Electrocatalytic processes promoted by diamond nanoparticles in enzymatic biosensing devices

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 (E = +0.15 V) appears concomitantly with the typical Fe/Fe peaks (E = +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, 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.This work has been supported by Ministerio de Economía y Competitividad (Project nos. CTQ2014-53334-C2-1-R, FIS2012-38866-C05-05 and CTQ2015-71955-REDT) and Comunidad Autónoma de Madrid (Project NANOAVANSENS S2013/MIT-3029)