A highly sensitive electrochemical biosensor based on zinc oxide nanotetrapods for l-lactic acid detection

An amperometric biosensor based on zinc oxide (ZnO) nanotetrapods was designed to detect L-lactic acid. The lactate oxidase was immobilized on the surface of ZnO nanotetrapods by electrostatic adsorption. Unlike traditional detectors, the special four-leg individual ZnO nanostructure, as an adsorption layer, provides multiterminal charge transfer channels. Furthermore, a large amount of ZnO tetrapods are randomly stacked to form a three-dimensional network naturally that facilitates the exchange of electrons and ions in the phosphate buffer solution. Utilizing amperometric response measurements, the prepared ZnO nanotetrapod L-lactic acid biosensor displayed a detection limit of 1.2 μM, a low apparent Michaelis–Menten constant of 0.58 mM, a high sensitivity of 28.0 μA cm⁻² mM⁻¹ and a good linear relationship in the range of 3.6 μM–0.6 mM for the L-lactic acid detection. This study shows that the biosensor based on ZnO tetrapod nanostructures is highly sensitive and able to respond rapidly in detecting lactic acid.