Ion-channel mimetic sensor incorporating an anion-binding cyclopeptide designed for sulfate determination in dilute aqueous solutions

A sensor designed for anion detection in water based on an ion-channel mimetic system is described. This sensor consists of a gold electrode modified with an anion-binding cyclopeptide CP that mediates the recognition of sulfate. The number of CP molecules covalently attached to the gold electrode via AuS bonds was controlled by using 6-mercapto-1-hexanol (MCH) as “diluent” molecule. The optimal molar ratio CP/MCH (10−6 M/10−6 M) in the solution used for electrode modification was determined experimentally. The presence of CP molecules as well as their orientation on the gold surface was studied by using voltammetry techniques, contact angle measurements, and atomic force microscopy. The electrolyte composition as well as the appropriate pH suitable for anion recognition was also determined. Anion detection was explored by using cyclic voltammetry (CV) and Osteryoung Square wave voltammetry (OSWV). The developed sensor was shown to allow detection of sulfate in highly dilute aqueous media with a 0.25 pM detection limit. Chloride, phosphate and acetate anions generated substantially lower responses. [Display omitted] •An electrochemical sensor for anion recognition in aqueous solutions based on an ion-channel mimetic system has been designed.•A unique cyclopeptide was used as receptor to mediate response towards sulfate anions.•The anion recognition was studied by using cyclic voltammetry (CV) and Osteryoung square wave voltammetry (OSWV).•The developed sensor is able to detect sulfate in highly diluted aqueous media with a detection limit of 0.25 pM.