Simple method for making MWCNTs/Au-NPs-based biosensor electrodes

Multiwalled carbon nanotubes have great potential when applied as biosensors. Their properties, especially as electrodes with electrochemical characteristics, offer strong benefits for developing biosensors. This research has been able to integrate multiwalled carbon nanotubes (MWCNTs) with Au nanoparticles (Au-NPs) to obtain several new superior properties. Cysteaminium chloride is used to link MWCNTs and Au-NPs while binding to specific antibodies to make them more sensitive to some diseases or viruses. The data on the success of the bonding of MWCNTs/Au-NPs were tested using three characterizations, namely FTIR, SEM, and XRD. Based on the results of testing electrochemical properties using the CV and EIS tests, the capacitance value of 6,363 Fg-1 and the Rct value of 717,9 Ω, respectively. This demonstrates good adhesion and electron transfer properties from the electrolyte to the probe and electrode.

Electrochemical Detection Platform Based on RGO Functionalized with Diazonium Salt for DNA Hybridization

In this paper, we propose an improved electrochemical platform based on graphene for the detection of DNA hybridization. Commercial screen-printed carbon electrodes (SPCEs) were used for this purpose due to their ease of functionalization and miniaturization opportunities. SPCEs were modified with reduced graphene oxide (RGO), offering a suitable surface for further functionalization. Therefore, aryl-carboxyl groups were integrated onto RGO-modified electrodes by electrochemical reduction of the corresponding diazonium salt to provide enough reaction sites for the covalent immobilization of amino-modified DNA probes. Our final goal was to determine the optimum conditions needed to fabricate a simple, label-free RGO-based electrochemical platform to detect the hybridization between two complementary single-stranded DNA molecules. Each modification step in the fabrication process was monitored by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) using [Fe(CN)6]3−/4− as a redox reporter. Although, the diazonium electrografted layer displayed the expected blocking effect of the charge transfer, the next steps in the modification procedure resulted in enhanced electron transfer properties of the electrode interface. We suggest that the improvement in the charge transfer after the DNA hybridization process could be exploited as a prospective sensing feature. The morphological and structural characterization of the modified electrodes performed by scanning electron microscopy (SEM) and Raman spectroscopy, respectively, were used to validate different modification steps in the platform fabrication process.

New Advances in Graphene-Based Three-Dimensional Structures

Graphene is defined as a two-dimensional network of carbon atoms with a single atom thickness and a hexagonal crystalline structure with sp2 hybridization compacted by covalent bonds. Due to its structure and geometry, graphene has unique properties, including a large specific surface area, rapid mobility of load carriers, and high thermal and electrical conductivity. However, these characteristics are limited due to the restructuring of graphene sheets. For this reason, there are many studies devoted to the synthesis of three-dimensional structures that prevent the agglomeration of the sheets and the loss of properties of the graphene structure. These three-dimensional structures have low density, high porosity and surface area, stable mechanical properties, and good mass and electron transfer properties. This chapter aims to summarize the synthesis methods of the different three-dimensional structures derived from graphene as well as their wide range of applications in environmental remediation, sensors, biomedical and energy-related applications, among many others.

Comparative Analysis of Three Pairs of Surrogate Redox Partners for in Vitro Activity Reconstitution of Class I Cytochrome P450 Enzymes

Cytochrome P450 enzymes (P450s) are highly attractive biocatalysts due to their versatile catalytic activities. A vast majority of P450s require redox partner (RP) proteins to sequentially transfer two electrons for O2 activation and substrate oxidation. However, little information is available on cognate RPs for P450s, which greatly limits P450 function exploration and practical application. Thus, the stategy of building various hybrid P450 catalytic systems with surrogate RPs has often adopted to engineer P450 biocatalysts for different purposes. In this study, we comprehensively compare three pairs of frequently-used surrogate redox partners SelFdx1499/SelFdR0978, Adx/AdR and Pdx/PdR and in terms of their electron transfer properties. The three selected bacterial Class I P450s to accept electrons from RPs include PikC, P450sca-2 and CYP-sb21, which are responsible for production of macrolide antibiotics, the cholesterol-lowering drug pravastatin, and a hair-growth-stimulating agent. Both experimental studies and structural analysis show that SelFdx1499/SelFdR0978 is the most promising RP compared to Adx/AdR and Pdx/PdR. The results provide insights into the domination for P450-redox partner interactions in modulating the catalytic activity of P450s. This study not only produces a more active biocatalyst but also suggests a general chose for a universal reductase which would facilitate engineering of P450 catalyst.

Application of Functionalized Graphene Oxide Based Biosensors for Health Monitoring: Simple Graphene Derivatives to 3D Printed Platforms

Biosensors hold great potential for revolutionizing personalized medicine and environmental monitoring. Their construction is the key factor which depends on either manufacturing techniques or robust sensing materials to improve efficacy of the device. Functional graphene is an attractive choice for transducing material due to its various advantages in interfacing with biorecognition elements. Graphene and its derivatives such as graphene oxide (GO) are thus being used extensively for biosensors for monitoring of diseases. In addition, graphene can be patterned to a variety of structures and is incorporated into biosensor devices such as microfluidic devices and electrochemical and plasmonic sensors. Among biosensing materials, GO is gaining much attention due to its easy synthesis process and patternable features, high functionality, and high electron transfer properties with a large surface area leading to sensitive point-of-use applications. Considering demand and recent challenges, this perspective review is an attempt to describe state-of-the-art biosensors based on functional graphene. Special emphasis is given to elucidating the mechanism of sensing while discussing different applications. Further, we describe the future prospects of functional GO-based biosensors for health care and environmental monitoring with a focus on additive manufacturing such as 3D printing.

The Intramolecular Electronic Interaction Regulated by Five-membered Heterocycle Spacer

The spacer in diferrocenyl derivatives has significant effects on intramolecular electronic interaction properties. In this work, nine diferrocenyl five-membered heterocyclic molecules are synthesized as models to investigate the effect of intramolecular electron-transfer properties systematically, including 2,5-diferrocenyl-1-phenyl-pyrrole (1), 2,5-diferrocenylfuran (2), 2,5-diferrocenylthiophene (3), 2,5-diferrocenyl-1H-imidazole (4), 2,5-diferrocenyloxazole (5), 2,5-diferrocenylthiazole (6), 2,5-diferrocenyl-1,3,4-triazole (7), 2,5-diferrocenyl-1,3,4-oxadiazole (8) and 2,5-diferrocenyl-1,3,4-thiadiazole (9). The molecules were prepared in cyclization reaction and characterized by Elemental analysis, FT-IR, MS and NMR. Moreover, the molecular structures of 2,5-diferrocenylthiazole and 2,5-diferrocenyl-1,3,4-oxadiazole were determined by the single crystal X-ray diffraction. The intramolecular electronic interactions were investigated through cyclic voltammetry in combination with density functional theory (DFT) calculations. The results revealed that the electronic interaction decreased with the increase of heteroatoms in central heterocycle spacer, and the electron-transfer property could be regulated by regulate central heterocycle spacer species.