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Purpose: Early prediction of any type of cancer is important for the treatment of this type of disease, therefore, our target to evaluate whether monitoring early changes in plasma human epidermal growth factor receptor 2 (HER2) levels (using EIS), could help in the treatment of breast cancer or not? Human epidermal growth factor receptor 2 (HER2) overexpression is an important biomarker for treatment selection in earlier stages of cancers. The combined detection of the HER2 gene in plasma for blood cancer provides an important reference index for the prognosis of metastasis to other tissues. For this purpose, the authors fabricated and characterized a model wireless biosensor-based electrochemical impedance spectroscopy (EIS) for detecting HER2 plasma as therapeutics. Design/methodology/approach: Most sensors generally are fabricated based on a connection between component of the sensors and the external circuits through wires. Although these types of sensors provide suitable sensitivities and also quick responses, the connection wires can be limited to the sensing ability in various devices approximately. Therefore, the authors designed a wireless sensor, which can provide the advantages of in vivo sensing and also long-distance sensing, quickly. Findings: The biosensor structure was designed for detection of HER2, HER3 and HER-4 from lab-on-chip approach with six units of screen-printed electrode (SPE), which is built of an electrochemical device of gold/silver, silver/silver or carbon electrodes. The results exhibited that the biosensor is completely selective at low concentrations of the plasma and HER2 detection via the standard addition approach has a linearity plot, therefore, by using this type of biosensors HER2 in plasma can be detected. Originality/value: This is then followed by detecting HER2 in real plasma using standard way which proved to have great linearity (R2 = 0.991) proving that this technique can be used to detect HER2 solution in real patients. [ABSTRACT FROM AUTHOR]

The quantification of alpha-fetoprotein (AFP) as a potential liver cancer biomarker which is generally found in ultratrace level is of significance in biomedical diagnostics. Therefore, it is challenging to find a strategy to fabricate a highly sensitive electrochemical device towards AFP detection through electrode modification for signal generation and amplification. This work shows the construction of a simple, reliable, highly sensitive, and label-free aptasensor based on polyethyleneimine-coated gold nanoparticles (PEI-AuNPs). A disposable ItalSens screen-printed electrode (SPE) is employed for fabricating the sensor by successive modifying with PEI-AuNPs, aptamer, bovine serum albumin (BSA), and toluidine blue (TB), respectively. The AFP assay is easily performed when the electrode is inserted into a small Sensit/Smart potentiostat connected to a smartphone. The readout signal of the aptasensor derives from the electrochemical response of TB intercalating into the aptamer-modified electrode after binding with the target. The decrease in current response of the proposed sensor is proportional to the AFP concentration due to the restriction of the electron transfer pathway of TB by a number of insulating AFP/aptamer complexes on the electrode surface. PEI-AuNPs improve SPE’s reactivity and provide a large surface area for aptamer immobilization whereas aptamer provides selectivity to the target AFP. Consequently, this electrochemical biosensor is highly sensitive and selective for AFP analysis. The developed assay reveals a linear range of detection from 10 to 50000 pg mL−1 with R2 = 0.9977 and provided a limit of detection (LOD) of 9.5 pg mL−1 in human serum. With its simplicity and robustness, it is anticipated that this electrochemical-based aptasensor will be a benefit for the clinical diagnosis of liver cancer and further developed for other biomarkers analysis.

An electrochemical HbA1c sensor with high sensitivity and good specificity is proposed based on the electrochemical immune principle. The reproducibility and conductivity of the electrode are improved by depositing gold nanoparticles (AuNPs) on the surface of the screen-printed electrode (SPE). The HbA1c antibodies are immobilized on the surface of the modified electrode by adsorption to capture the HbA1c in the sample. The hindering effect of HbA1c on the electrode transfer reaction was exploited as the HbA1c detection mechanism. The electrode's properties were characterized by electrochemical impedance spectroscopy (EIS), and the measurement properties of the electrode were analyzed using differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The experimental results show that the peak current signal of the electrochemical immunosensor produced a linear response to HbA1c in the concentration range of 20–200 μg/mL, a linear relationship coefficient of 0.9812, a detection limit of 15.5 µg/mL, and a sensitivity of 0.0938 µA/µg·mL−1. The sensor delivered satisfactory repeatability, stability, and anti-interference performance. Due to its small size, high sensitivity, and wide linear detection range, it is expected to play a significant role in managing diabetes at home. [ABSTRACT FROM AUTHOR]

In this work, an electrochemiluminescence (ECL) sensor chip for sensitive detection of thrombin (TB) was prepared using a screen‐printed electrode (SPE) as a working electrode and an aptamer as a specific recognition moiety. To produce an ECL sensor chip, a layer of pL‐Cys was immobilized on the surface of the SPE using the cyclic voltammetry scanning method. A layer of gold nanoparticles (AuNPs) was assembled through an Au–S bond and hairpin DNA was further immobilized on the electrode surface. Ru(bpy)2(mcpbpy)2+, as a luminescent reagent, was covalently bound to single‐stranded DNA (ssDNA) to prepare a luminescence probe ssDNA‐Ru. The probe was hybridized with TB aptamer to form a capture probe. In the presence of TB, the TB aptamer in the capture probe bound to TB, causing the release of ssDNA‐Ru that could bind to hairpin DNA on the electrode surface. The Ru(II) complex as a luminescent reagent was assembled onto the electrode, and pL‐Cys was used as a co‐reactant to enhance the ECL efficiency. The ECL signal of the sensor chip generated based on the above principles had a linear relationship with log TB concentration at the range 10 fM to1 nM, and the detection limit was 0.2 fM. Finally, TB detection using this method was verified using real blood samples. This work provides a new method using an aptamer as a foundation and SPE as a material for the detection of biological substances. [ABSTRACT FROM AUTHOR]

The Cyclic Voltammetric (CV) technique is one of the Ag/AgCl fabrication processes. In electrochemical processes using this CV technique, the microstructure of the surface of a substrate or electrode can affect the scan rate. Thus, this study aims to identify the scan rate effect of the Cl-ion sensor fabrication process using the CV technique on the performance of the Cl-ion sensor. First, the CV process was carried out in one cycle to grow the AgCl layer on the Ag surface. Then, this process was carried out at varied scan rates of 20, 40, 60, 80, and 100 mV/s. After completing the Ag/AgCl fabrication process, it was followed by the characterization process, selectivity coefficient test, lifetime test, and validation test to compare the test results of the Cl SPE Ag/AgCl ion sensor with Ag/AgCl commercial. The results showed that the optimum Cl-ion sensor response was obtained at the scan rate of 60 mV/s. Then, based on the validation test, the Cl-ion in the two samples did not show significant differences. Therefore, it indicates that the SPE Ag/AgCl ion sensor has the same performance as the Ag/AgCl commercial.

The design and synthesis of artificial receptors based on molecular imprinting (MI) technology for the development of a new MIP-based biosensor for detection of the stress biomarker α-amylase in human saliva in point-of-care (PoC) applications is described in this work. The portable electrochemical devices for monitoring α-amylase consists of cost-effective and disposable gold screen-printed electrodes (AuSPEs). To build the electrochemical device, the template biomolecule was firstly immobilized directly over the working area of the gold chip previously activated with a self-assembled monolayer (SAM) of cysteamine (CA). Then, pyrrole (Py) monomer was selected as building block of a polymeric network prepared by CV electropolymerization. After the electropolymerization process, the enzyme was removed from the polymer film in order to build the specific recognition sites for the target enzyme. The MIP biosensor showed a very wide linear concentration range (between 3.0 × 10−4 to 0.60 mg mL−1 in buffer solution and between 3.0 × 10−4 to 3.0 × 10−2 mg mL−1 in human saliva) and low detection levels were achieved (LOD < 3.0 × 10−4 mg mL−1) using square wave voltammetry (SWV) as the electroanalytical technique.

Globally, 70 million people are annually affected by TBI. A significant proportion of all TBI cases are actually mild TBI (concussion, 70–85%), which is considerably more difficult to diagnose due to the absence of apparent symptoms. Current clinical practice of diagnosing mTBI largely resides on the patients' history, clinical aspects, and CT and MRI neuroimaging observations. The latter methods are costly, time-consuming, and not amenable for decentralized or accident site measurements. As an alternative (and/or complementary), mTBI diagnostics can be performed by detection of mTBI biomarkers from patients' blood. Herein, we proposed two strategies for the detection of three mTBI-relevant biomarkers (GFAP, h-FABP, and S100β), in standard solutions and in human serum samples by using an electrochemiluminescence (ECL) immunoassay on (i) a commercial ECL platform in 96-well plate format, and (ii) a "POC-friendly" platform with disposable screen-printed carbon electrodes (SPCE) and a portable ECL reader. We further demonstrated a proof-of-concept for integrating three individually developed mTBI assays ("singleplex") into a three-plex ("multiplex") assay on a single SPCE using a spatially resolved ECL approach. The presented methodology demonstrates feasibility and a first step towards the development of a rapid POC multiplex diagnostic system for the detection of a mTBI biomarker panel on a single SPCE. [ABSTRACT FROM AUTHOR]

An electrochemical HbA1c sensor with high sensitivity and good specificity is proposed based on the electrochemical immune principle. The reproducibility and conductivity of the electrode are improved by depositing gold nanoparticles (AuNPs) on the surface of the screen-printed electrode (SPE). The HbA1c antibodies are immobilized on the surface of the modified electrode by adsorption to capture the HbA1c in the sample. The hindering effect of HbA1c on the electrode transfer reaction was exploited as the HbA1c detection mechanism. The electrode’s properties were characterized by electrochemical impedance spectroscopy (EIS), and the measurement properties of the electrode were analyzed using differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The experimental results show that the peak current signal of the electrochemical immunosensor produced a linear response to HbA1c in the concentration range of 20–200 μg/mL, a linear relationship coefficient of 0.9812, a detection limit of 15.5 µg/mL, and a sensitivity of 0.0938 µA/µg·mL−1. The sensor delivered satisfactory repeatability, stability, and anti-interference performance. Due to its small size, high sensitivity, and wide linear detection range, it is expected to play a significant role in managing diabetes at home.

This work reports the development of a simple and rapid electrochemical immunosensor for the determination of breast cancer biomarker Cancer Antigen 15–3 (CA 15–3). Disposable and cost-effective chips, consisting of gold screen-printed electrodes (AuSPEs), were used to develop the portable electrochemical devices for monitoring the biomarker in point-of-care (PoC), under clinical context.The biosensor preparation consisted of two simple steps. First, a self-assembled monolayer (SAM) of mercaptosuccinic acid (MSA) was formed at the AuSPE surface. Then, the CA 15–3 antibody was covalently bound to the carboxylic groups standing at the electrode surface using EDC/NHS chemistry.The performance of the developed immunosensor was evaluated by assessing the sensor sensitivity, linear response interval, selectivity and detection limit (LOD). The developed immunosensor provided a wide linear concentration range (from 1.0 to 1000 U mL−1) and low detection levels were achieved (LOD of 0.95 U mL−1), enabling the sensitive detection of the cancer biomarker at clinically relevant levels, using square wave voltammetry (SWV) as electroanalytical technique. Moreover, selectivity studies performed against other cancer biomarkers (CA 125 and CA 19–9) revealed that the antibody has high selectivity for CA 15–3 antigen. The immunosensor was applied to the quantification of CA 15–3 in artificial serum samples with satisfactory results.

Nicotinamide adenine dinucleotide (NADH) is an important cofactor involved in metabolic redox reactions in living cells. The detection of NADH in living animal cells is a challenge. We developed a one-step monitoring method for NADH via an electrocatalytic reaction that uses a surface-modified, screen-printed electrode (SPE) having a redox active monolayer 4′-mercapto-N-phenlyquinone diamine (NPQD) formed by a self-assembled monolayer (SAM) of an aromatic thiol, 4-aminothiophenol (4-ATP). This electrode has a limit of detection (LOD) of 0.49 μM and a sensitivity of 0.0076 ± 0.0006 μM/μA in cell culture media, which indicates that it retains its selectivity. The applicability of this NADH sensor was demonstrated for the first time by cell viability monitoring via NADH-sensing in cell culture supernatants.

In this work, three universally used redox probes in amperometric biosensing devices, [Fe(CN)6]3−/[Fe(CN)6]4−, Ru[(NH3)6]3+, and ferrocenedimethanol (FDM), were selected to evaluate the stability of electrochemical signals provide by the reporting systems. Studies were carried out at disposable gold screen‐printed electrode (AuSPE) biosensing platforms, commonly used for screening chemical and biological relevant biomolecules. Firstly, electrochemical combined‐surface plasmon resonance (eSPR) studies were performed to evaluated adsorption reversibility and/or formation of redox probe complexes at the bare gold surface when routinely used electrochemical techniques, namely cyclic voltammetry (CV) and square‐wave voltammetry (SWV), are recorded. Then, the results obtained were compared with those obtained at the AuSPE under the same electrochemical conditions. Based on our findings, best experimental conditions, including the type of electrochemical technique used, are speculated for each reporting system in order to improve the analytical signal stability. Finally, a methodology based on SWV technique was applied to modified electrodes to provide a simple and easy tool to ensure diffusion controlled permeability of probes thorough the films to electrode surface. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI) is a conducting polymer, widely used in gas-sensing applications. Due to its classification as a semiconductor, PANI is also used to detect reducing ammonia gas (NH3), which is a well-known and studied topic. However, easier, cheaper and more straightforward procedures for sensor fabrication are still the subject of much research. In the presented work, we describe a novel, more controllable, synthesis approach to creating NH3 PANI-based receptor elements. The PANI was electrochemically deposited via cyclic voltammetry (CV) on screen-printed electrodes (SPEs). The morphology, composition and surface of the deposited PANI layer on the Au electrode were characterised with electron microscopy, Fourier-transform infrared spectroscopy and profilometry. Prior to the gas-chamber measurement, the SPE was suitably modified by Au sputtering the individual connections between the three-electrode system, thus showing a feasible way of converting a conventional three-electrode electrochemical SPE system into a two-electrode NH3-gas detecting system. The feasibility of the gas measurements’ characterisation was improved using the gas analyser. The gas-sensing ability of the PANI-Au-SPE was studied in the range 32–1100 ppb of NH3, and the sensor performed well in terms of repeatability, reproducibility and sensitivity.

Electrochemical magnetoimmunosensors combine a number of issues that guarantee extremely high performance and also compatibility with the study of complex sample matrices. First, analyte immunocapture exploits the high affinity and specificity of antibodies. Second, magnetic particles (MP) provide faster and more efficient immunocapture than binding on two-dimensional structures, separation from nontarget sample components, and concentration of the target analyte. Finally, electrochemical detection supplies sensitivity and fast signal generation using robust and potentially miniaturized measurement equipment and transducers. On the contrary, MP handling is slightly more complex for end-users and more difficult to integrate in point-of-care devices than the manipulation of a classical biosensor. Attempts have been made to automate immunomagnetic binding, and the first robotized systems and platforms for the fluorescent and spectrophotometric detection of magnetoimmunoassays have already reached the market. Among the different types of electrodes available, screen-printed electrodes (SPE) stand out because of their low production cost and yet acceptable performance and interdevice reproducibility, which make them an excellent choice for analytical applications. In addition, each SPE entails a whole electrochemical cell stamped on a planar physical substrate, which makes it possible detection in small volumes and is especially favorable for the magnetic confinement of MP and the integration of microfluidic structures. In this article, we discuss the advantages obtained by using SPE and MP for the production of electrochemical magnetoimmunosensors and the clues for the successful development of such devices. We then revise some of the most outstanding works published in the literature.

[Display omitted] • Design of an electrochemical sensor with polyphenol imprinted polymer for selective detection of GU and AD. • Electrochemical determination of AD and GU were performed by differential pulse voltammetry and cyclic voltammetry techniques. • The fabricated sensors showed a wide linear range and lowest detection limits for two analytes. • The designed sensors successfully applied for reliable determination of AD and GU in human serum samples. Novel screen-printed gold electrodes (AuSPE) modified with molecularly imprinted (MIP) polyphenol were fabricated to detection of guanine (GU) and Adenine (AD) in the presence of each other species. The electrochemical polymerization method in the presence of specific analyte (GU or AD) as template molecules was used for synthesize of MIP thin layer on AuSPE surface. To investigate the effect of the presence of a molecular template in the surface layer via the produce of binding sites, MIP electrodes were compared with non-imprinted (NIP) electrodes. The fabricated MIP sensors (GU-MIP-AuSPE and AD-MIP-AuSPE) were used in the detection of GU and AD by differential pulse voltammetry (DPV) in 0.1 M phosphate buffer solution at pH 7.0 as optimized pH. Anodic peak currents for AD and GU show two linearity intervals in the range of 5 to 50 nM and 50 to 500 nM for GU and 5 to 50 nM and 50 to 700 nM for AD. Also, the values of limit of detection (LOD = 3 S b / m) and the limit of quantification (LOQ = 10 S b / m) were calculated as 0.37 × 10−9 M and 1.25 × 10−9 M for GU and 0.24 × 10−9 M and 0.80 × 10−9 M for AD, respectively. On the other hand, he fabricated MIP sensors exhibited high sensitivity, good repeatability and long-term stability. The MIP sensors were successfully utilized for the measurement of GU and AD in real human serum samples. [ABSTRACT FROM AUTHOR]

The quantification of alpha-fetoprotein (AFP) as a potential liver cancer biomarker which is generally found in ultratrace level is of significance in biomedical diagnostics. Therefore, it is challenging to find a strategy to fabricate a highly sensitive electrochemical device towards AFP detection through electrode modification for signal generation and amplification. This work shows the construction of a simple, reliable, highly sensitive, and label-free aptasensor based on polyethyleneimine-coated gold nanoparticles (PEI-AuNPs). A disposable ItalSens screen-printed electrode (SPE) is employed for fabricating the sensor by successive modifying with PEI-AuNPs, aptamer, bovine serum albumin (BSA), and toluidine blue (TB), respectively. The AFP assay is easily performed when the electrode is inserted into a small Sensit/Smart potentiostat connected to a smartphone. The readout signal of the aptasensor derives from the electrochemical response of TB intercalating into the aptamer-modified electrode after binding with the target. The decrease in current response of the proposed sensor is proportional to the AFP concentration due to the restriction of the electron transfer pathway of TB by a number of insulating AFP/aptamer complexes on the electrode surface. PEI-AuNPs improve SPE's reactivity and provide a large surface area for aptamer immobilization whereas aptamer provides selectivity to the target AFP. Consequently, this electrochemical biosensor is highly sensitive and selective for AFP analysis. The developed assay reveals a linear range of detection from 10 to 50000 pg mL -1 with R 2 = 0.9977 and provided a limit of detection (LOD) of 9.5 pg mL -1 in human serum. With its simplicity and robustness, it is anticipated that this electrochemical-based aptasensor will be a benefit for the clinical diagnosis of liver cancer and further developed for other biomarkers analysis., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Yaiwong, Anuthum, Sangthong, Jakmunee, Bamrungsap and Ounnunkad.)

Alzheimer's disease (AD) is a fatal neurodegenerative disease affecting approximately 26 million people world-wide, and the number is increasing as life expectancy increases. Since the only reliable diagnosis for the pathology is histochemical post-mortem examination, there is a rather urgent need for reliable, sensitive and quick detection techniques. Amyloid beta, being one of the established and widely accepted biomarkers of AD is a target biomolecule. Herein, we present fabrication of a labelless impedimetric amyloid beta immunosensor on carbon DEP (disposable electrochemical printed) chip. Three types of amyloid β impedimetric immunosensors were fabricated in a systematic step-wise manner in order to understand the effects that each surface modification chemistry had on detection sensitivity. We found that compared to a bare electrode, surface modification through formation of SAM of AuNPs increased sensitivity by approximately three orders of magnitude (LoD from 2.04 μM to 2.65 nM). A further modification using protein G, which helps orientate antibodies to an optimum position for interaction with antigen, lowered the LoD further to 0.57 nM. We have demonstrated that the presence of one of the most abundance proteins in biological fluids, bovine serum albumin (BSA), did not interfere with the sensitivity of the sensor. Since the DEP chips are disposable and the detection platform label-free, the developed sensor is relatively fast and cheap. These methods could easily be applied for detection of other antigens, with selection of the detection platform based on the desired for sensitivity. [ABSTRACT FROM AUTHOR]

Abstract: Electrochemical method and surface plasmon resonance (SPR) spectroscopic analysis are utilized herein to investigate antibody immobilization without and with orientation control for site-positioning paratopes (antigen binding site) of the antibody molecules. Biotin and its antibody were selected in current study as model. Such an approach employed thiophene-3-boronic acid (T3BA) as paratope orientation controller, (i) enabled site orientation of the antibody molecules reducing the hiding of paratopes, and (ii) maintained the activity of the captured antibodies, as confirmed by electrochemical and SPR anlysis. Anti-biotin antibody (a glycoprotein) was covalently bound to a self-assembled monolayer of T3BA modified on a nanogold-electrodeposited screen-printed electrode through boronic acid–saccharide interactions, with the boronic acid units specifically binding to the glycosylation sites of the antibody molecules. The immunosensor functioned based on competition between the analyte biotin and biotin-tagged, potassium hexacyanoferrate(II)-encapsulated liposomes. The current signal produced by the released liposomal , measured using square wave voltammetry, yielded a sigmoidally shaped dose–response curve that was linear over eight orders of magnitude (from 10–11 to 10–3 M). Furthermore this biosensing system fabricated based on T3BA approach was found to possess significantly improved sensitivity, and the limit of detection toward biotin was calculated as 0.102ngmL–1 (equivalent to 6μL of 4.19×10–10 M biotin). [Copyright &y& Elsevier]

Highlights: [•] Synthesis and characterization of nanowires. [•] Nanowires are unique 1-D nanostructures for chemical functionalization. [•] Nanowires for electrochemical sensing and biosensing. [•] Nanowires and electrochemical microfluidics. [•] Nanowires have plenty of possibilities on the horizon. [Copyright &y& Elsevier]

Highlights: [•] Graphene: terminology, synthesis and characterization. [•] Recent applications of graphene in electrochemistry. [•] Chemical interaction between graphene and target molecules. [ABSTRACT FROM AUTHOR]

Abstract: A sensitive, selective and reliable electrochemical method for the determination of nicotine using differential pulse voltammetry on a bare boron-doped diamond electrode has been developed. Nicotine yielded a single oxidation peak at a highly positive potential of +1.45V (vs. Ag/AgCl/3M KCl) in Britton–Robinson buffer solution at pH8. The influence of supporting electrolyte, pH and scan rate on the current response of NIC was investigated. At optimized experimental conditions, a linear relation between peak current and concentration of nicotine was found for the range from 0.5 to 200μM (0.08–32.9mgL−1) with a detection limit of 0.3μM (0.05mgL−1) and a good repeatability (relative standard deviation of 2.1% at 25μM concentration level, n =10) was achieved without any electrode surface modification. The practical usefulness of the developed procedure was successfully demonstrated with the determination of nicotine in tobacco products and anti-smoking pharmaceuticals with results similar to those obtained by a high-performance liquid chromatography and to the contents declared by the manufacturer, respectively. Prior to analysis, the sample pretreatment includes only sonication and/or simple liquid–liquid extraction. The proposed sensor represents an effective electrochemical tool and a promising alternative for quality control analysis of products in tobacco and pharmaceutical industry. [Copyright &y& Elsevier]

In this work, an electrochemiluminescence (ECL) sensor chip for sensitive detection of thrombin (TB) was prepared using a screen-printed electrode (SPE) as a working electrode and an aptamer as a specific recognition moiety. To produce an ECL sensor chip, a layer of pL-Cys was immobilized on the surface of the SPE using the cyclic voltammetry scanning method. A layer of gold nanoparticles (AuNPs) was assembled through an Au-S bond and hairpin DNA was further immobilized on the electrode surface. Ru(bpy) 2 (mcpbpy) 2+ , as a luminescent reagent, was covalently bound to single-stranded DNA (ssDNA) to prepare a luminescence probe ssDNA-Ru. The probe was hybridized with TB aptamer to form a capture probe. In the presence of TB, the TB aptamer in the capture probe bound to TB, causing the release of ssDNA-Ru that could bind to hairpin DNA on the electrode surface. The Ru(II) complex as a luminescent reagent was assembled onto the electrode, and pL-Cys was used as a co-reactant to enhance the ECL efficiency. The ECL signal of the sensor chip generated based on the above principles had a linear relationship with log TB concentration at the range 10 fM to1 nM, and the detection limit was 0.2 fM. Finally, TB detection using this method was verified using real blood samples. This work provides a new method using an aptamer as a foundation and SPE as a material for the detection of biological substances., (© 2022 John Wiley & Sons Ltd.)

Nicotinamide adenine dinucleotide (NADH) is an important cofactor involved in metabolic redox reactions in living cells. The detection of NADH in living animal cells is a challenge. We developed a one-step monitoring method for NADH via an electrocatalytic reaction that uses a surface-modified, screen-printed electrode (SPE) having a redox active monolayer 4′-mercapto-N-phenlyquinone diamine (NPQD) formed by a self-assembled monolayer (SAM) of an aromatic thiol, 4-aminothiophenol (4-ATP). This electrode has a limit of detection (LOD) of 0.49 μM and a sensitivity of 0.0076 ± 0.0006 μM/μA in cell culture media, which indicates that it retains its selectivity. The applicability of this NADH sensor was demonstrated for the first time by cell viability monitoring via NADH-sensing in cell culture supernatants. [ABSTRACT FROM AUTHOR]

Abstract: An amperometric biosensor based on malate quinone oxidoreductase (MQO) was developed for monitoring of the malolactic fermentation of wines. Screen-printed electrodes coupled with appropriate mediators were used as transducers for this novel biosensor. MQO was immobilized by physical entrapment in a photo-cross-linkable poly(vinyl alcohol) polymer (PVA-SbQ) on the surface of the working electrode. Several electrochemical mediators were studied in order to lower the applied potential and minimise the matrix effects. Among them, 2,6-dichlorophenol indophenol (DPIP) and phenazine methosulfate (PMS) were chosen for further development. The working conditions (mediator concentration, applied potential and pH) were optimised for both DPIP and PMS. Detection limits for both types of biosensors were of 5μM malic acid. Sensitivities obtained for the linear part of the calibration curve were 0.85 and 1.7mA/M for the biosensors based on DPIP and PMS, respectively. Interferences due to non-specific oxidations were shown to be negligible when using PMS as mediator. [Copyright &y& Elsevier]

Abstract: This work presents an automatic method able to identify the presence of neurotoxic insecticides using omethoate as a model compound. The acetylcholinesterase (AChE)-based biosensors used to detect the neurotoxic insecticides present two shortcomings: the weak limit of detection (LOD) and the lack of selectivity. An appropriate LOD is obtained in our work by using two sensitive AChEs from Drosophila melanogaster (Dm): the wild type (wt-Dm) and the E69W mutant. To discriminate between the insecticides and all other interferences, we use a FIA system that provides analytical information acquired from two enzymes: (i) the sensitive Dm-AChEs and (ii) an omethoate-resistant AChE from Electric Eel (Eel), which is equally affected by the matrix. The enzymes were immobilised on screen-printed electrodes by entrapment in a photocrosslinkable PVA-SbQ polymer used with a FIA system with three channels, each one of them simultaneously analysing the same sample using biosensors based on different AChEs. The biosensor based on the wt-Dm had a LOD of 2×10-6M omethoate, while the one based on the E69W mutant permitted to lower the LOD to 1×10-7M. Interferences produced by mercury and hypocloryte were successfully discriminated. Environmental water samples were also analysed. [Copyright &y& Elsevier]

Polyaniline (PANI) is a conducting polymer, widely used in gas-sensing applications. Due to its classification as a semiconductor, PANI is also used to detect reducing ammonia gas (NH3), which is a well-known and studied topic. However, easier, cheaper and more straightforward procedures for sensor fabrication are still the subject of much research. In the presented work, we describe a novel, more controllable, synthesis approach to creating NH3 PANI-based receptor elements. The PANI was electrochemically deposited via cyclic voltammetry (CV) on screen-printed electrodes (SPEs). The morphology, composition and surface of the deposited PANI layer on the Au electrode were characterised with electron microscopy, Fourier-transform infrared spectroscopy and profilometry. Prior to the gas-chamber measurement, the SPE was suitably modified by Au sputtering the individual connections between the three-electrode system, thus showing a feasible way of converting a conventional three-electrode electrochemical SPE system into a two-electrode NH3-gas detecting system. The feasibility of the gas measurements' characterisation was improved using the gas analyser. The gas-sensing ability of the PANI-Au-SPE was studied in the range 32–1100 ppb of NH3, and the sensor performed well in terms of repeatability, reproducibility and sensitivity. [ABSTRACT FROM AUTHOR]

The use of nanoimmunoconjugates displaying multiple electroactive labels for enhanced analyte quantification is scarce in the literature. In this work, new nanoimmunoconjugates, based on gold nanoparticles (AuNPs) and either methylene blue (MB) or an NHS ester MB derivative (MB NHS), have been developed by two chemical paths. They have then been used as dual-signal nanolabels in electrochemical biosensors by means of the MB oxidation and AuNPs reduction peaks. The optimization on bare screen-printed carbon electrodes (SPCE) revealed that the use of Fe(CN) 6 3−/4- in the measurement solution enhanced the currents displayed by the MB tag. Additionally, electrochemical SPCE activation in 70% ethanol improved significantly the electrode electrochemical properties compared with the untreated ones. Using 1 mM Fe(CN) 6 3−/4- , we found that this activation increased 6–10 times the peaks registered by CV and the electrode active area, and reduced significantly the charge-transfer resistance (Rct) obtained from the impedance curve (from 11.4 to 0.3 kΩ). This SPCE activation process allowed detecting the nanoimmunoconjugate in a model immunosensor using the MB tags nearly as sensitively as when measuring the AuNPs counterpart tags (limits of detection of 0.77 and 0.55 nM, respectively). However, while MB detection was faster and simpler, Au detection was less prone to sample matrix interference. This provided sensor efficient performance in a wider range of experimental conditions than when measuring each label independently. Image 1 • New dual-label AuNPs/MB-based immunoconjugates for biosensor purposes. • AuNPs used as MB and Ab carrier, and as signal producer tool as well. • PH 8 and Fe(CN) 6 3−/4- improve the MB signal of the conjugates. • EtOH activation exposes graphite particles and enhances SPCE behavior. • Dual-signal nanoconjugate quantification in diluted plasma using a model biosensor. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI) is a conducting polymer, widely used in gas-sensing applications. Due to its classification as a semiconductor, PANI is also used to detect reducing ammonia gas (NH 3 ), which is a well-known and studied topic. However, easier, cheaper and more straightforward procedures for sensor fabrication are still the subject of much research. In the presented work, we describe a novel, more controllable, synthesis approach to creating NH 3 PANI-based receptor elements. The PANI was electrochemically deposited via cyclic voltammetry (CV) on screen-printed electrodes (SPEs). The morphology, composition and surface of the deposited PANI layer on the Au electrode were characterised with electron microscopy, Fourier-transform infrared spectroscopy and profilometry. Prior to the gas-chamber measurement, the SPE was suitably modified by Au sputtering the individual connections between the three-electrode system, thus showing a feasible way of converting a conventional three-electrode electrochemical SPE system into a two-electrode NH 3 -gas detecting system. The feasibility of the gas measurements' characterisation was improved using the gas analyser. The gas-sensing ability of the PANI-Au-SPE was studied in the range 32-1100 ppb of NH 3 , and the sensor performed well in terms of repeatability, reproducibility and sensitivity.

• Paper device for electrochemical magneto-immunosensor wash and detection on-chip. • MMP-9 quantitation in 10 min with little handling by the user. • Sensor MMP-9 quantitation in patient plasma correlates with the >5 h reference ELISA. • Paper microfluidics provides fast, simple and sensitive magneto-immunosensors. Using magnetic beads (MB) allows producing relatively fast and simple electrochemical magneto-immunosensors. However, this type of sensor implies carrying out serial MB incubation and washing steps in tubes using external magnets, a procedure that requires user training and is tedious and time consuming. In this work, a paper device has been developed that allows performing MB washing and electrochemical detection on-chip with less intervention of the user. In order to achieve this goal, we optimized a single-step magneto-immunoassay for matrix metalloproteinase 9 (MMP-9) detection. Electrochemical detection was then carried out using a customized multiplexed holder that incorporated 8 screen-printed carbon electrodes (SPCE) and a movable multiplexed fluidic module. This paper device provided along the assay sequential MB confinement under static conditions, reagent adsorption and MB washing under flow conditions, and electrochemical detection under static conditions. As we show, the sensor produced in this way achieved detection of MMP-9 in about 10 min, with lineal response spanning 0.03–2 ng mL−1, detection limit of 0.01 ng mL−1 and quantification limit of 0.09 ng mL−1. Furthermore, MMP-9 quantification in 18 plasma samples from patients correlated linearly with the estimates of a reference ELISA that took >5 h. These results demonstrate that paper microfluidics can be exploited to simplify magneto-immunosensor manipulation, providing fast, simple and sensitive assay formats. [ABSTRACT FROM AUTHOR]