L-lactate selective impedimetric bienzymatic biosensor based on lactate dehydrogenase and pyruvate oxidase

•Lactate impedimetric biosensor has lactate dehydrogenase/pyruvate oxidase (LDH/PyrOx).•L-lactate enzymatic oxidation to pyruvate, then to enzymatically generated ions.•Pyruvate oxidation changes impedance characteristics.•Resistance and charge separation at LDH/PyrOx interface for L-Lactate monitoring.•Application to analysis of food samples.

A new L-lactate selective impedimetric biosensor based on a lactate dehydrogenase (LDH)/pyruvate oxidase (PyrOx) bioselective membrane is reported, fabricated using enzyme drop coating and cross-linking via glutaraldehyde vapours. The sensing strategy is based on the measurement of the change in impedance caused by the generation of charged ions (CH3COO−, H+ and HCO3−), from PyrOx catalysed pyruvate oxidation, the pyruvate resulting from L-lactate oxidation catalysed by LDH + nicotinamide adenine dinucleotide (NAD+). The experimental conditions, pH and buffer concentration, were optimized for best biosensor response, and operational/storage stability and selectivity/specificity were investigated. The limit of detection for L-lactate, was 17 and 20 μM, considering changes in resistance and charge separation parameters at and close to the LDH-NAD+/PyrOx interface, respectively. The biosensor was successfully employed for the determination of L-lactate in yogurt samples.

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