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A promising immunosensing strategy in diagnosing SARS-CoV-2 is proposed using a 10-µm gap-sized gold interdigitated electrode (AuIDE) to target the surface spike protein (SP). The microelectrode surface was modified by (3-glycidyloxypropyl) trimethoxysilane to enforce the epoxy matrix, which facilitates the immobilization of the anti-SP antibody. The immunosensing performance was evaluated by integrating a nanosized (~ 10 nm) diamond-complexed SP as a target. The proposed immunoassay was quantitatively evaluated through electrochemical impedance spectroscopy (EIS) with the swept frequency from 0.1 to 1 MHz using a 100 mV

A label-free chemical bonding strategy mediated by reduced graphene oxide (rGO) basal plane functional groups has been developed for cardiac Troponin I (cTnI) detection. Four different chemical strategies on respective electrode sensing surface were precedingly examined using electrochemical impedance spectroscopy. The impedimetric assessment was carried out by sweeping frequency at the range 0.1–500 kHz perturbated at a small amplitude of AC voltage (25 mV). The chemical strategy-4 denoted as S-4 shows a significant analytical performance on cTnI detection in spiked buffer and human serum, whereby the pre-mixture of rGO and (3-Aminopropyl)triethoxysilane (APTES) creates a large number of amine sites (−NH2), which significantly enhanced the antibody immobilization without excessive functionalization. The as-fabricated immunosensor exhibited an ultra-low limit of detection of 6.3 ag mL−1 and the lowest antigen concentration measured was at 10 ag mL−1. The immunosensor showed a linear and wide range of cTnI detection (10 ag mL−1–100 ng mL−1) in human serum with a regression coefficient of 0.9716, rapid detection (5 min of binding time), and stable and highly reproducible bioelectrode response with RSD

An abdominal aortic aneurysm (AAA) is abnormal swelling in the abdominal aorta and a prevalent life-threatening disease. This research introduces a new interdigitated microelectrode (IDME)-sensing surface modified by iron oxide nanoworms (IONWs) for detecting the AAA biomarker insulin-like growth factor-1 (IGF1). A sandwich pattern was formulated with the IGF1 aptamer and IGFBP1 (IGF binding protein-1) on the IONW-constructed IDME hybrid to identify IGF1. The surface morphology of the IONWs revealed a uniform distribution of worm-like structures (80–100 nm) as confirmed by FESEM and FETEM analyses. Further, the presence of the major elements, Fe and O, was confirmed by EDX and XPS studies. The crystal planes that appeared in the IONW reflect cubic magnetite. IONW-modified IDME attained a limit of detection for IGF1 of 1 fM (3σ) with an aptamer-IGF1-IGFBP1 sandwich. This sandwich with IGFBP1 enhanced the current level at all concentrations of IGF1 and displayed linearity in the range 1 fM to 100 pM with a determination coefficient of R2 = 0.9373 [y = 3.38221x – 4.79]. Control experiments with complementary aptamer sequences, IGF2 and IGFBP3 did not show notable signal changes, indicating the specific detection of IGF1. This IONW constructed electrode helps to achieve the detection of low amounts of IGF1 and diagnose AAA at the stage prior to rupture.

Molybdenum disulfide (MoS2) surface functionalization was performed with a catechol-containing polymer sodium alginate (SA) and dopamine (DA) through simultaneous MoS2 exfoliation and self-polymerization of DA. The MoS2/SA-PDA nanocomposite was characterized using spectroscopic, microscopic, and electroanalytical techniques to evaluate its electrocatalytic performance. The electrocatalytic behavior of the MoS2/SA-PDA nanocomposite modified electrode for the detection of acebutolol (ACE), a cardio-selective β-blocker drug was explored through cyclic voltammetric and differential pulse voltammetric techniques. The influence of scan rate, concentration, and pH value on the oxidation peak current of ACE was investigated to optimize the deducting condition. The electrochemical activity of the MoS2/SA-PDA nanocomposite electrode was attributed to the existence of reactive functional groups being contributed from SA, PDA, and MoS2 exhibiting a synergic effect. The MoS2/SA-PDA nanocomposite modified electrode exhibits admirable electrocatalytic activity with a wide linear response range (0.009 to 520 μM), low detection limit (5 nM), and high sensitivity (0.354 μA μM−1 cm−2) also in the presence of similar (potentially interfering) compounds. The fabricated MoS2/SA-PDA nanocomposite modified electrode can be useful for the detection of ACE in pharmaceutical analysis.

Two-dimensional (2D) MoS2core-shell nanoparticles were synthesized using an eco-friendly surface functionalization-agent with L-glutathione and cystamine (L-GSH–MoS2–CYS) using ultrasonic frequency of 20–25 kHz. The novel modified electrode was evaluated for the electrochemical detection of doxorubicin (DOX), through cyclic and differential pulse voltammetric techniques. The electro-catalytic oxidation currents of DOX exhibited a linear relationship in the concentration ranges 0.1–78.3 and 98.3–1218 μM, with a detection limit of 31 nM. A sensitivity of 0.017μA μM−1 cm−2 was acquired at 0.48 V. The fabricated L-GSH–MoS2–CYS modified electrode showed excellent precision, selectivity, repeatability, and reproducibility during the determination of DOX levels in blood serum samples. Thus, the fabricated L-GSH–MoS2–CYS/GCE modified electrode has potential for clinical applications for optimization of chemotherapeutic drugs owing to its selectivity, ease of preparation, and long-term stability.

The authors describe a voltammetric method for the simultaneous determination of acetaminophen (ACOP) and caffeine (CAF) using a glassy carbon electrode modified with a Nafion® protected halloysite nanotubular clay (GCE). Enhanced electrocatalytic oxidation behavior was observed at pH 4.5 in acetate buffer medium, with oxidation peak potentials of + 0.21 V for ACOP and + 1.0 V for CAF. The peak potential window (~ 800 mV) is quite large and hence differential pulse voltammetry (DPV) can be applied for simultaneous determination of both analytes. The calibration plots of ACOP and CAF are linear in the concentration ranges from 0.6 μM to 14 μM and 0.6 μM to 20 μM, and the detection limits are 1.1 × 10−8 M and 1.73 × 10−7 M, for ACOP and CAF, respectively. The method was applied to the determination of both analytes in drug formulations and human urine samples.

The authors describe an impedimetric nanosensor for aptamer-mediated detection of ATP. A triangular junction of polysilicon substrate is used as a transducer. The aptamer was immobilized on the substrate via biotin-streptavidin interaction. ATP can be detected by this method in the 10 to 100 nM concentration range at room temperature and estimated the signal to noise ratio above the range of 3σ. It was applied to the detection of ATP in 1:1000 diluted human urine. The desired transducer is highly reproducible and specific. It is selective over closely related molecules such as guanosine triphosphate, cytidine triphosphate and uridine triphosphate. The method is perceived to represent a valuable tool for the diagnosis for infections and inflammations. The novelties shown in this study compared to other sensors are, consumption of low sample volume (~ 1 μl), non-invasive and suitable with AC and DC currents.

The authors describe an electrochemical method for the determination of the blood clotting factor IX (FIX). A nanogapped dielectrode (with a

The authors describe an integrated biosensor for amperometric DNA detection of Dengue virus in real time. Cu2CdSnS4 (CCTS) quaternary alloy nanostructures were successfully synthesized, deposited on an oxygen-etched silicon substrate (O2/Si) via spin coating, and annealed at 400 °C. The nanostructures were investigated by using UV-vis spectroscopy, X-ray diffraction, atomic force microscopy and scanning electron microscopy. Interdigitated electrodes were fabricated using silver as a metal contact deposited on the CCTS/O2/Si substrate using a thermal evaporator vacuum coater and a hard mask. The quaternary alloy acts as a support for immobilization of a Dengue-specific DNA probe that is employed as the recognition element. Single-stranded DNA in concentrations from 100 f. to 10 nM were successfully recognized via amperometry, typically at a working voltage of 1.5 V. The lower detection limit is 17 nM. Sensitivity is found to be 24.2 μA nM−1 cm−2. The biosensor is inexpensive, fast, highly sensitive, and has low power consumption.

Simple and robustic mediator free graphene nanoflake modified glassy carbon electrode ( GNF/ GCE) was used for the simultaneous determination of vanillin (VAN) and guaiacol (GUA) in food products like chocolate and biscuits by using an amperometric method. Defect-free graphene nanoflakes were obtained by a surfactant assisted exfoliation approach. The resulting graphene flake was characterized by FE-SEM and Raman studies. The electrocatalytic oxidation of VAN and GUA occured at +0.59 V and +0.48 V vs. Ag/AgCl at GNF/GCE, under optimum experimental condition. A well-defined peak potential window ( ~1 6 0 mV) for the oxidation of VAn and GUA were observed in the modified electrode. Calibration curves of VAN and GUA were attained in the ranges of 0.1 × 10–7 M to 53 × 10–6 M and 0.3 × 10–7 M to 46 × 10–6 M with correlation coefficient of 0.9966 and 0.9951, respectively. A greater sensitivity and the detection limit of VAN and GUA at 1.24 × 10–8 M and 0.98 × 10–8 M were obtained by using mediator and metal free modified electrode system in phosphate buffer medium. The present method is quite modest and robustic for the detection of VAN and GUA at a trace level.

This article describes a sensitive impedimetric method for the determination of human blood coagulation factor IX protein (FIX) which is present in extremely low concentration in serum. An interdigitated electrode (IDE) whose surface was layered with zinc oxide was modified with two kinds of probes. One is an antibody, the other an aptamer against FIX. A comparative study between anti-FIX aptamer and anti-FIX antibody showed the aptamer to possess higher affinity for FIX. A sandwich aptamer assay was worked out by using the FIX-binding aptamer on the surface of the IDE. It has a detection limit as low as 10 pM which makes it 4 to 30-fold more sensitive than any other method reported for FIX. Moreover, to practice detection in clinical samples, FIX was detected from the human blood serum by spiking. In our perception, the sensitivity of the ZnO-modified IDE presented here makes it a promising tool for sensing clinically relevant analytes that are present in very low (sub-pM) concentrations.

The authors introduce a method for spatially arranged DNA immobilization on 10-nm gold nanoparticles (GNP) deposited on a silicon substrate carrying nanogapped interdigitated electrodes. The GNPs are covalently bound to the surface via silane chemistry, and the single steps of fabrication are monitored by FTIR spectroscopy and atomic force microscopy. This GNP deposition technique is shown to reduce the size of the nanogaps to 130 nm. FTIR also was used to monitor the immobilization of DNA on the surface of the interdigitated electrodes. This method allows DNA to be immobilized in a uniform and homogenous way. The utility of the method is demonstrated by immobilizing probe DNA on the surface and detecting target DNA specific for the human papilloma virus via fluorescence with a detection limit as low as 1 pM. In our perception, this method for GNP-mediated DNA immobilization enables high-performance sensing of a wide range of target (analyte) DNA.

The 16 kDa heat shock protein (16 kDa HSP) against Mycobacterium tuberculosis (MT), expressed during the growth phase of MT, is a potential target in diagnostic tests for tuberculosis (TB). We describe here a method for impedimetric determination of the antigen by using a nanogapped dielectric surface consisting of a silver support coated with a thin finger-shaped coating made from zinc oxide and gold and patterned through a lift-off process. The electrode was characterized by scanning electron microscopy, field emission scanning electron microscopy, atomic force microscopy, and energy-dispersive X-ray spectroscopy. Surface chemical functionalization and immobilization of antibody against the 16 kDa HSP was evidenced by FTIR. In order to improve the detection limit, the antigen was conjugated to 10 nm gold nanoparticles. The resulting biosensor is capable of detecting the 16 kDa HSP in concentrations as low as 100 fM. The method covers a wide analytical range that extends from 100 fM to 1 nM.

Differential pulse voltammetry (DPV) was employed for the determination of caffeic acid (CA) in acidic solutions by using a glassy carbon electrode (GCE) modified with a chitosan-protected nanohybrid composed of carbon black and reduced graphene oxide. Electrochemical impedance spectroscopy and cyclic voltammetry were utilized to study the interfacial electron transfer on the modified GCE. Cyclic voltammetry shows that CA exhibits a reversible redox reaction with an oxidation peak at + 0.30 V (vs. Ag/AgCl) and a reduction peak at + 0.24 V in pH 3.0 solution at a scan rate of 50 mV·s−1. Under the optimized experimental conditions, the response to CA is linear in 0.3× 10−9 to 57.3 × 10−5 M concentration range. The limit of detection is 0.03 × 10−9 M (at an S/N ratio of 3), and the electrochemical sensitivity is 5.96 μA∙ μM−1∙cm−2. This sensor for CA displays better sensitivity and a response over a wider concentration range. It was applied to the determination of CA at trace levels in various (spiked) wine samples.

A sensing device was constructed for the amperometric determination of nitrite. It is based on the use of titanium dioxide (TiO2) nanotubes template with natural fibers and carrying hemin acting as the electron mediator. A glassy carbon electrode (GCE) was modified with the hemin/TNT nanocomposite. The electrochemical response to nitrite was characterized by impedance spectroscopy and cyclic voltammetry. An amperometric study, performed at a working potential of + 0.75 V (vs. Ag/AgCl), showed the sensor to enable determination of nitrite with a linear response in the 0.6 to 130 μM concentration range and with a 59 nM limit of detection. Corresponding studies by differential study voltammetry (Ep = 0.75 V) exhibited a linear range from 0.6 × 10−6 to 7.3 × 10−5 M with a limit of detection of 84 nM. The sensing device was applied to the determination of nitrite in spiked tap and lake water samples.