Engineered Electroactive Solutions for Electrochemical Detection of Volatile Organic Biomarkers Associated with Disease

Abstract

Rapid screening of tuberculosis (TB) by evaluation of associated volatile organic biomarkers (VOBs) in breath has been shown to be a promising technology that is significantly faster and more convenient than traditional sputum culture tests. Methyl nicotinate and methyl p-anisate have been isolated as specific biomarkers for the mycobacterium tuberculosis, as they are not found in high concentrations in ambient air or the breath of healthy patients, but should be readily present in all patients with active TB. A novel approach to detection of these biomarkers in liquid form (e.g. from breath condensate) using inexpensive screen-printed electrodes will be presented. Previous modelling studies [1] suggest that these biomarkers complex with certain transition metals (such as cobalt and copper) given a particular bias voltage and oxidation state of the metal. This interaction can be exploited by mixing the sample solution containing the biomarkers into an electroactive solution (EAS) containing the functional metal ion, and observing the change electrochemically. For example, the cyclic voltammogram of copper (II) changes significantly when as little as 1 mM methyl nicotinate (MN) is added to the solution. The variation of peak oxidation voltage with MN concentration can be seen in Figure 1 below. In order to further understand the reactions taking place and specifically identify the biomarkers, square wave voltammetry (SWV) is employed to show which oxidation states of the functionalized metal are complexing with the biomarker of interest. Figure 2 shows the SWV of a copper EAS with and without 1 mM MN. The SWV shows a peak for each redox transition of copper, and how the area of each is affected by the addition of the biomarker. In this way, a “fingerprint” method can be used to identify biomarkers once their known interaction is established. [1] Ray R, Sarma B, Mohanty S, Prisbrey K, Misra M. Assessment of metals in detection of TB biomarkers: Novel computational approach. Journal of Materials Chemistry and Physics. 161 (2015) 1-8 Figure 1