Development of a third-generation electrochemical enzyme-based biosensor for a scalable detection of oxygen in power generation cells

Pencil graphite electrodes (PGEs) are another form of carbon electrodes with good mechanical strength and comparable electrical properties. Moreover. their low cost makes them an excellent alternative to more conventional electrodes. especially in disposable applications. In this study. the PGEs were constructed with a 2 mm diameter pencil graphite with hardness 4H. HB. and 4B. The electrodes were cleaned and modified with 1 mg/ml of graphene oxide (GO) to enhance the surface area of the electrodes. The PGE-GO was further reduced electrochemically using Na2S2O4 from -1.2 V to 0.8 V at 50 mV/s for 50 cyclic voltammetry scans in the presence of oxygen. using K3Fe(CN)6 / K4Fe(CN)6 as a redox couple. The performance of the PGE was evaluated with multi-walled carbon nanotubes and nanomaterials with various linking agents. A further evaluation was conducted with multi-copper oxidase (MCO) enzymes (Bilirubin oxidase (BOx) and Laccase oxidase) applied for the bio-catalytic reduction of oxygen. The outcome of this study showed that the modification with GO revealed redox peaks 3.6 times higher than the bare PGE. The immobilization of MCO was confirmed by cyclic voltammetry in the presence of a phosphate buffer. Furthermore. the amperometric measurements of O2 at a reducing potential of +0.34 V. showed linearity up to 0.36 mM and sensitivity of 520 μA/(mM.cm2) to O2. Furthermore. computational adsorption studies were performed for the layer-by-layer electrode modification steps. The adsorption simulations revealed a lowering of the energy favored between the designed electrode layers. suggesting a most favorable interaction for the GO/MWCNTs/PBSE/BOx layer. Overall the computational data correlated well with experimental work. Notably. the layer-by-layer adsorption of the GO/MWCNTs/PBSE/BOx showed excellent affinity 11.4 M−1 between PBSE and the enzyme interaction. The direct electron transfer (DET) of the enzymatic reaction integrated with nanotechnology. has led to a small. portable and renewable power generating device. Thus this study addresses the demand for implantable medical devices. in the absence of an external power source.