Chronoamperometric determination of D-lactate using screen-printed enzyme electrodes

A reagentless biosensor for D-lactate was developed using the screen-printing technology. In a simple design, D-lactate dehydrogenase and NAD+ were deposited onto the surface of a carbon electrode, modified with an insoluble salt of Meldolaʹs Blue. The detection of D-lactate was performed by chronoamperometry and took advantage of the constant potential oxidation of NADH, formed in the reaction catalysed by D-lactate dehydrogenase. The total of 150s were necessary for a measurement and linear detection of D-lactate was achieved over the range 0.1-1mM. Twenty-five microliter sample volumes were required for the assays. The choice of a properly applied potential together with the use of polyethyleneimine-Nafion in the sensing layer allowed to minimise the interferences for the detection of D-lactate in real samples of wine.