Graphite grains studded with silver nanoparticles: Description and application in promoting direct biocatalysis between heme protein and the resulting carbon paste electrode

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 16–25 nm, 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 ± 0.005 s−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 0.5–3000 μM and 30–150 μM, sensitivities of 73.6 ± 0.6 nA μM−1 and 5.72 ± 0.11 nA μM−1, and detection limits close to 0.08 μM and 5.80 μM, for these two analytes respectively. These results support the viability of this preliminary approach for the development of advanced third-generation biosensors.