Search Results (39)

With the goal of fast and accurate diagnosis of infectious diseases, this study presents a novel electrochemical biosensor that employs a refined aptamer (C9t) for the detection of spike (S) protein SARS-CoV-2 variants in a flexible multielectrode aptasensor array with PoC capabilities. Two aptamer modifications were employed: removing the primer binding sites and including two dithiol phosphoramidite anchor molecules. Thus, reducing fabrication time from 24 to 3 h and increasing the stability and sparseness for multi-thiol aptasensors compared to a standard aptasensor using single thiols, without a reduction in aptamer density. The biosensor fabrication, optimization, and detection were verified in detail by electrochemistry, QCM-D, SPR, and XPS. The analyte–receptor binding was further confirmed spectroscopically at the level of individual molecules by AFM-IR. The aptasensor possesses a low limit of detection (8.0 fg/mL), the highest sensitivity reported for S protein (209.5 signal per concentration decade), and a wide dynamic detection range (8.0 fg/mL–38 ng/mL) in nasopharyngeal samples, covering the clinically relevant range. Furthermore, the C9t aptasensor showed high selectivity for SARS-CoV-2 S proteins over biomarkers for MERS-CoV, RSV, and Influenza. Even more, it showed a three times higher sensitivity for the Omicron in comparison to the Wuhan strain (wild type), alpha, and beta variants of the SARS-CoV-2 virus. Those results demonstrate the creation of an affordable and variant-selective refined C9t aptasensor that outperformed current rapid diagnosis tests. Full article

Redox metabolism is an integral part of the glutathione system, encompassing reduced and oxidized glutathione, hydrogen peroxide, and associated enzymes. This core process orchestrates a network of thiol antioxidants like thioredoxins and peroxiredoxins, alongside critical thiol-containing proteins such as mercaptoalbumin. Modifications to thiol-containing proteins, including oxidation and glutathionylation, regulate cellular signaling influencing gene activities in inflammation and carcinogenesis. Analyzing thiol antioxidants, especially glutathione, in biological fluids offers insights into pathological conditions. This review discusses the analytical methods for biothiol determination, mainly in blood plasma. The study includes all key methodological aspects of spectroscopy, chromatography, electrochemistry, and mass spectrometry, highlighting their principles, benefits, limitations, and recent advancements that were not included in previously published reviews. Sample preparation and factors affecting thiol antioxidant measurements are discussed. The review reveals that the choice of analytical procedures should be based on the specific requirements of the research. Spectrophotometric methods are simple and cost-effective but may need more specificity. Chromatographic techniques have excellent separation capabilities but require longer analysis times. Electrochemical methods enable real-time monitoring but have disadvantages such as interference. Mass spectrometry-based approaches have high sensitivity and selectivity but require sophisticated instrumentation. Combining multiple techniques can provide comprehensive information on thiol antioxidant levels in biological fluids, enabling clearer insights into their roles in health and disease. This review covers the time span from 2010 to mid-2024, and the data were obtained from the SciFinder^® (ACS), Google Scholar (Google), PubMed^®, and ScienceDirect (Scopus) databases through a combination search approach using keywords. Full article

Electrochemiluminescence (ECL) is a light-emitting process triggered by the high energy redox between electrochemically oxidized and reduced luminophores or some coreactive intermediate radicals, representing a blooming hot topic over decades with a wide variety of bioanalytical applications. Due to the superb sensitivity, ultralow background noise, specificity, ease of integration, and real-time and in situ analysis, ECL has been developed as a convenient and versatile technique for immunodiagnostics, nucleic acid analysis, and bioimaging. Discovering highly-efficient ECL emitters has been a promising subject that will benefit the development of sensitive bioanalytical methods with prominent potential prospects. To date, the interdisciplinary integrations of electrochemistry, spectroscopy, and nanoscience have brought up the continuous emergences of novel nanomaterials which can be flexibly conjugated with specific bio-recognition elements as functional ECL emitters for bioassays. Therefore, a critical overview of recent advances in developing highly-efficient ECL emitters for ultrasensitive detection of protein biomarkers is presented in this review, where six kinds of the most promising ECL nanomaterials for biosensing and imaging of various disease-related protein biomarkers are separately introduced with references to representative works. Finally, this review discusses the ongoing opportunities and challenges of ECL emitters in developing advanced bioassays for single-molecule analysis and spatiotemporally resolved imaging of protein biomarkers with future perspectives. Full article

3D-RISM-KH molecular solvation theory based on statistical mechanics has been an engine of the multiscale methods framework, which also includes molecular simulation techniques. Its applications range from the solvation energy of small molecules to the phase behavior of polymers and biomolecules. Molecular solvation theory predicts and explains the molecular mechanisms and functioning of a variety of chemical and biomolecular systems. This includes the self-assembly and conformational stability of synthetic organic rosette nanotubes (RNTs), the aggregation of peptides and proteins related to neurodegeneration, the binding of ligands to proteins, and the solvation properties of biomolecules related to their functions. The replica RISM-KH-VM molecular solvation theory predicts and explains the structure, thermodynamics, and electrochemistry of electrolyte solutions sorbed in nanoporous carbon supercapacitor electrodes, and is part of recent research and development efforts. A new quasidynamics protocol couples multiple time step molecular dynamics (MTS-MD) stabilized with an optimized isokinetic Nosé–Hoover (OIN) thermostat driven by 3D-RISM-KH mean solvation forces at gigantic outer time steps of picoseconds, which are extrapolated forward at short inner time steps of femtoseconds with generalized solvation force extrapolation (GSFE). The OIN/3D-RISM-KH/GSFE quasidynamics is implemented in the Amber Molecular Dynamics package. It is validated on miniprotein 1L2Y and protein G in ambient aqueous solution, and shows the rate of sampling 150 times faster than in standard MD simulations on these biomolecules in explicit water. The self-consistent field version of Kohn–Sham DFT in 3D-RISM-KH mean solvation forces is implemented in the Amsterdam Density Functional (ADF) package. Its applications range from solvation thermochemistry, conformational equilibria, and photochemistry to activation barriers of different nanosystems in solutions and ionic liquids. Full article

Biosensors show promising prospects in the assays of various targets due to their advantages of high sensitivity, good selectivity and rapid response. Molecular recognition is a key event of biosensors, which usually involves the interaction of antigen–antibody, aptamer–target, lectin–sugar, boronic acid–diol, metal chelation and DNA hybridization. Metal ions or complexes can specifically recognize phosphate groups in peptides or proteins, obviating the use of biorecognition elements. In this review, we summarized the design and applications of biosensors with metal ion–phosphate chelation interaction for molecular recognition. The sensing techniques include electrochemistry, fluorescence, colorimetry and so on. Full article

Molecular immobilization and recognition are two key events for the development of biosensors. The general ways for the immobilization and recognition of biomolecules include covalent coupling reactions and non-covalent interactions of antigen–antibody, aptamer–target, glycan–lectin, avidin–biotin and boronic acid–diol. Tetradentate nitrilotriacetic acid (NTA) is one of the most common commercial ligands for chelating metal ions. The NTA–metal complexes show high and specific affinity toward hexahistidine tags. Such metal complexes have been widely utilized in protein separation and immobilization for diagnostic applications since most of commercialized proteins have been integrated with hexahistidine tags by synthetic or recombinant techniques. This review focused on the development of biosensors with NTA–metal complexes as the binding units, mainly including surface plasmon resonance, electrochemistry, fluorescence, colorimetry, surface-enhanced Raman scattering spectroscopy, chemiluminescence and so on. Full article

In the present work, screen-printed electrodes (SPE) modified with a synthetic surfactant, didodecyldimethylammonium bromide (DDAB) and streptolysin O (SLO) were prepared for cytochrome P450 3A4 (CYP3A4) immobilization, direct non-catalytic and catalytic electrochemistry. The immobilized CYP3A4 demonstrated a pair of redox peaks with a formal potential of −0.325 ± 0.024 V (vs. the Ag/AgCl reference electrode). The electron transfer process showed a surface-controlled mechanism (“protein film voltammetry”) with an electron transfer rate constant (k_s) of 0.203 ± 0.038 s⁻¹. Electrochemical CYP3A4-mediated reaction of N-demethylation of erythromycin was explored with the following parameters: an applied potential of −0.5 V and a duration time of 20 min. The system with DDAB/SLO as the electrode modifier showed conversion of erythromycin with an efficiency higher than the electrode modified with DDAB only. Confining CYP3A4 inside the protein frame of SLO accelerated the enzymatic reaction. The increases in product formation in the reaction of the electrochemical N-demethylation of erythromycin for SPE/DDAB/CYP3A4 and SPE/DDAB/SLO/CYP3A4 were equal to 100 ± 22% and 297 ± 7%, respectively. As revealed by AFM images, the SPE/DDAB/SLO possessed a more developed surface with protein cavities in comparison with SPE/DDAB for the effective immobilization of the CYP3A4 enzyme. Full article

In this study, coagulation combined with the electro-Fe⁰/H₂O₂ reaction was developed to treat refractory organics in the landfill leachate effluent of a membrane bioreactor (MBR), and the change in biodegradability was investigated. The results showed that polymerized ferric sulfate (PFS) was the best coagulant, with removal efficiencies of chemical oxygen demand (COD) and chromaticity of 74.18% and 72.22%, respectively, when the dosage was 2 g/L and the initial pH (pH₀) was 6. Under the optimal conditions of pH₀ of 3, current density of 5 mA/cm², Fe⁰ dosage of 3 g/L, and H₂O₂ dosage of 0.059 M, the electro-Fe⁰/H₂O₂ reaction showed the removal efficiencies of COD and chromaticity for coagulated effluent were 76.68% and 74%, respectively. UV-vis and 3D-EEM spectral analysis showed that humic and fulvic acids were effectively degraded, and the effluent was mostly small molecules of aromatic protein-like substances. The whole process increased the BOD₅/COD from 0.049 to 0.46, indicating that the biodegradability was substantially improved. This is due to the conjunction of the Fe⁰/H₂O₂ reaction with electrochemistry, which accelerated the reduction of Fe³⁺ to Fe²⁺ on the Fe⁰ surface and cathode and improved the efficiency of hydroxyl radical (•OH) generation, thus promoting the removal of pollutants. The operating cost was only 4.18 $/m³, with the benefits of less Fe⁰ loss and no pH adjustment. In summary, coagulation combined with the electro-Fe⁰/H₂O₂ reaction is a cost-effective method for treating refractory organics in leachate and enhancing biodegradability. Full article

The demonstration of the first enzyme-based electrode to detect glucose, published in 1967 by S. J. Updike and G. P. Hicks, kicked off huge efforts in building sensors where biomolecules are exploited as native or modified to achieve new or improved sensing performances. In this growing area, bionanotechnology has become prominent in demonstrating how nanomaterials can be tailored into responsive nanostructures using biomolecules and integrated into sensors to detect different analytes, e.g., biomarkers, antibiotics, toxins and organic compounds as well as whole cells and microorganisms with very high sensitivity. Accounting for the natural affinity between biomolecules and almost every type of nanomaterials and taking advantage of well-known crosslinking strategies to stabilize the resulting hybrid nanostructures, biosensors with broad applications and with unprecedented low detection limits have been realized. This review depicts a comprehensive collection of the most recent biochemical and biophysical strategies for building hybrid devices based on bioconjugated nanomaterials and their applications in label-free detection for diagnostics, food and environmental analysis. Full article

The coronavirus disease 2019 (COVID-19) pandemic has created an urgent need for accurate early diagnosis and monitoring. A label-free rapid electrochemical point-of-care (POC) biosensor for SARS-CoV-2 detection in human saliva is reported here to help address the shortcomings of traditional nucleic acid amplification methods and give a quantitative assessment of the viral load to track infection status anywhere, using disposable electrochemical sensor chips. A new chemical construct of gold nanoparticles (GNp) and thionine (Th) are immobilized on carboxylic acid functionalized carbon nanotubes (SWCNT-COOH) for high-performance biosensing. The sensor uses saliva with a one-step pretreatment and simple testing procedure as an analytical medium due to the user-friendly and non-invasive nature of its procurement from patients. The sensor has a response time of 5 min with a limit of detection (LOD) reaching 200 and 500 pM for the freely suspended spike (S) protein in phosphate buffer saline (PBS) and human saliva, respectively. The sensor’s performance was also proven for detecting a COVID-19 pseudovirus in an electrolyte solution with a LOD of 10⁶ copies/mL. The results demonstrate that the optimized POC sensor developed in this work is a promising device for the label-free electrochemical biosensing detection of SARS-CoV-2 and different species of viruses. Full article

An electrochemical method for the determination of the catalytic activity of L-asparaginase (ASNase) from Erwinia carotovora was proposed. Our approach is based on the electrooxidation of amino acids from L-asparaginase polypeptide backbones. The electrochemical behavior of ASNase on electrodes obtained by screen-printing modified with single-wall carbon nanotubes (SPE/SWCNTs) as sensing elements demonstrated a broad oxidation peak at 0.5–0.6 V centered at 0.531 ± 0.010 V. We have shown that in the presence of the substrate L-asparagine, the oxidation current of the enzyme was reduced in a concentration-dependent manner. The specificity of electrochemical analysis was confirmed in experiments with glycine, an amino acid with no substrate activity on ASNase and does not reduce the oxidation peak of L-asparaginase. The addition of glycine did not significantly influence the amplitude of the oxidation current. The innovative aspects of the proposed electrochemical sensor are the direct monitoring of ASNase catalytic activity and a reagentless approach, which does not require additional reagents or labels. Full article

In this work, glucose oxidase (GOx) has been immobilized onto graphite rod electrodes through an assisted-chitosan adsorption reaching an enzyme coverage of 4 nmol/cm². The direct and irreversible single adsorption of the Flavine Adenine Dinucleotide (FAD) cofactor has been minimized by electrode incubation in a chitosan (CH) solution containing the enzyme GOx. Chitosan keeps the enzyme structure and conformation due to electrostatic interactions preventing FAD dissociation from the protein envelope. Using chitosan, both the redox cofactor FAD and the protein envelope remain in the active form as demonstrated by the electrochemistry studies and the enzymatic activity in the electrochemical oxidation of glucose up to a concentration of 20 mM. The application of the modified electrodes for energy harvesting delivered a power density of 119 µW/cm² with a cell voltage of 0.3 V. Thus, chitosan presents a stabilizing effect for the enzyme conformation promoted by the confinement effect in the chitosan solution by electrostatic interactions. Additionally, it facilitated the electron transfer from the enzyme to the electrode due to the presence of embedded chitosan in the enzyme structure acting as an electrical wiring between the electrode and the enzyme (electron transfer rate constant 2.2 s⁻¹). This method involves advantages compared with previously reported chitosan immobilization methods, not only due to good stability of the enzyme, but also to the simplicity of the procedure that can be carried out even for not qualified technicians which enable their easy implementation in industry. Full article

Glycated hemoglobin (HbA1c) is the gold standard for measuring glucose levels in the diagnosis of diabetes due to the excellent stability and reliability of this biomarker. HbA1c is a stable glycated protein formed by the reaction of glucose with hemoglobin (Hb) in red blood cells, which reflects average glucose levels over a period of two to three months without suffering from the disturbance of the outside environment. A number of simple, high-efficiency, and sensitive electrochemical sensors have been developed for the detection of HbA1c. This review aims to highlight current methods and trends in electrochemistry for HbA1c monitoring. The target analytes of electrochemical HbA1c sensors are usually HbA1c or fructosyl valine/fructosyl valine histidine (FV/FVH, the hydrolyzed product of HbA1c). When HbA1c is the target analyte, a sensor works to selectively bind to specific HbA1c regions and then determines the concentration of HbA1c through the quantitative transformation of weak electrical signals such as current, potential, and impedance. When FV/FVH is the target analyte, a sensor is used to indirectly determine HbA1c by detecting FV/FVH when it is hydrolyzed by fructosyl amino acid oxidase (FAO), fructosyl peptide oxidase (FPOX), or a molecularly imprinted catalyst (MIC). Then, a current proportional to the concentration of HbA1c can be produced. In this paper, we review a variety of representative electrochemical HbA1c sensors developed in recent years and elaborate on their operational principles, performance, and promising future clinical applications. Full article

Copper-coated nanofibrous materials are desirable for catalysis, electrochemistry, sensing, and biomedical use. The preparation of copper or copper-coated nanofibers can be pretty challenging, requiring many chemical steps that we eliminated in our robust approach, where for the first time, Cu was deposited by magnetron sputtering onto temperature-sensitive polymer nanofibers. For the first time, the large-scale modeling of PCL films irradiation by molecular dynamics simulation was performed and allowed to predict the ions penetration depth and tune the deposition conditions. The Cu-coated polycaprolactone (PCL) nanofibers were thoroughly characterized and tested as antibacterial agents for various Gram-positive and Gram-negative bacteria. Fast release of Cu²⁺ ions (concentration up to 3.4 µg/mL) led to significant suppression of E. coli and S. aureus colonies but was insufficient against S. typhimurium and Ps. aeruginosa. The effect of Cu layer oxidation upon contact with liquid media was investigated by X-ray photoelectron spectroscopy revealing that, after two hours, 55% of Cu atoms are in form of CuO or Cu(OH)₂. The Cu-coated nanofibers will be great candidates for wound dressings thanks to an interesting synergistic effect: on the one hand, the rapid release of copper ions kills bacteria, while on the other hand, it stimulates the regeneration with the activation of immune cells. Indeed, copper ions are necessary for the bacteriostatic action of cells of the immune system. The reactive CO₂/C₂H₄ plasma polymers deposited onto PCL-Cu nanofibers can be applied to grafting of viable proteins, peptides, or drugs, and it further explores the versatility of developed nanofibers for biomedical applications use. Full article

The development of sensitive and selective assays for protein biomarkers and other biological analytes is important for advancing the fields of clinical diagnostics and bioanalytical chemistry. The potential advantages of using aptamers in electrochemical sandwich assays are being increasingly recognized. These assays may include an aptamer as both capture and detection agent or a combination of an aptamer with a different partner such as an antibody, a lectin or a nanomaterial. The second binding partner in the sandwich structure is typically conjugated to a redox marker, a catalyst or an enzyme that can be used to generate the signal needed for electrochemical detection. Nanoparticles and other nanostructures can be used as the carriers for multiple molecules of the detection partner and thereby increase the signal. Nanostructured surfaces can be used to increase surface area and improve electron transfer. Sensitive electrochemical methods including impedance, differential and square-wave voltammetry and chronocoulometry have been used for electrochemical signal read-out. Impressive results have been achieved using electrochemical sandwich assays in terms of limit of detection and linear range for a growing range of analytes. The recent progress for this type of assay for proteins and other biomarkers is the subject of this review. Full article