E-Cadherin (CDH1), and gene level downregulation of endothelial specific platelet endothelial cell adhesion molecule-1 (PECAM-1) and VE-cadherin (CDH5) but demonstrated higher barrier integrity. The CD strategy essentially presented iBCECs with a mean trans-endothelial electrical resistance (TEER) of ~ 2000 - 2500 Ω*cm2 and low permeability coefficients (PC) of < 0.50 μm/min for small molecule transport of sodium fluorescein (NaF) and characteristic BCEC tight junction (TJ) protein expression of claudin-5 and occludin. Additionally, iBCECs derived via CD did not form tubes in response to angiogenic stimuli. DD on the other hand resulted in iBCECs with similar down regulations in PECAM-1 and CDH5 gene expression. They were additionally characterized by lower barrier integrity, measured by mean TEER of only ~ 250 - 450 Ω*cm2 and high PC of > 5 μm/min in small molecule transport of NaF. Although iBCECs derived via DD formed tubes in response to angiogenic stimuli, they did not show positive protein expression of characteristic BCEC TJs such as claudin-5 and occludin. These results led to the hypothesis that maturity and lineage specification of iBCECs could be improved by incorporating in-vivo like characteristics in-vitro, such as direct co-culture with neurovascular unit (NVU) cell types via spheroid formation and by induction of shear stress and fluid flow. In comparison to standard iBCEC transwell mono-cultures, BBB spheroids showed enhanced transcript expression of PECAM-1 and reduced expression of epithelial markers such as CDH1 and claudin-6 (CLDN6). BBB spheroids showed classical BCEC-like ultrastructure that was identified by TJ particles on the protoplasmic face (P-face) and exoplasmic face (E-face) of the plasma membrane. TJ strands were organized as particles and particle-free grooves on the E-face, while on the P-face, partly beaded particles and partly continuous strands were identified. BBB spheroids also showed positive protein expression of claudin-5, VE-cadherin, PECAM-1, glucose transporter-1 (GLUT-1), P-glycoprotein (P-gp) and transferrin receptor-1 (Tfr-1). BBB spheroids demonstrated higher relative impedance percentages in comparison to spheroids without an iBCEC barrier. Barrier integrity assessments additionally corresponded with lower permeability to small molecule tracer NaF, with spheroids containing iBCECs showing higher relative fluorescence unit percentages (RFU\%) of ~ 90\% in apical compartments, compared to ~ 80\% in spheroids without iBCECs. In summary, direct cellular contacts in the complex spheroid model resulted in enhanced maturation of iBCECs. 8 A bioreactor system was used to further assess the effect of shear stress. This system enabled inclusion of fluidic flow and shear stress conditions in addition to non-invasive barrier integrity measurements (Choi, Mathew et al. 2022). iBCECs were cultured for a total of seven days post differentiation (d17) within the bioreactor and barrier integrity was non-invasively monitored. Until d17 of long-term culture, TEER values of iBCECs steadily dropped from ~ 1800 Ω*cm2 ~ 400 Ω*cm2 under static conditions and from ~ 2500 Ω*cm2 to ~ 250 Ω*cm2 under dynamic conditions. Transcriptomic analyses, morphometric analyses and protein marker expression showed enhanced maturation of iBECs under long-term culture and dynamic flow. Importantly, on d10 claudin-5 was expressed mostly in the cytoplasm with only ~ 5\% iBCECs showing continuous staining at the cell borders. With increase in culture duration, iBCECs at d17 of static culture showed ~ 18\% of cells having continuous cell border expression, while dynamic conditions showed upto ~ 30\% of cells with continuous cell-cell border expression patterns. Similarly, ~ 33\% of cells showed cell-cell border expression of occludin on d10 with increases to ~ 55\% under d17 static and up to ~ 65\% under d17 dynamic conditions, thereby indicating iBCEC maturation. In conclusion, the data presented within this thesis demonstrates the maturation of iBCECs in BBB spheroids, obtained via direct cellular contacts and by the application of flow and shear stress. Both established novel models need to be further validated for pharmaceutical drug applications together with in-vitro-in-vivo correlations in order to exploit their full potential.}, subject = {Blut-Hirn-Schranke}, language = {en} } @article{CalderonPenaSuarezetal.2019, author = {Calderon, Dayana and Pe{\~n}a, Luis and Suarez, Ang{\´e}lica and Villamil, Carolina and Ramirez-Rojas, Adan and Anzola, Juan M. and Garc{\´i}a-Betancur, Juan C. and Cepeda, Martha L. and Uribe, Daniel and Del Portillo, Patricia and Mongui, Alvaro}, title = {Recovery and functional validation of hidden soil enzymes in metagenomic libraries}, series = {MicrobiologyOpen}, volume = {8}, journal = {MicrobiologyOpen}, doi = {10.1002/mbo3.572}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-222016}, year = {2019}, abstract = {The vast microbial diversity on the planet represents an invaluable source for identifying novel activities with potential industrial and therapeutic application. In this regard, metagenomics has emerged as a group of strategies that have significantly facilitated the analysis of DNA from multiple environments and has expanded the limits of known microbial diversity. However, the functional characterization of enzymes, metabolites, and products encoded by diverse microbial genomes is limited by the inefficient heterologous expression of foreign genes. We have implemented a pipeline that combines NGS and Sanger sequencing as a way to identify fosmids within metagenomic libraries. This strategy facilitated the identification of putative proteins, subcloning of targeted genes and preliminary characterization of selected proteins. Overall, the in silico approach followed by the experimental validation allowed us to efficiently recover the activity of previously hidden enzymes derived from agricultural soil samples. Therefore, the methodology workflow described herein can be applied to recover activities encoded by environmental DNA from multiple sources.}, language = {en} } @article{GermainBrandBurlinaetal.2018, author = {Germain, Dominique P. and Brand, Eva and Burlina, Alessandro and Cecchi, Franco and Garman, Scott C. and Kempf, Judy and Laney, Dawn A. and Linhart, Aleš and Mar{\´o}di, L{\´a}szl{\´o} and Nicholls, Kathy and Ortiz, Alberto and Pieruzzi, Federico and Shankar, Suma P. and Waldek, Stephen and Wanner, Christoph and Jovanovic, Ana}, title = {Phenotypic characteristics of the p.Asn215Ser (p.N215S) GLA mutation in male and female patients with Fabry disease: A multicenter Fabry Registry study}, series = {Molecular Genetics \& Genomic Medicine}, volume = {6}, journal = {Molecular Genetics \& Genomic Medicine}, doi = {10.1002/mgg3.389}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-232976}, pages = {492-503}, year = {2018}, abstract = {Background The p.Asn215Ser or p.N215S GLA variant has been associated with late-onset cardiac variant of Fabry disease. Methods To expand on the scarce phenotype data, we analyzed natural history data from 125 p.N215S patients (66 females, 59 males) enrolled in the Fabry Registry (NCT00196742) and compared it with data from 401 patients (237 females, 164 males) harboring mutations associated with classic Fabry disease. We evaluated interventricular septum thickness (IVST), left ventricular posterior wall thickness (LVPWT), estimated glomerular filtration rate and severe clinical events. Results In p.N215S males, mildly abnormal mean IVST and LVPWT values were observed in patients aged 25-34 years, and values gradually increased with advancing age. Mean values were similar to those of classic males. In p.N215S females, these abnormalities occurred primarily in patients aged 55-64 years. Severe clinical events in p.N215S patients were mainly cardiac (males 31\%, females 8\%) while renal and cerebrovascular events were rare. Renal impairment occurred in 17\% of p.N215S males (mostly in patients aged 65-74 years), and rarely in females (3\%). Conclusion p.N215S is a disease-causing mutation with severe clinical manifestations found primarily in the heart. Cardiac involvement may become as severe as in classic Fabry patients, especially in males.}, language = {en} } @article{MirzaVainshteinDiRonzaetal.2019, author = {Mirza, Myriam and Vainshtein, Anna and DiRonza, Alberto and Chandrachud, Uma and Haslett, Luke J. and Palmieri, Michela and Storch, Stephan and Groh, Janos and Dobzinski, Niv and Napolitano, Gennaro and Schmidtke, Carolin and Kerkovich, Danielle M.}, title = {The CLN3 gene and protein: What we know}, series = {Molecular Genetics \& Genomic Medicine}, volume = {7}, journal = {Molecular Genetics \& Genomic Medicine}, doi = {10.1002/mgg3.859}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-224138}, year = {2019}, abstract = {Background One of the most important steps taken by Beyond Batten Disease Foundation in our quest to cure juvenile Batten (CLN3) disease is to understand the State of the Science. We believe that a strong understanding of where we are in our experimental understanding of the CLN3 gene, its regulation, gene product, protein structure, tissue distribution, biomarker use, and pathological responses to its deficiency, lays the groundwork for determining therapeutic action plans. Objectives To present an unbiased comprehensive reference tool of the experimental understanding of the CLN3 gene and gene product of the same name. Methods BBDF compiled all of the available CLN3 gene and protein data from biological databases, repositories of federally and privately funded projects, patent and trademark offices, science and technology journals, industrial drug and pipeline reports as well as clinical trial reports and with painstaking precision, validated the information together with experts in Batten disease, lysosomal storage disease, lysosome/endosome biology. Results The finished product is an indexed review of the CLN3 gene and protein which is not limited in page size or number of references, references all available primary experiments, and does not draw conclusions for the reader. Conclusions Revisiting the experimental history of a target gene and its product ensures that inaccuracies and contradictions come to light, long-held beliefs and assumptions continue to be challenged, and information that was previously deemed inconsequential gets a second look. Compiling the information into one manuscript with all appropriate primary references provides quick clues to which studies have been completed under which conditions and what information has been reported. This compendium does not seek to replace original articles or subtopic reviews but provides an historical roadmap to completed works.}, language = {en} } @article{JandkeGarzSchwankeetal.2018, author = {Jandke, Solveig and Garz, Cornelia and Schwanke, Daniel and Sendtner, Michael and Heinze, Hans-Jochen and Carare, Roxana O. and Schreiber, Stefanie}, title = {The association between hypertensive arteriopathy and cerebral amyloid angiopathy in spontaneously hypertensive stroke-prone rats}, series = {Brain Pathology}, volume = {28}, journal = {Brain Pathology}, doi = {10.1111/bpa.12629}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-323279}, pages = {844-859}, year = {2018}, abstract = {We aimed to test the hypothesis that in spontaneously hypertensive stroke-prone rats (SHRSP), non-amyloid cerebral small vessel disease/hypertensive arteriopathy (HA) results in vessel wall injury that may promote cerebral amyloid angiopathy (CAA). Our study comprised 21 male SHRSP (age 17-44 weeks) and 10 age- and sex-matched Wistar control rats, that underwent two-photon (2PM) imaging of the arterioles in the parietal cortex using Methoxy-X04, Dextran and cerebral blood flow (CBF) measurements. Our data suggest that HA in SHRSP progresses in a temporal and age-dependent manner, starting from small vessel wall damage (stage 1A), proceeding to CBF reduction (stage 1B), non-occlusive (stage 2), and finally, occlusive thrombi (stage 3). Wistar animals also demonstrated small vessel wall damage, but were free of any of the later HA stages. Nearly half of all SHRSP additionally displayed vascular Methoxy-X04 positivity indicative of cortical CAA. Vascular β-amyloid deposits were found in small vessels characterized by thrombotic occlusions (stage 2 or 3). Post-mortem analysis of the rat brains confirmed the findings derived from intravital 2PM microscopy. Our data thus overall suggest that advanced HA may play a role in CAA development with the two small vessel disease entities might be related to the same pathological spectrum of the aging brain.}, language = {en} } @article{KwokUedaKadarietal.2018, author = {Kwok, Chee Keong and Ueda, Yuichiro and Kadari, Asifiqbal and G{\"u}nther, Katharina and Erg{\"u}n, S{\"u}leyman and Heron, Antoine and Schnitzler, Aletta C. and Rook, Martha and Edenhofer, Frank}, title = {Scalable stirred suspension culture for the generation of billions of human induced pluripotent stem cells using single-use bioreactors}, series = {Journal of Tissue Engineering and Regenerative Medicine}, volume = {12}, journal = {Journal of Tissue Engineering and Regenerative Medicine}, doi = {10.1002/term.2435}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-234545}, pages = {e1076-e1087}, year = {2018}, abstract = {The production of human induced pluripotent stem cells (hiPSCs) in quantities that are relevant for cell-based therapies and cell-loaded implants through standard adherent culture is hardly achievable and lacks process scalability. A promising approach to overcoming these hurdles is the culture of hiPSCs in suspension. In this study, stirred suspension culture vessels were investigated for their suitability in the expansion of two hiPSC lines inoculated as a single cell suspension, with a free scalability between volumes of 50 and 2400 ml. The simple and robust two-step process reported here first generates hiPSC aggregates of 324 ± 71 μm diameter in 7 days in 125 ml spinner flasks (100 ml volume). These are subsequently dissociated into a single cell suspension for inoculation in 3000 ml bioreactors (1000 ml volume), finally yielding hiPSC aggregates of 198 ± 58 μm after 7 additional days. In both spinner flasks and bioreactors, hiPSCs can be cultured as aggregates for more than 40 days in suspension, maintain an undifferentiated state as confirmed by the expression of pluripotency markers TRA-1-60, TRA-1-81, SSEA-4, OCT4, and SOX2, can differentiate into cells of all three germ layers, and can be directed to differentiate into specific lineages such as cardiomyocytes. Up to a 16-fold increase in hiPSC quantity at the 100 ml volume was achieved, corresponding to a fold increase per day of 2.28; at the 1000 ml scale, an additional 10-fold increase was achieved. Taken together, 16 × 106 hiPSCs were expanded into 2 × 109 hiPSCs in 14 days for a fold increase per day of 8.93. This quantity of hiPSCs readily meets the requirements of cell-based therapies and brings their clinical potential closer to fruition.}, language = {en} } @article{HettichSchierjottRammetal.2019, author = {Hettich, Georg and Schierjott, Ronja A. and Ramm, Heiko and Graichen, Heiko and Jansson, Volkmar and Rudert, Maximilian and Traina, Francesco and Grupp, Thomas M.}, title = {Method for quantitative assessment of acetabular bone defects}, series = {Journal of Orthopaedic Research}, volume = {37}, journal = {Journal of Orthopaedic Research}, doi = {10.1002/jor.24165}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-320226}, pages = {181-189}, year = {2019}, abstract = {The objective of the study was to suggest a novel quantitative assessment of acetabular bone defects based on a statistical shape model, validate the method, and present preliminary results. Two exemplary CT-data sets with acetabular bone defects were segmented to obtain a solid model of each defect pelvis. The pathological areas around the acetabulum were excluded and a statistical shape model was fitted to the remaining healthy bone structures. The excluded areas were extrapolated such that a solid model of the native pelvis per specimen resulted (i.e., each pelvis without defect). The validity of the reconstruction was tested by a leave-one-out study. Validation results showed median reconstruction errors of 3.0 mm for center of rotation, 1.7 mm for acetabulum diameter, 2.1° for inclination, 2.5° for anteversion, and 3.3 mm3 for bone volume around the acetabulum. By applying Boolean operations on the solid models of defect and native pelvis, bone loss and bone formation in four different sectors were assessed. For both analyzed specimens, bone loss and bone formation per sector were calculated and were consistent with the visual impression. In specimen_1 bone loss was predominant in the medial wall (10.8 ml; 79\%), in specimen_2 in the posterior column (15.6 ml; 46\%). This study showed the feasibility of a quantitative assessment of acetabular bone defects using a statistical shape model-based reconstruction method. Validation results showed acceptable reconstruction accuracy, also when less healthy bone remains. The method could potentially be used for implant development, pre-clinical testing, pre-operative planning, and intra-operative navigation. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 9999:1-9, 2018.}, language = {en} } @article{GreberPolatFlentjeetal.2019, author = {Greber, Johannes and Polat, B{\"u}lent and Flentje, Michael and Bratengeier, Klaus}, title = {Properties of the anisotropy of dose contributions: A planning study on prostate cases}, series = {Medical Physics}, volume = {46}, journal = {Medical Physics}, doi = {10.1002/mp.13308}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-228237}, pages = {419-425}, year = {2019}, abstract = {Purpose To characterize the static properties of the anisotropy of dose contributions for different treatment techniques on real patient data (prostate cases). From this, we aim to define a class of treatment techniques with invariant anisotropy distribution carrying information of target coverage and organ-at-risk (OAR) sparing. The anisotropy presumably is a helpful quantity for plan adaptation problems. Methods The anisotropy field is analyzed for different intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) techniques for a total of ten planning CTs of prostate cases. Primary irradiation directions ranged from 5 to 15. The uniqueness of anisotropy was explored: In particular, the anisotropy distribution inside the planning treatment volume (PTV) and in its vicinity was investigated. Furthermore, deviations of the anisotropy under beam rotations were explored by direct plan comparison as an indicating the susceptibility of each planned technique to changes in the geometric plan configuration. In addition, plan comparisons enabled the categorization of treatment techniques in terms of their anisotropy distribution. Results The anisotropy profile inside the PTV and in the transition between OAR and PTV is independent of the treatment technique as long as a sufficient number of beams contribute to the dose distribution. Techniques with multiple beams constitute a class of almost identical and technique-independent anisotropy distribution. For this class of techniques, substructures of the anisotropy are particularly pronounced in the PTV, thus offering good options for applying adaptation rules. Additionally, the techniques forming the mentioned class fortunately allow a better OAR sparing at constant PTV coverage. Besides the characterization of the distribution, a pairwise plan comparison reveals each technique's susceptibility to deviations which decreases for an increasing number of primary irradiation directions. Conclusions Techniques using many irradiation directions form a class of almost identical anisotropy distributions which are assumed to provide a basis for improved adaptation procedures. Encouragingly, these techniques deliver quite invariant anisotropy distributions with respect to rotations correlated with good plan qualities than techniques using few gantry angles. The following will be the next steps toward anisotropy-based adaptation: first, the quantification of anisotropy regarding organ deformations; and second, establishing the interrelation between the anisotropy and beam shaping.}, language = {en} } @article{deRuijterHrynevichHaighetal.2018, author = {de Ruijter, Myl{\`e}ne and Hrynevich, Andrei and Haigh, Jodie N. and Hochleitner, Gernot and Castilho, Miguel and Groll, J{\"u}rgen and Malda, Jos and Dalton, Paul D.}, title = {Out-of-Plane 3D-Printed Microfibers Improve the Shear Properties of Hydrogel Composites}, series = {Small}, volume = {14}, journal = {Small}, doi = {10.1002/smll.201702773}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-223666}, year = {2018}, abstract = {One challenge in biofabrication is to fabricate a matrix that is soft enough to elicit optimal cell behavior while possessing the strength required to withstand the mechanical load that the matrix is subjected to once implanted in the body. Here, melt electrowriting (MEW) is used to direct-write poly(ε-caprolactone) fibers "out-of-plane" by design. These out-of-plane fibers are specifically intended to stabilize an existing structure and subsequently improve the shear modulus of hydrogel-fiber composites. The stabilizing fibers (diameter = 13.3 ± 0.3 µm) are sinusoidally direct-written over an existing MEW wall-like structure (330 µm height). The printed constructs are embedded in different hydrogels (5, 10, and 15 wt\% polyacrylamide; 65\% poly(2-hydroxyethyl methacrylate) (pHEMA)) and a frequency sweep test (0.05-500 rad s-1, 0.01\% strain, n = 5) is performed to measure the complex shear modulus. For the rheological measurements, stabilizing fibers are deposited with a radial-architecture prior to embedding to correspond to the direction of the stabilizing fibers with the loading of the rheometer. Stabilizing fibers increase the complex shear modulus irrespective of the percentage of gel or crosslinking density. The capacity of MEW to produce well-defined out-of-plane fibers and the ability to increase the shear properties of fiber-reinforced hydrogel composites are highlighted.}, language = {en} } @article{HrynevichElciHaighetal.2018, author = {Hrynevich, Andrei and El{\c{c}}i, Bilge Ş. and Haigh, Jodie N. and McMaster, Rebecca and Youssef, Almoatazbellah and Blum, Carina and Blunk, Torsten and Hochleitner, Gernot and Groll, J{\"u}rgen and Dalton, Paul D.}, title = {Dimension-Based Design of Melt Electrowritten Scaffolds}, series = {Small}, volume = {14}, journal = {Small}, doi = {10.1002/smll.201800232}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-322677}, year = {2018}, abstract = {The electrohydrodynamic stabilization of direct-written fluid jets is explored to design and manufacture tissue engineering scaffolds based on their desired fiber dimensions. It is demonstrated that melt electrowriting can fabricate a full spectrum of various fibers with discrete diameters (2-50 µm) using a single nozzle. This change in fiber diameter is digitally controlled by combining the mass flow rate to the nozzle with collector speed variations without changing the applied voltage. The greatest spectrum of fiber diameters was achieved by the simultaneous alteration of those parameters during printing. The highest placement accuracy could be achieved when maintaining the collector speed slightly above the critical translation speed. This permits the fabrication of medical-grade poly(ε-caprolactone) into complex multimodal and multiphasic scaffolds, using a single nozzle in a single print. This ability to control fiber diameter during printing opens new design opportunities for accurate scaffold fabrication for biomedical applications.}, language = {en} }