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1,171 results on '"Spatz, Joachim P."'

201. Antireflective subwavelength structures on microlens arrays - comparison of various manufacturing techniques

Author

Pacholski, Claudia, Morhard, Christoph, Spatz, Joachim P., Lehr, Dennis, Schulze, Marcel, Kley, Ernst-Bernhard, Tünnermann, Andreas, Helgert, Michael, Sundermann, Michael, Brunner, Robert, and Publica

Abstract

Antireflective subwavelength structures (ARS) resembling nanostructures found on the cornea of night-active insects reduce the reflection of light by providing a gradual change in the refractive index at the interface. These artificial ARS have mainly been fabricated by a combination of conventional lithography and reactive ion etching, which constrains their application to planar substrates. We report on the fabrication of ARS using three different techniques including bottom-up and top-down methods as well as their combination on microlens arrays (MLAs) made of fused silica. The optical performance of the resulting ARS on the MLAs is as good as ARS fabricated on planar substrates with increased transmission of up to 96% at certain wavelengths.

Published
2012

204. Minimal Synthetic Cells to Study Integrin-Mediated Adhesion

Author

Frohnmayer, Johannes P., primary, Brüggemann, Dorothea, additional, Eberhard, Christian, additional, Neubauer, Stefanie, additional, Mollenhauer, Christine, additional, Boehm, Heike, additional, Kessler, Horst, additional, Geiger, Benjamin, additional, and Spatz, Joachim P., additional

Published
2015
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206. Segregation Versus Colocalization: Orthogonally Functionalized Binary Micropatterned Substrates Regulate the Molecular Distribution in Focal Adhesions

Author

Guasch, Judith, primary, Conings, Bert, additional, Neubauer, Stefanie, additional, Rechenmacher, Florian, additional, Ende, Karen, additional, Rolli, Claudio G., additional, Kappel, Christian, additional, Schaufler, Viktoria, additional, Micoulet, Alexandre, additional, Kessler, Horst, additional, Boyen, Hans-Gerd, additional, Cavalcanti-Adam, Elisabetta Ada, additional, and Spatz, Joachim P., additional

Published
2015
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217. Impact of tumor cell cytoskeleton organization on invasiveness and migration: a microchannel-based approach

Author

Rolli, Claudio G., Seufferlein, Thomas, Kemkemer, Ralf, and Spatz, Joachim P.

Subjects
lcsh:R, Biophysics, lcsh:Medicine, Cell Biology/Extra-Cellular Matrix, Cell Biology/Cell Adhesion, Cell Biology/Cytoskeleton, Cell Line, Tumor, Humans, Keratins, Biophysics/Experimental Biophysical Methods, Neoplasm Invasiveness, lcsh:Q, Neoplasm Metastasis, lcsh:Science, Research Article
Abstract

Cell migration is a fundamental feature of the interaction of cells with their surrounding. The cell's stiffness and ability to deform itself are two major characteristics that rule migration behavior especially in three-dimensional tissue. We simulate this situation making use of a micro-fabricated migration chip to test the active invasive behavior of pancreatic cancer cells (Panc-1) into narrow channels. At a channel width of 7 microm cell migration through the channels was significantly impeded due to size exclusion. A striking increase in cell invasiveness was observed once the cells were treated with the bioactive lipid sphingosylphosphorylcholine (SPC) that leads to a reorganization of the cell's keratin network, an enhancement of the cell's deformability, and also an increase in the cell's migration speed on flat surfaces. The migration speed of the highly deformed cells inside the channels was three times higher than of cells on flat substrates but was not affected upon SPC treatment. Cells inside the channels migrated predominantly by smooth sliding while maintaining constant cell length. In contrast, cells on adhesion mediating narrow lines moved in a stepwise way, characterized by fluctuations in cell length. Taken together, with our migration chip we demonstrate that the dimensionality of the environment strongly affects the migration phenotype and we suggest that the spatial cytoskeletal keratin organization correlates with the tumor cell's invasive potential.

Published
2010

218. Distance-dependent adhesion of vascular cells on biofunctionalized nanostructures.

Author

Biela, Sarah, Striegl, Britta, Frey, Kerstin, Spatz, Joachim P., and Kemkemer, Ralf

Abstract

Cell-cell and cell-extracellular matrix (ECM) adhesion regulates fundamental cellular functions and is crucial for cell-material contact. Adhesion is influenced by many factors like affinity and specificity of the receptor-ligand interaction or overall ligand concentration and density. To investigate molecular details of cell-ECM and cadherins (cell-cell) interaction in vascular cells functional nanostructured surfaces were used Ligand-functionalized gold nanoparticles (AuNPs) with 6-8 nm diameter, are precisely immobilized on a surface and separated by non-adhesive regions so that individual integrins or cadherins can specifically interact with the ligands on the AuNPs. Using 40 nm and 90 nm distances between the AuNPs and functionalized either with peptide motifs of the extracellular matrix (RGD or REDV) or vascular endothelial-cadherins (VEC), the influence of distance and ligand specificity on spreading and adhesion of endothelial cells (ECs) and smooth muscle cells (SMCs) was investigated. We demonstrate that RGD-dependent adhesion of vascular cells is similar to other cell types and that the distance dependence for integrin binding to ECM-peptides is also valid for the REDV motif. VEC-ligands decrease adhesion significantly on the tested ligand distances. These results may be helpful for future improvements in vascular tissue engineering and for development of implant surfaces. [ABSTRACT FROM AUTHOR]

Published
2017
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219. Stem cell migration and mechanotransduction on linear stiffness gradient hydrogels.

Author

Hadden, William J., Young, Jennifer L., Holle, Andrew W., McFetridge, Meg L., Du Yong Kim, Wijesinghe, Philip, Taylor-Weiner, Hermes, Wen, Jessica H., Lee, Andrew R., Bieback, Karen, Vo, Ba-Ngu, Sampson, David D., Kennedy, Brendan F., Spatz, Joachim P., Engler, Adam J., and Yu Suk Choi

Subjects
STEM cell migration, MECHANOTRANSDUCTION (Cytology), HYDROGELS, ADIPOSE tissues, POLYACRYLAMIDE
Abstract

The spatial presentation of mechanical information is a key parameter for cell behavior. We have developed a method of polymerization control in which the differential diffusion distance of unreacted cross-linker and monomer into a prepolymerized hydrogel sink results in a tunable stiffness gradient at the cell-matrix interface. This simple, low-cost, robust method was used to produce polyacrylamide hydrogels with stiffness gradients of 0.5, 1.7, 2.9, 4.5, 6.8, and 8.2 kPa/mm, spanning the in vivo physiological and pathological mechanical landscape. Importantly, three of these gradients were found to be nondurotactic for human adipose-derived stem cells (hASCs), allowing the presentation of a continuous range of stiffnesses in a single well without the confounding effect of differential cell migration. Using these nondurotactic gradient gels, stiffness-dependent hASC morphology, migration, and differentiation were studied. Finally, the mechanosensitive proteins YAP, Lamin A/C, Lamin B, MRTF-A, and MRTF-B were analyzed on these gradients, providing higher-resolution data on stiffness-dependent expression and localization. [ABSTRACT FROM AUTHOR]

Published
2017
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224. Plasmonic Nanopipette Biosensor

Author

Masson, Jean-Francois, primary, Breault-Turcot, Julien, additional, Faid, Rita, additional, Poirier-Richard, Hugo-Pierre, additional, Yockell-Lelièvre, Hélène, additional, Lussier, Félix, additional, and Spatz, Joachim P., additional

Published
2014
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231. Investigation of early cell–surface interactions of human mesenchymal stem cells on nanopatterned β-type titanium–niobium alloy surfaces

Author

Medda, Rebecca, primary, Helth, Arne, additional, Herre, Patrick, additional, Pohl, Darius, additional, Rellinghaus, Bernd, additional, Perschmann, Nadine, additional, Neubauer, Stefanie, additional, Kessler, Horst, additional, Oswald, Steffen, additional, Eckert, Jürgen, additional, Spatz, Joachim P., additional, Gebert, Annett, additional, and Cavalcanti-Adam, Elisabetta A., additional

Published
2014
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232. Functionalizing avß3- or a5ß1-selective integrin antagonists for surface coating: A new tool to discriminate integrin subtypes in vitro

Author

Universitat Politècnica de Catalunya. Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Rechenmacher, Florian, Neubauer, Stefanie, Polleux, Julien, Mas Moruno, Carlos, De Simone, Mariarosaria, Cavalcanti-Adam, Elisabetta Ada, Spatz, Joachim P., Fässler, Reinhard, Kessler, Horst, Universitat Politècnica de Catalunya. Departament de Ciència dels Materials i Enginyeria Metal·lúrgica, Rechenmacher, Florian, Neubauer, Stefanie, Polleux, Julien, Mas Moruno, Carlos, De Simone, Mariarosaria, Cavalcanti-Adam, Elisabetta Ada, Spatz, Joachim P., Fässler, Reinhard, and Kessler, Horst

Abstract

Thumbnail image of graphical abstract Stuck with the right choice: avß3- or a5ß1-selective integrin ligands were functionalized for surface coating without losing activity and selectivity. The coating of nanostructured gold surfaces with these compounds stimulated subtype-selective cell adhesion of genetically modified avß3- or a5ß1-expressing fibroblasts in vitro., Postprint (published version)

Published
2013

233. The role of integrin-linked kinase in the molecular architecture of focal adhesions

Author

Elad, Nadav, Volberg, Tova, Patla, Israel, Hirschfeld-Warneken, Vera, Grashoff, Carsten, Spatz, Joachim P, Fässler, Reinhard, Geiger, Benjamin, Medalia, Ohad, Elad, Nadav, Volberg, Tova, Patla, Israel, Hirschfeld-Warneken, Vera, Grashoff, Carsten, Spatz, Joachim P, Fässler, Reinhard, Geiger, Benjamin, and Medalia, Ohad

Abstract

Integrin-mediated focal adhesions (FAs) are large, multi-protein complexes that link the actin cytoskeleton to the extracellular matrix and take part in adhesion-mediated signaling. These adhesions are highly complex and diverse at the molecular level; thus, assigning particular structural or signaling functions to specific components is highly challenging. Here, we combined functional, structural and biophysical approaches to assess the role of a major FA component, namely, integrin-linked kinase (ILK), in adhesion formation. We show here that ILK plays a key role in the formation of focal complexes, early forms of integrin adhesions, and confirm its involvement in the assembly of fibronectin-bound fibrillar adhesions. Examination of ILK-null fibroblasts by cryo-electron tomography pointed to major structural changes in their FAs, manifested as disarray of the associated actin filaments and an increase in the packing density of FA-related particles. Interestingly, adhesion of the mutant cells to the substrate required a higher ligand density than in control cells. These data indicate that ILK has a key role in integrin adhesion assembly and sub-structure, and in the regulation of the FA-associated cytoskeleton.

Published
2013

234. Sequential bottom-up assembly of mechanically stabilized synthetic cells by microfluidics

Author

Weiss, Marian, Frohnmayer, Johannes Patrick, Benk, Lucia Theresa, Haller, Barbara, Janiesch, Jan-Willi, Heitkamp, Thomas, Börsch, Michael, Lira, Rafael B., Dimova, Rumiana, Lipowsky, Reinhard, Bodenschatz, Eberhard, Baret, Jean-Christophe, Vidakovic-Koch, Tanja, Sundmacher, Kai, Platzman, Ilia, and Spatz, Joachim P.

Abstract

Compartments for the spatially and temporally controlled assembly of biological processes are essential towards cellular life. Synthetic mimics of cellular compartments based on lipid-based protocells lack the mechanical and chemical stability to allow their manipulation into a complex and fully functional synthetic cell. Here, we present a high-throughput microfluidic method to generate stable, defined sized liposomes termed ‘droplet-stabilized giant unilamellar vesicles (dsGUVs)’. The enhanced stability of dsGUVs enables the sequential loading of these compartments with biomolecules, namely purified transmembrane and cytoskeleton proteins by microfluidic pico-injection technology. This constitutes an experimental demonstration of a successful bottom-up assembly of a compartment with contents that would not self-assemble to full functionality when simply mixed together. Following assembly, the stabilizing oil phase and droplet shells are removed to release functional self-supporting protocells to an aqueous phase, enabling them to interact with physiologically relevant matrices.

Published
2018
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239. Self-assembly of rodlike hydrogen-bonded nanostructures

Author

Klok, Harm-Anton, Jolliffe, Katrina A., Schauer, Caroline L., Prins, Leonard J., Spatz, Joachim P., Moller, Martin, Timmerman, Peter, and Reinhoudt, David N.

Subjects
Nanotechnology -- Research, Polymers -- Research, Hydrogen bonding -- Research, Chemistry
Abstract

A new class of hydrogen-bonded polymeric nanostructures were characterized by tapping-mode scanning force microscopy (TM-SFM) and 1H NMR spectroscopy. Characterization by TM-SFM was done by applying a droplet of dilute equimolar solution of calix(4)arene dimelamine and calix(4)arene dicyanurate on a graphite substrate. Results showed that rodlike nanostructures can be prepared by self-assembly of small molecular components and that the nature of the solvent plays a role in the self-assembly.

Published
1999

240. Sub-10nm gold nanoarrays for tethering single molecules

Author

Chan, Vanessa Z.-H., Codd, Sarah L., van der Helm, Mark J., Spatz, Joachim P., Röcker, Carlheinz, Nienhaus, G. Ulrich, Levi, Stefano, van Veggel, Frank C.J.M., Reinhoudt, David N., Möller, Martin, Hahn, Horst W., Feldheim, Daniel L., Kubiak, Clifford P., Tannenbaum, Rina, Siegel, Richard W., and Materials Science and Technology of Polymers

Abstract

Nanometer sized gold patterns were produced with controlled spacings using the combination of a top-down (e-beam lithography) and a bottom-up (macromolecular chemistry) technique. Sub-10 nm nanoparticle arrays on silicon consisting of gold nanoparticles separated by micrometer spacings were fabricated with this approach. Using electron beam lithography, templates comprising of 150 nm to 1 mm sized trenches, holes and aperiodic patterns were made in an electron-beam resist. Block copolymer micelles were then patterned into this template by spincoating. The micelles acted as positioners for a nanometer sized gold precursor that is sequestered within its core. Subsequent removal of the resist layer left an array of Au loaded organic micelles ordered according to the pattern of the template. Exposure of this substrate to a hydrogen plasma removed the organic block copolymer and resulted in an array of sub-10 nm gold nanoparticles/nanoclusters with micron separations. The gold was then used as an anchor point for the tethering of functional molecules in order to localize fluorescent molecules.

Published
2001

241. Measuring Forces between Two Single Actin Filaments during Bundle Formation

Author

Streichfuss, Martin, Erbs, Friedrich, Uhrig, Kai, Kurre, Rainer, Clemen, Anabel E. -M., Boehm, Christian H. J., Haraszti, Tamas, Spatz, Joachim P., Streichfuss, Martin, Erbs, Friedrich, Uhrig, Kai, Kurre, Rainer, Clemen, Anabel E. -M., Boehm, Christian H. J., Haraszti, Tamas, and Spatz, Joachim P.

Abstract

Bundles of filamentous actin are dominant cytoskeletal structures, which play a crucial role in various cellular processes. As yet quantifying the fundamental interaction between two individual actin filaments forming the smallest possible bundle has not been realized. Applying holographic optical tweezers integrated with a microfluidic platform, we were able to measure the forces between two actin filaments during bundle formation. Quantitative analysis yields forces up to 0.2 pN depending on the concentration of bundling agents.

Published
2011

242. Polymeric substrates with tunable elasticity and nanoscopically controlled biomolecule presentation

Author

Aydin, Daniel, Louban, Ilia, Perschmann, Nadine, Blümmel, Jacque, Lohmüller, Theobald, Cavalcanti-Adam, Elisabetta Ada, Haas, Tobias Longin, Walczak, Henning, Kessler, Horst, Fiammengo, Roberto, Spatz, Joachim P., Haas, Tobias L. (ORCID:0000-0003-2336-0263), Aydin, Daniel, Louban, Ilia, Perschmann, Nadine, Blümmel, Jacque, Lohmüller, Theobald, Cavalcanti-Adam, Elisabetta Ada, Haas, Tobias Longin, Walczak, Henning, Kessler, Horst, Fiammengo, Roberto, Spatz, Joachim P., and Haas, Tobias L. (ORCID:0000-0003-2336-0263)

Abstract

Despite tremendous progress in recent years, nanopatterning of hydrated polymeric systems such as hydrogels still represents a major challenge. Here, we employ block copolymer nanolithography to arrange gold nanoparticles on a solid template, followed by the transfer of the pattern to a polymeric hydrogel. In the next step, these nanoparticles serve as specific anchor points for active biomolecules. We demonstrate the engineering of poly(ethylene glycol) hydrogel surfaces with respect to elasticity, nanopatterning, and functionalization with biomolecules. For the first time, biomolecule arrangement on the nanometer scale and substrate stiffness can be varied independently from each other. Young's moduli, a measure of the compliance of the substrates, can be tuned over 4 orders of magnitude, including the values for all of the different tissues found in the human body. Structured hydrogels can be used to pattern any histidinetagged protein as exemplified for his-protein A as an acceptor for immunoglobulin. When cell-adhesion-promoting peptide cRGDfK is selectively coupled to gold nanoparticles, the surfaces provide cues for cell-surface interaction and allow for the study of the modulation of cellular adhesion by the mechanical properties of the environment. Therefore, these substrates represent a unique multipurpose platform for studying receptor/ligand interactions with adhering cells, mechanotransduction, and cell-adhesion- dependent signaling. © 2010 American Chemical Society.

Published
2010

243. Micro-nanostructured protein arrays: a tool for geometrically controlled ligand presentation

Author

Aydin, Daniel, Schwieder, Marco, Louban, Ilia, Knoppe, Stefan, Ulmer, Jen, Haas, Tobias Longin, Walczak, Henning, Spatz, Joachim P., Haas, Tobias L. (ORCID:0000-0003-2336-0263), Aydin, Daniel, Schwieder, Marco, Louban, Ilia, Knoppe, Stefan, Ulmer, Jen, Haas, Tobias Longin, Walczak, Henning, Spatz, Joachim P., and Haas, Tobias L. (ORCID:0000-0003-2336-0263)

Abstract

The combination of block copolymer micelle nanolithography (BCMN) with standard electron-beam lithography (EBL) and photolithography for rapid patterning of gold nanoparticles on two different length scales was presented. Cut silicon (110) chips and standard glass overslips were used as solid supports, while the formed miceller monolayer was treated with reactive hydrogen plasma upon evaporation of the solvent. The substrates are processed to yield coverslip-sized areas of micro-nanostructres with a patch size of 3 Î1⁄4m realizing the rapid parallel fabrication of high-quality micro-nanostructured surfaces with relatively low material and equipment cost. Only the nanostructured parts of the surface are covered by histidine-tagged GFP, proving the full preservation of protein repellent properties of the coupled PEG after the particle modification process.

Published
2009

244. A polystyrene-oligothiophene-polystyrene triblock copolymer

Author

Martin Möller, John A. E. H. van Haare, E. W. Meijer, Spatz Joachim P, Sergei S. Sheiko, Mark A. Hempenius, B.M.W. Langeveld-Voss, René A. J. Janssen, Macromolecular and Organic Chemistry, Molecular Materials and Nanosystems, and Macro-Organic Chemistry

Subjects
chemistry.chemical_classification, Size-exclusion chromatography, General Chemistry, Nuclear magnetic resonance spectroscopy, Polymer, Biochemistry, Catalysis, chemistry.chemical_compound, Colloid and Surface Chemistry, chemistry, Transmission electron microscopy, Reagent, Polymer chemistry, Copolymer, Thiophene, Polystyrene
Abstract

A well-defined triblock copolymer is synthesized by using a strategy in which the α-coupling of 11 thiophene rings of the middle block and the monodispersity (DP = 30 and M̄w/M̄n = 1.1) of the two polystyrene outer blocks is ensured. Monofunctional polystyrene 1 is first modified with an α-terthiophene unit 2 to form 3, and two of these units are coupled in a double Stetter reaction of 4 with a difunctional α-terthiophene 5 to yield a tetraketone 6 as the precursor of the triblock copolymer, which was formed with excess Lawesson's reagent. The polymer 7 is fully characterized with IR and NMR spectroscopy and MALDI-TOF mass spectrometry. Size exclusion chromatography, transmission electron microscopy, and scanning force microscopy show that 7 is self-assembled into spherical, micellar structures with average diameters of 12 nm, which corresponds to about 60 block copolymer molecules per aggregate. The optical properties of 7 are in full agreement with an associated unsubstituted oligothiophene. Electrochemical doping is hampered by the polystyrene shell; however, chemical doping afforded small nanoscopic charged aggregates that are soluble in organic solvents.

Published
1998

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