Cell adhesion and polarisation on molecularly defined spacing gradient surfaces of cyclic RGDfK peptide patches

In vivo cell migration and location are orchestrally guided by soluble and bound chemical gradients. Here, gradients of extracellular matrix molecules are formed synthetically by the combination of a surface nanopatterning technique called block copolymer nanolithography (BCN) and a biofunctionalisation technique. A modified substrate dip-coating process of BCN allows for the formation of precise molecular gradients of cyclic RGDfK peptide patches at interfaces, which are presented to cells for testing cell adhesion and polarisation. Surfaces formed by BCN consist of hexagonally ordered gold dot patterns with a gradient in particle spacing. Each dot serves as a chemical anchor for the binding of cyclic RGDfK peptides, which are specifically recognised by αvβ3 integrins. Due to steric hindrance only up to one integrin binds to one functionalised gold dot which forms a peptide patch spacing. We demonstrate how cell morphology, adhesion area, actin and vinculin distribution as well as cell body polarisation are influenced by the peptide patch spacing gradient. As a consequence, these gradients of adhesive ligands induce cell orientation towards smaller particle spacing when the gradient strength is 15 nm/mm at least. This implicates that an adherent cell's sensitivity to differentiate between ligand patch spacing is approximately 1 nm across the cell body.