Growth mechanisms of phthalocyanine nanowires induced by Au nanoparticle templates.

We combine X-ray reflectivity and scanning electron microscopy measurements to investigate the mechanisms involved in the growth of vertical arrays of phthalocyanine nanowires directed by templates of Au nanoparticles. The study has been carried out for H(16)CuPc at different substrate temperatures. It is shown that three organic morphologies evolve during the growth: 1D nanostructures on top of the Au nanoparticles, a multilayer film on the substrate and a layer wetting the gold nanoparticles.

Simulating different manufactured antireflective sub-wavelength structures considering the influence of local topographic variations.

Laterally structured antireflective sub-wavelength structures show unique properties with respect to broadband performance, damage threshold and thermal stability. Thus they are superior to classical layer based antireflective coatings for a number of applications. Dependent on the selected fabrication technology the local topography of the periodic structure may deviate from the perfect repetition of a sub-wavelength unit cell.

Single cell force spectroscopy of T cells recognizing a myelin-derived peptide on antigen presenting cells.

T-cell recognition of peptide-MHC complexes on APCs requires cell-cell interactions. The molecular events leading to T-cell activation have been extensively investigated, but the underlying physical binding forces between T-cells and APCs are largely unknown. We used single cell force spectroscopy for quantitation of interaction forces between T-cells and APCs presenting a tolerogenic peptide derived from myelin basic protein.

Neoadjuvant chemotherapy affects staging of colorectal liver metastasis--a comparison of PET, CT and intraoperative ultrasound.

Purpose: Surgery for colorectal liver metastasis facilitates long-term survival, and neoadjuvant chemotherapy improves resectability but may also alter staging accuracy. The aim of this study was to evaluate the effects of neoadjuvant chemotherapy on the efficacy of positron emission tomography (PET), PET-computed tomography (CT), CT and intraoperative ultrasound (IUS) in the detection of liver metastasis.

Methods: Between January 2007 and January 2010, 34 patients with resectable colorectal liver metastasis were included in this retrospective analysis.

Integrin-linked kinase controls microtubule dynamics required for plasma membrane targeting of caveolae.

Caveolae are specialized compartments of the plasma membrane that are involved in signaling, endocytosis, and cholesterol transport. Their formation requires the transport of caveolin-1 to the plasma membrane, but the molecular mechanisms regulating the transport are largely unknown. Here, we identify a critical role for adhesion-mediated signaling through β1 integrins and integrin-linked kinase (ILK) in caveolae formation.

Conjugation of peptides to the passivation shell of gold nanoparticles for targeting of cell-surface receptors.

We report the preparation of gold nanoparticles (AuNPs) functionalized with the peptide-toxin conantokin-G and their selective binding to N-methyl-d-aspartate (NMDA) receptors recombinantly expressed by transfected HEK 293 cells. The AuNPs are passivated with a mixed self-assembled monolayer of ω-carboxy- and ω-amino-polyethylene glycol (PEG) thiols. We compare two different passivation systems: the alkyl-PEG600 system is characterized by a C(11)-alkyl chain between the thiol group and the PEG segment, whereas the PEG3000 system lacks this alkyl-chain.

Force-induced destabilization of focal adhesions at defined integrin spacings on nanostructured surfaces.

Focal adhesions are the anchoring points of cells to surfaces and are responsible for a large number of surface sensing processes. Nanopatterning studies have shown physiological changes in fibroblasts as a result of decreasing density of external binding ligands. The most striking of these changes is a decreased ability to form mature focal adhesions when lateral ligand distances exceed 76 nm.

Tailored antireflective biomimetic nanostructures for UV applications.

Antireflective surfaces composed of biomimetic sub-wavelength structures that employ the 'moth eye principle' for reflectance reduction are highly desirable in many optical applications such as solar cells, photodetectors and laser optics. We report an efficient approach for the fabrication of antireflective surfaces based on a two-step process consisting of gold nanoparticle mask generation by micellar block copolymer nanolithography and a multi-step reactive ion etching process. Depending on the RIE process parameters nanostructured surfaces with tailored antireflective properties can easily be fabricated that show optimum performance for specific applications.

Polymeric substrates with tunable elasticity and nanoscopically controlled biomolecule presentation.

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.

Dissecting the molecular architecture of integrin adhesion sites by cryo-electron tomography.

Focal adhesions are integrin-based multiprotein complexes, several micrometres in diameter, that mechanically link the extracellular matrix with the termini of actin bundles. The molecular diversity of focal adhesions and their role in cell migration and matrix sensing has been extensively studied, but their ultrastructural architecture is still unknown. We present the first three-dimensional structural reconstruction of focal adhesions using cryo-electron tomography.

Immobilized chemokine fields and soluble chemokine gradients cooperatively shape migration patterns of dendritic cells.

Chemokines orchestrate immune cell trafficking by eliciting either directed or random migration and by activating integrins in order to induce cell adhesion. Analyzing dendritic cell (DC) migration, we showed that these distinct cellular responses depended on the mode of chemokine presentation within tissues. The surface-immobilized form of the chemokine CCL21, the heparan sulfate-anchoring ligand of the CC-chemokine receptor 7 (CCR7), caused random movement of DCs that was confined to the chemokine-presenting surface because it triggered integrin-mediated adhesion.

Low-temperature growth of silicon nanotubes and nanowires on amorphous substrates.

Silicon one-dimensional (Si 1D) materials are of particular relevance due to their prospect as versatile building materials for nanoelectronic devices. We report the growth of Si 1D structures from quasi-hexagonally ordered gold (Au) nanoparticle (NP) arrays on borosilicate glass (BSG) and SiOx/Si substrates. Using hydrogen instead of oxygen plasma during NP preparation enhances the catalytic activity of AuNPs (diameters of 10-20 nm), enabling Si 1D growth at temperatures as low as 320 degrees C.

The kinetics of force-induced cell reorganization depend on microtubules and actin.

The cytoskeleton is an important factor in the functional and structural adaption of cells to mechanical forces. In this study we investigated the impact of microtubules and the acto-myosin machinery on the kinetics of force-induced reorientation of NIH3T3 fibroblasts. These cells were subjected to uniaxial stretching forces that are known to induce cellular reorientation perpendicular to the stretch direction.

Cell adhesion strength is controlled by intermolecular spacing of adhesion receptors.

Spatial patterning of biochemical cues on the micro- and nanometer scale controls numerous cellular processes such as spreading, adhesion, migration, and proliferation. Using force microscopy we show that the lateral spacing of individual integrin receptor-ligand bonds determines the strength of cell adhesion. For spacings > or = 90 nm, focal contact formation was inhibited and the detachment forces as well as the stiffness of the cell body were significantly decreased compared to spacings < or = 50 nm.

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

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.

Plasmodium sporozoite motility is modulated by the turnover of discrete adhesion sites.

Sporozoites are the highly motile stages of the malaria parasite injected into the host's skin during a mosquito bite. In order to navigate inside of the host, sporozoites rely on actin-dependent gliding motility. Although the major components of the gliding machinery are known, the spatiotemporal dynamics of the proteins and the underlying mechanism powering forward locomotion remain unclear.

Adaptive force transmission in amoeboid cell migration.

The leading front of a cell can either protrude as an actin-free membrane bleb that is inflated by actomyosin-driven contractile forces, or as an actin-rich pseudopodium, a site where polymerizing actin filaments push out the membrane. Pushing filaments can only cause the membrane to protrude if the expanding actin network experiences a retrograde counter-force, which is usually provided by transmembrane receptors of the integrin family. Here we show that chemotactic dendritic cells mechanically adapt to the adhesive properties of their substrate by switching between integrin-mediated and integrin-independent locomotion.

Immune synapse formation determines interaction forces between T cells and antigen-presenting cells measured by atomic force microscopy.

During adaptive immune responses, T lymphocytes recognize antigenic peptides presented by MHC molecules on antigen-presenting cells (APCs). This recognition results in the formation of a so-called immune synapse (IS) at the T-cell/APC interface, which is crucial for T-cell activation. The molecular composition of the IS has been extensively studied, but little is known about the biophysics and interaction forces between T cells and APCs.

Biomimetic F-actin cortex models.

Since its first production from muscle tissue more than 65 years ago, our knowledge about actin has come a long way. While at the beginning it was identified as a muscle protein, nowadays actin is considered as one of the most important components of the cytoskeleton, playing a crucial role in cell motility, adhesion, morphology and intracellular transport processes. In vitro models have been constructed for about 20 years to gain better insight into the chemophysical and biomechanical properties of actin networks by being able to reduce and tune its complexity.

Force-induced cell polarisation is linked to RhoA-driven microtubule-independent focal-adhesion sliding.

Mechanical forces play a crucial role in controlling the integrity and functionality of cells and tissues. External forces are sensed by cells and translated into signals that induce various responses. To increase the detailed understanding of these processes, we investigated cell migration and dynamic cellular reorganisation of focal adhesions and cytoskeleton upon application of cyclic stretching forces.

Myoblast morphology and organization on biochemically micro-patterned hydrogel coatings under cyclic mechanical strain.

Mechanical forces and geometric constraints play critical roles in determining cell functionality and tissue development. Novel experimental methods are essential to explore the underlying biological mechanisms of cell response. We present a versatile method to culture cells on adhesive micro-patterned substrates while applying long-term cyclic tensile strain (CTS).

Soft micropillar interfaces of distinct biomechanics govern behaviour of periodontal cells.

A soft micropillar extracellular environment of distinct biomechanics is established by fabricating polydimethylsiloxane (PDMS) interfaces with pillar distances of 5, 7, 9 and 11 microm and elasticity moduli of 0.6, 1.0 and 3.

Nanoscale arrangement of apoptotic ligands reveals a demand for a minimal lateral distance for efficient death receptor activation.

Cellular apoptosis, the prototype of programmed cell death, can be induced by activation of so-called death receptors. Interestingly, soluble and membrane-bound members of death receptor ligands can differentially activate their receptors. Using the death receptor ligand tumor necrosis factor (TNF) presented on a surface in a nanoscaled pattern with spacings between 58 and 290 nm, we investigated its requirements for spatial arrangement and motility to efficiently activate TNF receptor (TNFR)1 and TNFR2 as well as its chimeras TNFR1-Fas and TNFR2-Fas.

On the adsorption behavior of biotin-binding proteins on gold and silica.

Streptavidin (SAv), avidin (Av), and neutravidin (NAv) have become widely used molecular tools in biotechnology thanks to their remarkable affinity for biotin. Their tetravalency renders these molecules particularly interesting for the functionalization of solid-liquid interfaces. Using the quartz crystal microbalance with dissipation monitoring, we systematically investigate the deposition of biotin-binding proteins to two surfaces that are popular in biotechnology: gold and silica.