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In this study, we used a screen‐printed electrode (SPE) modified with polypyrrole (PP), ZnO/Co3O4 nanocomposite, and ds‐DNA as an extremely sensitive DNA biosensor to monitor tirapazamine (TPZ) real samples. To build the ds‐DNA/PP/ZnO/Co3O4 NC/SPE biosensor, the layer‐by‐layer manufacturing process was used. The proper alteration of the SPE surface as well as the effective fabrication of the ZnO/Co3O4 nanocomposite were both validated by the physicochemical characterization techniques. As a result of improving its conductivity of electricity along with allowing charged particles to move more easily, the modified SPE demonstrated much decreased the resistance of charge transfer based on the results of electrochemical impedance spectroscopy. With the 0.43 nM LOD value, the suggested biosensor effectively measured TPZ throughout a broad concentration between 0.001 and 120 µM. Additionally, the molecular docking investigation among the TPZ molecule as well as the DNA was conducted to anticipate the TPZ contact sites with DNA and verified the experimental results. By combining the benefits of ZnO/Co3O4 nanocomposite with vital information from the molecular docking investigation, the current research lays the door for the creation of very sensitive DNA biosensors, which can be utilized to track and measure TPZ of real samples. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Salivary thiocyanate is a biomarker of individual health that notably allows for the discrimination between smokers and non‐smokers. Recent studies have also demonstrated its potential as a biomarker of cystic fibrosis, thus rendering the development of methods for its determination in saliva of immense importance. In response, we report on the development of graphite screen‐printed electrodes (SPE) modified with cobalt(II) phthalocyanine nanosticks (CoPcNst), as low‐cost and semi‐disposable sensors for the determination of thiocyanate ion (SCN−) in human saliva. CoPCNst were synthesized and characterized using scanning electron microscopy, x‐ray diffraction, as well as infrared and Raman spectroscopies. The results revealed a structural proximity to the recently identified J‐polymorph. Compared with the electrode modified with commercial, beta‐structure cobalt(II) phthalocyanine, the CoPc Nst/SPE provided four times better LOD and LOQ (0.49 and 1.62 μM) for thiocyanate determination by differential pulse voltammetry. The response was linear up to 20 μM SCN− (R2=0.996) and it was not affected by excess of common electro active compounds, such as ascorbic and uric acid. The analytical utility of CoPc Nst/SPE in human saliva is demonstrated. [ABSTRACT FROM AUTHOR]

Growing demand for pesticides has created an environment prone to deceptive activities, where counterfeit or adulterated pesticide products infiltrate the market, often escaping rapid detection. This situation presents a significant challenge for sensor technology, crucial in identifying authentic pesticides and ensuring agricultural safety practices. Raman spectroscopy emerges as a powerful technique for detecting adulterants. Coupling the electrochemical techniques allows a more specific and selective detection and compound identification. In this study, we evaluate the efficacy of spectroelectrochemical measurements by coupling a potentiostat and Raman spectrograph to identify paraquat, a nonselective herbicide banned in several countries. Our findings demonstrate that applying −0.70 V during measurements yields highly selective Raman spectra, highlighting the primary vibrational bands of paraquat. Moreover, the selective Raman signal of paraquat was discernible in complex samples, including tap water, apple, and green cabbage, even in the presence of other pesticides such as diquat, acephate, and glyphosate. These results underscore the potential of this technique for reliable pesticide detection in diverse and complex matrices. [ABSTRACT FROM AUTHOR]

Screen-printed carbon electrodes (SPCE) functionalized with MXene-based three-dimensional nanomaterials are reported for rapid determination of creatinine. Ti3C2TX MXene with in situ reduced AuNPs (MXene@AuNP) were used as a coreactant accelerator for efficient immobilization of enzymes. Creatinine could be oxidized by chitosan-embedded creatinine amidohydrolase, creatine amidinohydrolase, or sarcosine oxidase to generate H2O2, which could be electrochemically detected enhanced by Prussian blue (PB). The enzyme@CS/PB/MXene@AuNP/SPCE detected creatinine within the range 0.03–4.0 mM, with a limit of detection of 0.01 mM, with an average recovery of 96.8–103.7%. This indicates that the proposed biosensor is capable of detecting creatinine in a short amount of time (4 min) within a ± 5% percentage error, in contrast with the standard clinical colorimetric method. With this approach, reproducible and stable electrochemical responses could be achieved for determination of creatinine in serum, urine, or saliva. These results demonstrated its potential for deployment in resource-limited settings for early diagnosis and tracking the progression of chronic kidney disease (CKD). [ABSTRACT FROM AUTHOR]

The concern regarding tetrodotoxin (TTX), a highly hazardous marine neurotoxin found in puffer fish, has expanded beyond Asia due to the migration of puffer fish caused by the rise in global temperatures. This highlights the urgent need to develop fast yet reliable methods for detecting TTX. In this study, we developed a peptide-based potentiometric TTX sensor based on a polypyrrole/Au nanoparticle-modified carbon screen-printed electrode (PPy/AuNP SPE). The bioreceptor responsible for recognizing TTX is a specific binding peptide that was discovered through phage display technique. The phage-displayed peptide candidates were sorted based on frequency and similarity, and their binding affinity was subsequently assessed via phage enzyme-linked immunosorbent assay. The C-terminal of the specific binding peptide was then modified with cysteamine to facilitate its immobilization through Au–S bonding on the PPy/AuNP SPE platform, thereby constructing the TTX sensor. The sensing platform was prepared by successive electrodeposition of polypyrrole and AuNP onto the surface of carbon SPE as a substrate. Both materials play significant roles to improve the poor conductivity of carbon SPE and provide sufficient immobilization sites for TTX receptors, respectively. Finally, the PPy/AuNP TTX sensor demonstrated a detection limit of around 2.80 ppb with a detection range from 2 to 1000 ppb, making it a promising platform for rapid and reliable marine toxin detection. [ABSTRACT FROM AUTHOR]

Electrochemical biosensors are valued for their sensitivity and selectivity in detecting biological molecules. Having the advantage of generating signals that can be directly or indirectly proportional to the concentration of the target analyte, these biosensors can achieve specificity by utilizing a specific biorecognition surface designed to recognize the target molecule. Electrochemical biosensors have garnered substantial attention, as they can be used to fabricate compact, cost-effective devices, making them promising candidates for point-of-care testing (POCT) devices. This study introduces a label-free electrochemical biosensor employing a gold screen-printed electrode (SPE) to detect lysophosphatidic acid (LPA), a potential early ovarian cancer biomarker. We employed the gelsolin–actin system, previously introduced by our group, in combination with fluorescence spectrometry, as a biorecognition element to detect LPA. By immobilizing a gelsolin–actin complex on an SPE, we were able to quantify changes in current intensity using cyclic voltammetry and differential pulse voltammetry, which was directly proportional to the LPA concentration in the solution. Our results demonstrate the high sensitivity of the developed biosensor for detecting LPA in goat serum, with a limit of detection (LOD) and a limit of quantification (LOQ) of 0.9 µM and 2.76 µM, respectively, highlighting its potential as a promising tool for early-stage diagnosis of ovarian cancer.

The ability to obtain accurate analytical results without sample pre‐treatment or derivatization is a key element for an eco‐friendly method of analysis. In this work, green electro analytical method was developed and evaluated for the selective determination of the anti‐cholinergic drug Procyclidine Hydrochloride in both pure and dosage forms as well as in dissolution medium without sample pre‐treatment. Firstly, screening of four ionophore‐doped polyvinyl chloride‐based membranes were conducted to detect the one with highest affinity towards the studied drug. Accordingly, calix[4]arene‐doped membrane exhibited the optimum results. Then optimization was carried out by designing screen‐printed and glassy carbon solid‐contact ion‐selective electrodes with multiwall carbon nanotube and graphene nanocomposite as ion to electron transducers. The fabricated screen‐printed sensor with graphene nanocomposite was characterized according to IUPAC recommendations. It acquired the fastest and most stable response, along with thermal stability up to 30 °C. It also displayed a slope of 43.9±0.2 mV/decade in a pH range of 2–5. The proposed sensor successfully obtained a linear range of 1×10−5–1×10−2 M and the theoretical limit of detection was 6.3×10−6 M. Finally, it was used in applications such as in‐line dissolution monitoring and quantification of procyclidine in its dosage form without prior sample pre‐treatment or derivatization steps. Furthermore, the graphene nanocomposite transducer has been imaged by Scanning Electron Microscope (SEM). [ABSTRACT FROM AUTHOR]

A renewable electrochemical screen-printed electrode (SPE) is proposed based on magnetic bamboo-like nitrogen-carbon (N–C) nanotubes loaded with nickel–cobalt alloy (NiCo) nanoparticles (NiCo@N-CNTs) for the determination of ractopamine (RAC). During the preparation of NiCo@N-CNTs, Co-MOF-67 (ZIF-67) was firstly synthesized, and then blended with dicyandiamide and nickel acetate, followed by a one-step pyrolysis procedure to prepare NiCo@N-doped carbon nanotubes. The surface morphology, structure, and chemical composition of NiCo@N-CNTs were characterized by SEM, TEM, XRD, XPS, and EDS. The electrocatalytic and electrochemical behavior of NiCo@N-CNTs were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results demonstrated that NiCo@N-CNTs possessed remarkable conductivity and electrocatalysis to the oxidation of ractopamine (RAC). By using screen-printed electrode (SPE), NiCo@N-CNTs, and a designed base support, a magnetic RAC sensor (NiCo@N-CNTs/SPE) was successfully constructed. It presented a detection linear range of 0.05–80 μM with a detection limit of 12 nM (S/N = 3). It also exhibited good sensitivity, reproducibility, and practicability in spiked real pork samples. Since the adhesion of NiCo/N-CNTs on SPE was controlled by magnet, the NiCo@N-CNTs was easily detached from the SPE surface by magnetism and thus displayed excellent renewability. This work broadened insights into portable devices for on-site and real-time analysis. [ABSTRACT FROM AUTHOR]

A neckband-integrated soft microfluidic biosensor was developed for real-time glucose monitoring in sweat. Flexible screen-printed electrodes were prepared and utilized for developing oxidase enzyme-based amperometric sensors. The electrochemical oxidation of glucose was catalyzed and mediated by bimetallic palladium and platinum-supported reduced graphene oxide and 1,10-phenanthroline-5,6-dione, respectively. Soft, microfluidic channels were prepared by developing clean-room free, 3D-printed master and integrated with the flexible sensors. The fluidic channel provides autonomous capillary flow of liquids through the sensor surface and facilitates real-time detection. The fluid flow analysis demonstrated homogeneous filling of the sensing chamber and the outlets within 8s. The developed biosensor showed good selectivity, sensitivity, and stability toward glucose in phosphate buffer solution as well as in human sweat samples. The sensor showed linear amperometric responses for glucose at 0.2 V ranging from 50 to 900 μM with a limit of detection of 37 μM and sensitivity of 30 μA cm-2 mM-1. For real-life application, the pump-less microfluidic sensor was mounted on a 3D-printed neckband and coupled with a Bluetooth-enabled miniature potentiostat for wireless sweat glucose analysis. The real-time sweat glucose monitoring at the fasting stage and after spiking with glucose-rich meal showed good correlation with corresponding capillary blood glucose readings with a Pearson correlation coefficient of 0.87. Further, the sensor performances have been successfully validated by high-performance liquid chromatography. The presented wearable sensor offers facile noninvasive measurement of glucose levels from exercise-induced sweat samples for personalized diabetes monitoring. [ABSTRACT FROM AUTHOR]

The introduced work represents an implementation of the automatic benchtop electrochemical station (BES) as an effective tool for the possibilities of high-throughput preparation of modified sensor/biosensors, speeding up the development of the analytical method, and automation of the analytical procedure for the determination of paracetamol (PAR) and dopamine (DOP) as target analytes. Within the preparation of gold nanoparticles modified screen-printed carbon electrode (AuNPs-SPCE) by electrodeposition, the deposition potential EDEP, the deposition time tDEP, and the concentration of HAuCl4 were optimized and their influence was monitored on 1 mM [Ru(NH3)6]3+/2+ redox probe and 50 μM DOP. The morphology of the AuNPs-SPCE prepared at various modification conditions was observed by SEM. The analytical performance of the AuNPs-SPCE prepared at different modification conditions was evaluated by a construction of the calibration curves of DOP and PAR. SPCE and AuNPs-SPCE at modification condition providing the best sensitivity to PAR and DOP, were successfully used to determine PAR and DOP in tap water by "spike-recovery" approach. The BES yields better reproducibility of the preparation of AuNPs-SPCE (RSD = 3.0%) in comparison with the case when AuNPs-SPCE was prepared manually by highly skilled laboratory operator (RSD = 7.0%). [ABSTRACT FROM AUTHOR]

The development of an ultrasensitive and precise measurement of a breast cancer biomarker (cancer antigen 15-3; CA15-3) in complex human serum is essential for the early diagnosis of cancer in groups of healthy populations and the treatment of patients. However, currently available testing technologies suffer from insufficient sensitivity toward CA15-3, which severely limits early large-scale screening of breast cancer patients. We report a versatile electrochemical immunoassay method based on atomically cobalt-dispersed nitrogen-doped carbon (Co-NC)–modified disposable screen-printed carbon electrode (SPCE) with alkaline phosphatase (ALP) and its metabolite, ascorbic acid 2-phosphate (AAP), as the electrochemical labeling and redox signaling unit for sensitive detection of low-abundance CA15-3. During electrochemical detection by differential pulse voltammetry (DPV), it was found that the Co-NC-SPCE electrode did not have a current signal response to the AAP substrate; however, it had an extremely favorable response current to ascorbic acid (AA). Based on the above principle, the target CA15-3-triggered immunoassay enriched ALP-catalyzed AAP produces a large amount of AA, resulting in a significant change in the system current signal, thereby realizing the highly sensitive detection of CA15-3. Under the optimal AAP substrate concentration and ALP catalysis time, the Co-NC-SPCE-based electrochemical immunoassay demonstrated a good DPV current for CA15-3 in the assay interval of 1.0 mU/mL to 10,000 mU/mL, with a calculated limit of detection of 0.38 mU/mL. Since Co-NC-SPCE has an excellent DPV current response to AA and employs split-type scheme, the constructed electrochemical immunoassay has the merits of high preciseness and anti-interference, and its clinical diagnostic results are comparable to those of commercial kits. [ABSTRACT FROM AUTHOR]

Excessive use of azithromycin (AZM) is associated with resistance and negative impacts on the environment. Therefore, this study aimed to develop an electrochemical sensor for AZM. The screen‐printed carbon electrode (SPCE) modified with boron‐doped diamond nanoparticle (BDDNP) and reduced‐graphene oxide (rGO) was successfully applied to measure the AZM concentration. The morphology of the modified electrode was characterized by scanning electron microscopy‐energy dispersive X‐ray (SEM‐EDX). Furthermore, the effect of electrochemical parameters, such as signal per background, scan rate, and selectivity was determined. The results showed that under optimum conditions, the plot of AZM demonstrated linearity in the range of 30–100 μM with a limit of detection (LOD) at 1.6 μM. The repeatability and recovery were also investigated, and the sensor was applied to real samples obtained from hospital wastewater. A remarkable 93.27 % recovery rate and excellent precision were recorded with an %RSD of 2.41 %. This study underscores the potential of SPCE modified with rGO/BDDNP for accurate and reliable measurement of AZM levels, showcasing great applicability in addressing the challenges associated with monitoring AZM in various environmental settings. [ABSTRACT FROM AUTHOR]

Ochratoxin A (OTA) is a toxic fungal metabolite that is commonly found in cereals and animal feed. It is economically damaging and potentially hazardous to human health. Herein, we propose an electrochemical immunosensor for the rapid detection of OTA using anti-OTA antibodies and diazonium-functionalized, screen-printed electrodes. We attached 4-aminobenzoic acid to an electrode surface, activated the carboxyl groups on the surface with carbodiimide, and attached an antibody to the diazo layer. Subsequently, we used bovine serum protein as a blocker to prevent non-specific antigens from binding to the antibody. We evaluated the performance of the sensor by cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry. The sensor is highly specific and sensitive, has good linear responses in the range 20–200 ng/mL, a limit of detection of 0.5 ng/mL, and good recoveries of 90.5%–100.9% in spiked samples. It can be stored at 4 °C for approximately 2 weeks, and is highly stable, with a current response variation of no more than 4.6%. [ABSTRACT FROM AUTHOR]

Copper levels in biological fluids are associated with Wilson's, Alzheimer's, Menke's, and Parkinson's diseases, making them good biochemical markers for these diseases. This study introduces a miniaturized screen-printed electrode (SPE) for the potentiometric determination of copper(II) in some biological fluids. Manganese(III) oxide nanoparticles (Mn2O3-NPs), dispersed in Nafion, are drop-casted onto a graphite/PET substrate, serving as the ion-to-electron transducer material. The solid-contact material is then covered by a selective polyvinyl chloride (PVC) membrane incorporated with 18-crown-6 as a neutral ion carrier for the selective determination of copper(II) ions. The proposed electrode exhibits a Nernstian response with a slope of 30.2 ± 0.3 mV/decade (R2 = 0.999) over the linear concentration range 5.2 × 10–9 – 6.2 × 10–3 mol/l and a detection limit of 1.1 × 10–9 mol/l (69.9 ng/l). Short-term potential stability is evaluated using constant current chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS). A significant improvement in the electrode capacitance (91.5 μF) is displayed due to the use of Mn2O3-NPs as a solid contact. The presence of Nafion, with its high hydrophobicity properties, eliminates the formation of the thin water layer, facilitating the ion-to-electron transduction between the sensing membrane and the conducting substrate. Additionally, it enhances the adhesion of the polymeric sensing membrane to the solid-contact material, preventing membrane delamination and increasing the electrode's lifespan. The high selectivity, sensitivity, and potential stability of the proposed miniaturized electrode suggests its use for the determination of copper(II) ions in human blood serum and milk samples. The results obtained agree fairly well with data obtained by flameless atomic absorption spectrometry. [ABSTRACT FROM AUTHOR]

Copyright of China Condiment is the property of China Condiment and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Electrochemical biosensors are valued for their sensitivity and selectivity in detecting biological molecules. Having the advantage of generating signals that can be directly or indirectly proportional to the concentration of the target analyte, these biosensors can achieve specificity by utilizing a specific biorecognition surface designed to recognize the target molecule. Electrochemical biosensors have garnered substantial attention, as they can be used to fabricate compact, cost-effective devices, making them promising candidates for point-of-care testing (POCT) devices. This study introduces a label-free electrochemical biosensor employing a gold screen-printed electrode (SPE) to detect lysophosphatidic acid (LPA), a potential early ovarian cancer biomarker. We employed the gelsolin–actin system, previously introduced by our group, in combination with fluorescence spectrometry, as a biorecognition element to detect LPA. By immobilizing a gelsolin–actin complex on an SPE, we were able to quantify changes in current intensity using cyclic voltammetry and differential pulse voltammetry, which was directly proportional to the LPA concentration in the solution. Our results demonstrate the high sensitivity of the developed biosensor for detecting LPA in goat serum, with a limit of detection (LOD) and a limit of quantification (LOQ) of 0.9 µM and 2.76 µM, respectively, highlighting its potential as a promising tool for early-stage diagnosis of ovarian cancer. [ABSTRACT FROM AUTHOR]

In this work, a new and convenient fabrication process for screen-printed reduced graphene oxide-molybdenum disulfide electrode (SPrGO-MoS2E) was proposed. Reduced graphene oxide-molybdenum disulfide (rGO-MoS2) composite was hydrothermally synthesized and then dispersed in deionized water and ethanol with a ratio of 2:3 (v/v) to form a conductive suspension. The suspension was then blended with carbon paste at a ratio of 0.1:9.9 (g/g) to obtain a screen-printable rGO-MoS2 conductive ink. An electrochemical sensing electrode was formed by screening this conductive ink onto a polyethylene terephthalate substrate. The characteristics of this electrode were investigated by scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray diffractometry, Raman spectroscopy, and electrochemical impedance spectroscopy. Overall, the conductive suspension comprising the rGO-MoS2 composite showed higher electrochemical sensing performance compared with electrodes containing only rGO or MoS2. Cyclic voltammetry revealed that the SPrGO-MoS2 electrode exhibited excellent electrochemical sensing performance toward several electroactive species, namely, potassium hexacyanoferrate (III) ([Fe(CN6)]3−/4−), nicotinamide adenine dinucleotide (NAD+/NADH), and hydrogen peroxide (H2O2) dissolved in 0.1 M PBS (pH 7.4). The limits of detection for [Fe(CN6)]3−/4−, NAD+/NADH, and H2O2 were 0.34, 0.25, and 1.36 μM, respectively. In addition, the reproducibility, repeatability, and stability determined from the relative standard deviations (RSDs, n = 7) of these analytes were less than 12.1 %, 8.6 %, and 7.4 %, respectively. Therefore, the ready-to-use SPrGO-MoS2E could be an alternative material for advanced chemical and biological sensing applications.

A novel electrochemical sensor for paraquat determination was facilely developed using nanocomposites of cellulose incorporated with manganese oxide (MnO2@cellulose) modified screen-printed carbon electrode (SPCE). In this study, SPCE was fabricated on a low-cost poster paper, and nanocellulose from sugarcane bagasse was employed to enhance the electrode's surface area and improve the dispersion of MnO2. The MnO2@cellulose modified poster-SPCE exhibited a high electrochemical response toward paraquat. Various influencing factors, including differential pulse voltammetric parameters and accumulation time, were systematically explored. Under the optimal conditions, the cathodic peak current was linearly proportional to paraquat concentration in a range of 2 to 200 µM, featuring a low detection limit of 1 µM. The proposed sensor offers cost-effectiveness and can be readily prepared via a simple procedure. Moreover, this method exhibits excellent reproducibility, high selectivity, and a short analysis time. The portable electrochemical sensor was able to determine paraquat in water samples with acceptable recoveries from 95.45 to 109.20%, indicating that the sensor based on MnO2@cellulose/SPCE is reliable for paraquat quantification. [ABSTRACT FROM AUTHOR]

In this study, a novel analytical method was developed for determining piroxicam, employing a modified screen-printed carbon electrochemical sensor. This sensor utilizes a nanomaterial composed of reduced graphene oxide with antimony nanoparticles (rGO-SbNPs), which was characterized by transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and electrochemical methods. The rGO-SbNPs demonstrated a significant synergistic effect on the sensor's performance. Utilizing the cyclic voltammetry technique, the analyte was found to oxidize irreversibly around + 0.30 V. Employing differential pulse voltammetry, the sensor exhibited a broad linear range from 0.808 to 130.0 µmol L−1, with a detection limit of 0.0201 µmol L−1 — the lowest reported for piroxicam on screen-printed carbon electrodes in the literature — and a quantification limit of 0.0610 µmol L−1. It also demonstrated good reproducibility, evidenced by a relative standard deviation of 4.66%. Additionally, the sensor showed high selectivity for the analyte even in the presence of various compounds and ions such as flunixin meglumine, ascorbic acid, glucose, lactose, galactose, Ca2+, Cl−, and Na+. The device was successfully applied to tap water and bovine milk samples, yielding satisfactory recoveries: 106.0, 104.0, and 101.0% for water, and 89.9, 97.4, and 93.7% for milk. [ABSTRACT FROM AUTHOR]

Bacillus sp. possessing a periplasmic nitrate reductase was used as a recognition element to develop a nitrate biosensor. The bacteria was embedded within a polyaniline (PANI) electro-conductive matrix via electro-polymerization on miniaturized carbon screen-printed electrodes (SPE) at 100 mV/s and scan rate from −0.35 V to + 1.7 V. Surface medication of SPE was verified via Fourier Transform Infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The optimal bacterial density was OD600 1.2. To enhance the biosensors performance, Bacillus sp. was (1) grown in riboflavin (RF) inducing media as an endogenous redox mediator and (2) exposed to different gamma radiation doses as a physical method to increase electron transfer. Results show a link between exposing cells to gamma irradiation stress, this was evident by electron spin resonance (ESR) and changes in FTIR spectrum, in addition to the increase in catalase enzyme. The nitrate limit of detection (LOD) was 0.5–25 mg/L for non-irradiated RF induced immobilized cells and LOD was 0.5–75 mg/L nitrate for 2 kGy gamma irradiated cells. The prepared biosensor showed acceptable reproducibility and multiple usages after storage at 4°C over 3 months. Low cost and simple preparation allow the biosensor to be mass-produced as a disposable device. Bacillus sp. and its endogenous redox mediator immobilized within polyaniline are good candidates for the improvement of amperometric biosensors for the quantification of nitrate in aqueous solutions. [ABSTRACT FROM AUTHOR]

Enzyme-based biosensors commonly utilize the drop-casting method for their surface modification. However, the drawbacks of this technique, such as low reproducibility, coffee ring effects, and challenges in mass production, hinder its application. To overcome these limitations, we propose a novel surface functionalization strategy of enzyme crosslinking via inkjet printing for reagentless enzyme-based biosensors. This method includes printing three functional layers onto a screen-printed electrode: the enzyme layer, crosslinking layer, and protective layer. Nanomaterials and substrates are preloaded together during our inkjet printing. Inkjet-printed electrodes feature a uniform enzyme deposition, ensuring high reproducibility and superior electrochemical performance compared to traditional drop-casted ones. The resultant biosensors display high sensitivity, as well as a broad linear response in the physiological range of the serum phosphate. This enzyme crosslinking method has the potential to extend into various enzyme-based biosensors through altering functional layer components. [ABSTRACT FROM AUTHOR]

A simple and fast stripping voltammetric procedure for trace determination of Ce(III) in environmental water samples has been developed. The procedure of cerium determination in the presence of Alizarin S and acetate buffer was employed as the initial method. The adsorption material, multi-walled carbon nanotubes, was used as a screen-printed electrode modifier ensuring efficient accumulation of the Ce(III)-Alizarin S complex. The calibration graph for Ce(III) for an accumulation time of 60 s was linear in the range from 1 × 10−8 to 7 × 10−7 mol L−1 with the linear correlation coefficient r = 0.997. The detection limit was estimated from three times the standard deviation of low Ce(III) concentration and an accumulation time of 60 s was about 3.5 × 10−9 mol L−1. The proposed method was successfully applied to Ce(III) determination at trace levels in environmental water samples, such as river, lake and rain water with recoveries ranged from 93% to 98%. [ABSTRACT FROM AUTHOR]

A disposable voltammetric immunosensor was developed to measure breast cancer biomarker 15-3 (CA 15-3) in human saliva and serum samples. Screen-printed paper-based electrodes (f-SPE) previously fabricated by our research group using homemade conductive inks were used as transducers, which were later modified only with gold nanoparticles to immobilize anti-CA 15-3 antibodies. The sensor was operated using antigen–antibody interactions in conjunction with a redox species (ferrocyanide potassium) for the indirect determination of the CA 15-3 antigen. The device characterization involved atomic force microscopy (AFM) and electrochemical analysis. Optimization of the construction and response of the immunosensor was achieved at incubation times of 6 h for anti-CA 15-3, 1 h for bovine serum albumin, and 1 h for interaction with CA 15-3. The sensor displays a linear range between 2 and 16 U/mL, with a sensitivity of 0.012 μA/U mL−1, a limit of detection (LOD) of 0.56 U/mL, and a limit of quantification (LOQ) of 1.88 U/mL. The interfering substances minimally affected the signal, with 4.94% response variation, and the reproducibility of the immunosensor demonstrated a relative standard deviation (RSD) of 5.65%. The sensor successfully determined the CA 15-3 concentration in human serum and saliva, demonstrating its potential for clinical analysis. [ABSTRACT FROM AUTHOR]

An innovative electrochemical sensor is introduced that utilizes bipolar electrochemistry on a paper substrate for detecting glucose in sweat. The sensor employs a three-dimensional porous nanocomposite (MXene/NiSm-LDH) formed by decorating nickel-samarium nanoparticles with double-layer MXene hydroxide. These specially designed electrodes exhibit exceptional electrocatalytic activity during glucose oxidation. The glucose sensing mechanism involves enzyme-free oxidation of the analyte within the sensor cell, achieved by applying an appropriate potential. This leads to the reduction of K3Fe(CN)6 in the reporter cell, and the resulting current serves as the response signal. By optimizing various parameters, the measurement platform enables the accurate determination of sweat glucose concentrations within a linear range of 10 to 200 µM. The limit of detection (LOD) for glucose is 3.6 µM (S/N = 3), indicating a sensitive and reliable detection capability. Real samples were analysed to validate the sensor's efficiency, and the results obtained were both promising and encouraging. [ABSTRACT FROM AUTHOR]

Calcium ion is a type of indispensable metal elements in biology, which participates in processes like maintaining the excitability of neuromuscular muscles. However, calcium content should be monitored in a safety range. Herein, a novel electrochemical method is developed for Ca2+ assay by monitoring electrochemical response after DNAzyme catalyzed DNA hydrogel degradation. Pure DNA hydrogel is first built with three-way junction scaffolds and linkers containing Ca2+-dependent DNAzyme sequence. In the presence of target Ca2+, the substrates in linkers are cleaved and DNA hydrogel can be degraded gradually. The encapsulated electrochemical species thus facilely interact with the electrode, leading to the increase of electrochemical responses. This electrochemical method for Ca2+ quantification is selective and sensitive, which also performs satisfactorily challenging biological samples like sweat and urine.

The current study presents the creation of a straightforward and sensitive sensor based on ZnO/Co3O4 nanocomposite modified screen-printed electrode (ZnO/Co3O4NC/SPE) for levodopa determination. At ZnO/Co3O4NC/SPE, an oxidative peak for levodopa solution in pH 6.0 phosphate buffer solution (PBS) were seen that were both more resolved and more enhanced. Levodopa was measured using differential pulse voltammetry (DPV), which showed an excellent linear range (0.001–800.0 μM) and detection limit (0.81 nM). The presence of interference did not affect the electrochemical response of levodopa at ZnO/Co3O4NC/SPE, demonstrating high selectivity. Levodopa in a real samples have been successfully detected using the manufactured sensor.

Bisphenol S (BPS) is a common, persistent, and mobile chemical found in everyday products such as thermal paper. BPS can easily enter the body by migrating from the paper to the fingers, disrupting the endocrine system by mimicking the oestrogen hormone, thus negatively influencing human health. Assessing BPS levels in daily life is of great importance. This study introduces a rapid and reliable approach for detecting BPS in thermal paper and tap water by developing an electrochemical analytical method. This method allows for in-situ, real-time measurements. We present a simple, low-cost electrochemical sensor for detecting BPS using screen-printed electrodes based on carbon (SPEC) and single-wall carbon-nanotube (SPE-SWCNT) working electrodes. BPS was detected over a wide linear range from 1 to 400 μM. The detection limits were 0.73 μM and 0.87 μM for the SPE-C and SPE-SWCNT electrodes, respectively. Good repeatability was observed for both sensors when using one electrode 16 times, which demonstrates its potential for real-time environmental monitoring. Additionally, traditional chromatographic methods, high-performance liquid chromatography with a diode-array detector (HPLC-DAD), and liquid chromatography-mass spectrometry triple quadrupole (LCMS), were incorporated to enhance analytical capabilities. HPLC-DAD achieved a detection limit of 3 nM after solid-phase extraction preconcentration, while LCMS triple quadrupole demonstrated a detection limit of 10 pM without preconcentration. Electrochemical screen-printed electrodes can be employed for on-site analysis and health-risk assessments in everyday settings, such as shops. However, for detecting very low concentrations where time is not a constraint, LCMS quadrupole remains the preferred technique.

A disposable voltammetric immunosensor was developed to measure breast cancer biomarker 15-3 (CA 15-3) in human saliva and serum samples. Screen-printed paper-based electrodes (f-SPE) previously fabricated by our research group using homemade conductive inks were used as transducers, which were later modified only with gold nanoparticles to immobilize anti-CA 15-3 antibodies. The sensor was operated using antigen–antibody interactions in conjunction with a redox species (ferrocyanide potassium) for the indirect determination of the CA 15-3 antigen. The device characterization involved atomic force microscopy (AFM) and electrochemical analysis. Optimization of the construction and response of the immunosensor was achieved at incubation times of 6 h for anti-CA 15-3, 1 h for bovine serum albumin, and 1 h for interaction with CA 15-3. The sensor displays a linear range between 2 and 16 U/mL, with a sensitivity of 0.012 μA/U mL−1, a limit of detection (LOD) of 0.56 U/mL, and a limit of quantification (LOQ) of 1.88 U/mL. The interfering substances minimally affected the signal, with 4.94% response variation, and the reproducibility of the immunosensor demonstrated a relative standard deviation (RSD) of 5.65%. The sensor successfully determined the CA 15-3 concentration in human serum and saliva, demonstrating its potential for clinical analysis.

Objective: In order to achieve rapid detection of methyl parathion. Methods: An acetylcholinesterase sensor was prepared based on gold nanoparticles and reduced graphene oxide for quantitative detection of Methyl parathion. Reduced graphene oxide, gold nanoparticles and acetylcholinesterase were successively modified on the surface of the screen printing electrode by layer-by-layer assembly method. The catalytic activity and impedance characteristics of the sensor, the relationship between the sensor's inhibition rate and MP concentration, and the actual sample detection were evaluated. Results: The prepared acetylcholinesterase biosensors showed excellent affinity for acetylthiocholine chloride with the Michaelis-Menten constant of 2.76 mmol/L. Under the optimal conditions, Methylparathion could be effectively detected with a linear range of 5 ng/mL to 500 ng/mL and a detection limit of 0.692 ng/mL. Conclusion: The method is simple, practical and stable. It provides a reliable method for rapid detection of organophosphorus pesticides.

In this work, a new voltammetric procedure for acyclovir (ACY) trace-level determination has been described. For this purpose, an electrochemically activated screen-printed carbon electrode (aSPCE) coupled with well-conductive electrolyte (CH3COONH4, CH3COOH and NH4Cl) was used for the first time. A commercially available SPCE sensor was electrochemically activated by conducting cyclic voltammetry (CV) scans in 0.1 mol L−1 NaOH solution and rinsed with deionized water before a series of measurements were taken. This treatment reduced the charge transfer resistance, increased the electrode active surface area and improved the kinetics of the electron transfer. The activation step and high conductivity of supporting electrolyte significantly improved the sensitivity of the procedure. The newly developed differential-pulse adsorptive stripping voltammetry (DPAdSV) procedure is characterized by having the lowest limit of detection among all voltammetric procedures currently described in the literature (0.12 nmol L−1), a wide linear range of the calibration curve (0.5–50.0 and 50.0–1000.0 nmol L−1) as well as extremely high sensitivity (90.24 nA nmol L−1) and was successfully applied in the determination of acyclovir in commercially available pharmaceuticals. [ABSTRACT FROM AUTHOR]

This work represents the development of natural kaolinite mineral (Kao)-gold nanoparticles (GNPs) modified screen-printed carbon electrode (SPCE) based on biocompatible electrode material for the electrochemical quantification of propyphenazone and the investigation of the interaction between propyphenazone and ds-DNA. The surface characteristics of the Kao-GNPs/SPCE were examined by cyclic voltammetry, electrochemical impedance spectroscopy, and field-emission scanning electron microscopy with energy dispersive X-ray spectroscopy methods. The effect of Kao and gold compositions, pH, and interferences studied the analytical performance of this sensor. Propyphenazone has an irreversible oxidation signal on the Kao-GNPs/SPCE sensor surface. Based on this oxidation signal, calibration works were carried out using differential pulse voltammetry, and linear working range, LOD, and LOQ were determined. The real sample analysis of propyphenazone was implemented in human serum samples with a recovery value of 99.43%. Binding constant (K) and Gibbs free energy change (ΔG°) relating to the interaction between propyphenazone and ds-DNA were calculated to be 2.14 (± 0.42) × 104 M−1 and − 24.70 kJ mol−1, respectively. [ABSTRACT FROM AUTHOR]

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Background: Catheter line infection is a common complication within clinical environments, and there is a pressing need for technological options to aid in reducing the possibility of sepsis. The early identification of contamination could be pivotal in reducing cases and improving outcomes. Method: A sensing rationale based on a riboflavin-modified electrode system integrated within a modified 3D-printed catheter needle-free connector is proposed, which can monitor changes in pH brought about by bacterial contamination. Results: Riboflavin, vitamin B2, is a biocompatible chemical that possesses a redox-active flavin core that is pH dependent. The oxidation peak potential of the adsorbed riboflavin responds linearly to changes in pH with a near-Nernstian behavior of 63 mV/pH unit and is capable of accurately monitoring the pH of an authentic IV infusate. Conclusions: The proof of principle is demonstrated with an electrode-printed hub design offering a valuable foundation from which to explore bacterial interactions within the catheter lumen with the potential of providing an early warning of contamination. [ABSTRACT FROM AUTHOR]

The present work reports the synthesis of MgCo2O4-rGO nanohybrid by a simple method. The nanohybrid was characterised by XRD, Raman spectroscopy, EDX, SEM, and TEM. An effective electrochemical sensing platform to detect Sudan I based on MgCo2O4-rGO nanohybrid modified screen-printed electrode (MgCo2O4-rGO/SPE) is reported. Electrocatalytic sensing of Sudan I is carried out using cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CHA) as well as differential pulse voltammetry (DPV) measurements. Interestingly, this newly developed sensor showed greater peak currents with the decreased anodic potential than that of the bare SPE. The modified electrode demonstrated distinctive electrocatalytic activities to detect Sudan I with the longer linear response range between 0.04 and 580.0 µM, low limit of detection (LOD) of 9.0 nM, and high sensitivity of 0.0838 µA µM−1. In addition, MgCo2O4-rGO/SPE sensor exhibited excellent electrochemical stability, repeatability and reproducibility for Sudan I detection. Analytical utility of our method revealed acceptable detection outputs for Sudan I. Therefore, it could be concluded that this sensor (MgCo2O4-rGO/SPE) exhibited very good electrochemical behaviour for electrochemical detection of Sudan I oxidation. [ABSTRACT FROM AUTHOR]

The control of the precise concentration of steroid hormones and their synthetic analogs in biomedical objects is a relevant analytical task. A method for selective and highly sensitive simultaneous amperometric determination of adrenaline, melatonin, and cortisol with the use of a two-detector flow-injection system is developed. Screen-printed carbon electrodes (SPE) with one or two working electrodes modified with a gold–palladium binary system that exhibits catalytic activity upon electrooxidation of the organic compounds under consideration are used as detectors. The high sensitivity of determination is attributed to the catalytic properties of the metal modifier: the transition from the metal to the binary system leads to an increase in the catalytic oxidation current of hormones. The selectivity of determination of adrenaline in the presence of melatonin and cortisol is provided by the difference in the oxidation potentials of the hormones on the proposed electrode. For selective determination of melatonin and cortisol, the surface of the modified working electrode is coated with a Nafion film. The difference of potentials of the peaks of oxidation of adrenaline, melatonin, and cortisol on such an electrode is 300 mV. The proposed method is tested in the analysis of urine samples. The flow-injection scheme is supplemented with a dialyzer and a chromatographic minicolumn to eliminate the interfering effect of electrophilic compounds. The linear bilogarithmic dependence of the analytical signal on the concentration of adrenaline, melatonin, and cortisol is observed in the ranges of 5.0 × 10–10–5.0 × 10–3, 5.0 × 10–11–5.0 × 10–3, and 5.0 × 10–12–5.0 × 10–3 mol/L, respectively. Amperometric determination of the hormones in the flow-injection system leads to an increase in the productivity of the analysis and a decrease in the consumption of the sample and makes it possible to automate the process. [ABSTRACT FROM AUTHOR]

In this study, boron-doped diamond nanoparticles modified on the surface of a screen-printed electrode (SPE) were prepared for the sensitive and selective determination of Sb3+ using square wave voltammetry. The effect of electrochemical parameters such as the type of supporting electrolyte, pH, signal per background, and scan rate on the sensitivity of the sensor for the detection of Sb3+ was investigated. Under optimized conditions with an amplitude of 0.05 V, a frequency of 50 Hz, and an E-step of 0.05 V, the square wave voltammogram between -1.0 and 1.0 V gave a limit of detection of 2.41 × 10-8 M for an Sb3+ concentration range from 0.19 to 0.59 µM. The method was used to determine Sb3+ ions in river water with satisfactory results. The modified electrode displayed benefits such as high sensitivity and selectivity, long-term stability, easy preparation, and wide linear range. [ABSTRACT FROM AUTHOR]

In this study, a screen-printed electrode (SPE) for nitrite (NO2 -) sensing was fabricated through an inkjet printing technique using a commercial printer machine and preparing an ink composite solution containing graphene oxide (GO) and poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS) as conductive materials. The optimum ink materials for SPE fabrication comprised GO and PEDOT:PSS with binders that resemble the viscosity of commercial ink. The surface topography of the fabricated SPE, which was characterized using scanning electron microscopy and atomic force microscopy, showed a smoother surface compared to the commercial screen-printed carbon electrode, with conductive ink materials deposited primarily from GO/PEDOT:PSS composites. This NO2 - sensor exhibited a linear response at the concentration range of 50-1000 µM, with limit of detection and limit of quantification as 25 and 50 µM, respectively. In addition, the stability, reproducibility, and selectivity of this sensor presented acceptable values in the analytical range. Furthermore, the performance of this sensor was compared with that of a spectrophotometry technique using synthetic water samples, and the results revealed its good analytical recovery at a confidence interval of 95%. Thus, our sensor based on SPE-modified GO/PEDOT:PSS, fabricated via the inkjet printing technique, can be potentially applied in monitoring NO2 - concentration in real samples. [ABSTRACT FROM AUTHOR]

In this work, we detailed the improvement of a hand-made screen-printed electrode (SPE), which has easy production with conductive ink. The preparation of the hand-made SPE based on conductive ink to be transferred to cardboard substrates as electrochemical sensors. Thanks to its advantages such as being cheap and easy to obtain, cardboard was preferred as a substrate. As a new approach, we report for the first time in the literature the alkaline pretreatment applied for the cardboard substrate. The conductive ink was used as a working electrode, a counter electrode, and a reference electrode. The components of the developed conductive ink are carboxymethyl cellulose (CMC) as binder, water:ethanol:ethylene glycol as solvent and graphite as conductive material. The SPE was characterized by Fourier-transformed infrared spectroscopy, scanning electron microscopy energy-dispersive X-ray spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The developed electrode was used in the voltammetric determination of dopamine, an important neurotransmitter for human health. The device achieved a linear response between 5.0 and 1000 μM and a limit of detection (LOD) of 1.25 μM. Thus, these developed hand-made SPE was used in the determination of dopamine in a selective, fast, and cost-effective way. It provides a new device approach for electrochemical biosensors and wearable technologies with hand-made screen-printed electrodes developed as easy to prepare, inexpensive and disposable. [ABSTRACT FROM AUTHOR]

Trans-endothelial electrical resistance (TEER) is one of the most widely used indicators to quantify the barrier integrity of endothelial layers. Over the last decade, the integration of TEER sensors into organ-on-a-chip (OOC) platforms has gained increasing interest for its efficient and effective measurement of TEER in OOCs. To date, microfabricated electrodes or direct insertion of wires has been used to integrate TEER sensors into OOCs, with each method having advantages and disadvantages. In this study, we developed a TEER-SPE chip consisting of carbon-based screen-printed electrodes (SPEs) embedded in a poly(methyl methacrylate) (PMMA)-based multi-layered microfluidic device with a porous poly(ethylene terephthalate) membrane in-between. As proof of concept, we demonstrated the successful cultures of hCMEC/D3 cells and the formation of confluent monolayers in the TEER-SPE chip and obtained TEER measurements for 4 days. Additionally, the TEER-SPE chip could detect changes in the barrier integrity due to shear stress or an inflammatory cytokine (i.e., tumor necrosis factor-α). The novel approach enables a low-cost and facile fabrication of carbon-based SPEs on PMMA substrates and the subsequent assembly of PMMA layers for rapid prototyping. Being cost-effective and cleanroom-free, our method lowers the existing logistical and technical barriers presenting itself as another step forward to the broader adoption of OOCs with TEER measurement capability. [ABSTRACT FROM AUTHOR]

In the last decades, a significant amount of research has been focused on the development of miniaturized and portable electrochemical sensors in the form of screen-printed electrodes (SPEs). When performing voltammetric measurements using SPEs, especially in the case of carbon-based electrodes, additional peaks can appear and overlap with analytes’ signals or otherwise interfere with results. Therefore, the development of pretreatment methods that enable the removal of interferences is of great importance for SPEs utilization, e.g. for sensor applications. Moreover, electrode pretreatment can also be used to improve electron transfer kinetics, including reversibility of the studied redox processes. In this work, we present the evaluation of different pretreatment methods using cyclic voltammetry and potentiostatic anodization, applied on an in-house graphite-glass composite working electrodes. With the use of X-ray photoelectron spectroscopy and scanning electron microscopy it was confirmed that the surface of working electrode was contaminated by sub-micrometer sized silver particles, which resulted in two interference peaks. Several strong acids, including H2SO4, HNO3, and HCl, as well as phosphate buffer solution, were evaluated as electrolytes for electrochemical pretreatment. A rapid, simple, and low-cost pretreatment protocol that enables the removal of the interference peaks, as well as improved voltammetric signals for [Fe(CN)6]3−/4− redox probe was developed. We propose the optimal pretreatment method in H2SO4 as a protocol that could be universally applied for carbon, carbon-glass, or similar types of SPEs before performing voltammetric experiments and/or further modifications of SPEs.

Excessive consumption of antibiotics like gentamicin (GEN) can lead to hostile effects as antibiotic resistance. Therefore, the detection is important for which, reduced graphene oxide-Gadolinium oxide nanocomposite (rGO@Gd2O3 NC) was composed through co-precipitation method for the detection of GEN. The structural, morphological and functional group characterizations were done using XRD, FT-IR, SEM and TEM techniques. The cyclic voltammetry (CV) showed excellent electrocatalytic activity and superior performance towards GEN detection. Through the use of GEN monoclonal antibodies (anti-GEN) on a screen-printed electrode (SPE), a very sensitive electrochemical immunosensor was fabricated. Covalent interactions were employed to construct the electrochemical immunosensor, while bovine serum albumin (BSA) was employed as a blocking agent on the anti-GEN/rGO@Gd2O3/SPE electrode surface. The analysis of the CV response of the BSA/anti-GEN/rGO@Gd2O3/SPE bioelectrode demonstrated linear detection range from 1 pM – 100 μM, along with limit of detection (LOD) of 0.424 pM and sensitivity of 44.87 μA pM-1 cm− 2. Additionally, rGO@Gd2O3 immunosensor, exhibited a good level of linearity with R2 value of 0.978. These findings indicate the excellent potential of the rGO@Gd2O3 electrochemical immunosensor for accurately detecting GEN in spiked milk samples at different concentrations.

A screen-printed electrode (SPE) modified with the flower-like nanostructures of zinc oxide doped with terbium for forming FL-NS Tb3+/ZnO/SPE-modified electrode (electrochemical sensor) was provided for effective and rapid detection of sulfamethoxazole (SMX) and trimethoprim (TMP). Therefore, structure, composition, as well as the impact of process variables of the modified electrode, electrochemical response features of SMX and TMP, sensitivity of both simultaneous detections, and scan rate were examined in this research. According to the examinations, synergy of Tb and ZnO resulted in the promotion of the electrochemical reaction of SMX and TMP. Moreover, the difference in their oxidation peak potential was < 220 mV. In addition, the modified electrode linearly ranged from 0.001 to 900.0 μM, with the detection limit of 0.14 nM and 0.23 nM (S/N = 5) for SMX and TMP, respectively. Finally, it was found that this new FL-NS Tb3+/ZnO/SPE-modified electrode enjoys a broader smaller detection limits, linear range, and very good stability and reproducibility. [ABSTRACT FROM AUTHOR]