Screen-Printed Graphite Electrode Modified with Graphene-Co3O4 Nanocomposite: Voltammetric Assay of Morphine in the Presence of Diclofenac in Pharmaceutical and Biological Samples

Synergistic effect of manganese (II) phosphate & diamond nanoparticles in electrochemical sensors for reactive oxygen species determination in seminal plasma

In this work, we explore the ability of manganese (II) phosphate (MnP) as a catalytic element for the determination of reactive oxygen species (ROS) in seminal plasma, when MnP is employed as modifier of a glassy carbon electrode. The electrochemical response of the manganese (II) phosphate-modified electrode shows a wave at around +0.65 V due to the oxidation of Mn²⁺ to MnO₂⁺, which is clearly enhanced after addition of superoxide, the molecule considered as the mother of ROS. Once proved the suitability of manganese (II) phosphate as catalyst, we evaluate the effect of including a 0D (diamond nanoparticles) or a 2D (ReS₂) nanomaterial in the sensor design. The system consisting of manganese (II) phosphate and diamond nanoparticles yielded the largest improvement of the response. The morphological characterization of the sensor surface was performed by scanning electron microscopy and atomic force microscopy, while cyclic and differential pulse voltammetry were employed for the electrochemical characterization of the sensor. After optimizing the sensor construction, calibration procedures by chronoamperometry were performed, leading to a linear relation between peak intensity and the superoxide concentration in the range of 1.1 10^-4 M - 1.0 10^-3 M with a limit of detection of 3.2 10^-5 M. Seminal plasma samples were analysed by the standard addition method. Moreover, the analysis of samples fortified with superoxide at the μM level leads to recoveries of 95%.

Fully optimized new sensitive electrochemical device for the selective determination of 6-thioguanine anticancer drug in wastewater and biological samples

In present work, a novel voltammetric sensor for the determination of 6-thioguanine (6-TG) was fabricated. First, a graphite rod electrode (GRE) surface was modified via drop-coating of graphene oxide (GO) to increase the surface area of the electrode. Subsequently, molecularly imprinted polymer (MIP) network was prepared using a facile electro-polymerization procedure, using o-aminophenol (as functional monomer) and 6-TG (as template molecule). Influences of test solution pH, dropped GO concentration and incubation time on the performance of GRE-GO/MIP were studied, and their values determined as 7.0, 1.0 mg/mL and 90 s, respectively. Using GRE-GO/MIP, 6-TG was measured in the range of 0.5-60 μM with a low detection limit (DL) of 80 nM (based on S/N = 3). In addition, the electrochemical device demonstrated good reproducibility (3.8%) and anti-interference ability toward 6-TG monitoring. The as-prepared sensor illustrated satisfactory sensing performance in real samples with recovery ranging from 96.5% to 102.5%. For the determination of trace amounts of anticancer drug (6-TG) in real matrices (biological samples and pharmaceutical wastewater sample), this study is expected to provide an effective strategy with high selectivity, stability, and sensitivity.

A dual-mode ratiometric aptasensor for accurate detection of pathogenic bacteria based on recycling of DNAzyme activation

Pathogenic bacteria have a significant impact on food safety. Herein, an innovative dual-mode ratiometric aptasensor was constructed for ultrasensitive and accurate detection of Staphylococcus aureus (S. aureus) based on recycling of DNAzyme activation on gold nanoparticles-functionalized MXene nanomaterials (MXene@Au NPs). Electrochemiluminescent (ECL) emitter-labeled probe DNA (probe 2-Ru) containing the blocked DNAzyme was partly hybridized with aptamer and then captured by electrochemical (EC) indicator-labeled probe DNA (probe 1-MB) on electrode surface. When S. aureus presented, the conformation vibration of probe 2-Ru activated the blocked DNAzymes, leading to recycling cleavage of probe 1-MB and ECL tag close to electrode surface. Based on the reverse change tendencies of ECL and EC signals, aptasensor achieved S. aureus quantification from 5 to 10⁸ CFU/mL. Moreover, the self-calibration characteristic of the aptasensor with dual-mode ratiometric readout ensured the reliable measurement of S. aureus in real samples. This work showed useful insight into sensing foodborne pathogenic bacteria.