Herein, a highly sensitive and selective aptamer biosensor for quantitative detection of a model target, dopamine (DA), was developed by using a gold (Au) electrode modified with highly dispersed gold nanoparticles (AuNPs) and acid-oxidized carbon nanotubes (CNTs-COOH) functionalized with polyethyleneimine (PEI). Amine-terminated12- mercaptureprobe (ssDNA1) as a capture probe and specific DA-aptamer (ssDNA2) as a detection probe was immobilized on the surface of a modified electrode via the formation of covalent amide bond and hybridization, respectively. Methylene blue (MB) was used as the redox probe, which was intercalated into the aptamer through the specific interaction with its guanine bases. In the presence of DA, the interaction between aptamer and DA displaced theMB fromthe electrode surface, rendering a lowered electrochemical signal attributed to decreased amount of adsorbedMB. The developed electrochemical DA aptasensor showed a good linear response to DA from 5 to 300 nM with detection limit of 2.1 nM. The biosensor also exhibited satisfactory selectivity and could be successfully used to detect DA in blood serum sample. ©
