Exploring the Effect of Tris Buffer Concentration on Electrochemical Biosensors

Electrochemical biosensors show promise in the medical field for detection of genetic mutations and could translate well into point-of-care devices. Mutations of DNA can be sensitively and accurately detected through a series of electrochemical melts in which the less stable mutated DNA melts faster than the unmutated DNA. In previous work in our laboratory, we measured the extent of this melting by using square wave voltammetry and comparing peak heights. In this work we explored the effects of varied Tris buffer concentrations (5 mM, 10 mM, 20 mM, 30 mM, 40mM, 50 mM, and 100 mM) on cyclic and square wave voltammograms obtained in a cell with a gold working electrode modified with methylene-blue tagged DNA with the goal of optimizing our existing laboratory procedure. This work suggests that there is a maximum peak height signal between 5 mM and 50 mM in square wave voltammograms, and between 50mM and 100 mM in cyclic voltammograms. The effects of varying Tris buffer was also found to depend on the concentration of DNA probe that each electrode was pulsed in, with reproducible differences between electrodes originally pulsed in 0.5 μM and 0.125 μM solutions of probe DNA. We did not find the use of cyclic voltammetry (as opposed to square wave voltammetry) or the use of peak area (as opposed to peak height) to mitigate signal changes as buffer concentration varies.