Direct electron transfer of bilirubin oxidase at a carbon flow-through electrode

The kinetics and isotherms of adsorption of Myrothecium verrucaria bilirubin oxidase (Mv BOD) on nanoporous carbons (CNP) and carbon nanofibers (CNF) were studied by the solution depletion method. The kinetics of adsorption of Mv BOD on both carbons are very fast, reaching equilibrium within 10 min and 30 min for CNP and CNF, respectively. The adsorption isotherms reveal a strong affinity between Mv BOD and both carbons. An original flow-through device based on electrodes filled with CNP and CNF connected to an UV-vis spectrophotometer was used to correlate the dioxygen catalytic current reduction to the amount of Mv BOD adsorbed on the carbons. It was shown that although the amount of BOD adsorbed on CNP is much lower than the amount adsorbed on CNF, the currents are comparable, suggesting that the Mv BOD orientation is more favourable for direct electron transfer in the case of CNP. Chronoamperometry experiments showed that the catalytic current is stable for a few days (70 h). It was emphasized by stop and flow experiments that the current is limited by mass transport inside the column. (C) 2018 Elsevier Ltd. All rights reserved.