Abstract
Improving direct electron transfer between heme protein (a) and graphite (b) studded with AgNPs (c). [Display omitted]
► Graphite studded with AgNPs is proposed as basic for carbon paste electrode. ► Embedding of heme proteins in this material achieves third generation biosensors. ► Peroxide and nitrite was determined without need of any mediator.
The impregnation of graphite grains with silver nanoparticles (AgNPs) is proposed for making a novel carbon paste electrode (CPE). The resulting material promotes direct electron transfer and direct biocatalysis of embedded heme protein. It is demonstrated that the impregnation of graphite grains with AgNPs of 16–25nm, incorporated in a CPE, can promote measurable bio-electrochemical phenomena involving hemoglobin and myoglobin. Unlike other biosensors prepared with simple carbon, those based on carbon grains studded with AgNPs show well-defined and quasi-reversible voltammetric peak with heterogeneous electron transfer rate ks of approximately 0.037±0.007 and 0.013±0.005s−1 for hemoglobin and myoglobin, respectively. The embedded proteins also retain their bio-catalytical activity for hydrogen peroxide and nitrite reduction with linear ranges of 0.5–3000μM and 30–150μM, sensitivities of 73.6±0.6nAμM−1 and 5.72±0.11nAμM−1, and detection limits close to 0.08μM and 5.80μM, for these two analytes respectively. These results support the viability of this preliminary approach for the development of advanced third-generation biosensors.