Electrocatalytic processes promoted by diamond nanoparticles in enzymatic biosensing devices

• Diamond nanoparticles promote electrocatalytic processes in lactate biosensors.
• Lactate addition produces double catalytic effect at + 0.15 V and + 0.30 V (vs Ag/AgCl).
• Response to lactate at + 0.15 V (vs Ag/AgCl) is convenient for avoiding interferents.
• DNP based biosensors for lactate determination present good analytical properties.

We have developed a biosensing platform for lactate determination based on gold electrodes modified with diamond nanoparticles of 4 nm of nominal diameter, employing the enzyme lactate oxidase and (hydroxymethyl)ferrocene (HMF) as redox mediator in solution. This system displays a response towards lactate that is completely different to those typically observed for lactate biosensors based on other nanomaterials, such as graphene, carbon nanotubes, gold nanoparticles or even diamond nanoparticles of greater size. We have observed by cyclic voltammetry that, under certain experimental conditions, an irreversible wave (E0 = + 0.15 V) appears concomitantly with the typical FeII/FeIII peaks (E0 = + 0.30 V) of HMF. In this case, the biosensor response to lactate shows simultaneous electrocatalytic peaks at + 0.15 V and + 0.30 V, indicating the concurrence of different feedback mechanisms. The achievement of a biosensor response to lactate at + 0.15 V is very convenient in order to avoid potential interferences. The developed biosensor presents a linear concentration range from 0.02 mM to 1.2 mM, a sensitivity of 6.1 μA mM− 1, a detection limit of 5.3 μM and excellent stability. These analytical properties compare well with those obtained for other lactate-based biosensors that also include nanomaterials and employ HMF as redox mediator.

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