Nanoporous Gold Microelectrode as Scanning Electrochemical Microscopy (SECM) Probe for the Study of Dopamine (DA) Diffusion

A nanoporous gold microelectrode (NPG-μE) with enlarged electroactive surface area, high sensitivity and selectivity was fabricated for detection of DA. Aiming to demonstrate the applicability of this device, an electrochemical cell with two compartments separated by an impermeable membrane containing a micrometric hole in the middle was used to simulate the DA release (assuming like a living cell). Hence, the monitoring of DA diffusion through the membrane hole was performed using the NPG-μE as SECM probe as a proof-ofconcept. The bottom compartment of the electrochemical cell was filled with a 20mmol L -1 DA in 0.1 mol L-1 PBS solution (pH 7), whereas the upper compartment contained only a 0.1 mol L-1 PBS solution. The microelectrode was polarized at 0.25V and kept at a fixed height (20 μm) during the scanning along the xy plan of the membrane. The Fig.1 exhibits the optical image of the microelectrode near to the membrane hole and two SECM images regarding the DA diffusion. The expressive current increase shown in both images when the tip was moved close to the hole is a consequence of the transport of DA from the lower compartment to the upper one, producing a concentration gradient that can be visualized by the 3D image. These results suggest that the NPG-μE can be a suitable sensor platform for electrochemical detection of DA in microbiological environments.