fig3

Figure 3. Response mechanisms of non-enzymatic electrochemical sensors. (A) Scheme for aptamer-based electrochemical sensors of competitive format and sandwich format; (B) An electrochemical aptamer-based sensor blinds and releases a target molecule; (C) Scheme for the synthesis and re-binding of molecular imprinted polymers; (D) Representation of an electrochemical sensor for ion measurement having a polymeric ion-selective membrane, showing the movement of ion and charge separation that results in the surface potential which is measured.