49 results on '"Hochleitner G"'
Search Results
2. Medical-grade polycaprolactone scaffolds made by melt electrospinning writing for oral bone regeneration – a pilot study in vitro
- Author
-
Fuchs, A., Youssef, A., Seher, A., Hochleitner, G., Dalton, P. D., Hartmann, S., Brands, R. C., Müller-Richter, U. D. A., and Linz, C.
- Published
- 2019
- Full Text
- View/download PDF
Catalog
3. Theoretical modelling of fibrinogen supplementation with therapeutic plasma, cryoprecipitate, or fibrinogen concentrate
- Author
-
Collins, P.W., Solomon, C., Sutor, K., Crispin, D., Hochleitner, G., Rizoli, S., Schöchl, H., Schreiber, M., and Ranucci, M.
- Published
- 2014
- Full Text
- View/download PDF
4. Mapping of local argon impingement on a virtual surface: an insight for gas injection during FEBID
- Author
-
Wanzenboeck, H. D., Hochleitner, G., Mika, J., Shawrav, M. M., Gavagnin, M., and Bertagnolli, E.
- Published
- 2014
- Full Text
- View/download PDF
5. In search for in vivo methods to visualize clot forming in cut vessels and interrupted flow
- Author
-
Solomon, C., White, N. J., Hochleitner, G., Hermann, M., and Fries, D.
- Published
- 2016
- Full Text
- View/download PDF
6. Nanowire-metal heterostructures for high performance MOSFETs
- Author
-
Burchhart, T., Lugstein, A., Zeiner, C., Hyun, Y. J., Hochleitner, G., and Bertagnolli, E.
- Published
- 2010
- Full Text
- View/download PDF
7. Multibeam mask requirements for advanced EUV patterning
- Author
-
Kasprowicz, Bryan S., Liang, Ted, Chandramouli, M., Liu, B., Alberti, Z., Abboud, F., Hochleitner, G., Wroczewski, W., Kuhn, S., Klein, C., and Platzgummer, E.
- Published
- 2022
- Full Text
- View/download PDF
8. P463Engineering myocardial tissue in vitro using stretchable microfiber scaffolds and human iPSC-derived cardiomyocytes
- Author
-
Van Mil, A, primary, Castilho, M, additional, Maher, M, additional, Metz, C H, additional, Maas, RGC, additional, Hochleitner, G, additional, Groll, J, additional, Ito, K, additional, Malda, J, additional, and Sluijter, JPG, additional more...
- Published
- 2018
- Full Text
- View/download PDF
9. Focused electron beam induced etching of silicon by chlorine gas: Negative effects of residual gas contamination on the etching process.
- Author
-
Roediger, P., Wanzenboeck, H. D., Hochleitner, G., Bertagnolli, E., and Buehler, W.
- Subjects
ELECTRON beam research ,SILICON research ,CHLORINE ,HYDROCARBONS ,RESIDUAL stresses - Abstract
For the first time focused electron beam induced etching of silicon using molecular chlorine has been developed as reliable and reproducible process. Around the etched pits the etching process was found to be accompanied by carbonaceous deposition from hydrocarbon contamination of the residual gas typically present in a scanning electron microscope (SEM). This work will focus on the effect of residual gas deposition on this silicon etch process using chlorine. The process mechanisms for residual gas deposition (in the absence of chlorine) as well as the silicon etch process in the presence of chlorine are discussed in terms of precursor replenishment of the sample surface and precursor delivery to the processed area. The formation of carbonaceous deposits from undesired contaminants can block the surface from an etch process. Especially for low beam currents this problem was encountered. Results suggest that the presence of chlorine when processed with a high electron beam current dominates over residual gas deposition. On the other hand, the etch-inhibiting effect of an increased level of SEM chamber contamination (resulting in increased residual gas deposition rates) is shown. [ABSTRACT FROM AUTHOR] more...
- Published
- 2010
- Full Text
- View/download PDF
10. Out-of-plane 3D-printed microfibers improve the shear properties of hydrogel composites
- Author
-
de Ruijter, M., Hrynevich, A., Haigh, J.N., Hochleitner, G., Castilho, M., Groll, J., Malda, J., Dalton, P.D., de Ruijter, M., Hrynevich, A., Haigh, J.N., Hochleitner, G., Castilho, M., Groll, J., Malda, J., and Dalton, P.D. more...
- 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. more...
- Published
- 2018
11. Mechanical behavior of a soft hydrogel reinforced with three-dimensional printed microfibre scaffolds
- Author
-
Castilho, M., Hochleitner, G., Wilson, W.E., van Rietbergen, B., Dalton, P.D., Groll, J., Malda, J., Ito, K., Castilho, M., Hochleitner, G., Wilson, W.E., van Rietbergen, B., Dalton, P.D., Groll, J., Malda, J., and Ito, K. more...
- 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. more...
- Published
- 2018
12. Melt electrospinning writing of poly-Hydroxymethylglycolide-co-ε-Caprolactone-based scaffolds for cardiac tissue engineering
- Author
-
Castilho, M., Feyen, D., Flandes-Iparraguirre, M., Hochleitner, G., Groll, J., Doevendans, P.A.F., Vermonden, T., Ito, K., Sluijter, J.P.G., Malda, J., Castilho, M., Feyen, D., Flandes-Iparraguirre, M., Hochleitner, G., Groll, J., Doevendans, P.A.F., Vermonden, T., Ito, K., Sluijter, J.P.G., and Malda, J. more...
- Abstract
Current limitations in cardiac tissue engineering revolve around the inability to fully recapitulate the structural organization and mechanical environment of native cardiac tissue. This study aims at developing organized ultrafine fiber scaffolds with improved biocompatibility and architecture in comparison to the traditional fiber scaffolds obtained by solution electrospinning. This is achieved by combining the additive manufacturing of a hydroxyl-functionalized polyester, (poly(hydroxymethylglycolide-co-ε-caprolactone) (pHMGCL), with melt electrospinning writing (MEW). The use of pHMGCL with MEW vastly improves the cellular response to the mechanical anisotropy. Cardiac progenitor cells (CPCs) are able to align more efficiently along the preferential direction of the melt electrospun pHMGCL fiber scaffolds in comparison to electrospun poly(ε-caprolactone)-based scaffolds. Overall, this study describes for the first time that highly ordered microfiber (4.0–7.0 µm) scaffolds based on pHMGCL can be reproducibly generated with MEW and that these scaffolds can support and guide the growth of CPCs and thereby potentially enhance their therapeutic potential. more...
- Published
- 2017
13. Over 50 Years of Fibrinogen Concentrate
- Author
-
Costa-Filho, R, Hochleitner, G, Wendt, M, Teruya, A, Spahn, D R, Costa-Filho, R, Hochleitner, G, Wendt, M, Teruya, A, and Spahn, D R
- Published
- 2016
14. Multi-beam patterning technology and mask making beyond 5nm.
- Author
-
Shamoun, B., Alberti, Z., Bucay, I., Ellis, S., Erickson, M., Liu, B., Chandramouli, M., Sowers, A. T., Abboud, F. E., Hochleitner, G., Tomandl, M., Klein, C., and Platzgummer, E.
- Published
- 2023
- Full Text
- View/download PDF
15. Multibeam mask requirements for advanced EUV patterning.
- Author
-
Chandramouli, M., Liu, B., Alberti, Z., Abboud, F., Hochleitner, G., Wroczewski, W., Kuhn, S., Klein, C., and Platzgummer, E.
- Published
- 2022
- Full Text
- View/download PDF
16. Multi-beam patterning technology and mask making beyond 5nm
- Author
-
Liddle, J. Alexander, Ruiz, Ricardo, Shamoun, B., Alberti, Z., Bucay, I., Ellis, S., Erickson, M., Liu, B., Chandramouli, M., Sowers, A. T., Abboud, F. E., Hochleitner, G., Tomandl, M., Klein, C., and Platzgummer, E. more...
- Published
- 2023
- Full Text
- View/download PDF
17. Focused-ion-beam-inflicted surface amorphization and gallium implantation—new insights and removal by focused-electron-beam-induced etching
- Author
-
Roediger, P, primary, Wanzenboeck, H D, additional, Waid, S, additional, Hochleitner, G, additional, and Bertagnolli, E, additional
- Published
- 2011
- Full Text
- View/download PDF
18. Novel method for cleaning a vacuum chamber from hydrocarbon contamination
- Author
-
Wanzenboeck, H. D., primary, Roediger, P., additional, Hochleitner, G., additional, Bertagnolli, E., additional, and Buehler, W., additional
- Published
- 2010
- Full Text
- View/download PDF
19. High performance Ω-gated Ge nanowire MOSFET with quasi-metallic source/drain contacts
- Author
-
Burchhart, T, primary, Zeiner, C, additional, Hyun, Y J, additional, Lugstein, A, additional, Hochleitner, G, additional, and Bertagnolli, E, additional
- Published
- 2010
- Full Text
- View/download PDF
20. Focused electron beam induced etching of silicon using chlorine
- Author
-
Roediger, P, primary, Hochleitner, G, additional, Bertagnolli, E, additional, Wanzenboeck, H D, additional, and Buehler, W, additional
- Published
- 2010
- Full Text
- View/download PDF
21. Atomic Scale Alignment of Copper-Germanide Contacts for Ge Nanowire Metal Oxide Field Effect Transistors
- Author
-
Burchhart, T., primary, Lugstein, A., additional, Hyun, Y. J., additional, Hochleitner, G., additional, and Bertagnolli, E., additional
- Published
- 2009
- Full Text
- View/download PDF
22. Evaluation of chamber contamination in a scanning electron microscope
- Author
-
Roediger, P., primary, Wanzenboeck, H. D., additional, Hochleitner, G., additional, and Bertagnolli, E., additional
- Published
- 2009
- Full Text
- View/download PDF
23. Electron beam induced deposition of iron nanostructures
- Author
-
Hochleitner, G., primary, Wanzenboeck, H. D., additional, and Bertagnolli, E., additional
- Published
- 2008
- Full Text
- View/download PDF
24. Effects of fibrinogen concentrate as first-line therapy during major aortic replacement surgery: a randomized, placebo-controlled trial.
- Author
-
Rahe-Meyer N, Solomon C, Hanke A, Schmidt DS, Knoerzer D, Hochleitner G, Sørensen B, Hagl C, Pichlmaier M, Rahe-Meyer, Niels, Solomon, Cristina, Hanke, Alexander, Schmidt, Dirk S, Knoerzer, Dietrich, Hochleitner, Gerald, Sørensen, Benny, Hagl, Christian, and Pichlmaier, Maximilian more...
- Published
- 2013
- Full Text
- View/download PDF
25. P463Engineering myocardial tissue in vitro using stretchable microfiber scaffolds and human iPSC-derived cardiomyocytes.
- Author
-
Mil, A Van, Castilho, M, Maher, M, Metz, C H, Maas, RGC, Hochleitner, G, Groll, J, Ito, K, Malda, J, and Sluijter, JPG
- Subjects
MYOCARDIUM ,TISSUE engineering ,PLURIPOTENT stem cells - Published
- 2018
- Full Text
- View/download PDF
26. Controlling Topography and Crystallinity of Melt Electrowritten Poly(ɛ-Caprolactone) Fibers.
- Author
-
Blum C, Weichhold J, Hochleitner G, Stepanenko V, Würthner F, Groll J, and Jungst T
- Abstract
Melt electrowriting (MEW) is an aspiring 3D printing technology with an unprecedented resolution among fiber-based printing technologies. It offers the ability to direct-write predefined designs utilizing a jet of molten polymer to fabricate constructs composed of fibers with diameters of only a few micrometers. These dimensions enable unique construct properties. Poly(ɛ-caprolactone) (PCL), a semicrystalline polymer mainly used for biomedical and life science applications, is the most prominent material for MEW and exhibits excellent printing properties. Despite the wealth of melt electrowritten constructs that have been fabricated by MEW, a detailed investigation, especially regarding fiber analysis on a macro- and microlevel is still lacking. Hence, this study systematically examines the influence of process parameters such as spinneret diameter, feeding pressure, and collector velocity on the diameter and particularly the topography of PCL fibers and sheds light on how these parameters affect the mechanical properties and crystallinity. A correlation between the mechanical properties, crystallite size, and roughness of the deposited fiber, depending on the collector velocity and applied feeding pressure, is revealed. These findings are used to print constructs composed of fibers with different microtopography without affecting the fiber diameter and thus the macroscopic assembly of the printed constructs., Competing Interests: No competing financial interests exist., (Copyright 2021, Mary Ann Liebert, Inc., publishers.) more...
- Published
- 2021
- Full Text
- View/download PDF
27. Melt Electrospinning of Nanofibers from Medical-Grade Poly(ε-Caprolactone) with a Modified Nozzle.
- Author
-
Großhaus C, Bakirci E, Berthel M, Hrynevich A, Kade JC, Hochleitner G, Groll J, and Dalton PD
- Abstract
Melt electrospun fibers, in general, have larger diameters than normally achieved with solution electrospinning. This study uses a modified nozzle to direct-write melt electrospun medical-grade poly(ε-caprolactone) onto a collector resulting in fibers with the smallest average diameter being 275 ± 86 nm under certain processing conditions. Within a flat-tipped nozzle is a small acupuncture needle positioned so that reduces the flow rate to ≈0.1 µL h
-1 and has the sharp tip protruding beyond the nozzle, into the Taylor cone. The investigations indicate that 1-mm needle protrusion coupled with a heating temperature of 120 °C produce the most consistent, small diameter nanofibers. Using different protrusion distances for the acupuncture needle results in an unstable jet that deposited poor quality fibers that, in turn, affects the next adjacent path. The material quality is notably affected by the direct-writing speed, which became unstable above 10 mm min-1 . Coupled with a dual head printer, first melt electrospinning, then melt electrowriting could be performed in a single, automated process for the first time. Overall, the approach used here resulted in some of the smallest melt electrospun fibers reported to date and the smallest diameter fibers from a medical-grade degradable polymer using a melt processing technology., (© 2020 The Authors. Published by Wiley-VCH GmbH.) more...- Published
- 2020
- Full Text
- View/download PDF
28. Permanent Hydrophilization and Generic Bioactivation of Melt Electrowritten Scaffolds.
- Author
-
Bertlein S, Hochleitner G, Schmitz M, Tessmar J, Raghunath M, Dalton PD, and Groll J
- Subjects
- Cell Adhesion, Collagen chemistry, Humans, Hydrogels chemistry, Hydrophobic and Hydrophilic Interactions, Leucine chemistry, Lysine analogs & derivatives, Lysine chemistry, Mesenchymal Stem Cells cytology, Mesenchymal Stem Cells metabolism, Oligopeptides chemistry, Polyesters chemistry, Polyethylenes chemistry, Polypropylenes chemistry, Ultraviolet Rays, Tissue Scaffolds chemistry
- Abstract
Melt electrowriting (MEW) is an emerging additive manufacturing technology that direct-writes low-micron diameter fibers into 3D scaffolds with high porosities. Often, the polymers currently used for MEW are hydrophobic thermoplastics that induce unspecific protein adsorption and subsequent uncontrolled cell adhesion. Here are developed a coating strategy for MEW scaffolds based on six-arm star-shaped NCO-poly(ethylene oxide-stat-propylene oxide) (sP(EO-stat-PO)). This permanently hydrophilizes the PCL through the formation of a hydrogel coating and minimizes unspecific interactions with proteins and cells. It also provides the option of simultaneous covalent attachment of bioactive molecules through reaction with isocyanates before these are hydrolyzed. Furthermore, a photoactivatable chemical functionalization is introduced that is not dependent on the time-limited window of isocyanate chemistry. For this, photo-leucine is covalently immobilized into the sP(EO-stat-PO) layer, resulting in a photoactivatable scaffold that enables the binding of sterically demanding molecules at any timepoint after scaffold preparation and coating and is decoupled from the isocyanate chemistry. A successful biofunctionalization of MEW scaffolds via this strategy is demonstrated with streptavidin and collagen as examples. This hydrogel coating system is a generic one that introduces flexible specific and multiple surface functionalization, potentially for a spectrum of polymers made from different manufacturing processes., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.) more...
- Published
- 2019
- Full Text
- View/download PDF
29. Dimension-Based Design of Melt Electrowritten Scaffolds.
- Author
-
Hrynevich A, Elçi BŞ, Haigh JN, McMaster R, Youssef A, Blum C, Blunk T, Hochleitner G, Groll J, and Dalton PD
- Subjects
- Adipose Tissue cytology, Humans, Pressure, Stem Cells cytology, Electrochemistry methods, Tissue Engineering methods, Tissue Scaffolds chemistry
- 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., (© 2017 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.) more...
- Published
- 2018
- Full Text
- View/download PDF
30. Melt electrowriting below the critical translation speed to fabricate crimped elastomer scaffolds with non-linear extension behaviour mimicking that of ligaments and tendons.
- Author
-
Hochleitner G, Chen F, Blum C, Dalton PD, Amsden B, and Groll J
- Subjects
- Animals, Cell Line, Fibroblasts cytology, Materials Testing, Mice, Photochemical Processes, Tensile Strength, Biomimetic Materials chemical synthesis, Biomimetic Materials chemistry, Elastomers chemical synthesis, Elastomers chemistry, Fibroblasts metabolism, Ligaments, Tendons, Tissue Scaffolds chemistry
- Abstract
Ligaments and tendons are comprised of aligned, crimped collagen fibrils that provide tissue-specific mechanical properties with non-linear extension behaviour, exhibiting low stress at initial strain (toe region behaviour). To approximate this behaviour, we report fibrous scaffolds with sinusoidal patterns by melt electrowriting (MEW) below the critical translation speed (CTS) by exploitation of the natural flow behaviour of the polymer melt. More specifically, we synthesised photopolymerizable poly(L-lactide-co-ε-caprolactone-co-acryloyl carbonate) (p(LLA-co-ε-CL-co-AC)) and poly(ε-caprolactone-co-acryloyl carbonate) (p(ε-CL-co-AC)) by ring-opening polymerization (ROP). Single fibre (fØ = 26.8 ± 1.9 µm) tensile testing revealed a customisable toe region with Young's Moduli ranging from E = 29 ± 17 MPa for the most crimped structures to E = 314 ± 157 MPa for straight fibres. This toe region extended to scaffolds containing multiple fibres, while the sinusoidal pattern could be influenced by printing speed. The synthesized polymers were cytocompatible and exhibited a tensile strength of σ = 26 ± 7 MPa after 10
4 cycles of preloading at 10% strain while retaining the distinct toe region commonly observed in native ligaments and tendon tissue., Statement of Significance: Damaged tendons and ligaments are serious and frequently occurring injuries worldwide. Recent therapies, including autologous grafts, still have severe disadvantages leading to a demand for synthetic alternatives. Materials envisioned to induce tendon and ligament regeneration should be degradable, cytocompatible and mimic the ultrastructural and mechanical properties of the native tissue. Specifically, we utilised photo-cross-linkable polymers for additive manufacturing (AM) with MEW. In this way, we were able to direct-write cytocompatible fibres of a few micrometres thickness into crimp-structured elastomer scaffolds that mimic the non-linear biomechanical behaviour of tendon and ligament tissue., (Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.) more...- Published
- 2018
- Full Text
- View/download PDF
31. Melt Electrowriting of Thermoplastic Elastomers.
- Author
-
Hochleitner G, Fürsattel E, Giesa R, Groll J, Schmidt HW, and Dalton PD
- Subjects
- Printing, Three-Dimensional, Biocompatible Materials chemistry, Elastomers chemistry, Polyesters chemistry, Polymers chemistry, Tissue Engineering methods
- Abstract
Melt electrowriting (MEW), an additive manufacturing process, is established using polycaprolactone as the benchmark material. In this study, a thermoplastic elastomer, namely, poly(urea-siloxane), is synthesized and characterized to identify how different classes of polymers are compatible with MEW. This polyaddition polymer has reversible hydrogen bonding from the melt upon heating/cooling and highly resolved structures are achieved by MEW. The influence of applied voltage, temperature, and feeding pressure on printing outcomes behavior is optimized. Balancing these parameters, highly uniform and smooth-surfaced fibers with diameters ranging from 10 to 20 µm result. The quality of the 3D MEW scaffolds is excellent, with very accurate fiber stacking capacity-up to 50 layers with minimal defects and good fiber fusion between the layers. There is also minimal fiber sagging between the crossover points, which is a characteristic of thicker MEW scaffolds previously reported with other polymers. In summary, poly(urea-siloxane) demonstrates outstanding compatibility with the MEW process and represents a class of polymer-thermoplastic elastomers-that are, until now, untested with this approach., (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.) more...
- Published
- 2018
- Full Text
- View/download PDF
32. Out-of-Plane 3D-Printed Microfibers Improve the Shear Properties of Hydrogel Composites.
- Author
-
de Ruijter M, Hrynevich A, Haigh JN, Hochleitner G, Castilho M, Groll J, Malda J, and Dalton PD
- 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., (© 2017 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.) more...- Published
- 2018
- Full Text
- View/download PDF
33. Mechanical behavior of a soft hydrogel reinforced with three-dimensional printed microfibre scaffolds.
- Author
-
Castilho M, Hochleitner G, Wilson W, van Rietbergen B, Dalton PD, Groll J, Malda J, and Ito K
- 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. more...
- Published
- 2018
- Full Text
- View/download PDF
34. Development of Endothelial Cell Networks in 3D Tissues by Combination of Melt Electrospinning Writing with Cell-Accumulation Technology.
- Author
-
Bertlein S, Hikimoto D, Hochleitner G, Hümmer J, Jungst T, Matsusaki M, Akashi M, and Groll J
- Subjects
- Animals, Biocompatible Materials, Humans, Printing, Three-Dimensional, Tissue Engineering methods, Tissue Scaffolds, Endothelial Cells cytology
- Abstract
A remaining challenge in tissue engineering approaches is the in vitro vascularization of engineered constructs or tissues. Current approaches in engineered vascularized constructs are often limited in the control of initial vascular network geometry, which is crucial to ensure full functionality of these constructs with regard to cell survival, metabolic activity, and potential differentiation ability. Herein, the combination of 3D-printed poly-ε-caprolactone scaffolds via melt electrospinning writing with the cell-accumulation technique to enable the formation and control of capillary-like network structures is reported. The cell-accumulation technique is already proven itself to be a powerful tool in obtaining thick (50 µm) tissues and its main advantage is the rapid production of tissues and its ease of performance. However, the applied combination yields tissue thicknesses that are doubled, which is of outstanding importance for an improved handling of the scaffolds and the generation of clinically relevant sample volumes. Moreover, a correlation of increasing vascular endothelial growth factor secretion to hypoxic conditions with increasing pore sizes and an assessment of the formation of neovascular like structures are included., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.) more...
- Published
- 2018
- Full Text
- View/download PDF
35. Melt Electrospinning Writing of Poly-Hydroxymethylglycolide-co-ε-Caprolactone-Based Scaffolds for Cardiac Tissue Engineering.
- Author
-
Castilho M, Feyen D, Flandes-Iparraguirre M, Hochleitner G, Groll J, Doevendans PAF, Vermonden T, Ito K, Sluijter JPG, and Malda J
- Subjects
- Biocompatible Materials chemistry, Microscopy, Electron, Scanning methods, Porosity, Tissue Engineering methods, Caproates chemistry, Heart physiology, Lactones chemistry, Polyesters chemistry, Polymers chemistry, Tissue Scaffolds chemistry
- Abstract
Current limitations in cardiac tissue engineering revolve around the inability to fully recapitulate the structural organization and mechanical environment of native cardiac tissue. This study aims at developing organized ultrafine fiber scaffolds with improved biocompatibility and architecture in comparison to the traditional fiber scaffolds obtained by solution electrospinning. This is achieved by combining the additive manufacturing of a hydroxyl-functionalized polyester, (poly(hydroxymethylglycolide-co-ε-caprolactone) (pHMGCL), with melt electrospinning writing (MEW). The use of pHMGCL with MEW vastly improves the cellular response to the mechanical anisotropy. Cardiac progenitor cells (CPCs) are able to align more efficiently along the preferential direction of the melt electrospun pHMGCL fiber scaffolds in comparison to electrospun poly(ε-caprolactone)-based scaffolds. Overall, this study describes for the first time that highly ordered microfiber (4.0-7.0 µm) scaffolds based on pHMGCL can be reproducibly generated with MEW and that these scaffolds can support and guide the growth of CPCs and thereby potentially enhance their therapeutic potential., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.) more...
- Published
- 2017
- Full Text
- View/download PDF
36. Via precise interface engineering towards bioinspired composites with improved 3D printing processability and mechanical properties.
- Author
-
Hanßke F, Bas O, Vaquette C, Hochleitner G, Groll J, Kemnitz E, Hutmacher DW, and Börner HG
- Abstract
Precise interface engineering in inorganic-organic hybrid materials enhances both the elastic moduli and toughness of a biodegradable composite, which is of relevance for load-bearing applications in bone tissue engineering. Tailor-made MgF
2 -binding peptide-polymer conjugates (MBC) are utilized as precision compatibilizers, having sequence-specific affinity for the surfaces of the inorganic MgF2 fillers to stabilize these particles and to contribute to the interactions with the continuous polymer matrix. The effects of the coupling agents are investigated in additively biomanufactured scaffolds from composites composed of MBC compatibilized magnesium fluoride nanoparticles (cMgF2 ) and poly(ε-caprolactone). Mechanical properties, degradation behavior, ion release kinetics and in vitro cell viability are positively influenced by the presence of the compatibilized nanoparticles cMgF2 compared to pure, non-compatibilized MgF2 (pMgF2 ). Mechanical tensile, compression and indentation experiments with single filaments as well as with scaffolds a reveal strong improvement of both elastic moduli and material toughness. more...- Published
- 2017
- Full Text
- View/download PDF
37. Revisiting Hartert's 1962 Calculation of the Physical Constants of Thrombelastography.
- Author
-
Hochleitner G, Sutor K, Levett C, Leyser H, Schlimp CJ, and Solomon C
- Subjects
- Humans, Mechanical Phenomena, Viscoelastic Substances, Elasticity physiology, Models, Theoretical, Thrombelastography methods, Thrombosis pathology
- Abstract
Thrombelastography (TEG)/thromboelastometry (ROTEM) devices measure viscoelastic clot strength as clot amplitude (A). Transformation of clot amplitude into clot elasticity (E with TEG; CE with ROTEM) is sometimes necessary (eg, when calculating platelet component of the clot). With TEG, clot amplitude is commonly transformed into shear modulus (G; expressed in Pa or dyn/cm
2 ) as follows: G = (5000 × A)/(100 - A). Use of the constant "5000" stems from Hartert's 50-year-old calculation of G for a normal blood clot. We question the value of calculating G as follows: (1) It may be questioned whether TEG/ROTEM analysis enable measurement of elasticity because viscosity may also contribute to clot amplitude. (2) It has been suggested that absolute properties of a blood clot cannot be measured with TEG/ROTEM analysis because the strain amplitude applied by the device is uncontrolled and changes during the course of coagulation. (3) A review of the calculation of G using Hartert's methods and some updated assumptions suggests that the value of 5000 is unreliable. (4) Recalculation of G for the ROTEM device yields a different value from that with Hartert TEG, indicating a degree of inaccuracy with the calculations. (5) Shear modulus is simply a multiple of E/CE and, because of the unreliability of G in absolute terms, it provides no additional value versus E/CE. The TEG and ROTEM are valuable coagulation assessment tools that provide an evaluation of the viscoelastic properties of a clot, not through measuring absolute viscoelastic forces but through continuous reading of the clot amplitude relative to an arbitrary, preset scale. more...- Published
- 2017
- Full Text
- View/download PDF
38. Over 50 Years of Fibrinogen Concentrate.
- Author
-
Costa-Filho R, Hochleitner G, Wendt M, Teruya A, and Spahn DR
- Subjects
- Anniversaries and Special Events, Fibrinogen history, Hemorrhage history, History, 20th Century, History, 21st Century, Humans, Fibrinogen therapeutic use, Hemorrhage drug therapy
- Abstract
March 2013 represented the 50th anniversary of the first license granted for a fibrinogen concentrate. In this review, we look at the history of bleeding management that led to the development of fibrinogen concentrate, discuss its current use, and consider future developments for this product., (© The Author(s) 2015.) more...
- Published
- 2016
- Full Text
- View/download PDF
39. Additive Manufacturing of a Photo-Cross-Linkable Polymer via Direct Melt Electrospinning Writing for Producing High Strength Structures.
- Author
-
Chen F, Hochleitner G, Woodfield T, Groll J, Dalton PD, and Amsden BG
- Subjects
- Polyesters chemistry, Polymers chemistry, Printing, Three-Dimensional, Biocompatible Materials chemistry, Biodegradable Plastics chemistry, Connective Tissue physiology, Polymers chemical synthesis, Tissue Engineering methods, Tissue Scaffolds chemistry
- Abstract
Melt electrospinning writing (MEW) is an emerging additive manufacturing technique that enables the design and fabrication of micrometer-thin fibrous scaffolds made of biocompatible and biodegradable polymers. By using a computer-aided deposition process, a unique control over pore size and interconnectivity of the resulting scaffolds is achieved, features highly interesting for tissue engineering applications. However, MEW has been mainly used to process low melting point thermoplastics such as poly(ε-caprolactone). Since this polymer exhibits creep and a reduction in modulus upon hydration, we manufactured scaffolds of poly(L-lactide-co-ε-caprolactone-co-acryloyl carbonate) (poly(LLA-ε-CL-AC)), a photo-cross-linkable and biodegradable polymer, for the first time. We show that the stiffness of the scaffolds increases significantly (up to ∼10-fold) after cross-linking by UV irradiation at room temperature, compared with un-cross-linked microfiber scaffolds. The preservation of stiffness and high average fiber modulus (370 ± 166 MPa) within the cross-linked hydrated scaffolds upon repetitive loading (10% strain at 1 Hz up to 200,000 cycles) suggests that the prepared scaffolds may be of potential interest for soft connective tissue engineering applications. Moreover, the approach can be readily adapted through manipulation of polymer properties and scaffold geometry to prepare structures with mechanical properties suitable for other tissue engineering applications. more...
- Published
- 2016
- Full Text
- View/download PDF
40. Assessing the Methodology for Calculating Platelet Contribution to Clot Strength (Platelet Component) in Thromboelastometry and Thrombelastography.
- Author
-
Solomon C, Ranucci M, Hochleitner G, Schöchl H, and Schlimp CJ
- Subjects
- Elasticity physiology, Humans, Platelet Count methods, Platelet Count standards, Blood Coagulation physiology, Blood Platelets physiology, Thrombelastography methods, Thrombelastography standards
- Abstract
The viscoelastic properties of blood clot have been studied most commonly using thrombelastography (TEG) and thromboelastometry (ROTEM). ROTEM-based bleeding treatment algorithms recommend administering platelets to patients with low EXTEM clot strength (e.g., clot amplitude at 10 minutes [A10] <40 mm) once clot strength of the ROTEM® fibrin-based test (FIBTEM) is corrected. Algorithms based on TEG typically use a low value of maximum amplitude (e.g., <50 mm) as a trigger for administering platelets. However, this parameter reflects the contributions of various blood components to the clot, including platelets and fibrin/fibrinogen. The platelet component of clot strength may provide a more sensitive indication of platelet deficiency than clot amplitude from a whole blood TEG or ROTEM® assay. The platelet component of the formed clot is derived from the results of TEG/ROTEM® tests performed with and without platelet inhibition. In this article, we review the basis for why this calculation should be based on clot elasticity (e.g., the E parameter with TEG and the CE parameter with ROTEM®) as opposed to clot amplitude (e.g., the A parameter with TEG or ROTEM®). This is because clot elasticity, unlike clot amplitude, reflects the force with which the blood clot resists rotation within the device, and the relationship between clot amplitude (variable X) and clot elasticity (variable Y) is nonlinear. A specific increment of X (ΔX) will be associated with different increments of Y (ΔY), depending on the initial value of X. When calculated correctly, using clot elasticity data, the platelet component of the clot can provide a valuable insight into platelet deficiency in emergency bleeding. more...
- Published
- 2015
- Full Text
- View/download PDF
41. Additive manufacturing of scaffolds with sub-micron filaments via melt electrospinning writing.
- Author
-
Hochleitner G, Jüngst T, Brown TD, Hahn K, Moseke C, Jakob F, Dalton PD, and Groll J
- Subjects
- Biocompatible Materials pharmacology, Cell Adhesion drug effects, Cells, Cultured, Humans, Mesenchymal Stem Cells, Polyesters chemistry, Biocompatible Materials chemistry, Electrochemical Techniques methods, Nanostructures chemistry, Printing, Three-Dimensional, Tissue Scaffolds chemistry
- 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. more...
- Published
- 2015
- Full Text
- View/download PDF
42. Rapid measurement of fibrinogen concentration in whole blood using a steel ball coagulometer.
- Author
-
Schlimp CJ, Khadem A, Klotz A, Solomon C, Hochleitner G, Ponschab M, Redl H, and Schöchl H
- Subjects
- Animals, Feasibility Studies, Healthy Volunteers, Hemodilution, Hemostasis, Humans, Steel, Swine, Thrombelastography, Fibrinogen analysis, Hematology instrumentation
- Abstract
Background: Fibrinogen plays a key role in hemostasis and is the first coagulation factor to reach critical levels in bleeding patients. Current European guidelines on the management of traumatic or perioperative bleeding recommend fibrinogen supplementation at specific threshold levels. Whole blood viscoelastic tests provide fast evaluation of fibrin deficits. Fast measurement of plasma fibrinogen concentration is not yet available. We investigated a method to rapidly determine whole blood fibrinogen concentration using standard Clauss assays and a steel ball coagulometer and provide an estimate of the "plasma-equivalent" fibrinogen concentration within minutes by adjustment of the measured whole blood fibrinogen concentration with a quickly measureable hemoglobin-derived hematocrit., Methods: The feasibility of this approach was tested with a Clauss assay using multiple porcine fresh blood samples obtained during in vivo bleeding, hemodilution, and after treatment with hemostatic therapy. Two different Clauss assays were then tested using multiple human volunteers' blood samples diluted in vitro and supplemented with fibrinogen concentrate. Comparative measurements with fibrin-based thromboelastometry tests were performed., Results: Regression and Bland-Altman analyses of derived "plasma-equivalent" fibrinogen and measured plasma fibrinogen concentration was excellent in porcine and human blood samples, especially in the ranges relevant to traumatic or perioperative bleeding., Conclusion: Fast whole blood fibrinogen measurements could be considered as an alternative to plasma fibrinogen measurement for acute bleeding management in trauma and perioperative care settings. Further studies are needed to prove this concept and determine the turnaround times for its clinical application in emergency departments and operating theaters. more...
- Published
- 2015
- Full Text
- View/download PDF
43. The effectiveness of different functional fibrinogen polymerization assays in eliminating platelet contribution to clot strength in thromboelastometry.
- Author
-
Schlimp CJ, Solomon C, Ranucci M, Hochleitner G, Redl H, and Schöchl H
- Subjects
- Abciximab, Adult, Antibodies, Monoclonal chemistry, Blood Coagulation physiology, Cytochalasin D chemistry, Elasticity, Fibrin chemistry, Fibrinogen therapeutic use, Glycoproteins chemistry, Humans, Immunoglobulin Fab Fragments chemistry, Male, Platelet Count, Polymerization, Regression Analysis, Signal Processing, Computer-Assisted, Viscosity, Blood Platelets cytology, Fibrinogen chemistry, Thrombelastography methods
- Abstract
Background: Viscoelastic tests such as functional fibrinogen polymerization assays (FFPAs) in thrombelastography (TEG®) or thromboelastometry (ROTEM®) measure clot elasticity under platelet inhibition. Incomplete platelet inhibition influences maximum clot firmness (MCF) of FFPAs. We compared the ability of existing and newly developed FFPAs to eliminate the platelet contribution to clot strength., Methods: MCF of whole blood (WB), platelet-rich plasma (PRP), and platelet-poor plasma samples was recorded using a ROTEM device with different FFPAs, including the TEG functional fibrinogen test (FFTEG) and different ROTEM-based assays: the standard fib-tem reagent (FIBTEM), a lyophilized single-portion reagent fib-tem S (FIBTEM-S), a newly developed reagent FIBTEM PLUS, as well as FIBTEM or the standard extrinsic activation reagent ex-tem® (EXTEM) combined with 10-μg abciximab (FIBTEM-ABC/EXTEM-ABC)., Results: In WB (platelet count [mean ± SD], 183 ± 37 × 10/μL; plasma fibrinogen concentration, 2.49 ± 0.58 g/L), FFTEG and EXTEM-ABC showed higher MCF (15.7 ± 2.8 mm) than FIBTEM or FIBTEM-S (11.4 ± 3.3 mm, P < 0.001), whereas FIBTEM-ABC and FIBTEM PLUS resulted in lower MCF (9.3 ± 2.8 mm, P < 0.001). In 2 different PRP samples, with platelet counts of 407 ± 80 × 10/μL and 609 ± 127 × 10/μL, FIBTEM-ABC and FIBTEM PLUS reduced platelet contribution to clot strength within 95% confidence interval limits of -1.4 to 0.1 mm and -1.2 to 0.4 mm, respectively. Using all FFPAs it was observed that the Pearson correlation coefficient between plasma fibrinogen concentration and WB MCF was high (range, 0.75-0.93) and significant, regardless of the underlying platelet inhibiting component. Evaluating differences in the interception of regression lines by using analysis of covariance, we compared platelet-poor plasma and both PRP samples within the same assays and found that in contrast to the FIBTEM-ABC and FIBTEM PLUS assays, the FFTEG, EXTEM-ABC, FIBTEM, and FIBTEM-S methods still detected residual platelet activity and grossly overestimated fibrin clot strength in samples with high platelet counts., Conclusions: FFPAs based solely on glycoprotein-IIb/IIIa inhibition, such as FFTEG or EXTEM-ABC, are less effective than cytochalasin D-based assays, such as FIBTEM or FIBTEM-S, at inhibiting the platelet component of clot strength. The FIBTEM PLUS assay, and the combination of FIBTEM and abciximab, sufficiently inhibits platelet contribution to clot elasticity. The combination of a glycoprotein-IIb/IIIa receptor blocker and cytochalasin D allows evaluation of functional fibrinogen polymerization without platelet "noise." In a clinical setting, the significance of potent platelet inhibition ensures a more accurate assessment of MCF and therefore the need for fibrinogen supplementation therapy. Further studies are necessary to investigate the application and impact of these tests in a clinical situation. more...
- Published
- 2014
- Full Text
- View/download PDF
44. Thromboelastometric maximum clot firmness in platelet-free plasma is influenced by the assay used.
- Author
-
Schlimp CJ, Solomon C, Hochleitner G, Zipperle J, Redl H, and Schöchl H
- Subjects
- Blood Coagulation Tests methods, Blood Coagulation Tests standards, Humans, Plasma cytology, Blood Coagulation physiology, Plasma physiology, Thrombelastography methods, Thrombelastography standards
- Abstract
Background: Viscoelastic tests such as functional fibrinogen polymerization assays (FFPAs) in thrombelastography (TEG(®)) or thromboelastometry (ROTEM(®)) measure the elasticity of extrinsically activated clotting under conditions of platelet inhibition. There are no reports on whether components of the FFPAs have any effects on fibrin polymerization, aside from the effects of platelet inhibition., Methods: Using various platelet-free plasma (PFP) preparations, we compared the extrinsically activated EXTEM thromboelastometric assay with 3 FFPAs: FIBTEM, FIBTEM PLUS, and the Functional Fibrinogen Test(®) (FFTEG). These FFPAs activate coagulation extrinsically but additionally inhibit platelet function. We used calibration plasma (Instrumentation Laboratory and Siemens), pooled fresh-frozen plasma (Octaplas) and freshly prepared PFP from a healthy volunteer. EXTEM and all FFPAs were run in parallel on a ROTEM device., Results: Median (interquartile range) maximum clot firmness (MCF) values for all plasma preparations were: 20.5 mm (17.25-22.0 mm) in EXTEM, 23.0 mm (18.5-24.0 mm) in FIBTEM, 23.0 mm (18.25-24.75 mm) in FIBTEM PLUS, and 18.0 mm (16.0-19.0 mm) in FFTEG. Compared with EXTEM, FIBTEM and FIBTEM PLUS (P < 0.01) showed increased MCF values whereas FFTEG (P < 0.001) showed decreased MCF values. Further experiments in PFP showed that the platelet inhibitors used in the FFPAs (cytochalasin D or the glycoprotein-IIb/IIIa inhibitor abciximab) were not causing these alterations in MCF. However, reducing the activating tissue factor concentration (by diluting the extrinsic assay) decreased the MCF., Conclusions: We speculate that FIBTEM and FIBTEM PLUS may contain stabilizing agents that enhance fibrin polymerization whereas FFTEG might contain less tissue factor than the ROTEM assays. more...
- Published
- 2013
- Full Text
- View/download PDF
45. Levels of fibrinogen and thromboelastometry fibrin polymerisation following treatment with desmopressin (DDAVP).
- Author
-
Sørensen B, Moore G, Hochleitner G, and Fenger-Eriksen C
- Subjects
- Adult, Female, Hemostatics administration & dosage, Humans, Male, Treatment Outcome, Deamino Arginine Vasopressin administration & dosage, Fibrin analysis, Fibrinogen analysis, Hemorrhage blood, Hemorrhage prevention & control, Thrombelastography
- Published
- 2012
- Full Text
- View/download PDF
46. Comparison of whole blood fibrin-based clot tests in thrombelastography and thromboelastometry.
- Author
-
Solomon C, Sørensen B, Hochleitner G, Kashuk J, Ranucci M, and Schöchl H
- Subjects
- Adult, Female, Fibrinogen analysis, Heparin pharmacology, Humans, Male, Middle Aged, Blood Coagulation Tests methods, Elasticity Imaging Techniques methods, Fibrin analysis, Thrombelastography methods
- Abstract
Background: Fibrin-based clot firmness is measured as maximum amplitude (MA) in the functional fibrinogen (FF) thrombelastographic assay and maximum clot firmness (MCF) in the FIBTEM thromboelastometric assay. Differences between the assays/devices may be clinically significant. Our objective was to compare clot firmness parameters through standard (FF on a thrombelastography device [TEG®]; FIBTEM on a thromboelastometry device [ROTEM®]) and crossover (FF on ROTEM®; FIBTEM on TEG®) analyses., Methods: Whole-blood samples from healthy volunteers were subjected to thrombelastography and thromboelastometry analyses. Samples were investigated native and following stepwise dilution with sodium chloride solution (20%, 40%, and 60% dilution). Samples were also assessed after in vitro addition of medications (heparin, protamine, tranexamic acid) and 50% dilution with hydroxyethyl starch, gelatin, sodium chloride, and albumin., Results: FF produced higher values than FIBTEM, regardless of the device, and TEG® produced higher values than ROTEM®, regardless of the assay. With all added medications except heparin 400 U/kg bodyweight, FF MA remained significantly higher (P < 0.05) than FIBTEM MCF, which was largely unchanged. FF MA was significantly reduced (P = 0.04) by high-dose heparin and partially restored with protamine. Fifty percent dilution with hydroxyethyl starch, albumin, and gelatin decreased FIBTEM MCF and FF MA by >50%., Conclusions: These results demonstrate differences when measuring fibrin-based clotting via the FF and FIBTEM assays on the TEG® and ROTEM® devices. Point-of-care targeted correction of fibrin-based clotting may be influenced by the assay and device used. For the FF assay, data are lacking. more...
- Published
- 2012
- Full Text
- View/download PDF
47. A comparison of fibrinogen measurement methods with fibrin clot elasticity assessed by thromboelastometry, before and after administration of fibrinogen concentrate in cardiac surgery patients.
- Author
-
Solomon C, Cadamuro J, Ziegler B, Schöchl H, Varvenne M, Sørensen B, Hochleitner G, and Rahe-Meyer N
- Subjects
- Aged, Blood Coagulation Tests, Blood Component Transfusion methods, Cardiopulmonary Bypass, Female, Fibrin metabolism, Fibrinogen metabolism, Hemostasis drug effects, Hemostatics administration & dosage, Hemostatics analysis, Hemostatics metabolism, Humans, Male, Middle Aged, Thrombelastography methods, Blood Coagulation physiology, Cardiac Surgical Procedures rehabilitation, Fibrin analysis, Fibrinogen administration & dosage, Fibrinogen analysis
- Abstract
Background: Fibrinogen concentrate administration can be guided by measuring fibrinogen concentration or quality of the fibrin-based clot. This study compared different fibrinogen concentration measurement methods with maximum clot firmness (MCF) of the fibrin clot, assessed by thromboelastometry (FIBTEM), in 33 cardiovascular surgery patients receiving fibrinogen concentrate for hemostatic therapy., Study Design and Methods: Blood samples were collected after cardiopulmonary bypass (CPB) and after fibrinogen concentrate administration. FIBTEM MCF was measured using a rotational thromboelastometry device (ROTEM, Tem International). Fibrinogen concentration was measured using photo-optical (CA-7000, Siemens Healthcare Diagnostics), mechanical (KC-10 steel ball, Schnitger and Gross hook, Amelung GmbH), and electromechanical (STA-R, Diagnostica Stago) coagulometers. Assessments included agreement between fibrinogen concentration measurements and correlations between fibrinogen concentration and FIBTEM MCF., Results: After CPB, correlations were significant (p < 0.001) between FIBTEM MCF and fibrinogen concentration determined by steel ball (r = 0.71), hook (r = 0.73), STA-R (r = 0.81), and CA-7000 (r = 0.82) coagulometers. After fibrinogen concentrate administration, agreement between fibrinogen measurement methods was severely impaired, and correlations with FIBTEM MCF were 0.39 (steel ball), 0.33 (hook), 0.59 (STA-R), and 0.33 (CA-7000)., Conclusion: Agreement between fibrinogen concentration measurement methods decreased considerably after fibrinogen concentrate administration. All methods correlated acceptably with FIBTEM MCF at the end of CPB, but not after hemostatic therapy. Further investigation is needed to explain these findings., (© 2011 American Association of Blood Banks.) more...
- Published
- 2011
- Full Text
- View/download PDF
48. Focused electron beam induced deposition of gold catalyst templates for Si-nanowire synthesis.
- Author
-
Hochleitner G, Steinmair M, Lugstein A, Roediger P, Wanzenboeck HD, and Bertagnolli E
- Abstract
A new approach using focused electron beam induced deposition (FEBID) to deposit catalyst particles is reported for the synthesis of single crystalline silicon nanowires (SiNWs) grown by low pressure chemical vapor deposition (LPCVD). The FEBID deposited gold dot arrays fabricated from an acac-Au(III)-Me(2) precursor were investigated by AFM and EDX. The depositions were found to form a sharp tip and a surrounding halo and consist of only 10 at.% Au. However, SiNWs could be synthesized on the deposited catalyst using the vapor-liquid-solid (VLS) method with a mixture of 2% SiH(4) in He at 520 °C. NW diameters from 30 nm up to 150 nm were fabricated and the dependency of the NW diameter on the FEBID deposition time was observed. TEM analysis of the SiNWs revealed a [110] growth direction independent of the NW diameter. This new method provides a maskless and resistless approach for generating catalyst templates for SiNW synthesis on arbitrary surfaces. more...
- Published
- 2011
- Full Text
- View/download PDF
49. Transfusion in trauma: thromboelastometry-guided coagulation factor concentrate-based therapy versus standard fresh frozen plasma-based therapy.
- Author
-
Schöchl H, Nienaber U, Maegele M, Hochleitner G, Primavesi F, Steitz B, Arndt C, Hanke A, Voelckel W, and Solomon C
- Subjects
- Adult, Female, Humans, Male, Middle Aged, Retrospective Studies, Treatment Outcome, Young Adult, Blood Transfusion methods, Fibrinogen metabolism, Plasma, Thrombelastography methods, Wounds and Injuries therapy
- Abstract
Introduction: Thromboelastometry (TEM)-guided haemostatic therapy with fibrinogen concentrate and prothrombin complex concentrate (PCC) in trauma patients may reduce the need for transfusion of red blood cells (RBC) or platelet concentrate, compared with fresh frozen plasma (FFP)-based haemostatic therapy., Methods: This retrospective analysis compared patients from the Salzburg Trauma Centre (Salzburg, Austria) treated with fibrinogen concentrate and/or PCC, but no FFP (fibrinogen-PCC group, n = 80), and patients from the TraumaRegister DGU receiving ≥ 2 units of FFP, but no fibrinogen concentrate/PCC (FFP group, n = 601). Inclusion criteria were: age 18-70 years, base deficit at admission ≥ 2 mmol/L, injury severity score (ISS) ≥ 16, abbreviated injury scale for thorax and/or abdomen and/or extremity ≥ 3, and for head/neck < 5., Results: For haemostatic therapy in the emergency room and during surgery, the FFP group (ISS 35.5 ± 10.5) received a median of 6 units of FFP (range: 2, 51), while the fibrinogen-PCC group (ISS 35.2 ± 12.5) received medians of 6 g of fibrinogen concentrate (range: 0, 15) and 1200 U of PCC (range: 0, 6600). RBC transfusion was avoided in 29% of patients in the fibrinogen-PCC group compared with only 3% in the FFP group (P< 0.001). Transfusion of platelet concentrate was avoided in 91% of patients in the fibrinogen-PCC group, compared with 56% in the FFP group (P< 0.001). Mortality was comparable between groups: 7.5% in the fibrinogen-PCC group and 10.0% in the FFP group (P = 0.69)., Conclusions: TEM-guided haemostatic therapy with fibrinogen concentrate and PCC reduced the exposure of trauma patients to allogeneic blood products. more...
- Published
- 2011
- Full Text
- View/download PDF
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.