4.1. Photo-Micropatterning

20 × 20 mm2 or 24 × 24 mm2 coverslips (Carl Roth, Karlsruhe, Germany) were placed in a sonication bath (Sonorex Super RK102H, Bandelin, Berlin, Germany) in ethanol for 30 min and dried. The surfaces were passivated with 0.1 mg/ml poly-L-lysine-polyethylene-glycol (PLL-PEG, Surface solutions, Dübendorf, Switzerland) in HEPES solution before photo-micropatterning using a UV-ozone cleaner (Model 342-220, Jelight Company Inc., Irvine, CA, USA). The surfaces were subsequently equilibrated in PBS and incubated with 0.0625 μg/cm2 human cellular fibronectin (Sigma Aldrich, St. Louis, MO, USA) in PBS for one hour before washing with PBS. For the experiments a circle- and crossbow-pattern was used, where every spot has a diameter of 50 µm, to ensure only one cell spreads on every micropattern.