One-step enzyme-free dual electrochemical immunosensor for histidine-rich protein 2 determination

In the present work, we describe a novel one-step enzyme-free dual electrochemical immunosensor for the determination of histidine-rich protein 2 (Ag-PfHRP2), a specific malaria biomarker. A gold electrode (GE) was functionalized with thePfHRP2 antibody (Ab-PfHRP2) using dihexadecyl phosphate (DHP) polymer as an immobilization platform. The Ab-PfHRP2/DHP/GE sensor was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. The developed immunosensor was employed for indirect Ag-PfHRP2 determination by differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The linear range was 10-400 ng mL−1and 10-500 ng mL−1for EIS and DPV, while the limit of detection was 3.3 ng mL−1and 2.8 ng mL−1, respectively. The electrochemical immunosensor was successfully applied for Ag-PfHRP2 determination in human serum samples. Its performance was compared with an ELISA test, and good correspondence was achieved. The coefficients of intra- and inter-assay variations were less than 5%. The electrochemical immunosensor is a useful and straightforward tool forin situmalaria biomarker determination.Fil: Dip Gandarilla, Ariamna María. Universidad Federal del Amazonas.; BrasilFil: Regiart, Daniel Matias Gaston. Universidade de Sao Paulo; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Química de San Luis. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Instituto de Química de San Luis; ArgentinaFil: Bertotti, Mauro. Universidade de Sao Paulo; BrasilFil: Correa Glória, Juliane. Fundación Oswaldo Cruz; BrasilFil: Morais Mariuba, Luís André. Fundación Oswaldo Cruz; BrasilFil: Brito, Walter Ricardo. Universidad Federal del Amazonas.; Brasi

Effects of Substitution and Substrate Strain on the Structure and Properties of Orthorhombic Eu1-xYxMnO3 (0 ≤ x ≤ 0.5) Thin Films

The effects on the structure and magnetic properties of Eu1-xYxMnO3 (0.0 ≤ x ≤ 0.5) thin films due to lattice strain were investigated and compared with those obtained in equivalent composition ceramics. The films were deposited by spin-coating chemical solution onto Pt\TiO2\SiO2\Si (100) standard substrates. X-ray diffraction and Raman spectroscopy measurements revealed that all films crystallize in orthorhombic structure with space group Pnma, observing an added contraction of the unit cell with increasing Y-substitution ou Eu, corresponding to a broadening of the Mn-O1-Mn angle and a gradual decrease in magnetic order response.CNPq, FAPEAM, and CAPES; Postdoctoral National Program (PNPD/CAPES), Edital No. 047/2016– PPGFIS/UFAM

Effect of the Deposition Time on the Structural, 3D Vertical Growth, and Electrical Conductivity Properties of Electrodeposited Anatase–Rutile Nanostructured Thin Films

TiO2 time-dependent electrodeposited thin films were synthesized using an electrophoretic apparatus. The XRD analysis revealed that the films could exhibit a crystalline structure composed of ~81% anatase and ~6% rutile after 10 s of deposition, with crystallite size of 15 nm. AFM 3D maps showed that the surfaces obtained between 2 and 10 s of deposition exhibit strong topographical irregularities with long-range and short-range correlations being observed in different surface regions, a trend also observed by the Minkowski functionals. The height-based ISO, as well as specific surface microtexture parameters, showed an overall decrease from 2 to 10 s of deposition, showing a subtle decrease in the vertical growth of the films. The surfaces were also mapped to have low spatial dominant frequencies, which is associated with the similar roughness profile of the films, despite the overall difference in vertical growth observed. The electrical conductivity measurements showed that despite the decrease in topographical roughness, the films acquired a thickness capable of making them increasingly insulating from 2 to 10 s of deposition. Thus, our results prove that the deposition time used during the electrophoretic experiment consistently affects the films’ structure, morphology, and electrical conductivity

An Electrochemical Immunosensor Based on Carboxylated Graphene/SPCE for IgG-SARS-CoV-2 Nucleocapsid Determination

The COVID-19 pandemic has emphasized the importance and urgent need for rapid and accurate diagnostic tests for detecting and screening this infection. Our proposal was to develop a biosensor based on an ELISA immunoassay for monitoring antibodies against SARS-CoV-2 in human serum samples. The nucleocapsid protein (N protein) from SARS-CoV-2 was employed as a specific receptor for the detection of SARS-CoV-2 nucleocapsid immunoglobulin G. N protein was immobilized on the surface of a screen-printed carbon electrode (SPCE) modified with carboxylated graphene (CG). The percentage of IgG-SARS-CoV-2 nucleocapsid present was quantified using a secondary antibody labeled with horseradish peroxidase (HRP) (anti-IgG-HRP) catalyzed using 3,3′,5,5′-tetramethylbenzidine (TMB) mediator by chronoamperometry. A linear response was obtained in the range of 1:1000–1:200 v/v in phosphate buffer solution (PBS), and the detection limit calculated was 1:4947 v/v. The chronoamperometric method showed electrical signals directly proportional to antibody concentrations due to antigen-antibody (Ag-Ab) specific and stable binding reaction

Morphology, microstructure, and electrocatalytical properties of sol-gel spin-coated Bi0.5Na0.5Ba(TiO3)2 thin films

Herein, we report, for the first time, the reduction reaction kinetics of ciprofloxacin organic molecules based on structural and micromorphological conditions of an electrocatalytic system of Bi05Na05Ba(TiO3)2 (BNT-BT) thin films. XRD analysis showed the coexistence of rhombohedral and tetragonal structures for the BNT-BT thin films annealed at 600, 650, and 700 degrees C, showing that the first one had a greater number of surface defects, which Raman spectroscopy confirmed. Analysis of the 3D micromorphological evaluation showed that an annealing temperature increase from 600 to 700 degrees C does not induce significant changes in the topographical profile. However, BNT-BT thin films annealed at 600 degrees C displayed more anisotropic surface microtexture, high spatial complexity, and low spatial frequencies. For the reactive surface of BNT-BT films, the electroanalytical assays showed that electrons from the conduction band are captured by oxygen adsorbed on the film surface, forming superoxide radicals that attack ciprofloxacin molecules, promoting their degradation. The best performance observed for the BNT-BT thin films annealed at 600 degrees C is attributed to their unique structural and micromor-phological properties compared to the films annealed at higher temperatures. Our results prove that the proposed thin film deposition process is promising for developing new electrocatalytic devices