Abstract: The present invention details a nanostructured electrochemical biosensor based on aptamer as the molecular recognition probe. The biosensor is comprised of an electrochemical cell that can be plugged into an electric controller. This electrochemical biosensor contains a working electrode made of the micro-/nano-scale gold dot array pattern, on which aptamer is immobilized on the surface of the dot array as the molecular recognition probe. The aptamer is labeled with an electrochemical indicator. Reversible binding of an analyte to the aptamer causes the change in the conformation of aptamer, consequently brings the electrochemical indicator close to the electrode surface. This results in the electron transfer from the electrochemical indicator to the electrode, which can be read as a change in output current or potential.