A self-powered biosensor for glucose detection using modified pencil graphite electrodes as transducers

Abstract

Biofuel cells are an interesting way of microenergy production that can be advantageously channeled for biosensing applications. In this study, a biofuel cell was developed and applied as a self-powered biosensor for glucose detection. Glucose oxidase was initially tested for the bioanode and, since no evidence of direct electron transfer was observed in the absence of the co-substrate, it was not further considered. The enzymes Pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQGDH) and Bilirubin oxidase (BOx) were immobilized on Pencil graphite electrodes (PGE), previously nanostructured with MWCNT, serving as bioanode and biocathode, respectively. The bifunctional crosslinker 1-pyrenebutanoic acid succinimidyl ester (PBSE) was used as a simple but efficient tethering agent, enabling the establishment of direct electron transfer events. Cyclic and linear sweep voltammetry, and amperometry were employed for individual characterization of bioanode and biocathode as biosensors for the respective enzymatic substrates. A mean sensitivity of 77.7 ± 5.9 μA cm−2 mM−1 was obtained for glucose with a Limit of detection (LOD) of 4.0 ± 2.2 μM, whereas in the detection of O2, the sensitivity and LOD achieved were 336 ± 22 μA cm−2 mM−1 and 3.2 ± 1.0 μM, respectively. Finally, the PQQGDH bioanode and BOx biocathode were conjugated into a biofuel cell and further characterized as a self-powered biosensor for glucose, exhibiting a linear range up to 1 mM, an excellent sensitivity of 8.08 μW cm−2 mM−1, a low LOD of 0.084 mM and long stability (94% of the original response after 12 days). Therefore, PGE transducers and PBSE are valuable strategies for the design of simple and efficient self-powered biosensors.