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Zusammenfassung:
To study the dependence of unbinding forces on the distance of molecularly defined and integrin specific c(−RGDfK−) ligand patches in initial cellular adhesion processes, we developed a magnetic tweezers setup for applying vertical forces of up to 200 pN to rat embryonic fibroblasts. The ligand patch distance is controlled with a hexagonally close packed pattern of biofunctionalized gold nanoparticles prepared by block−copolymer micelle nanolithography. Each gold nanoparticle potentially activates up to one αvβ3-integrin. The distances between the gold nanoparticles determine the separation of individual integrins and thus the assembly of integrin clusters. The results show an increase in cellular unbinding forces from approximately 6 to more than 200 pN for a decreasing ligand distance of 145 to 58 nm after 5 min of cell adhesion. Furthermore, we observe a strong dependence on adhesion time during the first 10 min of cell surface contact suggesting an active, cooperative cell response that is controlled by the spacing between individually activated integrins.
