Flow injection enzymatic biosensor for aldehydes based on a Meldola Blue-Ni complex electrochemical mediator.

Abstract

Carbon nanofibers (CNF) are efficient electrode modifiers in electrochemical biosensors that enhance the electrochemical active area, induce electrocatalytic effect toward the oxidation of the enzymatic cofactor nicotinamide adenine dinucleotide (reduced form, NADH), and enable the quantitative immobilization of enzymes. Combining CNF with efficient and stable mediators radically augments the speed of electron transfer between NADH and solid electrodes and leads to electrochemical sensorscharacterized by high sensitivity and stability. The main aim of this work was to investigate the performance of a novel mediator for NADH with advantageously low solubility in an electrochemical detector based on a screen-printed CNF electrode as well as its potential in biosensing. Using amediator, prepared from Meldola Blue and Ni hexamine chloride, a stable and sensitive electrochemical NADH sensor is providedwith a detection limit of 0.5μmolL-1. Further on, covalent immobilization of a recently described aldehyde dehydrogenase from the Antarctic Flavobacterium PL002 strain on the surface of the mediator-modified electrode produced a stable biosensor for the detection of aldehydes. When integrated in a flow injection analysis (FIA) setup with amperometric detection at 0.1V vs. Ag/AgCl, the measurement of benzaldehyde with a detection limit of 10μmolL-1 over a linear range of 30-300μmolL-1 is possible. Determination of trace benzaldehyde impurities in a pharmaceutical excipient was also demonstrated and resultscompared with a chromatographic method. Graphical abstract.