Measuring the adhesion limit of fibronectin for fibroblasts with a narrow-gap rotational rheometer.

We study the adhesion limit of 3T6 fibroblasts, cultured in Dulbecco's modified Eagle's medium with 10% fetal bovine serum at 37 °C and 5% CO2, with a narrow-gap rotational rheometer in the parallel-disk configuration. Reducing the uncertainty in gap width to about 1 µm allows studying the cells at narrow gaps, which enables to study the critical shear stress of the cells in low-viscous media. The adhesion limit on fibronectin-coated glass plates is determined as a function of concentration and adhesion time. We found that cells in groups have a tendency to detach at slightly higher shear stresses than single cells. Moreover, 60 min after the settling phase are enough for the cells to adhere to the coated plate at maximum strength. We show that the setup may also be used for cells that are not adhered from suspension, but are grown directly on the substrate.