Over-oxidized carbon paste electrode modified with pretreated carbon nanofiber for the simultaneous detection of epinephrine and uric acid in the presence of ascorbic acid

Application of a simple copper(II) complex compound as an epinephrine selective voltammetric sensor in the presence of uric acid under aqueous conditions

Developing sensors with high sensitivity and selectivity for detecting neurotransmitters under near-physiological conditions is a major challenge and is crucial for preventing diseases of the nervous, cardiovascular, and endocrine systems. Most existing systems that meet these requirements involve either complicated synthesis processes, require sulfur groups, or are not functional under aqueous conditions. Herein, we report that the self-organisation of a simple imine ligand L with copper(II) tetrafluoroborate leads to the formation of a [CuL2](BF4)2 complex (CuL2) with a 2 : 1 ligand-to-metal ratio, as confirmed by high-resolution electrospray ionization mass spectrometry (HR ESI-MS), Fourier-transform infrared (FT-IR) spectroscopy and single-crystal X-ray analysis. Surprisingly, modifying a gold surface with a self-assembled monolayer of the CuL2 complex created a stable sensor for selective detection of epinephrine (EP) using differential pulse voltammetry (DPV) in phosphate buffer solution (PBS) at pH 7.0. A linear correlation between the current response and the concentration of EP was observed with a detection limit of 0.03 μM, high reproducibility and good stability in the range of 0.0001 to 0.875 mM. These results show that the new sensor (Cu/Au) can serve as a reliable analytical tool to selectively detect EP alone and in a mixture with coexisting uric acid (UA) in tested samples.

Expression and purification of epitope vaccine against four virulence proteins from Helicobacter pylori and construction of label-free electrochemical immunosensor

The epitope vaccine against four virulence proteins (FVpE) from Helicobacter pylori (H. pylori) was expressed and purified. Western blot and Enzyme-linked Immunosorbent Assays (ELISA) were used to identify and investigate the immunoreactivity of FVpE protein. The immune-sensing platform based on titanium carbide/colloidal gold nanoparticles@carbon nanofiber/ionic liquid composites electrode was constructed for immobilizing FVpE. Electrochemical impedance spectroscopy (EIS) was used to study the electrochemical properties of the modified electrodes. The relevant influenced factors were optimized including pH value, antigen concentration, and incubating time. The prepared H. pylori label-free electrochemical immunosensor was used for antibody detection using differential pulse voltammetry (DPV). Under the optimal experimental conditions, the linear ranges of H. pylori antibodies, including anti-H. pylori, cytotoxin-associated gene A (CagA), vacuolating cytotoxin-associated gene A (VacA), and urease A (UreA), were all 0.1-5 ng mL-1, except urease B (UreB, 0.1-4.5 ng mL-1). The selectivity study showed that other antibodies had little influence on the detection of H. pylori antibodies. The immunosensor could be used to detect serum samples, and the recoveries were in the range of 68.5%-100.5%.