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Accelerated synthesis of gold nanoparticles (AuNPs) in charged microdroplets produced by electrospray ionization (ESI) was exploited to modify the surface of graphite screen-printed electrodes (GSPEs). The deposited AuNPs were then functionalized by the charged microdroplets deposition of 6-ferrocenyl-hexanethiol (6Fc-ht) solutions that act as reducing and stabilizing agents and provide electrochemical properties for the modified electrodes. The morphology and composition of the AuNPs were characterized by scanning electron microscopy (SEM). Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical behavior of the modified electrodes. The results showed that the ESI microdroplets deposition technique produces uniform and well-dispersed AuNPs on GSPE, and optimal conditions for deposition were identified, enhancing GSPE electrocatalytic performance. Further functionalization by ESI microdroplets of AuNPs with 6Fc-ht demonstrated improved redox properties compared with the conventional self-assembled monolayer (SAM) method, highlighting the technique's potential for the easy and fast functionalization of electrochemical sensors. [ABSTRACT FROM AUTHOR]

A highly sensitive and selective label-free impedimetric immunosensor based on AuNPs@pDA@NiCo2S4@MoS2 nanocomposite modified on the surface of a screen-printed electrode (SPE) was designed for the detection of interleukin-6 (IL-6). The distribution of NiCo2S4 nanoparticles on MoS2 nanosheets was able to prevent them from agglomerating. The polydopamine (pDA) layer was coated on the surface of NiCo2S4@MoS2 nanosheets by self-polymerization, which improved the stability and biocompatibility of the nanomaterial. The excellent reduction ability of pDA promoted the synthesis of gold nanoparticles (AuNPs), which increased the amount of antibody adsorption and the conductivity of the material. Finally, the antibody (Ab) of IL-6 was immobilized on the surface of AuNPs@pDA@NiCo2S4@MoS2 nanocomposite. Electrochemical impedance spectroscopy (EIS) was used to detect the change of impedance before and after the immune response between Ab and IL-6 antigen (IL-6). Under the optimal experimental conditions, the relative change in impedance and the logarithmic concentration of IL-6 showed a good linear relationship in the range 1.00 to 1.00 × 106 pg/mL, with a low detection limit of 0.97 pg/mL. In addition, the proposed immunosensor performed with good reproducibility, stability, and specificity. It was successfully applied to the determination of IL-6 in patient's serum samples of head and neck carcinoma with recoveries of 98.40% to 106.5%. To sum up, the proposed label-free impedimetric immunosensor was successfully constructed for IL-6 detection in real samples. [ABSTRACT FROM AUTHOR]

Electrochemical impedance spectroscopy (EIS) is a suitable analytical technique to detect interfacial phenomena and analyte binding at electrode surfaces. In contrast to metallic electrodes, carbon‐based electrodes are more suited due to the low cost and the availability of more versatile methods for chemical functionalization. For (bio) sensing, often the Faradaic version of EIS in a three‐electrode configuration is used, where a redox‐active species is used as a marker. In order to avoid interference due to the redox‐active marker with the interfacial interaction, we focus here on the use of non‐Faradaic EIS in the absence of any added markers. First, we utilize the sedimentation of silica beads as a model system, which reduces the complexity of the interaction simplifying the interpretation of the measured signals. Moreover, we introduce two improvements. First, impedance measurements are performed in a three‐electrode configuration with applied potential as an additional variable, which serves as a handle to optimize the sensitivity. Secondly, we present a time‐differential strategy to detect subtle changes and demonstrate that we can consistently follow the sedimentation of beads using the non‐Faradaic impedance as a function of the applied potential. Finally, we show a proof‐of‐principle demonstration for the biosensing of cell attachment on the electrodes in real‐time using the proposed technique. [ABSTRACT FROM AUTHOR]

This paper introduces a quantitative method for dopamine determination. The method is based on a molecularly imprinted polypyrrole (e-MIP)-modified screen-printed electrode, with differential pulse voltammetry (DPV) as the chosen measurement technique. The dopamine molecules are efficiently entrapped in the polymeric film, creating recognition cavities. A comparison with bare and non-imprinted polypyrrole-modified electrodes clearly demonstrates the superior sensitivity, selectivity, and reproducibility of the e-MIP-based one; indeed, a sensitivity of 0.078 µA µM−1, a detection limit (LOD) of 0.8 µM, a linear range between 0.8 and 45 µM and a dynamic range of up to 350 µM are achieved. The method was successfully tested on fortified synthetic and human urine samples to underline its applicability as a screening method for biomedical tests. [ABSTRACT FROM AUTHOR]

Screen-printed electrodes (SPEs) are reliable, portable, affordable, and versatile electrochemical platforms for the real-time analytical monitoring of emerging analytes in the environmental, clinical, and agricultural fields. The aim of this study was to evaluate the electrochemical behavior of gold screen-printed electrodes (SPGEs) modified with molecules containing amino (Tr-N) or α-aminophosphonate (Tr-P) groups for the selective and sensitive detection of the toxic metal ions Pb2+ and Hg2+ in aqueous samples. After optimizing the analytical parameters (conditioning potential and time, deposition potential and time, pH and concentration of the supporting electrolyte), anodic square wave stripping voltammetry (SWASV) was used to evaluate and compare the electrochemical performance of bare or modified electrodes for the detection of Hg2+ and Pb2+, either alone or in their mixtures in the concentration range between 1 nM and 10 nM. A significative improvement in the detection ability of Pb2+ ions was recorded for the amino-functionalized gold sensor SPGE-N, while the presence of a phosphonate moiety in SPGE-P led to greater sensitivity towards Hg2+ ions. The developed sensors allow the detection of Pb2+ and Hg2+ with a limit of detection (LOD) of 0.41 nM and 35 pM, respectively, below the legal limits for these heavy metal ions in drinking water or food, while the sensitivity was 5.84 µA nM−1cm−2 and 10 µA nM−1cm−2, respectively, for Pb2+ and Hg2+. The reported results are promising for the development of advanced devices for the in situ and cost-effective monitoring of heavy metals, even in trace amounts, in water resources. [ABSTRACT FROM AUTHOR]

Cancer remains one of the leading causes for death worldwide. Palliative chemotherapy is vital for certain cancer patients, highlighting the critical need for treatment monitoring tools to prevent drug accumulation and mitigate the risk of high toxicity. Therefore, our aim was to evaluate the potential of screen-printed electrodes for the development of sensitive and accurate biosensors for the detection/quantification of antineoplastic drugs. To this purpose, we developed a cisplatin sensor. By functionalizing the gold electrode with human serum albumin and by collecting the electrochemical signal obtained in a H2O2 solution, through voltammetry measurements, we were able to correlate the current measured at 430 mV with the concentration of cisplatin present in human serum samples, with a correlation coefficient of R2 = 0.99. Also, a bleomycin biosensor was developed and proven functional, but further optimization steps were employed in order to improve the accuracy. The developed biosensors have a detection range of 0.0006–43.2 mg/mL for cisplatin and 0.23–7.56 μg/mL for bleomycin in the serum samples. Our preliminary results show that these biosensors can facilitate the real-time monitoring of cisplatin and bleomycin serum levels, allowing healthcare professionals to tailor treatment strategies based on individual patient responses. [ABSTRACT FROM AUTHOR]

In the era of liquid biopsy, microRNAs emerge as promising candidates for the early diagnosis and prognosis of cancer, offering valuable insights into the disease's development. Among all the existing analytical approaches, even if traditional approaches such as the nucleic acid amplification ones have the advantages to be highly sensitive, they cannot be used at the point-of-care, while sensors might be poorly sensitive despite their portability. In order to improve the analytical performance of existing electroanalytical systems, we demonstrate how a simple chromatographic paper-based disk might be useful to rationally improve the sensitivity, depending on the number of preconcentration cycles. A paper-based electrochemical platform for miRNA detection has been developed by modifying a paper-based electrode with a methylene blue (MB)-modified single-stranded sequence (ssDNA) complementary to the chosen miRNA, namely miR-224 that is associated with lung cancer. A detection limit of ca. 0.6 nM has been obtained in spiked human serum samples. To further enhance the sensitivity, an external chromatographic wax-patterned paper-based disk has been adopted to preconcentrate the sample, and this has been demonstrated both in standard and in serum solutions. For each solution, three miR-224 levels have been preconcentrated, obtaining a satisfactory lowering detection limit of ca. 50 pM using a simple and sustainable procedure. This approach opens wide possibilities in the field of analytical and bioanalytical chemistry, being useful not only for electrochemistry but also for other architectures of detection and transduction. [ABSTRACT FROM AUTHOR]

The progressive increase in nitrate's (NO3−) presence in surface and groundwater enhances environmental and human health risks. The aim of this work is the fabrication and characterization of sensitive, real-time, low-cost, and portable amperometric sensors for low NO3− concentration detection in water. Copper (Cu) micro-flowers were electrodeposited on top of carbon screen-printed electrodes (SPCEs) via cyclic voltammetry (with voltage ranging from −1.0 V to 0.0 V at a scan rate of 0.1 V s−1). The obtained sensors exhibited a high catalytic activity toward the electro-reduction in NO3−, with a sensitivity of 44.71 μA/mM. They had a limit of detection of 0.87 µM and a good dynamic linear concentration range from 0.05 to 3 mM. The results were compared to spectrophotometric analysis. In addition, the devices exhibited good stability and a maximum standard deviation (RSD) of 5% after ten measurements; reproducibility, with a maximum RSD of 4%; and repeatability after 10 measurements with the RSD at only 5.63%. [ABSTRACT FROM AUTHOR]

Sensitivity in the sub-nanomolar concentration region is required to determine important protein biomarkers, e.g., ferritin. As a prerequisite for high sensitivity, in this paper, the affinity of the functional monomer to the macromolecular target ferritin in solution was compared with the value for the respective molecularly imprinted polymer (MIP)-based electrodes, and the influence of various surface modifications of the electrode was investigated. The analytical performance of ferritin sensing was investigated using three different carbon electrodes (screen-printed carbon electrodes, single-walled-carbon-nanotube-modified screen-printed carbon electrodes, and glassy carbon electrodes) covered with a scopoletin-based MIP layer. Regardless of the electrode type, the template molecule ferritin was mixed with the functional monomer scopoletin, and electropolymerization was conducted using multistep amperometry. All stages of MIP preparation were followed by evaluating the diffusional permeability of the redox marker ferricyanide/ferrocyanide through the polymer layer by differential pulse voltammetry. The best results were obtained with glassy carbon electrodes. The MIP sensor responded up to 0.5 µM linearly with a Kd of 0.30 µM. Similar results were also obtained in solution upon the interaction of scopoletin and ferritin using fluorescence spectroscopy, resulting in the quenching of the scopoletin signal, with a calculated Kd of 0.81 µM. Moreover, the binding of 1 µM ferritin led to 49.6% suppression, whereas human serum albumin caused 8.6% suppression. [ABSTRACT FROM AUTHOR]

Numerical models of electrochemical sensors using screen-printed electrodes (SPEs) are limited. Simulating the dynamic response of SPEs is challenging due to their complex geometry and kinetic behavior. In this paper, we present a general process by which SPEs can be modeled using commercial finite element software, COMSOL Multiphysics. Parameters such as electroactive surface area and the heterogenous rate constant were derived empirically using a commonly used redox couple of hexaammineruthenium (III), [ R u (N H 3) 6 ] 3 + , and hexaammineruthenium (II), [ R u (N H 3) 6 ] 2 + . Experimentally derived parameters were used in the model and a transient numerical simulation was run to replicate the cyclic voltagramms procured from experiment. The results show that the electroactive area was measured to be 2.3 m m 2 (± 0.674), which was less than the 3.14 m m 2 geometric area. In addition, the heterogeneous kinetic constant at various voltage scanning rates, ranging from 25 to 500 mV/s, were measured. Uncompensated resistance was measured as 301.9 Ω (± 1.6) and was also incorporated as a parameters in the model. Numerical results as represented by voltagramms shapes were consistent with experimental results. The model was able to predict the maximum anodic current density with an accuracy of 30.5%, 22.9%, 13.4%, 16.2%, 12.8%, 14.8%, and 14.6% for scan rates ranging from 25 to 500 mV/s (25, 50, 75, 100, 200, 300, 400, and 500 mV/s, respectively). The model was more accurate in predicting maximum cathodic currents with accuracy values of 1.7%, 1.2%, 5.5%, 4.1%, 1.7%, 2.4%, and 2.2% for scan rates ranging from 25 to 500 mV/s. The results demonstrate the first attempt to model the SPEs which incorporate experimentally derived parameters. These types of models are expected to help biosensor researchers simulate sensor response before fabrication and testing. [ABSTRACT FROM AUTHOR]

The growth of liquid biopsy, i. e., the possibility of obtaining health information by analysing circulating species (nucleic acids, cells, proteins, and vesicles) in peripheric biofluids, is pushing the field of sensors and biosensors beyond the limit to provide decentralised solutions for nonspecialists. In particular, among all the circulating species that can be adopted in managing cancer evolution, both for diagnostic and prognostic applications, microRNAs have been highly studied and detected. The development of electrochemical devices is particularly relevant for liquid biopsy purposes, and the screen‐printed electrodes (SPEs) represent one of the building blocks for producing novel portable devices. In this work, we have taken miR‐2115‐3p as model target (it is related to lung cancer), and we have developed a biosensor by exploiting the use of a complementary DNA probe modified with methylene blue as redox mediator. In particular, the chosen sensing architecture was applied to serum measurements of the selected miRNA, obtaining a detection limit within the low nanomolar range; in addition, various platforms were interrogated, namely commercial and hand‐made SPEs, with the aim of providing the reader with some insights about the optimal platform to be used by considering both the cost and the analytical performance. [ABSTRACT FROM AUTHOR]

In recent years, the detection and determination of numerous drugs and pharmaceuticals in various media have become crucial aspects of modern healthcare and environmental management. Among the available sensing techniques, electrochemical methods, particularly those utilising screen-printed electrodes (SPEs) and different portable equipment have emerged as rapid, effective, sensitive, and inexpensive. This study focuses on the detection of the anti-inflammatory drug diclofenac in neutral media. Cyclic voltammetry measurements were conducted to identify diclofenac and determine the kinetics and electrochemical mechanism of its oxidation, along with assessing the surface characteristics of the employed SPEs. Graphene and modified graphene SPEs were explored as nanosensors for this purpose. The surface of the graphene SPE was modified using polyvinylidene fluoride, applied through a drop modification procedure. The morphology of the examined SPEs was observed by means of scanning electron microscope, while the electrolyte (0.1 g of diclofenac per litre of phosphate-buffered solution, pH = 7.4) was analysed using UV-Vis spectroscopy. The results indicate that the studied SPEs exhibit promising potential for the detection of diclofenac. [ABSTRACT FROM AUTHOR]

The presence of water micropollutants, such as antibiotics, has proved the necessity to develop novel and cost‐effective devices for their identification and quantification. These devices aim to save time, reagent usage, and costs associated with conventional analytical methods. In this work, we introduce poly(methylene blue) based screen‐printed electrodes (SPE‐PMB) as electrochemical sensors designed for the quantification of levofloxacin (LVX), given its current prevalence as a micropollutant. Integrating the fabrication and measurement processes into a single electrochemical device is a significant step in creating affordable detection tools. The proposed sensor was assessed using LVX solutions prepared in real groundwater samples, demonstrating its selectivity and achieving a detection limit of 3.3 μM. Finally, we compared the SPE‐PMB sensor and high‐performance liquid chromatography (HPLC) to validate its operation and performance. Consequently, our results suggest that the sensor can be a viable alternative to chromatographic methods for identifying and quantifying micropollutants at very low concentrations in complex matrices. [ABSTRACT FROM AUTHOR]

This paper reports a rapid and sensitive sensor for the detection and quantification of the COVID-19 N-protein (N-PROT) via an electrochemical mechanism. Single-frequency electrochemical impedance spectroscopy was used as a transduction method for real-time measurement of the N-PROT in an immunosensor system based on gold-conjugate-modified carbon screen-printed electrodes (Cov-Ag-SPE). The system presents high selectivity attained through an optimal stimulation signal composed of a 0.0 V DC potential and 10 mV RMS−1 AC signal at 100 Hz over 300 s. The Cov-Ag-SPE showed a log response toward N-PROT detection at concentrations from 1.0 ng mL−1 to 10.0 μg mL−1, with a 0.977 correlation coefficient for the phase (θ) variation. An ML-based approach could be created using some aspects observed from the positive and negative samples; hence, it was possible to classify 252 samples, reaching 83.0, 96.2 and 91.3% sensitivity, specificity, and accuracy, respectively, with confidence intervals (CI) ranging from 73.0 to 100.0%. Because impedance spectroscopy measurements can be performed with low-cost portable instruments, the immunosensor proposed here can be applied in point-of-care diagnostics for mass testing, even in places with limited resources, as an alternative to the common diagnostics methods. [ABSTRACT FROM AUTHOR]

This paper presents a low-cost disposable sensor for gallic acid (GA) detection in non-alcoholic and alcoholic beverages using a screen-printed cell (SPC) whose working electrode (in graphite) is modified with electrosynthesized molecularly imprinted polypyrrole (eMIP). Our preliminary characterization of the electrochemical process shows that gallic acid (GA) undergoes irreversible oxidation at potentials of about +0.3 V. The peak potential is not affected by the presence of the eMIP film and alcohol percentages (ethanol) up to 20%. The GA determination is based on a differential pulse voltammetry (DPV) analysis leveraging its oxidation peak. The calibration data and the figures of merit of the analytical method (LOD, LOQ, and linear range) are calculated. To validate the feasibility of the sensor's application for the dosing of GA in real matrices, some non-alcoholic and alcoholic beverages are analyzed. The results are then compared with those reported in the literature and with the total polyphenol content determined by the Folin–Ciocalteu method. In all cases, the concentrations of GA align with those previously found in the literature for the beverages examined. Notably, the values are consistently lower than the total polyphenol content, demonstrating the sensor's selectivity in discriminating the target molecule from other polyphenols present. [ABSTRACT FROM AUTHOR]

Bare, non-pretreated platinum wires and screen-printed platinum electrodes were used as both working and counter electrodes in the measurement of dissolved oxygen using a chronoamperometric method. The oxygen reduction current response in the diffusion state was used for a linear determination of air saturation. We evaluated the two different materials in general for their sensing performance such as conditioning time, accuracy, resolution and stability over 13 h of continuous mid-term measurement. A good performance was found for the wire electrodes in terms of accuracy with a current slope of 1.0–1.6 µA (% as)-1 and a resolution of 10–15 nA (Lowest Level of Detection = 0.1% as), but with an unstable current response result over the course of the measurement. The screen-printed electrodes have a resolution of 10–18 nA (Lowest Level of Detection = 0.6–0.8% as) and an accuracy of 620–660 nA (% as)-1 but they showed promising reproducibility and stability. Both materials require several hours of conditioning in the chronoamperometric method before a stable current response is achieved. For biotechnological applications, the platinum screen printed electrodes were evaluated in typical parameter settings (pH 4.0 and 7.4, salinity 0.1 to 10x phosphate buffered saline and temperature 12 to 42 °C) and showed correlations between the response time and stability and the temperature. No correlations were found between salinity, pH and the current response. In this paper, we present inexpensive electrode materials and a simple to implement chronoamperometric method for reliable direct measurement of dissolved oxygen in aqueous media. [ABSTRACT FROM AUTHOR]

A new bioinformatic platform (APTERION) was used to design in a short time and with high specificity an aptamer for the detection of the spike protein, a structural protein of SARS-CoV-2 virus, responsible for the COVID-19 pandemic. The aptamer concentration on the carbon electrode surface was optimized using static contact angle and fluorescence method, while specificity was tested using differential pulse voltammetry (DPV) associated to carbon screen-printed electrodes. The data obtained demonstrated the good features of the aptamer which could be used to create a rapid method for the detection of SARS-CoV-2 virus. In fact, it is specific for spike also when tested against bovine serum albumin and lysozyme, competitor proteins if saliva is used as sample to test for the virus presence. Spectrofluorometric characterization allowed to measure the amount of aptamer present on the carbon electrode surface, while DPV measurements proved the affinity of the aptamer towards the spike protein and gave quantitative results. The acquired data allowed to conclude that the APTERION bioinformatic platform is a good method for aptamer design for rapidity and specificity. Key points: • Spike protein detection using an electrochemical biosensor • Aptamer characterization by contact angle and fluorescent measurements on electrode surface • Computational design of specific aptamers to speed up the aptameric sequence time [ABSTRACT FROM AUTHOR]

In this work, we present a multiphysics modeling approach capable of simulating electrochemical impedance spectroscopy (EIS) responses of screen-printed electrodes (SPEs) modified with self-assembled monolayers of 11-Mercaptoundecanoic acid (MUA). Commercially available gold SPEs are electrochemically characterized through experimental cyclic voltammetry and EIS measurements with 10 mM [Fe(CN)6]3−/4− redox couple in phosphate buffered saline before and after the surface immobilization of MUA at different concentrations. We design the multiphysics model through COMSOL Multiphysics® based on the 3D geometry of the devices under test. The model includes four different physics considering the metal/solution interface electrochemical phenomena, the ion and electron potentials and currents, and the measurement set-up. The model is calibrated through a set of experimental measurements, allowing the tuning of the parameters used by the model. We use the calibrated model to simulate the EIS response of MUA-modified SPEs, comparing the results with experimental data. The simulations fit the experimental curves well, following the variation of MUA concentration on the surface from 1 µM to 100 µM. The EIS parameters, retrieved through a CPE-modified Randles' circuit, confirm the consistency with the experimental data. Notably, the simulated surface coverage estimates and the variation of charge transfer resistance due to MUA-immobilization are well matched with their experimental counterparts, reporting only a 2% difference and being consistent with the experimental electrochemical behavior of the SPEs. [ABSTRACT FROM AUTHOR]

A new bioinformatic platform (APTERION) was used to design in a short time and with high specificity an aptamer for the detection of the spike protein, a structural protein of SARS-CoV-2 virus, responsible for the COVID-19 pandemic. The aptamer concentration on the carbon electrode surface was optimized using static contact angle and fluorescence method, while specificity was tested using differential pulse voltammetry (DPV) associated to carbon screen-printed electrodes. The data obtained demonstrated the good features of the aptamer which could be used to create a rapid method for the detection of SARS-CoV-2 virus. In fact, it is specific for spike also when tested against bovine serum albumin and lysozyme, competitor proteins if saliva is used as sample to test for the virus presence. Spectrofluorometric characterization allowed to measure the amount of aptamer present on the carbon electrode surface, while DPV measurements proved the affinity of the aptamer towards the spike protein and gave quantitative results. The acquired data allowed to conclude that the APTERION bioinformatic platform is a good method for aptamer design for rapidity and specificity. Key points: • Spike protein detection using an electrochemical biosensor • Aptamer characterization by contact angle and fluorescent measurements on electrode surface • Computational design of specific aptamers to speed up the aptameric sequence time [ABSTRACT FROM AUTHOR]

This work developed a conductive ink composed of carbonaceous material for printing electrochemical sensors. The optimized ink comprises graphite, carbon black, and nail polish, respectively (35.3:11.7:53%), as well as acetone as a solvent. The proportion was optimized with consideration of the binder's solubilization, the ink's suitability for the screen-printing process, and lower electrical resistance. The materials used, and the resulting ink, were analyzed by way of Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), Raman spectroscopy, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). The charge transfer resistance (Rct) obtained was 0.348 kΩ. The conductive ink was used to print an electrode on a PET substrate, and a flexible and disposable electrode was obtained. The electroactive area obtained was 13.7 cm2, which was calculated by the Randles-Sevcik equation. The applicability of the device was demonstrated with a redox probe, providing a sensitivity of 0.02 µ A L mmol−1. The conductive ink has adequate homogeneity for producing electrodes using the screen-printing technique, with a low estimated production cost of $ 0.09 mL−1. [ABSTRACT FROM AUTHOR]

This paper focuses on the development of a novel electrode based on boron-doped diamond nanosheet full-volume-enriched screen-printed carbon electrodes (BDDPE) for use as an impedimetric biosensor. Impedimetric biosensors offer high sensitivity and selectivity for virus detection, but their use as point-of-care devices is limited by the complexity of nanomaterials' architecture and the receptor immobilisation procedures. The study presents a two-step modification process involving the electroreduction of diazonium salt at the BDDPE and the immobilisation of antibodies using zero-length cross-linkers for a selective impedimetric biosensor of Haemophilus influenzae (Hi). The incorporation of diamond nanosheets into BDDPE leads to enhanced charge transfer and electrochemical behaviour, demonstrating greatly improved electrochemically active surface area compared with unmodified screen-printed electrodes (by 44% and 10% on average for [Ru(NH3)6]Cl2 and K3[Fe(CN)6], respectively). The presented sensing system shows high specificity towards protein D in Hi bacteria, as confirmed by negative controls against potential interference from other pathogens, with an estimated tolerance limit for interference under 12%. The Hi limit of detection by electrochemical impedance spectroscopy was 1 CFU/mL (measured at − 0.13 V vs BDDPE pseudo-reference), which was achieved in under 10 min, including 5 min sample incubation in the presence of the analyte. [ABSTRACT FROM AUTHOR]

A original electrochemical sensing platform, based on screen-printed electrodes modification with plasma polymerized acrylonitrile (pp-AN) nanofilms is proposed. For that purpose, plasma-enhanced chemical vapor deposition (PECVD) process was conducted in a parallel plate (13.56 MHz) plasma reactor for 2 min with discharge power of 10 W. The surface topography and electrochemical properties of prepared sensors were investigated by X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersion spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. The electrochemical characteristics of pp-AN/SPCE and pp-AN/SPAuE sensors was investigated for model redox pair [Fe(CN)6]4−/3−. Conducted research confirmed the excellent chemical stability, durability, wide potential window, high signal-to-noise (S/N) ratio, and, most importantly, the ability to standardize the sensors. The pp-AN/SPCE sensor was applied to the determination of bupropion, an antidepressant drug whose intake has increased dramatically during the COVID-19 pandemic. The voltammetric response of pp-AN/SPCE for BUP was linear in two concentration ranges of 0.63–10.0 and 10.0–50.0 μmol L−1, with a detection limit of 0.21 μmol L−1. Satisfactory recoveries (96.2–102%) and good precision (RSD below 4.1%) obtained for environmental and biological samples confirmed the usefulness of the sensor for the analysis of various kinds of samples. [ABSTRACT FROM AUTHOR]

Rapid and reliable point-of-care (POC) diagnostic tests can have a significant impact on global health. One of the most common approaches for developing POC systems is the use of target-specific biomolecules. However, the conjugation of biomolecules can result in decreased activity, which may compromise the analytical performance and accuracy of the developed systems. To overcome this challenge, we present a polymer-based cross-linking protocol for controlled and directed conjugation of biological molecules. Our protocol utilizes a bifunctional thiol-polyethylene glycol (PEG)-hydrazide polymer to enable site-directed conjugation of IgG antibodies to the surface of screen-printed metal electrodes. The metal surface of the electrodes is first modified with thiolated PEG molecules, leaving the hydrazide groups available to react with the aldehyde group in the Fc fragments of the oxidized IgG antibodies. Using anti-Klebsiella pneumoniae carbapenemase-2 (KPC-2) antibody as a model antibody used for antimicrobial resistance (AMR) testing, our results demonstrate a ~10-fold increase in antibody coupling compared with the standard N-hydroxysuccinimide (NHS)-based conjugation chemistry and effective capture (>94%) of the target KPC-2 enzyme antigen on the surface of modified electrodes. This straightforward and easy-to-perform strategy of site-directed antibody conjugation can be engineered for coupling other protein- and non-protein-based biological molecules commonly used in POC testing and development, thus enhancing the potential for improved diagnostic accuracy and performance. [ABSTRACT FROM AUTHOR]

The application of copper-based nanoparticles synthesized via green synthesis and their integration with a wearable electrode is reported for designing a flexible catalytic electrode on a glove for onsite electroanalysis of paraquat. A copper precursor and an orange extract from Citrus reticulata are used to synthesize an economical electrocatalytic material for supporting the selective and sensitive detection of paraquat. The electrode yields multidimensional fingerprints due to two redox couples in a square wave voltammogram, corresponding to the presence of paraquat. The developed lab-on-a-finger sensor provides the fast electroanalysis of paraquat within 10 s, covering a wide range from 0.50 to 1000 µM, with a low detection limit down to 0.31 µM and high selectivity. It is also possible to use this sensor at a fast scan rate as high as 6 V s−1 (< 0.5 s for a scan). This wearable glove sensor allows the user to directly touch and analyze samples, such as surfaces of vegetables and fruits, to screen the contamination. It is envisioned that these glove-embedded sensors can be applied to the on-site analysis of food contamination and environments. [ABSTRACT FROM AUTHOR]

The development and analytical applications of electrochemical sensors based on antimony tin oxide (ATO)–Prussian blue (PB) screen-printed electrode (SPE) and PEDOT-PB modified glassy carbon electrode are presented. The ATO-PB electrode was successfully applied in the electrochemical detection of K+ ions. The detection and quantification limits value of 1.1 mM and of 3.7 mM, respectively, have been obtained. A high sensitivity of 0.035 A M−1 cm−2 has been also obtained. In addition, a sensing material based on poly(3,4-ethylenedioxythiophene) (PEDOT) and PB has been developed by a sinusoidal voltage electrochemical procedure and tested toward the potassium ion detection. The PEDOT-PB sensing material displayed the characteristic redox wave of the PB component and good analytical performance toward potassium ion detection. These results demonstrate the utility of the novel electrode materials in the development of electrochemical sensors for electroinactive analytes. [ABSTRACT FROM AUTHOR]

In the quest to find powerful modifiers of screen-printed electrodes for sensing applications, a set of rare earth-doped Ca10−xREx(PO4)6(OH)2 (RE = La, Nd, Sm, Eu, Dy, and Tm and x = 0.01, 0.02, 0.10, and 0.20) hydroxyapatite (HAp) samples were subjected to an in-depth electrochemical characterization using electrochemical impedance spectroscopy and cyclic and square wave voltammetry. Among all of these, the inorganic phosphates doped with lanthanum proved to be the most reliable, revealing robust analytical performances in terms of sensitivity, repeatability, reproducibility, and reusability, hence paving the way for their exploitation in sensing applications. Structural data on La-doped HAp samples were also provided by using different techniques, including optical microscopy, X-ray diffraction, Rietveld refinement from X-ray data, Fourier transform infrared, and Raman vibrational spectroscopies, to complement the electrochemical characterization. [ABSTRACT FROM AUTHOR]

We present in detail the most known and commonly used methods for the calculation of electrode electroactive area (A ) and heterogeneous electron transfer rate constants ( k 0 ). The correct procedure for the calculation of these parameters is often disregarded due to either lack of a minimum theoretical background or oversimplification of each method's limitations and prerequisites. The aim of this work is to provide the theoretical background as well as a detailed guide for the implementation of these measurements by impressing upon the electrochemists the parameters that need to be considered so that the obtained results are safe and useful. Using graphite screen-printed electrodes, A , and k 0 were calculated with different methods and techniques. Data are compared and discussed. [ABSTRACT FROM AUTHOR]

Screen-printed electrodes (SPEs) have the advantage of being considered electrochemical cells that can be implemented in portable sensor applications. With the aim to improve the SPE performance, herein, we present different electrochemical surface modifications of carbon-based SPEs by cyclic voltammetry in hydrogen peroxide or sodium peroxide solution. SPEs were characterized using contact angle, Raman spectroscopy, laser-induced breakdown spectroscopy (LIBS), and electrochemical methods, including cyclic voltammetry (CV), electrochemical impedance spectroscopy, and square wave voltammetry (SVW). Main results agree with the observed changes by Raman spectroscopy and the sp2/sp3 ratio (ID/IG) of carbon vibrational bands. The diminishing of C2 Swan signal determined by LIBS suggests that the activation steps produced defects onto the working electrode in the SPE. Considering that the different intermolecular forces of the redox couples are useful to indirectly evaluate the different functional groups, the activated SPEs were studied in the presence of rutin and [Fe(CN)6]3−/[Fe(CN)6]4− redox couples. Main results show that the electrochemical response of the activated electrode surfaces can be properly used to improve the rutin electrochemical determination. [ABSTRACT FROM AUTHOR]

This work presents quantification of proanthocyanidins (PAs) isolated from grapevine using disposable screen‐printed carbon electrodes (SPCE). Procyanidin B2 (B2) used as a model to investigate the electrochemical characteristics of complicated PAs structures in Britton Robinson buffer solution using cyclic voltammetry and square wave voltammetry. B2 exhibits a well‐defined reversible redox wave at +0.49 V vs. Ag/AgCl. Significantly, the B2 was determined over a linear concentration range of 3.45–34.6 μM with a detection limit of 2.07 μM. The SPCE was used to analyze PAs in grapevine samples, and the results were consistent with those obtained using Folin‐Ciocalteu standard method. [ABSTRACT FROM AUTHOR]

The development of an electrochemical procedure for the determination of 4-ethylguaiacol and its application to wine analysis is described. Modified screen-printed carbon electrodes (SPCEs) with fullerene C60 (C60) have been shown to be efficient in this kind of analysis. The developed activated C60/SPCEs (AC60/SPCEs) were adequate for the determination of 4-ethylguaicol, showing a linear range from 200 to 1000 µg/L, a reproducibility of 7.6% and a capability of detection (CCβ) value of 200 µg/L, under optimized conditions. The selectivity of the AC60/SPCE sensors was evaluated in the presence of possibly interfering compounds, and their practical applicability was demonstrated in the analysis of different wine samples obtaining recoveries ranging from 96 to 106%. [ABSTRACT FROM AUTHOR]

This review article summarizes recent achievements in developing portable electrochemical sensing systems for the detection and/or quantification of controlled substances with potential on-site applications at the crime scene or other venues and in wastewater-based epidemiology. Electrochemical sensors employing carbon screen-printed electrodes (SPEs), including a wearable glove-based one, and aptamer-based devices, including a miniaturized aptamer-based graphene field effect transistor platform, are some exciting examples. Quite straightforward electrochemical sensing systems and methods for controlled substances have been developed using commercially available carbon SPEs and commercially available miniaturized potentiostats. They offer simplicity, ready availability, and affordability. With further development, they might become ready for deployment in forensic field investigation, especially when fast and informed decisions are to be made. Slightly modified carbon SPEs or SPE-like devices might be able to offer higher specificity and sensitivity while they can still be used on commercially available miniaturized potentiostats or lab-fabricated portable or even wearable devices. Affinity-based portable devices employing aptamers, antibodies, and molecularly imprinted polymers have been developed for more specific and sensitive detection and quantification. With further development of both hardware and software, the future of electrochemical sensors for controlled substances is bright. [ABSTRACT FROM AUTHOR]

Recently, nanotechnology and nanoparticles (NPs) such as AgNPs and AuNPs have become important in analytical chemistry due to their great potential to improve the performance of electrochemical sensors. In this work, Ag and Au nanoparticles have been synthesized using a green route in which a grape stalk waste extract is used as a reducing agent to obtain metallic nanoparticles. These NPs were used to customize the surface of commercial screen-printed electrodes (SPCNFEs). The spin-coating method was used to modify commercial SPCNFEs under a nitrogen atmosphere. The resulting electrodes were used in a determination study of Cd(II), Pb(II), and U(VI) with differential pulse anodic stripping voltammetry (DPASV). The customized green AgNPs and AuNPs electrodes presented higher sensitivity and electroanalytical performance than the non-modified SPCNFE. The results showed that the best analytical parameters were obtained with the green, silver nanoparticle SPCNFEs, with a LOD of 0.12 μg L−1 for Pb(II), which is a lower value compared to the most restrictive regulation guidelines. Additionally, the U(VI) ion was successfully determined using the developed G-AgNPs-SPCNFE in spiked tap water, showing comparable results with the ICP-MS technique. [ABSTRACT FROM AUTHOR]

Composites based on poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS)—graphene oxide (GO) are increasingly considered for sensing applications. In this work we aim at patterning and prototyping microscale geometries of PEDOT:PSS: GO composites for the modification of commercially available electrochemical sensors. Here, we demonstrate the laser-induced forward transfer of PEDOT:PSS: GO composites, a remarkably simple procedure that allows for the fast and clean transfer of materials with high resolution for a wide range of laser fluences (450–750 mJ/cm2). We show that it is possible to transfer PEDOT:PSS: GO composites at different ratios (i.e., 25:75 %wt and 50:50 %wt) onto flexible screen-printed electrodes. Furthermore, when testing the functionality of the PEDOT:PSS: GO modified electrodes via LIFT, we could see that both the PEDOT:PSS: GO ratio as well as the addition of an intermediate release layer in the LIFT process plays an important role in the electrochemical response. In particular, the ratio of the oxidation peak current to the reduction peak current is almost twice as high for the sensor with a 50:50 %et PEDOT:PSS: GO pixel. This direct transfer methodology provides a path forward for the prototyping and production of polymer: graphene oxide composite based devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Cu/Fe complex conductive hydrogel for non-invasive sweat glucose detection was constructed. • The hydrophilic nature of the hydrogel facilitates the easier diffusion of glucose, thereby improving the sensing efficiency. • Owing to the outstanding self-healing property of the hydrogel, the sensor is capable of tolerating deformation and damage. • The biosensor exhibits a wide glucose range (0–0.2 mM and 0.2–4 mM) and low detection limit (9.99 μM). Wearable electrochemical sensors for glucose analysis hold significant potential for non-invasive monitoring of sweat biomarkers. However, the complex and expensive preparation process has limited the application of these sensors. In this study, we proposed an electrochemical glucose biosensor based on poly (2-hydroxyethyl methacrylate) (PHEMA) hydrogel initiated via iron ion and phenol hydroxyl groups. Copper nanoparticles are then incorporated into the hydrogel, enhancing the conductivity and electrocatalytic performance of the hydrogel electrode. The composite hydrogel, characterized by its rich metal coordination and hydrogen bonds, demonstrated remarkable cyclic adhesion properties, stretchability, and self-healing capability. Subsequently, this hydrogel is modified onto a screen-printed electrode (SPE) to create an in vitro skin patch for glucose detection in human sweat. The biosensor exhibits a wide linear range for glucose concentration of 0–0.2 mM and 0.2–4 mM, with low detection limit of 9.99 μM. The sensor exhibits good stability, selectivity and flexibility, and demonstrates a strong correlation with glucose measurements obtained from real sweat using a glucose assay kit. This sweat sensor holds great development potential, providing broad prospects for future non-invasive detection applications. [ABSTRACT FROM AUTHOR]

To overcome the limitations of insufficient sensitivity and poor specificity of portable screen-printed carbon electrode-electrochemical sensors (SPCE-EC) in practical applications, we prepared carrier composites of carboxylic single-walled carbon nanotubes vertically grafted by covalent organic frameworks (v-COF@SWCNTs-COOH) and coated with a molecularly imprinted polymer (MIP) of sulfadimidine (SM 2). 55 °C hot steam elution is more eco-friendly than traditional organic solvent elution. The results showed that when the mass ratio of DBA to DBA-SWCNTs was 1:1, the v-COF@SWCNTs-COOH obtained by the two-step synthesis method could increase the electrical signal up to 2.33-fold of the bare electrode. The bifunctional monomer MIP prepared on the above structure enhanced the signal response by 2.91-fold, with a high imprint factor of 20. The assembled MIP/v-COF@SWCNTs-COOH/SPCE were analyzed by differential pulse voltammetry (DPV) with a high sensitivity of 0.21 nM for LOD and 0.70 nM for LOQ. In milk and fish samples, the recovery rate was 95.0 %–104.8 %. The validation of authentic pork samples with the statutory LC-MS/MS method showed no significant difference (P > 0.05). The sensor's performance indicators remained robust after five repeated uses. Therefore, the MIP/v-COF@SWCNTs-COOH/SPCE combines the cheapness and portability of SPCE, while the sensitivity and specificity of small molecule detection were significantly improved. [Display omitted] • The v-COF@SWCNTs-COOH/SPEC carrier was beneficial for signal amplification. • The signal amplification carries endow MIPs with high selectivity for sulfadimidine. • The steam elution method was affordable and environmental for sensor recycling. • The on-site detection of SM 2 by an electrochemical sensor was robust and fast. [ABSTRACT FROM AUTHOR]

• Development of an eco-friendly electrochemical textile-based sensor using recycled polyester and hemp fibers. • Textile-based SPE shows better electrochemical behavior and 1.58% RSD for 20 measurements, outperforming commercial SPEs. • Natural, renewable, cost-effective material, compatible with health applications and easy integration into wearables. • Sustainable materials reduce the environmental impact of discarded SPEs, promoting sustainability in point-of-care devices. • Offers flexibility and comfort for continuous health monitoring while maintaining high electrochemical performance. Electronic sensors are essential in applications like biosensors and fuel cells, providing rapid solutions for substance detection. Integrating electrochemical sensors into textiles offers advantages such as flexibility, comfort, and potential for wearable applications. This study explores the suitability of three textile substrates—100 % polyester knit mesh (S1), 100 % recycled polyester knit mesh (S2), and 50 % recycled polyester/50 % hemp fabric (S3)—for constructing screen-printed electrodes (SPEs). The goal is to develop a textile-based electrochemical sensor with a 3-electrode system (reference, auxiliary, and working electrode) using semi-automated screen printing. The electrochemical performance of two carbon inks, Elantas 9553 and DuPont BQ242, was evaluated to select the best working electrode (WE) ink. DuPont BQ242 was found most suitable for WE production, exhibiting quasi-reversible behavior and temperature stability. The electrochemical behavior of the textile-SPEs printed with DuPont BQ242 revealed that substrate S3 had superior properties, with higher peak currents (peak current ratio of 1.2) and smaller peak potential separation (602 n/V). Carbon Elantas 9553 was more sensitive to temperature changes (1 % variation) than the more stable DuPont BQ242 (0.03 % variation). The stability of the inks on substrates was examined using the 4-point probe method, highlighting excellent electrical stability under UV, high temperatures, cosmetics, and artificial sweat. The final textile-based SPE outperformed commercial SPEs, showing superior redox properties, with a peak potential separation (ΔEp) 56 % smaller and a relative standard deviation (RSD) of 1.58 % over 20 measurements. These textile-based SPEs present a valuable alternative to conventional rigid sensors, which are typically single-use and less durable. [ABSTRACT FROM AUTHOR]

[Display omitted] • A hybrid hydrogel nanocomposite immunosensor for the electrochemical detection of hemoglobin. • A combined carbon black screen-printed electrode modified with a gold nanoparticles doped hydrogel for antibodies immobilization. • The PEGDA-AuNPs/CB-SPE immunosensor demonstrated ability to detect hemoglobin in standard solution and serum samples. A novel hybrid hydrogel nanocomposite immunosensor was developed for the electrochemical detection of hemoglobin in blood. The transducing element was based on carbon black (CB)-nanomodified screen-printed electrodes (SPEs) on which a poly(ethylene glycol)-diacrylate hydrogel (PEGDA) doped with gold nanoparticles (AuNPs) was photopolymerized in situ. The fabricated PEGDA-AuNPs/CB-SPEs were then functionalized with oriented anti-hemoglobin antibodies. The immunosensor was analyzed by Electrochemical Impedance Spectroscopy (EIS) and Differential Pulse Voltammetry (DPV) at different modification steps, while its morphology was evaluated by Scanning Electron Microscopy (SEM). The analytical performances of the resulting PEGDA-AuNPs/CB-SPE immunosensor were assessed by DPV analysis, demonstrating the ability of the proposed system to detect hemoglobin in both standard solution and serum samples with a limit of detection (LOD) of 0.005 mg/mL within a dynamic response in a concentration range from 0.005 to 0.1 mg/mL. Slight interference was observed in the presence of glucose and ascorbic acid at concentrations much higher than those physiologically present in the blood. Moreover, any matrix effect was evidenced in serum samples, with a good recovery value of 107 ± 4 % obtained for a hemoglobin concentration of 0.025 mg/mL. [ABSTRACT FROM AUTHOR]

Due to the great significance of amino acids, a substantial number of research studies has been directed toward the development of effective and reliable platforms for their evaluation, detection, and identification. In order to support these studies, a new electrochemical platform based on PANI/ZnO nanowires' modified carbon inks screen-printed electrodes was developed for qualitative analysis of electroactive amino acids, with emphasis on tyrosine (Tyr) and tryptophan (Trp). A comparative investigation of the carbon ink before and after modification with the PANI/ZnO was performed by scanning electron microscopy and by Raman spectroscopy, confirming the presence of PANI and ZnO nanowires. Electrochemical investigations by cyclic voltammetry and electrochemical impedance spectroscopy have shown a higher charge-transfer rate constant, which is reflected into lower charge-transfer resistance and higher capacitance values for the PANI/ZnO modified ink when compared to the simple carbon screen-printed electrode. In order to demonstrate the electrochemical performances of the PANI/ZnO nanowires' modified carbon inks screen-printed electrodes for amino acids analysis, differential pulse voltammograms were obtained in individual and mixed solutions of electroactive amino acids. It has been shown that the PANI/ZnO nanowires' modified carbon inks screen-printed electrodes allowed for tyrosine and tryptophan a peak separation of more than 100 mV, enabling their screening and identification in mixed solutions, which is essential for the electrochemical analysis of proteins within the proteomics research field. [ABSTRACT FROM AUTHOR]

In this study, a screen-printed electrode (SPE) modified with cobalt oxide nanoparticles (Co3O4 NPs) was used to create an all-solid-state ion-selective electrode used as a potentiometric ion sensor for determining nitrate ion (NO3−) concentrations in aquaculture water. The effects of the Co3O4 NPs on the characterization parameters of the solid-contact nitrate ion-selective electrodes (SC-NO3−-ISEs) were investigated. The morphology, physical properties and analytical performance of the proposed NO3−-ion selective membrane (ISM)/Co3O4 NPs/SPEs were studied by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), potentiometric measurements, and potentiometric water layer tests. Once all conditions were optimized, it was confirmed that the screen-printed electrochemical sensor had high potential stability, anti-interference performance, good reproducibility, and no water layer formation between the selective membrane and the working electrode. The developed NO3−-ISM/Co3O4 NPs/SPE showed a Nernstian slope of −56.78 mV/decade for NO3− detection with a wide range of 10−7–10−2 M and a quick response time of 5.7 s. The sensors were successfully used to measure NO3− concentrations in aquaculture water. Therefore, the electrodes have potential for use in aquaponic nutrient solution applications with precise detection of NO3− in a complicated matrix and can easily be used to monitor other ions in aquaculture water. [ABSTRACT FROM AUTHOR]

A simple, sensitive, cost effective, and reliable enzymatic glucose biosensor was developed and tested. Nitrogen-doped heat-treated graphene oxide nanoribbons (N-htGONR) were used for modification of commercially available screen-printed carbon electrodes (SPCEs), together with MnO2 and glucose oxidase. The resulting sensors were optimized and used to detect glucose in a wide linear range (0.05–5.0 mM) by a simple amperometric method, where the limit of detection was determined to be 0.008 mM. (lifetime), and reproducibility studies were also carried out and yielded favorable results. The sensor was then tested against potential interfering species present in food and beverage samples before its application to real matrix. Spiked beer samples were analyzed (with glucose recovery between 93.5 and 103.5%) to demonstrate the suitability of the developed sensor towards real food and beverage sample applications. [ABSTRACT FROM AUTHOR]

Two analytical methods based on miniaturized electrochemical sensors, voltammetric and amperometric sensors, have been developed for the determination of 6-methyl-2-thiouracil (MTU) in meat consumption samples (beef liver and foie). A multivariate approach has been considered to optimize the experimental procedure including extraction and electrochemical detection. Under optimal conditions and at a typical working potential of 1.55 V (vs Ag pseudo-reference electrode), response is linear in the range 0 to 20 µg L−1 MTU concentration range. The empirical limit of detection is 0.13 µg L−1, lower than the maximum concentration established by legislation. The electrochemical methods have been used to analyze MTU-spiked meat samples, and recovery values varying between 85 and 95% with coefficients of variation <30%. The analytical methods developed with the miniaturized electrochemical sensors can successfully determine the concentration of MTU in real meat samples with high accuracy, being the results obtained similar to those provided by other methods such as UV-Vis spectrophotometry. Finally, the degree of sustainability of the electrochemical sensors-based developed method has been quantified by means of the Analytical Eco-Scale. [ABSTRACT FROM AUTHOR]

Soil tests for plant-available phosphorus (P) are suggested to provide offsite P analysis required to monitor P fertilizer application and reduce P losses to downstream water. However, procedural and cost limitations of current soil phosphate tests have restricted their widespread use and have made them accessible only in laboratories. This study proposes a novel paper-based reagentless electrochemical soil phosphate sensor to extract and detect soil phosphate using an inexpensive and simple approach. In this test, concentrated Mehlich-3 and molybdate ions were impregnated in filter paper, which served as the phosphate extraction and reaction zone, and was followed by electrochemical detection using cyclic voltammetry signals. Soil samples from 22 sampling sites were used to validate this method against inductively coupled plasma optical emission spectroscopy (ICP) soil phosphate tests. Regression and correlation analyses showed a significant relationship between phosphate determinations by ICP and the proposed method, delivering a correlation coefficient, r, of 0.98 and a correlation slope of 1.02. The proposed approach provided a fast, portable, low-cost, accessible, reliable, and single-step test to extract and detect phosphate simultaneously with minimum waste (0.5 mL per sample), which made phosphate characterization possible in the field. [ABSTRACT FROM AUTHOR]

A facile and rapid strategy to generate polypyrrole microcapsules is reported. The strategy is compatible with a vortex mixer and with a microfluidic chip for droplet generation, allowing a > 100-fold reduction in particle size. The sub-micron particle sizes obtained can also be tuned to some extent based on the chip geometry. The capsules can be kept stably in solution and can be transferred onto electrochemical devices. As an application example, we casted the polypyrrole capsules generated onto screen-printed electrodes, leading to a significant increase in their electroactive surface area and capacitance. The electrodes were further modified with glucose dehydrogenase (GDH) to fabricate glucose biosensors. The introduction of polypyrrole microcapsules increased the dynamic range of the glucose sensor to ca. 300% compared with that of the electrode without polypyrrole microcapsules. The resulting glucose sensor is operated at a constant applied potential of 0.20 V vs. Ag/AgCl (3 M KCl) in an air-equilibrated electrolyte. At this potential, the sensor showed a linear range from 1.0 to 9.0 mM glucose with a sensitivity of 3.23 µA cm−2 mM−1 (R2 = 0.993). The limit of detection obtained was 0.09 mM, and the reproducibility was 3.6%. The method allows generating polypyrrole microcapsules without surfactants or organic solvents and may enable new opportunities in the design of biosensors, electronic devices, and molecular delivery. [ABSTRACT FROM AUTHOR]

This paper proposes a deep leaning technique for accurate detection and reliable classification of organic pollutants in water. The pollutants are detected by means of cyclic voltammetry characterizations made by using low-cost disposable screen-printed electrodes. The paper demonstrates the possibility of strongly improving the detection of such platforms by modifying them with nanomaterials. The classification is addressed by using a deep learning approach with convolutional neural networks. To this end, the results of the voltammetry analysis are transformed into equivalent RGB images by means of Gramian angular field transformations. The proposed technique is applied to the detection and classification of hydroquinone and benzoquinone, which are particularly challenging since these two pollutants have a similar electroactivity and thus the voltammetry curves exhibit overlapping peaks. The modification of electrodes by carbon nanotubes improves the sensitivity of a factor of about ×25, whereas the convolution neural network after Gramian transformation correctly classifies 100% of the experiments. [ABSTRACT FROM AUTHOR]

Human Papilloma Virus 16 (HPV 16) is the well-known causative species responsible for triggering cervical cancer. When left undiagnosed and untreated, this disease leads to life-threatening events among the female populace, especially in developing nations where healthcare resources are already being stretched to their limits. Considering various drawbacks of conventional techniques for diagnosing this highly malignant cancer, it becomes imperative to develop miniaturized biosensing platforms which can aid in early detection of cervical cancer for enhanced patient outcomes. The current study reports on the development of an electrochemical biosensor based on reduced graphene oxide (rGO)/DNA hybrid modified flexible carbon screen-printed electrode (CSPE) for the detection of HPV 16. The carbon-coated SPEs were initially coated with rGO followed by probe DNA (PDNA) immobilization. The nanostructure characterization was performed using UV-Vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and X-ray diffraction (XRD) techniques. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to study the electrochemical characterization of the nano-biohybrid sensor surface. The optimization studies and analytical performance were assessed using differential pulse voltammetry (DPV), eventually exhibiting a limit of detection (LoD) ~2 pM. The developed sensor was found to be selective solely to HPV 16 target DNA and exhibited a shelf life of 1 month. The performance of the developed flexible sensor further exhibited a promising response in spiked serum samples, which validates its application in future point-of-care scenarios. [ABSTRACT FROM AUTHOR]

The present work reports the development of screen-printed electrode (SPE) using flexible polyester sheets modified with nanodiamond (ND), Au nanoparticles (AuNPs), and poly(3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS), and its application for the detection of tryptophan in synthetic urine, milk, and dark chocolate samples. The ND/AuNPs/PEDOT:PSS nanocomposite was characterized by cyclic voltammetry, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The proposed ND/AuNPs/PEDOT:PSS-based SPE was applied for the detection of tryptophan using square-wave voltammetry in a linear detection range of 0.8 µmol L−1–18 µmol L−1, with limits of detection (LOD) and quantification (LOQ) of 0.2 µmol L−1 and 0.8 µmol L−1, respectively. The sensor was successfully applied for tryptophan quantification in dark chocolate, milk and synthetic urine where good recovery percentages were obtained. The results obtained from the analysis of interference in the presence of dopamine and caffeine showed that the ND/AuNPs/PEDOT:PSS-based SPE exhibited excellent selectivity toward tryptophan. The findings of this study show that metallic nanoparticles, nanodiamonds and biocompatible conductive composites can be used as a suitable, affordable alternative tool for fast, simple, and low-cost detection of tryptophan in non-invasive testing and analysis of food products. [ABSTRACT FROM AUTHOR]

Sweat lactate levels are closely related to an individual's physiological state and serve as critical indicators for assessing exercise intensity, muscle fatigue, and certain pathological conditions. Screen-printed electrodes (SPEs) offer a promising avenue for the development of low-cost, high-performance wearable devices for electrochemical sweat analysis. The material composition of SPEs significantly impacts their detection sensitivity and stability. In this study, we designed a screen-printed carbon electrode (SPCE) modified with Ti 3 C 2 T x Polydopamine (PDA), and silver nanoparticles (AgNPs) (Ti 3 C 2 T x -PDA-AgNPs) for lactate detection in sweat. The accordion-like structure of Ti 3 C 2 T x provides a large specific surface area and exceptional electrical conductivity. PDA, acting as both a reducing agent and binder, supports the in-situ formation of AgNPs on the Ti 3 C 2 T x nanosheets. These AgNPs prevent the restacking of Ti 3 C 2 T x layers, further improving conductivity. The sensor exhibited sensitivities of 0.145 μA mM−1, with limit of detection (LOD) of 0.181 mM (S/N = 3) in phosphate-buffered saline (PBS), meeting the requirements for for sweat lactate detection. The sensor was integrated into a wearable micro-electrochemical platform paired with a custom Android application for real-time sweat analysis. Testing on human sweat demonstrated the platform's potential for practical fitness monitoring and healthcare diagnostics applications. [ABSTRACT FROM AUTHOR]

Accurate determination of dopamine (DA) and uric acid (UA) in biological samples is crucial in diagnosing neurodegenerative disorders and gout, respectively. Here we report a highly sensitive and inexpensive, flexible screen-printed sensor for determining DA and UA in sweat samples. Beta-cyclodextrin-based (βCD) composite gel with reduced graphene oxide (rGO) was synthesized by self-polymerization of βCD at an optimum ratio of "good" and "poor solvent". Multiwall carbon nanotubes (MWCNTs) were incorporated into the composite as a conductive filler. The MWCNTs-βCD-rGO gel provides selective biorecognition of DA and UA at the electrode surface through guest-host interaction. The gels were characterized by XRD, TGA, FTIR, UV–Vis, 1H NMR, FESEM, XPS and optical microscopy. The flexible printed sensor showed linear DA detection in the range 0.25 to 16 μM with a correlation coefficient (R2) of 0.9890, limit of detection (LoD) of 0.08 μM and sensitivity of 3.63 μA μM−1 cm−2. Similarly, UA calibration showed linear detection from 50 to 700 μM with a R2 value of 0.9860, LoD of 0.078 μM and sensitivity of 0.118 μA μM−1 cm−2. The SPE/MWCNTs-βCD-rGOsensor showed simultaneous determination of DA and UA from exercise induced sweat samples. The proposed sensor demonstrated excellent repeatability and satisfactory recoveries in human sweat. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Enhancing Electroanalytical Performance: Selecting Optimal Carbon Inks for Screen-Printed Electrodes. • Characterization revealed differences in (electro)chemical properties of electrodes. • The critical role of selecting suitable inks for diverse electroanalytical analyses. • Variations in ink formulation led to differences in the sensing abilities. • Enhanced selective reductive sensing due to an ion-exchange polymer layer. Carbon-based screen-printed electrodes (SPEs) are extensively employed in electrochemistry due to their reproducibility, low-cost production, disposability and versatility. It is commonly accepted that batch to batch variations may occur due to variations in the ink formulation or the use of a different ink to print the electrodes. In this paper, three different commercial carbon-based inks (DuPont, Loctite and SunChemical) were used to manufacture SPEs, referred to respectively as Dup-SPE, Loc-SPE and Sun-SPE, using a semi-automated screen-printing technology. This study focuses on evaluating the quality, characteristics and electrochemical performance of the fabricated SPEs. Furthermore, the study aimed to investigate potential correlations between the ink composition and the nature of different target molecules, as well as their electroanalytical responses. Specifically, phenolic compounds and cocaine cutting agents are tested in alkaline conditions, while benzodiazepines and cephalosporine antibiotics are investigated in acidic media using square wave voltammetry (SWV). This aims to extract insights for the proper selection of inks and SPEs in both conditions. Additionally, a scan rate study of cephalosporine antibiotics using linear sweep voltammetry (LSV) is performed confirming the ion-exchange polymer layer on the electrode surface of Loc-SPE, which impact surface and electrochemical properties, leading to drawbacks in alkaline SWV sensing, but strategic benefits in reductive sensing resulting in an enhanced selective detection of specific targets. The insights on ink-specific influences on the surface and electrochemical properties of the SPEs obtained, may be useful for facilitating the electrode selection in diverse electrochemical applications, emphasizing the critical role of ink composition in achieving desired sensing capabilities. [ABSTRACT FROM AUTHOR]

The availability of new surface enhanced Raman scattering (SERS) substrates is essential to develop quantitative analytical methods. Electrochemistry is an easy, fast and reproducible methodology to prepare SERS substrates on screen-printed electrodes (SPEs). This work proposes new SPEs based on a three-electrode system all made of silver. Using the same ink for the whole electrode system facilitates the fabrication process, reduces production costs, and leads to excellent analytical performance. The results showed that Raman enhancement depends strongly on the type of silver ink. To demonstrate the capabilities of the new electrodes developed, 4-aminosalicylic acid was determined in complex matrices and in the presence of strong interfering compounds such as salicylic acid and acetylsalicylic acid. The proposed analytical method is based on the electrochemical surface oxidation enhanced Raman scattering (EC-SOERS) strategy. AgCl nanocrystals are generated on the working electrode surface, which amplify the Raman signal of 4-aminosalicylic acid. Good figures of merit were obtained both in the absence and in the presence of the interfering compounds, achieving a correct estimation of a 4-aminosalicylic test sample in complex matrices. The new SPEs have been demonstrated to be very sensitive and reproducible which, together to the high specificity of the Raman signal, makes this methodology very attractive for chemical analysis. [Display omitted] • New screen-printed electrodes for EC-SOERS analysis. • Three electrode system based on silver. • Raman enhancement depends on the type of silver ink. • Determination of 4-aminosalicylic acid in complex matrices. [ABSTRACT FROM AUTHOR]