Aptamer-Modified Electrode Biosensors for Npy Detection Using Methylene Blue Redox Probe

Abstract

A biosensor is a device that can determine the concentration or presence of chemicals, such as neurotransmitters and neuropeptides. Certain excitatory neurotransmitters and neuropeptides can be measured by Methylene blue (MB), a synthetic dye that stains to negatively charged cell components. For the modification process in this work, aptamers are used because they possess the advantage of binding to any given target molecule and, when they bind, they undergo conformational changes, which is where MB comes into play. This research focuses on the modification of the surface of Gold (Au) and Highly Oriented Pyrolytic Graphite (HOPG) electrodes using MB as a redox label probe for the detection of neurotransmitters and neuropeptides in aptamer-modified electrodes. Electrochemical Impedance Spectroscopy (EIS) was used to understand the adsorption properties of molecules that stick to the surface of the electrode and Atomic Force Microscopy (AFM) was used to measure the topography of the electrodes before and after the aptamer modification. As results, we were able to prove that AFM cannot monitor the changes on the surface of the Au electrodes with the different modifications due to the roughness of the surface, and that, electrochemically, the capacitance of the gold electrode decreases at higher concentrations of NPY. Different NPY measurements were made, ranging from femtograms to picograms, and different molecules such as dopamine, epinephrine, and PYY were also tested to determine if the sensor system has the same affinity with different types of molecules. These results give us a better understanding of the use of these techniques for the monitoring of biomolecules.