Understanding cell adhesion

Schneider/Wixforth, Netz

Chemically nano-tailored surfaces in combination with surface acoustic waves (SAW) will build the foundation to construct an artificial blood vessel system on a planar surface (Wixforth group). Biophysically, our main target is a better comprehension of the effects of branched, clogged or narrowed vessels on cell-tissue and cell-surface interaction. As a test system blood platelets as well as cancer cells (malignant melanoma) will be investigated in order to observe cell-substrate interactions as it occurs during immune response or cancer metastasis. To achieve this, we first will use soft lithography to chemically pattern the solid surface (hydrophobic/hydrophilic) before functionalizing the hydrophilic pattern with protein coatings or cells. The planar substrate produced in the clean room uses a piezoelectric crystal, which builds the source for the surface acoustic waves (SAWs). These nanoscale acoustic waves form the “heart” of our artificial blood circulation system in which their interaction with the liquid causes a hydrodynamic flow (acoustic streaming).

For all experiments described so far, a theoretical understanding of the statics and dynamics of aqueous interfaces is helpful. In the theoretical work we will focus on how neutral and charged groups and molecules adsorb on various surfaces, and how the adsorption process (both static and dynamic) is controlled and modified by the interfacial water structure (Netz group). A complex interplay of the solvation structure of the adsorbant and of the surface is anticipated. Some expertise in modeling hydrophilic as well as hydrophobic surfaces, neutral and charged surfaces exists. An important future goal is to link simulation techniques at different length scales. As an example, the elasticity of single molecules, which is now understood quantitatively, can be included in large-scale simulations by appropriately chosen force-field parametrization. Also, the hydrophobic interaction, which plays a crucial role for protein folding, denaturation and adsorption, will be obtained from atomistic MD simulations. The aim on the theoretical side would be to develop appropriate force fields and feed them into coarse-grained simulations where the solvent is replaced by a continuum and molecular groups are coarse grained such that calculations of complex nanosystems are possible. Direct comparison with results from dynamic force spectroscopy data that resolve cell-to-cell adhesion is possible. Here promising contributions come from single molecule studies in research area H (Gaub) complemented by theoretical investigations, which are employed to characterize adhesion of polymers to solid surfaces at the level of individual polymers.