A Quartz Crystal Microbalance (QCM) was used to create a biosensor utilizing living adherent endothelial cells (ECs) as the biological sensing element. This EC QCM biosensor detected the effect of varying concentrations of nocodazole, a microtubule binding and disrupting drug, on the adherent cells as they altered the underlying QCM device state frequency, Δf, and motional Resistance, ΔR, shift values. Over the dose range 0.11-15 μM nocodazole, the Δf shift values decreased significantly in magnitude in a dose dependent fashion over a 5-6 hr incubation period following drug addition to a limiting value, with a 900 nM midpoint. This effect is consistent with nocodazole's known dose dependent effect on the disruption of microtubules. At all drug concentrations, the relative Δf decrease with time was found to be very similar and well fit by a single exponential decay equation. For all nocodazole doses, t 0.5 was invariant, averaging t 0.5 = 0.83 ± 0.14 hr. These data demonstrate that a single dynamic sensing system within the cell, the microtubules, responds to the addition of nocodazole and its response can be quantified by the biosensor. These results indicate that the EC QCM biosensor can be used to detect EC cytoskeletal alterations and dynamics and may be a valuable screening method for all classes of biologically active drugs or biological macromolecules that affect cytoskeleton perturbations or cellular attachment.