Figure 2.

Packing density of aptamers on the electrode surface is readily controlled by varying the concentration of probe DNA employed during sensor fabrication. As shown, ACV peak current (top) and chronocoulometry (bottom) methods produce correlated, but significant different estimates of probe density. We believe this occurs because the AC method is highly dependent on electron transfer efficiency, which in turn is dependent on probe geometry. We have thus reported chronocoulometric measurements throughout the body of this work. Values represent the average and standard deviations from three independent sensors at each probe density.