Deciphering electron-shuttling characteristics of epinephrine and dopamine for bioenergy extraction using microbial fuel cells

This first-attempt study provided novel electrochemical exploration via microbial fuel cells (MFCs), suggesting why catecholamine hormone-neurotransmitters epinephrine (EP) and dopamine (DA) could effectively trigger acute stress responses for humans. According to bioelectrochemical engineering, EP and DA are ortho-diphydroxyl (o-diOH) substituent(s)-bearing electron shuttles (ESs) that could effectively mediate electron-transfer capabilities for bioenergy extraction. This study quantitatively compared redox-mediating characteristics of EP and DA with other antioxidants and ESs, suggesting possible mechanisms of bioenergy-driven responses to organisms. Although some electrochemical activities of EP and DA were characterized in medical literature, this work clarified that EP and DA were also electrochemically favorable ESs for efficient bioenergy extraction. Compared to vitamin B₂ (VB), vitamin C (VC) and gallic acid (GA), quantitative evaluation upon bioenergy-stimulating capabilities of EP and DA were clearly revealed via MFC modules. Apparently, both EP and DA as ESs significantly exhibited stable and reversible redox potential peaks in cyclic voltammetry. Evidently, power density performances of MFCs supplemented with EP and DA considerably increased ca. 127–385%, suggesting that DA and EP would be the most appropriate ESs to effectively stimulate electron-mediating capabilities in multicellular organisms. It was also suspected that highly efficient power-stimulating capabilities of DA and EP could be strongly associated with their electrochemically-steered disease-curative and life-threatening capabilities to humans.