(188cx) Optimization of Redox Reporter Molecule Sensing Parameters for Square Wave Voltammetry

Aptamers have been used in previous studies to detect various biomarkers. Aptamers are low cost, single stranded oligonucleotides that can bind to target molecules with high specificity and selectivity. One method for detecting the capture of target molecules with aptamers is using electrochemistry. The selected aptamer is immobilized onto an electrode surface at one end, while the opposite end of the aptamer is modified with a redox reporter molecule. Target molecules, when they are present in a sample, will selectively bind to the immobilized aptamer causing it to undergo a conformational change. This change partially restricts or enhances the number of interactions that a redox reporter molecule has with the electrode, thereby changing the rate of electron transfer between the redox reporter and the electrode (current). However, the fundamental rate of electron exchange between the redox molecule and the electrode is intrinsically controlled by a number of experimental parameters including the amplitude and frequency of the square wave, the chemical structure of the redox reporter molecule, and the electrode surface properties.

The aim of this study was to investigate the effect that the amplitude and frequency parameters in square wave voltammetry have on electron transfer for a variety of possible redox reporter molecules (azure A, phenosafranine, methylene blue, and neutral red). Amplitude and frequency parameters were varied from 10 to 80 mV and from 10 to 5000 Hz, respectively. Phosphate buffer saline solution at pH 7.2 was used as the test solution and disposable screen-printed carbon electrochemical sensors were utilized in the experiments. For some of the redox reporter molecules that were tested, we observed additional current peaks at specific amplitude and frequency combinations.

The individual peak currents at the various amplitude and frequency combinations were analyzed after subtraction of the baseline currents from the voltammograms. The topographical heat maps that were developed allow for the selection of optimal conditions for sensing applications utilizing a variety of redox molecules. Additionally, by tuning the electrochemical parameters it may be possible to develop new sensing strategies for simultaneous multiplexed detection of target analytes using a single electrode.