Cell migration in wound healing and disease is critically dependent on integration with the extracellular matrix, but the receptors that couple matrix topography to migratory behavior remain obscure. Using nano-engineered fibronectin surfaces and cell-derived matrices, we identify syndecan-4 as a key signaling receptor determining directional migration. In wild-type fibroblasts, syndecan-4 mediates the matrix-induced protein kinase Cα (PKCα)–dependent activation of Rac1 and localizes Rac1 activity and membrane protrusion to the leading edge of the cell, resulting in persistent migration. In contrast, syndecan-4–null fibroblasts migrate randomly as a result of high delocalized Rac1 activity, whereas cells expressing a syndecan-4 cytodomain mutant deficient in PKCα regulation fail to localize active Rac1 to points of matrix engagement and consequently fail to recognize and respond to topographical changes in the matrix.

The authors describe the deposition of single biomolecules on substrates at defined spacing by pure self-assembly. The substrate is equipped with an array of 8 nm large gold particles which form the template for biomolecule binding. The authors verified the successful binding of single biomolecules via specific antibody labeling and imaging by fluorescence microscopy. Scanning force microscopy provided evidence that every gold nanoparticle of the pattern is occupied by at least one biomolecule. Furthermore, gold conjugated secondary antibodies in combination with scanning electron microscopy proved that at least 75% of the nanoparticles carried only one active biomolecule. The precision given by such surface densities is molecularly defined and such considerably higher than in any other case reported so far.

SummaryCellular response to both surface topography and surface chemistry has been studied for several years. However, most of the studies focus on only one of the two parameters and do not consider their possible synergistic effects. Here, we report on a fabrication method for nanostructured surfaces composed of highly ordered arrays of silica nanocones with gold tips. By using a combination of block copolymer nanolithography, electroless deposition, and reactive ion etching several parameters such as structure height and structure distance could easily be adjusted to the desired values. The gold tips allow for easy functionalization of the substrates through a thiol linker system. Improved neural cell adhesion can be obtained and is dependent on the nature of the nanocone surface, thus illustrating the influence of different surface topographies on the nanometer length scale, on a complex cellular behavior such as cell adhesion. Substrate and surface functionality are shown to last over several days, leading to the conclusion that the features of our substrates can also be used for longer term experiments. Finally, initial neural cell adhesion is found to be more prominent on substrates with short intercone distances, which is an important finding for research dealing with the reactions of neuron-like tissue in the immediate moments after direct contact with an implanted surface.