Figure 4.

Characterization of Serotonin- and Dopamine-Aptamer-Functionalized Sensors

(A) Some aptamers, such as the aptamer used here to recognize serotonin, reorient a portion of their backbones away from semiconductor channels upon target binding, thereby increasing transconductance for n-type semiconductors.

(B) Normalized (I/I₀; unitless) real-time sensing results from three In₂O₃ nanoribbon biosensors functionalized with the serotonin aptamer. Devices showed responses to serotonin (in undiluted artificial cerebrospinal fluid) at concentrations ranging from 10 fM to 1 μM.

(C) Relationship between serotonin concentration and current responses from nine different devices. Results from unfunctionalized devices lacking aptamers are plotted for comparison.

(D) Other aptamers, such as the dopamine aptamer used here, reorient a portion of their negatively charged oligonucleotide backbones closer to field-effect transistors upon target recognition to deplete channels electrostatically.

(E) Normalized (I/I₀; unitless) real-time sensing results from three In₂O₃ nanoribbon biosensors functionalized with the dopamine aptamer. Devices showed responses to dopamine (in undiluted artificial cerebrospinal fluid) at concentrations ranging from 10 fM to 1 μM.

(F) Relationship between dopamine concentration and current responses from nine different devices. Results from devices lacking the dopamine aptamer are also plotted. All devices were operated with V_DS = 0.2 V and V_GS = 0.25 V. Errors bars in (C) and (F) are standard deviations for N = 9 devices (from three separate substrates where each substrate had three devices) and are too small to be visualized in some cases.

See also Figures S3–S5.