Although E-DNA signal gain is a strong function of the density with which the DNA probes are packed on the surface,11,24 the amplitude/frequency pairing at which this is observed is itself independent of probe density. To see this, we recorded signal gain maps for the aminoglycoside sensor (with a methylene blue reporter) fabricated by depositing the probe at concentrations of either (A) 20 nM or (B) 500 nM. These resulted in 1.1-fold and 1.4-fold decreases in signal gain, respectively, in comparison to sensors fabricated using a more optimal probe concentration of 200 nM (Figure 2A). The optimal amplitude/frequency pairing, however, is effectively indistinguishable across all three packing densities.