Résumé
We perform active and passive microrheology experiments on living cells using laser deflection particle tracking. The probe bead is specifically attached to cell integrins surface receptors via RGD-peptide. In the active case, a oscillatory field drives bead rocking, exerting a stress on the cytoskeleton. The rheology can be then deduced by measuring both the phase shift and the amplitude of the induced deformation. As previously reported by other groups, a power law behaviour is found, the exponent of which can be determined in real time. In the passive case, the mean square displacement shows three scaling regimes. At long times, a super-diffusive behavior is obtained, consistent with two-point microrheology experiments performed in our laboratory. This behavior is driven by active forces generated inside the cell. For shorter lag times, the mean square displacement varies as a power law with an exponent in agreement with active rheology. Finally at the shortest lag times, the mean square displacement reports the polymer filaments properties themselves.