Developing fast scan cyclic voltammetry at carbon fiber microelectrodes to quantify short chain fatty acids in situ

Acetic, propionic, and butyric acids are short chain fatty acids (SCFAs) and the most abundant metabolites produced by gut bacteria. To uncover mechanistic insights of their function throughout the body, it is critical to measure rapid SCFA fluxes in sites of action such as brain, muscle, and skin. Current approaches have focused on fecal and plasma measurements, where SCFA levels are low and not representative of tissue-specific concentrations or fluxes. Thus, a rapid, in situ methodology is needed. Fast scan cyclic voltammetry (FSCV) at carbon fiber microelectrodes (CFMs) has the spatiotemporal resolution to fill this need. However, the electrochemical response of CFMs to SCFAs have not been explored until now. By coupling FSCV at CFMs with flow injection analysis of each SCFA, we demonstrate there are distinct peaks in the cyclic voltammograms for each fatty acid. Some of these peaks display faradaic behavior in scan rate, holding potential, and switching potential experiments. Interestingly, we identify several peaks that are concentration-sensitive and therefore are promising quantifiable markers of SCFA dynamics and fluxes. This work lays the foundation in understanding the response of CFMs to fatty acids and demonstrate the utility of FSCV at CFMs for the in situ quantitation of SCFAs.