Nanostructured rough gold electrodes for the development of lactate oxidase-based biosensors

The design and characterization of a lactate biosensor using a nanostructured rough gold surface as a transducer is reported. The biosensor is developed by immobilization of lactate oxidase (LOx), on a rough gold electrode modified with a self-assembled monolayer of dithiobis-N-succinimidyl propionate (DTSP). This bifunctional reagent preserves the rough gold structure and allows further covalent immobilization of the enzyme through the terminal succinimidyl groups. The rough gold electrode is characterized using field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The preferential orientation and average crystallite size are obtained by X-ray diffraction (XRD). The resulting lactate oxidase monolayers are characterized by electrochemical impedance spectroscopy (EIS). This nanostructured transducer allows higher mediated electrocatalytic activity than polycrystalline ones. The biosensor response to increasing lactate concentrations, using hydroxymethylferrocene as a redox mediator in solution, is linear up to 1.2 mM with a sensitivity of 1.49 μA mM−1.