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Hepatitis C virus (HCV) is a common blood-borne infection that can lead to long-term illnesses such as hepatocellular cancer and liver cirrhosis. Early diagnosis is crucial for effective management, as no vaccine is available for preventing HCV infection. However, the high cost and complexity of current molecular diagnostic tools hinder efforts to achieve early diagnosis and prevent transmission, particularly in resource-limited settings. We developed a novel electrochemical biosensor for point-of-care testing (POCT) of HCV RNA. The sensor utilizes a strand displacement method, where the target RNA displaces a gold nanoparticle-labeled reporter probe (AuRP) from a pre-hybridized duplex with a magnetic nanoparticle (MNP)-labeled capture probe. The amount of displaced AuRP, detected using differential pulse anodic stripping voltammetry (DPASV), is directly proportional to the target RNA concentration. The biosensor exhibited excellent analytical performance, with a detection limit of 4 fM for synthetic targets and 43 ng/µL for RT-PCR products. Importantly, it successfully detected HCV RNA directly in clinical plasma samples without the need for RNA extraction or amplification. The sensor was used to analyze 30 RNA samples from HCV-positive patients, 20 cDNA samples from viral RNA, 30 HCV-positive plasma samples, and 22 HCV-negative plasma samples. The sensor results show good concordance with the RT-PCR results, demonstrating the sensor's potential for detecting HCV in clinical samples. [ABSTRACT FROM AUTHOR]

Electron transfer flavoprotein subunit beta (ETFB) of Leptospira interrogans is a biomarker for diagnosing leptospiral infection. Thus, the ETFB-specific nuclease-resistant RNA aptamer ETFB3-63 was developed and used in an electrochemical aptasensor to assay ETFB. Although the majority of reported biosensors detect various genes and antibodies of L. interrogans, this is the first attempt to construct an electrochemical biosensor to detect ETFB protein for the diagnosis of leptospiral infection. The ETFB protein can be detected without any extraction phase. In this assay, a single-stranded DNA probe complementary to the ETFB3-63 sequence was immobilized on a screen-printed carbon electrode (SPCE). The aptamer was then incubated and hybridized with the antisense probe on the SPCE. In the presence of ETFB, the aptamer dissociates from the aptamer/probe complex on the SPCE to bind with the protein. Methylene blue was then added to intercalate with the remaining hybridized aptamers, and its signal was measured using differential pulse voltammetry. The signal arising from the intercalated methylene blue decreased with increasing concentration of ETFB, showing a linear response in the range of 50–500 nM of ETFB and 10 to 109 leptospira cells per mL, respectively. The aptasensor signal was also specific to L. interrogans but not to 12 related bacteria tested. In addition, the aptasensor showed similar performance in detecting ETFB spiked in human serum to that in buffer, indicating that proteins in the serum do not interfere with the assay. Therefore, this assay has great potential to develop into a point-of-care electrochemical device that is accurate, cost-effective, and user-friendly for leptospirosis diagnosis. [ABSTRACT FROM AUTHOR]

We report a simple and rapid method for the synthesis of fluorescent gallium oxyhydroxide (GaOOH) nanoparticles from liquid Ga by a probe sonication method in the presence of H2O2 as an oxidant. The aspect ratio of the GaOOH nanoparticles is determined by the concentration of H2O2 and solution pH, as well as the probe energy and sonication time. Further surface modification with cyclodextrin to achieve biocompatibility for potential biomedical applications is reported where an example of cell uptake and fluorescence imaging is shown. [ABSTRACT FROM AUTHOR]

The ability of the technique of large-amplitude Fourier transformed (FT) ac voltammetry to facilitate the quantitative evaluation of electrode processes involving electron transfer and catalytically coupled chemical reactions has been evaluated. Predictions derived on the basis of detailed simulations imply that the rate of electron transfer is crucial, as confirmed by studies on the ferrocenemethanol (FcMeOH)-mediated electrocatalytic oxidation of ascorbic acid. Thus, at glassy carbon, gold, and boron-doped diamond electrodes, the introduction of the coupled electrocatalytic reaction, while producing significantly enhanced dc currents, does not affect the ac harmonics. This outcome is as expected if the [FcMeOH.sup.o/+] process remains fully reversible in the presence of ascorbic acid. In contrast, the ac harmonic components available from FT-ac voltammetry are predicted to be highly sensitive to the homogeneous kinetics when an electrocatalytic reaction is coupled to a quasi-reversible electron-transfer process. The required quasi-reversible scenario is available at an indium tin oxide electrode. Consequently, reversible potential, heterogeneous charge-transfer rate constant, and charge-transfer coefficient values of 0.19 V vs Ag/AgCl, 0.006 cm [s.sup.-1] and 0.55, respectively, along with a second-order homogeneous chemical rate constant of 2500 [M.sup.-1] [s.sup.-1] for the rate-determining step in the catalytic reaction were determined by comparison of simulated responses and experimental voltammograms derived from the dc and first to fourth ac harmonic components generated at an indium fin oxide electrode. The theoretical concepts derived for large-amplitude FT ac voltammetry are believed to be applicable to a wide range of important solution-based mediated electrocatalytic reactions.

Abstract: In this work, the underpotential deposition of metals such as copper and lead during the electrochemical deposition of gold is investigated to understand the influence that the incorporation of a second metal has on the morphology of gold nanostructures. The incorporation of Pb or Cu, even at concentrations as low as 0.2 %, significantly influences the morphology of the deposit, where the formation of elongated structures from a central gold structure is favored. These nanostructures are characterized by cyclic voltammetry, X‐ray diffraction, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy and are tested for their suitability as a sensing layer for the electrochemical detection of nitrite ions in aqueous solution. A limit of detection of 0.3 μM is achieved with a linear range up to 1 mM, which is adequate for the determination of nitrite contained within food products. [ABSTRACT FROM AUTHOR]

We report a simple and rapid method for the synthesis of fluorescent gallium oxyhydroxide (GaOOH) nanoparticles from liquid Ga by a probe sonication method in the presence of H 2 O 2 as an oxidant. The aspect ratio of the GaOOH nanoparticles is determined by the concentration of H 2 O 2 and solution pH, as well as the probe energy and sonication time. Further surface modification with cyclodextrin to achieve biocompatibility for potential biomedical applications is reported where an example of cell uptake and fluorescence imaging is shown.