An amperometric pyruvate biosensor based on pyruvate oxidase nanoparticles immobilized onto pencil graphite electrode

A novel high-stability bioelectrochemical sensor based on sol-gel immobilization of lactate dehydrogenase and AuNPs-rGO signal enhancement for serum pyruvate detection

Pyruvate participates in diverse metabolic pathways in the body and is normally present in human blood at 40-120 μM, with concentrations outside this range associated with various diseases. Therefore, accurate and stable blood pyruvate level tests are necessary for effective disease detection. However, traditional analytical techniques require complicated instrumentation and are time consuming and expensive, prompting researchers to develop improved methods based on biosensors and bioassays. Here, we designed a highly stable bioelectrochemical pyruvate sensor affixed to a glassy carbon electrode (GCE). To maximize biosensor stability, 0.1 U of lactate dehydrogenase was affixed to the GCE using a sol-gel process, resulting in generation of Gel/LDH/GCE. Next, 2.0 mg/mL AuNPs-rGO was added to enhance current signal strength, resulting in generation of the bioelectrochemical sensor Gel/AuNPs-rGO/LDH/GCE. AuNPs-rGO synthesized in advance was verified as correct using transmission electron microscopy and UV-Vis, Fourier-transform infrared and X-ray photoelectron spectroscopy. Pyruvate detection conducted via differential pulse voltammetry in phosphate buffer (pH 7.4, 100 mM) at 37 °C for 1-4500 μM pyruvate provided detection sensitivity as high as 254.54 μA/mM/cm². The reproducibility, regenerability and storage stability were analyzed with the relative standard deviation of 5 bioeletrochemical sensors detection was 4.60% and biosensor accuracy after 9 cycles was 92%, with accuracy remaining at 86% after 7 days. In the presence of D-glucose, citric acid, dopamine, uric acid and ascorbic acid, the Gel/AuNPs-rGO/LDH/GCE sensor exhibited excellent stability, high anti-interference ability and better performance than conventional spectroscopic methods for detection of pyruvate in artificial serum.

Novel solid inks based on beeswax, graphite and graphene applied to the fabrication of paper-based sensor for galactose determination

In this study, we present for the first time a simple and novel method for the fabrication of paper-based electrochemical sensors. The device development was carried out in a single stage with a standard wax printer. Hydrophobic zones were delimited with commercial solid ink, while electrodes were generated using new composite solid inks of graphene oxide/graphite/beeswax (GO/GRA/beeswax) and graphite/beeswax (GRA/beeswax). Subsequently, the electrodes were electrochemically activated by applying an overpotential. Various experimental variables for the GO/GRA/beeswax composite synthesis and electrochemical system obtention were evaluated. The activation process was examined by SEM, FTIR, cyclic voltammetry, electrochemical impedance spectroscopy and contact angle measurement. These studies showed morphological and chemical changes in the electrode active surface. As a result, the activation stage considerably improved the electron transfer on the electrode. The manufactured device was successfully applied for galactose (Gal) determination. This method presented a linear relation in the Gal concentration range from 84 to 1736 μmol L^-1, with a LOD of 0.1 μmol L^-1. The variation within and between-assay coefficients were 5.3% and 6.8%, respectively. The strategy here exposed for paper-based electrochemical sensors design is an unprecedented alternative system and represents a promising tool for mass production of economic analytical devices.

Electronic, transport, magnetic and optical properties of graphene nanoribbons review

Low dimensional materials have attracted great research interest from both theoretical and experimental point of view. These materials exhibit novel physical and chemical properties due to the confinement effect in low dimensions. The experimental observations of graphene open a new platform to study the physical properties of materials restricted to two dimensions. This featured article provides a review on the novel properties of quasi one-dimensional (1D) material known as graphene nanoribbon. Graphene nanoribbons can be obtained by unzipping carbon nanotubes (CNTs) or cutting the graphene sheet. Alternatively, it is also called the finite termination of graphene edges. It gives rise different edge geometries namely zigzag and armchair among others. There are various physical and chemical techniques to realize these materials. Depending on the edge type termination, these are called the zigzag and armchair graphene nanoribbons (ZGNR and AGNR). These edges play an important role in controlling the properties of graphene nanoribbons. The present review article provides an overview of the electronic, transport, optical and magnetic properties of graphene nanoribbons. However, there are different ways to tune these properties for device applications. Here, some of them are highlighted such as external perturbations and chemical modifications. Few applications of graphene nanoribbon have and chemical modifications. Few applications of graphene nanoribbon have also been briefly discussed.

Reagentless Amperometric Pyruvate Biosensor Based on a Prussian Blue- and Enzyme Nanoparticle-Modified Screen-Printed Carbon Electrode

We report a facile strategy for developing reagentless amperometric pyruvate biosensors based on enzyme nanoparticles (EnNPs). The EnNPs were prepared using pyruvate oxidase crosslinked with graphene quantum dots. Before EnNP immobilization, screen-printed carbon electrodes (SPCEs) were modified with Prussian blue, a biocompatible coordination polymer. The biosensor system was optimized in terms of the working potential and pH value. At pH 7.0 in 50 mM phosphate-buffered solution, the biosensor showed optimal characteristics under an applied potential of -0.10 V versus an internal pseudo-Ag reference electrode. Using these optimized conditions, the biosensor performance was characterized via the chronoamperometric technique. The EnNP-immobilized SPCE exhibited a dynamic linear range from 10 to 100 μM for pyruvate solution, and a sensitivity of 40.8 μA mM^-1 cm^-2 was recorded. The observed detection limit of the biosensor was 0.91 μM (S/N = 3) and it showed strong anti-inference capability under the optimized working potential. Furthermore, the practical applicability of the proposed biosensor was studied in fish serum samples.