Soft/elastic nanopatterned biointerfaces in the service of cell biology.

Engineering of biomimetic interfaces has become a valuable tool for guiding cellular processes such as adhesion, spreading, motility, as well as proliferation, differentiation, and apoptosis. The interaction of cells with the extracellular matrix (ECM) or with other cells is involved in nearly every cellular response in vivo. Recent wide-ranging evidence shows that crosstalk between different environmental stimuli can have a tremendous impact on various cell functions.

Surface Properties of Nanostructured Bio-Active Interfaces: Impacts of Surface Stiffness and Topography on Cell-Surface Interactions.

Due to their ability to confer key functions of the native extracellular matrix (ECM) poly(ethylene glycol) (PEG)-based and PEG-modified materials have been extensively used as biocompatible and biofunctionalized substrate systems to study the influence of environmental parameters on cell adhesion Given wide-ranging recent evidence that ECM compliance influences a variety of cell functions, the detailed determination and characterization of the specific PEG surface characteristics including topography, stiffness and chemistry is required. Here, we studied two frequently used bio-active interfaces - PEG-based and PEG-modified surfaces - to elucidate the differences between the physical surface properties, which cells can sense and respond to. For this purpose, two sets of surfaces were synthesized: the first set consisted of nanopatterned glass surfaces containing RGD-functionalized gold nanoparticles surrounded by a passivated PEG-silane layer and the second set consisted of PEG-diacrylate (PEG-DA) hydrogels decorated with RGD-functionalized gold nanoparticlesAlthough the two sets of nanostructured materials compared here were highly similar in terms of density and geometrical distribution of the presented bio-ligands as well as in terms of mechanical bulk properties, the topography and mechanical properties of the surfaces were found to be substantially different and are described in detail.

Benzyl alcohol and block copolymer micellar lithography: a versatile route to assembling gold and in situ generated titania nanoparticles into uniform binary nanoarrays.

Simultaneous synthesis and assembly of nanoparticles that exhibit unique physicochemical properties are critically important for designing new functional devices at the macroscopic scale. In the present study, we report a simple version of block copolymer micellar lithography (BCML) to synthesize gold and titanium dioxide (TiO(2)) nanoarrays by using benzyl alcohol (BnOH) as a solvent. In contrast to toluene, BnOH can lead to the formation of various gold nanopatterns via salt-induced micellization of polystyrene-block-poly(vinylpyridine) (PS-b-P2VP).

Age-dependent changes in microscale stiffness and mechanoresponses of cells.

Cellular ageing can lead to altered cell mechanical properties and is known to affect many fundamental physiological cell functions. To reveal age-dependent changes in cell mechanical properties and in active mechanoresponses, the stiffness of human fibroblasts from differently aged donors was determined, as well as the cell's reaction to periodic mechanical deformation of the culture substrate, and the two parameters were correlated. A comparison of the average Young's moduli revealed that cells from young donors (<25 years) are considerably stiffer than cells from older donors (>30 years).

Nanopatterning by block copolymer micelle nanolithography and bioinspired applications.

This comprehensive overview of block copolymer micelle nanolithography (BCMN) will discuss the synthesis of inorganic nanoparticle arrays by means of micellar diblock copolymer approach and the resulting experimental control of individual structural parameters of the nanopattern, e.g., particle density and particle size.

Impact of local versus global ligand density on cellular adhesion.

α(v)β(3) integrin-mediated cell adhesion is crucially influenced by how far ligands are spaced apart. To evaluate the impact of local ligand density versus global ligand density of a given surface, we used synthetic micronanostructured cell environments with user-defined ligand spacing and patterns to investigate cellular adhesion. The development of stable focal adhesions, their number, and size as well as the cellular adhesion strength proved to be influenced by local more than global ligand density.

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.

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.

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.