Fig. 7.

Monolayers produced on carbon via electrografting of aliphatic amines allow covalent coupling of aptamers to support sensing of small molecules and complimentary DNA strands. We illustrate this by coupling tobramycin-binding aptamers to electrografted monolayers of aminohexanoic acid, and challenging the resulting sensors with saturating target concentrations. First, to demonstrate E-AB sensing of small molecules, we challenged the sensors with tobramycin, observing (A) ON and (B) OFF responses that depended on square wave frequency, a behavior that is similar to that of benchmark, gold-based E-AB sensors. C Frequency map showing signal change calculated as the difference between sensors exposed to saturating tobramycin concentrations (1 µM) and sensors in blank buffered solutions. Second, we demonstrated sensing of DNA hybridization. We challenged our carbon-based sensors with saturating concentrations (10 µM) of DNA strands fully complementary to our aptamer sequence. Doing so we observed sensor (D) OFF and (E) ON responses that depended on square wave frequency. F Frequency map showing signal change calculated as the difference between sensors exposed to fully complementary DNA and sensors in blank buffered solutions. All measurements show the average of n = 4 sensors and corresponding standard deviations