Preparation of gold nanoparticles supported on graphene oxide with flagella as the template for nonenzymatic hydrogen peroxide sensing

Highly Sensitive Detection of Hydrogen Peroxide in Cancer Tissue Based on 3D Reduced Graphene Oxide-MXene-Multi-Walled Carbon Nanotubes Electrode

Hydrogen peroxide (H2O2) is a signaling molecule that has the capacity to control a variety of biological processes in organisms. Cancer cells release more H2O2 during abnormal tumor growth. There has been a considerable amount of interest in utilizing H2O2 as a biomarker for the diagnosis of cancer tissue. In this study, an electrochemical sensor for H2O2 was constructed based on 3D reduced graphene oxide (rGO), MXene (Ti3C2), and multi-walled carbon nanotubes (MWCNTs) composite. Three-dimensional (3D) rGO-Ti3C2-MWCNTs sensor showed good linearity for H2O2 in the ranges of 1-60 μM and 60 μM-9.77 mM at a working potential of -0.25 V, with sensitivities of 235.2 µA mM-1 cm-2 and 103.8 µA mM-1 cm-2, respectively, and a detection limit of 0.3 µM (S/N = 3). The sensor exhibited long-term stability, good repeatability, and outstanding immunity to interference. In addition, the modified electrode was employed to detect real-time H2O2 release from cancer cells and cancer tissue ex vivo.

In situ engineering of Au-Ag alloy embedded PEDOT nanohybrids at a solvent/non-solvent interface for the electrochemical enzyme-free detection of histamine

Steadfast efforts have been made to develop novel materials and incorporate them into functional devices for practical applications, pushing the research on electroactive materials to the forefront of nano electronics. Liquid/liquid interface-assisted polymerization offers a scalable methodology to fabricate hybrid materials with multifunctional applications, in contrast to the conventional and ubiquitous routes. Here, we explored this efficient and versatile approach toward the in situ tailoring of Au-Ag alloy nanostructures with a conducting polymer, poly(3,4-ethylene-dioxythiophene) (PEDOT). With the appropriate choice of organic and inorganic phases for the distribution of monomer and oxidant, the miscibility restraints of the reactants in a single phase were alleviated. Effective nanostructure tuning of highly crystalline and electroactive PEDOT/Au-Ag alloy has been achieved by varying the molar ratio of Au³⁺/Ag⁺ in the reaction mixture. The as-synthesized composite is further explored to detect neuromodulator histamine (HA), which displays high sensitivity with a limit of detection (LOD) of 1.5 nM, and selectivity even in the presence of various interfering analogs of 10-fold concentration. Subsequently, density functional theory (DFT) simulations are employed to assess the mode of interaction between HA and the electroactive surfaces. The competency to detect HA in preserved food entails its potential in food spoilage monitoring. Furthermore, the detection of histamine generated by sub-cultured human neuronal cells SH-SY5Y proves its practical viability in health monitoring devices.

Chemically synthesized chevron-like graphene nanoribbons for electrochemical sensors development: determination of epinephrine

We employ chevron-like graphene nanoribbons (GNRs) synthesized by a solution-based chemical route to develop a novel electrochemical sensor for determination of the neurotransmitter epinephrine (EPI). The sensor surface, a glassy carbon electrode modified with GNRs, is characterized by atomic force microscopy, scanning electron microscopy and Raman spectroscopy, which show that the electrode surface modification comprises of bi-dimensional multilayer-stacked GNRs that retain their molecular structure. The charge transfer process occurring at the electrode interface is evaluated by electrochemical impedance spectroscopy. The sensor is applied to the determination of EPI, employing as an analytical signal the reduction peak corresponding to the epinephrinechrome–leucoepinephrinechrome transition (E = − 0.25 V) instead of the oxidation peak usually employed in the literature (E =  + 0.6 V) in order to minimize interferences. The results obtained demonstrate that chevron-like nanoribbons synthesized by solution methods exhibit reliable electrocatalytic activity for EPI determination. Using differential pulse voltammetry, we obtain a linear concentration range from 6.4 × 10^–6 to 1.0 × 10^–4 M and a detection limit of 2.1 × 10^–6 M. The applicability of the sensor was evaluated by determining EPI in pharmaceutical samples with satisfactory results.

Natural flagella-templated Au nanowires as a novel adjuvant against Listeria monocytogenes

A simple method was developed for the extraction and purification of bacterial flagella with a yield of a concentration of 113.22 ± 5.64 mg mL^-1. Gold (Au) nanowires were synthesized using the bacterial flagella as the template. Transmission Electron Microscopy (TEM) analysis showed that the nanowires were scarcely clustered as stiff (no tendency to bend or fold) and straight nanorods with homogeneous surface and a uniform aspect ratio over 60. Fourier Transform Infrared (FT-IR) spectroscopic studies revealed the deep involvement of the functional groups located within and on the surface of flagellin, including C-N, N-H, O-H, and C[double bond, length as m-dash]O. The profound transformation observed in the absorption profiles of these groups supported the notion that both chemical (reduction) reaction and physical (electrostatic) binding of Au occurred during the formation of Au nanowires. Verbascoside, oleuropein, and olive leaf extract (OLE) have been shown to inhibit the growth of Listeria monocytogenes completely at their respective Minimal Inhibitory Concentrations (MICs) of 20, 64, and 64 mg mL^-1. In contrast, the synthesized Au nanowires demonstrated high electrocatalytic activity and reduced the MICs of the three antibacterial compounds by half. Moreover, results from the AMES assays indicated that the synthesized Au nanowires had no mutagenic activities at the catalytic concentration used, 128 μg mL^-1. Therefore, the Au nanowires fabricated in this work have the potential to be used as new antimicrobial food packaging materials to enhance food safety.