Colchicine is an efficient drug for the management of inflammatory diseases, such as gouty arthritis and familial Mediterranean fever. It affects neutrophil activity by interfering with the formation of microtubules. To test the hypothesis that therapeutic concentrations of colchicine modulate the mechanical properties of these cells, we applied a combination of biophysical techniques (optical stretching and microrheology) to analyze cellular deformability. The contribution of the subcellular compartments to the regulation of cell mechanics was determined by fitting a multicomponent model of cellular viscoelasticity to time-dependent deformation curves. Neutrophils were found to be less deformable in response to 10 ng/ml colchicine. The model-based analysis of cellular deformation revealed a decrease in cytoplasmatic elasticity and a substantial increase in both elasticity and viscosity of the cell membrane compartment in response to colchicine. These results correlate with a reduced number of cytoplasmatic microtubules and an increase in subcortical actin filaments. The latter finding was confirmed by microrheology and fluorescence microscopy. Neutrophil migration through small pores requiring substantial cellular deformations, but not through large pores, was significantly impaired by colchicine. These data demonstrate that colchicine determines mechanics of neutrophils and, thereby, motility in confined spaces, which is crucial during extravasation of neutrophils in response to inflammatory stimuli.

Summary Dopamine offers the possibility to build polymer films on any substrates via an oxidative process. This redox process cannot only be used for self‐oxidation in air, but also in an electrochemical deposition process using cyclic voltammetry. Electropolymerization provides the opportunity to customize film thicknesses on surfaces detectable by X‐ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The topography and nanomechanical properties of the films have been characterized in liquid via AFM. Electrochemical quartz crystal microbalance (EQCM) allows the determination of the deposited polymer quantities during the polymerization process and the ultra‐thin films have been detected by attenuated total reflection Fourier transform infrared spectroscopy (ATR‐FTIR).

The mechanical properties of epithelial cells are modulated by structural changes in keratin intermediate filament networks. To investigate the relationship between network architecture and viscoelasticity, we assembled keratin filaments from recombinant keratin proteins 8 (K8) and 18 (K18) in the presence of divalent ions (Mg(2+)). We probed the viscoelastic modulus of the network by tracking the movement of microspheres embedded in the network during assembly, and studied the network architecture using scanning electron microscopy. Addition of Mg(2+) at physiological concentrations (<1 mM) resulted in networks whose structure was similar to that of keratin networks in epithelial cells. Moreover, the elastic moduli of networks assembled in vitro were found to be within the same magnitude as those measured in keratin networks of detergent-extracted epithelial cells. These findings suggest that Mg(2+)-induced filament cross-linking represents a valid model for studying the cytoskeletal mechanics of keratin networks.

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The site-specific attachment of nanoparticles is of interest for biomaterials or biosensor applications. Polymer brushes can be used to regulate this adsorption, so the conditions for selective adsorption of phosphonate-functionalized nanoparticles onto micropatterned polymer brushes with different functional groups are optimized. By choosing the strong polyelectrolytes poly(3-sulfopropyl methacrylate), poly(sulfobetaine methacrylate), and poly[2-(methacryloyloxy)ethyl trimethylammonium chloride], it is possible to direct the adsorption of nanoparticles to specific regions of the patterned substrates. A pH-dependent adsorption can be achieved by using the polycarboxylate brush poly(methacrylic acid) (PMAA) as substrate coating. On PMAA brushes, the nanoparticles switch from attachment to the brush regions to attachment to the grooves of a patterned substrate on changing the pH from 3 to 7. In this manner, patterned substrates are realized that assemble nanoparticles in pattern grooves, in polymer brush areas, or substrates that resist the deposition of the nanoparticles. The nanoparticle deposition can be directed in a pH-dependent manner on a weak polyelectrolyte, or is solely charge-dependent on strong polyelectrolytes. These results are correlated with surface potential measurements and show that an optical trap is a versatile method to directly probe interactions between nanoparticles and polymer brushes. A model for these interactions is proposed based on the optical trap measurements.