Search Results (86)

Field-effect transistor (FET) biosensors enable label-free and real-time electrical transduction; however, their practical deployment is often constrained by the need for bulky benchtop instrumentation to provide stable biasing, low-noise readout, and data processing. Here, we report a portable extended-gate FET (EG-FET) integrated sensing system that consolidates the sensing interface, analog front-end conditioning, embedded acquisition/control, and user-side visualization into an end-to-end prototype suitable for on-site operation. The system couples a screen-printed Au extended-gate electrode to a MOSFET and employs a low-noise signal-conditioning chain with microcontroller-based digitization and real-time data streaming to a host graphical interface. As a proof-of-concept, enterohemorrhagic Escherichia coli O157:H7 was selected as the target. A bacteria-specific immunosensing interface was constructed on the Au extended gate via covalent immobilization of monoclonal antibodies. Measurements in buffered samples produced concentration-dependent current responses, and a linear calibration was experimentally validated over 10⁴–10¹⁰ CFU/mL. In specificity evaluation against three common foodborne pathogens (Staphylococcus aureus, Salmonella typhimurium, and Listeria monocytogenes), the sensor showed a maximum interference response of only 13% relative to the target signal (ΔI/ΔImax) with statistical significance (p < 0.001). Our work establishes a practical hardware–software architecture that mitigates reliance on benchtop instruments and provides a scalable route toward portable EG-FET sensing for rapid, point-of-need detection of foodborne pathogens and other biomarkers. Full article

Reliable models of the lung environment are important for research on inhalation products, drug delivery, and how aerosols interact with tissue. pH fluctuations frequently accompany real physiological processes in pulmonary environments, so monitoring pH changes in lung-on-a-chip devices is of considerable relevance. Presented here are flexible, miniaturized, inkjet-printed pH sensors that have been developed with the aim of integration into lung-on-a-chip systems. Different types of functional pH-sensitive materials were tested: hydrogen-selective plasticized PVC membranes and polyaniline (both electrodeposited and dropcast). Their deposition and performance were evaluated on different flexible conducting substrates, including screen-printed carbon electrodes (SPE) and inkjet-printed graphene electrodes (IJP-Gr). Finally, a biocompatible dropcast polyaniline-modified IJP was selected and paired with an inkjet-printed Ag/AgCl quasireference electrode. The printed potentiometric device showed Nernstian sensitivity (58.8 mV/pH) with good reproducibility, reversibility, and potential stability. The optimized system was integrated with a developed lung-on-a-chip model with an electrospun polycaprolactone membrane and alginate, simulating the alveolar barrier and the natural mucosal environment, respectively. The permeability of the system was studied by monitoring the pH changes upon the introduction of a 10 wt.% acetic acid aerosol. Overall, the presented approach shows that electrospun-hydrogel materials together with integrated microsensors can help create improved models for studying aerosol transport, diffusion, and chemically changing environments that are relevant for inhalation therapy and respiratory research. These results show that our system can combine mechanical behavior with chemical sensing in one platform, which may be useful for future development of lung-on-a-chip technologies. Full article

A multimodal sensor was developed to record dissolved oxygen, L*a*b* colour, temperature, and pH. This work builds on an existing model that correlates blood oxygen saturation with L*a*b* colour values. An L*a*b* colour sensor was constructed from an RGB sensor and validated against a commercial colourimeter. Sensor performance was confirmed using reference colours. Dissolved oxygen was measured with a screen-printed electrode and an analogue-to-digital converter. The results highlight potential for future optical determination of oxygen saturation, combined with electrochemical measurement of oxygen partial pressure, and compensation for pH and temperature. Full article

This study presents the design and application of an electrochemical sensor for selective detection of lead ions (Pb²⁺) based on ionophore-modified raspberry-like Fe₃O₄–Au nanostructures. The material was engineered with a magnetic Fe₃O₄ core, coated with polyethyleneimine (PEI) to facilitate nucleation, and subsequently decorated with Au nanoparticles, providing a raspberry-like (Fe₃O₄@PEI@AuNPs) nanostructure with high surface area and excellent electrochemical conductivity. Surface functionalization with Lead Ionophore IV (ionophore thiol) introduced Pb²⁺-selective binding sites, whose presence and structural evolution were verified by TEM and Raman spectroscopy. The Fe₃O₄ core endowed strong magnetic properties, enabling facile manipulation and immobilization onto screen-printed carbon electrodes (SPCEs) via physical adsorption, while the Au nanoparticles enhanced electron transfer, supplied thiol-binding sites for stable ionophore anchoring, and increased the effective electroactive surface area. Operational conditions were systematically optimized, with acetate buffer (HAc/NaAc, pH 5.7) and chronoamperometric preconcentration (CA) at −1.0 V for 175 s identified as optimal for differential pulse voltammetry (DPV) measurements. Under these conditions, the sensor exhibited a linear response toward Pb²⁺ from 0.025 mM to 2.00 mM with superior sensitivity and reproducibility compared to conventional AuNP-modified SPCEs. Furthermore, the ionophore-modified Fe₃O₄–Au nanostructure-based sensor demonstrated outstanding selectivity for Pb²⁺ over competing heavy metal ions (Cd²⁺, Hg²⁺, Cr³⁺), owing to the specific coordination interaction of Lead Ionophore IV with target ions. These findings highlight the potential of raspberry-like Fe₃O₄@PEI@AuNP nanostructures as a robust and efficient electrochemical platform for the sensitive and selective detection of toxic heavy metal ions. Full article

Acute Myocardial Infarction (AMI) is a critical cardiac condition that poses a substantial threat to myocardial function. Expedient diagnosis of AMI is paramount and relies on serological assays for rapid and accurate quantification of relevant biomarkers. Electrochemical sensors have emerged as promising candidates for this application, owing to their accessibility, operational simplicity, and high specificity. In this study, we developed a paper-based electrochemical immunosensor to detect cardiac troponin I in serum and saliva specimens. The electrode was fabricated using screen-printing technology with photographic paper as the substrate, employing graphite-based ink, nail polish, and acetone as the solvent. A quasi-reference electrode was constructed using silver powder-based ink, nail polish, and acetone. The immunosensor was prepared by modifying the working electrode with gold nanoparticles (AuNP) functionalized with cardiac troponin I antibodies (anti-cTnI) and bovine serum albumin (BSA). This modified electrode was subsequently used to detect the troponin I antigen. The analyses were performed in 0.1 mol L⁻¹ phosphate buffer medium, pH 7.00, in the presence of 5.0 mmol L⁻¹ of the potassium ferrocyanide probe. The immunosensor exhibited a sensitivity of 0.006 µA/fg mL⁻¹, a limit of detection of 9.83 fg mL⁻¹, and a limit of quantification of 32.79 fg mL⁻¹. Specificity studies conducted in the presence of other macromolecules demonstrated minimal interference, with relative standard deviations (RSD) below 5.00%, indicating a specific interaction with troponin I. Furthermore, the immunosensor demonstrated excellent reproducibility and stability. Upon application to serum and saliva samples, the immunosensor presented recoveries of approximately 99–105%, suggesting its potential applicability in clinical analyses. Full article

Electrochemical aptasensors have been successfully applied in a number of fields, including food safety, environmental monitoring, and the health sector. They offer a robust and environmentally friendly alternative to antibody-based detection, with the added benefits of flexible design, high chemical and thermal stability, and low immunogenicity. In this work, we present an electrochemical aptasensor based on a semiconducting mesoporous TiO₂:Mn working electrode (WE) for the sensitive detection of tetracycline (TET). The TiO₂:Mn electrodes were fabricated using a scalable screen-printing process, providing a cost-efficient and reproducible platform for sensor development. Specifically, a 5 μM solution of the DNA aptamer with the sequence 5′-CCC CCG GCA GGC CAC GGC TTG GGTTGG TCC CAC TGC GCG-3′ was utilized for the detection of tetracycline (TET) in spiked aqueous samples, across a concentration range of 0.3 to 25.0 ng/mL. Detection was performed via differential pulse voltammetry (DPV) using a Pt wire cathode. The buffer used in the experiment was Tris–HCl (20 mM, pH 7.6), 100 mM of NaCl, MgCl₂ (2 mM), KCl (5 mM), and CaCl₂ (1 mM). The limit of detection (LOD) was calculated to be approximately 1 ng/mL. Full article

In this study, multilayer biopolymer films composed of furcellaran, chitosan, and gelatin were incorporated with aqueous extracts of Lavandula angustifolia and Clitoria ternatea. These materials were engineered as sustainable, biodegradable substrates suitable for screen-printing applications. The primary objective was to enhance the films’ functional properties, including their mechanical integrity, barrier performance, and printability, thereby broadening their potential utility in environmentally responsible technological applications. FTIR and UV–Vis analyses confirmed the presence of functional groups associated with the contained plant extracts and showed significantly improved UV-blocking properties. Thermal and mechanical tests showed that the films maintained good structural integrity, and only high extract concentrations slightly affected tensile strength. Importantly, the materials exhibited gradual but limited thermal shrinkage (<3.7%) up to 130 °C, while maintaining their multilayer structure. Water-related evaluations, including WCA, solubility, pH, and conductivity, confirmed their biodegradability in aqueous environments without exceeding ecotoxicological thresholds. Microbiological tests demonstrated selective antimicrobial activity. The key novelty of this work is the evaluation of these active multilayer biopolymer films as screen-printing substrates. This is the first report in which screen-printing compatibility with active multilayer biopolymer systems is presented, highlighting their potential in sustainable packaging that integrates biodegradable matrices with printed sensor layers. Full article

In this work, we designed a novel and simple electrochemical approach for the determination of daidzein antioxidant (Dz) in peanut oil samples. The Dz determination was based on anodic stripping linear voltammetry using screen-printed graphene electrodes (SPGEs) activated in acidic media, where a strong adsorption of Dz on activated graphene was obtained. In this regard, electroanalytical parameters such as the scan rate, supporting electrolyte, pH, and accumulation step were optimized to ensure the best conditions for the selective and sensitive Dz quantification. The electrochemical method developed for the determination of Dz exhibits a linear behavior of the anodic peak current in the concentration range from 0.05 to 1 μM, with a limit of detection of 0.012 μM. The electrochemical sensor demonstrated to the capacity to quantify Dz in peanut oil samples at low concentrations without the necessity of an extensive sample pretreatment. Therefore, the electrochemical method proposed can be used as a new portable analytical tool for the in situ quality control of peanut oil samples. Full article

The rapid growth of the dairy sector requires advanced monitoring tools to ensure sustainable practices that benefit the environment, economy, and human health. Current monitoring devices often lack multi-parametric capabilities, limiting their ability to provide comprehensive data on critical chemical and biochemical parameters. To address this challenge, this work presented the integration of a real-time multi-parametric device with sensors for pH, temperature, nitrate, and nitrite, providing a comprehensive solution to dairy cattle health monitoring. This solution included an electrochemical platform, Portable Unit for Lab-on-Site Electrochemistry (PULSE), and an application for data processing and display. In-house fabricated flexible gold-printed electrodes demonstrated accurate detection of nitrite and nitrate when integrated with the PULSE, achieving sensitivities of 6.32 $\mathsf{\mu }$A/ppm/${\mathrm{cm}}^2$ in artificial interstitial fluid and 1.92 $\mathsf{\mu }$A/ppm/${\mathrm{cm}}^2$ in phosphate buffered saline, respectively. The PULSE achieved 65.83% and 58.3% lower limits of detection in phosphate buffered saline than a benchtop potentiostat, for nitrate and nitrite, respectively, along with a 24.5% increase in nitrite sensitivity, enhancing its ability to detect lower analyte concentrations. pH sensing was carried out with a commercial screen-printed electrode coated with a layer of iridium oxide. The pH was tested in ruminal complex fluid, obtaining a pH sensitivity of −59.63 mV/pH and an accuracy of 98.9%. These findings highlighted the potential of this technology as an effective tool for dairy cattle health monitoring and its deployment in real-world scenarios. Full article

The assessment of fish welfare is crucial to prevent economic losses in aquaculture and ensure reliable results in research. A quick, non-invasive device to measure cortisol levels in fish farm water facilitates welfare evaluation and corrective actions when compromised. To address this need, an innovative sensor was developed using screen-printed carbon electrodes (SPCEs) functionalized with reduced graphene oxide/Prussian blue nanocubes (rGO/PBNCs) for direct selective detection of cortisol. A molecularly imprinted polymer (MIP) was synthesized on rGO/PBNCs/SPCEs by electropolymerization (ELP) of pyrrole in the presence of cortisol. The polymerization solution was prepared by adding cortisol (5 mM) and pyrrole (0.3 M) to a DMF/PBS (1:4) solution (pH 7.4). Following ELP, the electrodes were washed with PBS, and pyrrole overoxidation was used to extract cortisol from the polymer matrix. For comparison purposes, a non-imprinted polymer (NIP) was also fabricated. The electrodes were characterized using scanning electron microscopy (SEM) and Raman spectroscopy to assess their morphological and chemical features. Under optimized conditions, the sensor showed a linear range from 0.1 nM to 0.1 mM in artificial saltwater. This sensor combines simplicity and affordability while providing reliable detection of chemical and biological compounds. Full article

Vitamin C, an antioxidant in most fruits and vegetables, is highly sensitive to heat, pH, metals, light, and oxidation, making it a key marker for nutrient degradation in thermal processing. Research aimed at improving processing methods to maximize vitamin C retention is usually limited to expensive laboratory equipment, which does not reflect real-world conditions in the food industry. On the other hand, traditional methods are not suitable for on-line monitoring. This paper proposes bridging the gap in liquid food processing with a voltammetric sensor based on poly(3,4-ethylenedioxythiophene)-modified screen-printed carbon electrodes. The sensor showed excellent repeatability, with intra-sensor RSD below 5% and inter-sensor RSD below 10% at 250 mg/L of ascorbic acid. Detection and quantification limits were 0.7 and 2.1 mg/L, respectively. Trueness assessment in commercial orange juice with a declared vitamin C content yielded a recovery rate of 94 ± 1%. Selectivity tests with citric acid at concentrations equal to and 20 times higher than that of ascorbic acid showed no significant interference. Shelf-life studies confirmed the stability of the sensor for at least two months. This nanocomposite-based approach balances performance and cost with simple preparation, affordable materials, and a stable coating that allows long-term storage in uncontrolled environments. Full article

Water is critical for the sustenance of life and pH is an important parameter in monitoring its quality. Solid-state pH sensors provide a worthy alternative to glass-based electrodes due to many advantages such as low cost, longer shelf life, simpler manufacturing, easier operation, miniaturization, and integration into electronic systems. Cobalt oxides are relatively cheaper and more abundantly available than ruthenium oxide. This work aims to reduce the environmental impact of screen-printed pH sensors by mixing Co₃O₄ and RuO₂ in five molar proportions (30%, 40%, 50%, 60%, and 70%) and investigating the influence of oxide proportions on the pH-sensing properties of the resulting composition using potentiometric characterization, scanning electron microscopy, X-ray diffraction, surface profilometry, and electron dispersive spectroscopy. Although all the developed compositions showed super- or near-Nernstian sensitivity with good linearity, the sensors based on 50 mol% Co₃O₄-50 mol% RuO₂ were the best due to superior sensitivity, selectivity, and stability. Fabricated sensors were applied in real-life environmental, municipal, and commercial water samples, including those from various depths in the Baltic Sea, and were found to be accurate in comparison to a glass electrode. Full article

The application of membrane sensors for the detection and quantification of pharmaceutical environmental contaminants has become a significant goal in recent years. Due to the widespread application of levofloxacin hemihydrate (LEVO) in medicine, its occurrence in the environment, especially in surface water bodies like rivers, is quite likely. Extended exposure of river water to sunlight and the photo-degradability of LEVO may facilitate its photo-degradation. To measure LEVO in the presence of its principal photo-degradants, two sensitive and selective membrane electrodes were designed. A polyvinyl chloride electrode (PVCE) and a screen-printed electrode (SPE) were constructed for the selective analysis of the investigated drug. Phosphomolybdic acid was used to prepare a lipophilic ion pair with the studied drug. All test parameters were optimized to achieve the best electrochemical performance. The electrodes demonstrated a linear range from 1 × 10⁻⁶ M to 1 × 10⁻² M. The PVCE and SPE demonstrated slopes of 55.80 ± 0.70 mV/decade and 56.90 ± 0.50 mV/decade, respectively. The aforementioned sensors demonstrated satisfactory performance within a pH range of 3.0 to 5.0. The fabricated sensors were successfully utilized to accurately quantify LEVO in the presence of its primary photo-degradants. The membranes were effectively utilized to measure LEVO in river water samples without requiring pre-treatment processes. Full article

Bisphenol A (BPA) is a commonly synthetic chemical mainly used in producing plastic items. It is an endocrine-disrupting compound that causes irreversible health and environmental damage. Developing a simple method for BPA effective quantitative monitoring is emergently necessary. Herein, a novel electrochemical sensor for BPA detection based on [(5,10,15,20-tetrakis(p-bromophenyl) porphyrinato] cadmium (II) [(CdTBrPP)] and gold nanoparticle (AuNPs)-modified screen-printed carbon electrode (SPCE) was elaborated. CdTBrPP was synthesized and then characterized with Ultraviolet–Visible Spectroscopy (UV/vis), Infrared Spectroscopy (IR), and Proton Nuclear Magnetic Resonance Spectroscopy (¹H NMR) to confirm its successful synthesis. After drop-coating AuNPs and CdTBrPP on the SPCE, the sensor performance was evaluated using square wave voltammetry (SWV), a linear response in a concentration range from 10⁻¹¹ M to 10⁻² M, with a low detection limit (LOD) of 9.5 pM. The CdTBrPP/AuNPs/SPCE sensor demonstrates a high selectivity and reproducibility, making it a promising candidate for developing a low-cost water-monitoring system for detecting BPA. Additionally, the proposed sensor effectively detected BPA in both tap and mineral water samples. Full article

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. Full article