The extracellular matrix in tissues such as bone, tendon and cornea contains ordered, parallel arrays of collagen type I fibrils. Cells embedded in these matrices frequently co-align with the collagen fibrils, suggesting that ordered fibrils provide structural or signalling cues for cell polarization. To study mechanisms of matrix-induced cell alignment, we developed nanoscopically defined two-dimensional matrices assembled of highly aligned collagen type I fibrils. The matrices were characterized by atomic force microscopy (AFM) to study the influence of buffer conditions on the collagen type I assembly. The growth of collagen fibrils into these matrices was followed by high-resolution time-lapse AFM. Individual fibrils exhibited an axial D-periodicity of ≈ 67 nm such as typically observed for in vivo assembled collagen fibrils from tendon. When seeded onto the collagen matrices, cells started to reorganize the collagen I matrices. This cellular remodelling of individual fibrils could be visualized by time-lapse AFM. Next we studied specifically the role of integrin alpha2beta1 in mediating adhesion to the collagen matrices by single-cell force spectroscopy. In the early steps (5-30sec) the integrin alpha2beta1 -mediated cell adhesion was dominated by the binding of individual integrins. At prolonged adhesion time (60-600sec), the cellular adhesion process significantly increased suggesting that integrins switched from individual to a cooperative binding behavior. 

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