Electrochemical sensor devices are of interest in planetary exploration missions where detection of life is a goal. All forms of life on Earth contain cellular machinery that can transform and regulate chemical energy through metabolic pathways. These processes are oxidation-reduction reactions that are performed by four key classes of molecules: flavins, nicotinamides, porphyrins, and quinones (Crawford, 2001). Electrochemical redox may prove a valuable technique for identifying and differentiating these biomolecules and become a useful tool in future life-detecting missions. In this study, we used cyclic voltammetry (CV) and differential pulse voltammetry (DPV) to measure these molecules in a 3D printed flow cell. Electrodes were fabricated from metal wires and interfaced with the flow cell through compression fittings. Glassy carbon (GC) and boron-doped diamond (BDD) electrodes were chosen as working electrodes and used to detect flavin adenine dinucleotide (FAD), riboflavin, plumbagin, anthraquinone, protoporphyrin IX and nicotinamide adenine dinucleotide (NAD). All procedures were performed in a synthetic sea water solution with a Ag/AgCl reference electrode and a platinum wire counter electrode. Limits of detection down to 10 nM were achieved by the GCE. The wide potential window of BDD proved successful in the detection all four classes of redox-active molecules in complex mixtures. Introduction of electrodes into the 3D-printed flow-cell resulted in reliable CV and DPV data, and present this electrode-integrated system as a robust device suitable for future life-detection missions.

Crawford, R. (2001). In Search of the Molecules of Life. Icarus, 154(2), 531–539. https://doi.org/10.1006/icar.2001.6714