Search Results (1,842)

Electrochemical impedance spectroscopy (EIS) is a highly versatile electrochemical technique capable of discretizing each electrochemical parameter in complex systems by employing a broad frequency spectrum. When EIS is employed in (bio)sensing applications, the electrochemical parameters are usually fitted into a relatively limited equivalent circuit model regardless of the system at hand. This work thoroughly discusses the meaning of each physical parameter in the Randles circuit, the most common equivalent circuit to model (bio)sensing systems based on EIS transduction. Additionally, it pinpoints the most suitable modifications to the Randles circuit for modern-day electrodes, where coatings of non-biological and/or biological materials can radically impact the measured impedance compared to that of unmodified electrodes. The discussion is supported by simulations that clearly exhibit the effect of each examined parameter, providing guidance for experimentalists to improve the accuracy of their work. Full article

Most biomarkers exhibit abnormal expression in more than one disease, making conventional single-biomarker detection strategies prone to false-negative results. Detecting multiple biomarkers associated with a single disease can therefore substantially improve diagnostic accuracy. Accordingly, recent research has focused on precise multiplex detection, leading to the development of sensors employing various readout methods, including electrochemical, fluorescence, Raman, and colorimetric approaches. This review focuses on optical sensing applications, such as fluorescence, Raman spectroscopy, and colorimetry, which offer rapid and straightforward detection and are well suited for point-of-care testing (POCT). These optical sensors exploit nanoscale phenomena derived from the intrinsic properties of nanomaterials, including metal-enhanced fluorescence (MEF), Förster resonance energy transfer (FRET), and surface-enhanced Raman scattering (SERS), which can be tailored through modifications in material type and structure. We summarize the types and properties of commonly used nanomaterials, including plasmonic and carbon-based nanoparticles, and provide a comprehensive overview of recent advances in multiplex biomarker detection. Furthermore, we address the potential of these nanosensors for clinical translation and POCT applications, highlighting their relevance for next-generation disease diagnostic platforms. Full article

SPCEs are crucial for electrochemical sensing because of their portability, low cost, disposability, and ease of mass production. This study details their manufacture, surface modifications, electrochemical characterization, and use in chemical and biosensing. SPCEs integrate working, reference, and counter electrodes on PVC or polyester substrates for compact sensor design. Surface modifications, such as plasma treatment (O₂, Ar), nanomaterial addition (AuNPs, GO, CNTs), polymer coatings, and MIPs, enhance performance. These changes improve sensitivity, selectivity, stability, and electron transport. Electrochemical methods such as CV, DPV, SWV, and EIS detect analytes, including biomolecules (glucose, dopamine, and pathogens) and heavy metals (Pb²⁺, As³⁺). Their applications include healthcare diagnostics, environmental monitoring, and food safety. Modified SPCEs enable rapid on-site analysis and offer strong potential to transform our understanding of the physical world. Full article

Nickel oxide (NiO), a wide bandgap p-type semiconductor, has emerged as a promising material for electrochemical sensing owing to its excellent redox properties, chemical stability, and facile synthesis. Its strong electrocatalytic activity enables effective detection of diverse analytes, including glucose, hydrogen peroxide, environmental pollutants, and biomolecules. Advances in nanotechnology have enabled the development of NiO-based nanostructures such as nanoparticles, nanowires, and nanoflakes, which offer enhanced surface area and improved electron transfer. Integration with conductive materials like graphene, carbon nanotubes, and metal–organic frameworks (MOFs) further enhance sensor performance through synergistic effects. Innovations in synthesis techniques, including hydrothermal, sol–gel, and green approaches, have expanded the applicability of NiO in next-generation sensing platforms. This review summarizes recent progress in the structural engineering, composite formation, and electrochemical mechanisms of NiO-based materials for advanced electrochemical sensing applications. Full article

Electrochemical sensors have emerged as powerful analytical tools for the detection of anti-inflammatory and antibiotic drugs due to their high sensitivity, rapid response, and cost-effectiveness compared to conventional chromatographic and spectrophotometric methods. This review highlights recent advances in electrode materials, surface modification strategies, and signal amplification approaches for quantifying nonsteroidal anti-inflammatory drugs (NSAIDs) and various antibiotic classes, including sulfonamides, tetracyclines, macrolides, and quinolones. Particular attention is given to nanostructured carbon-based materials, metal nanoparticles, and polymer composites that enhance electron transfer, improve selectivity, and lower limits of detection (LODs). The analytical performance of different electrochemical techniques such as cyclic voltammetry, differential pulse voltammetry, and square-wave voltammetry is critically compared across various drug targets. Trends indicate that hybrid nanomaterial-modified electrodes consistently achieve sub-micromolar detection limits in biological and environmental samples, offering potential for point-of-care diagnostics and environmental monitoring. Current challenges include improving sensor stability, mitigating fouling effects, and ensuring reproducibility in complex matrices. Future research should focus on integrated, miniaturized sensing platforms capable of multiplex detection, paving the way for rapid, portable, and sustainable analytical solutions in pharmaceutical and biomedical applications. Full article

Reversible addition–fragmentation chain-transfer (RAFT) polymerization has become an efficient method in the field of polymer synthesis. Recently, the RAFT polymerization technique has been successfully used to prepare functional materials and develop various sensing methods used in different scenarios. The polymerization reaction can be initiated by thermal, electrochemical, photochemical, enzymatic, and mechanical stimulation. More interestingly, RAFT polymerization can be performed in situ by recruiting a large number of signal tags at the solid interface to amplify the signals. In this review, we addressed the latest achievements in the preparation of sensing materials and the design of different sensors based on the RAFT polymerization technique for sensing ions and small molecules and bioimaging of tumor cells and viruses. Then, electrochemical and optical biosensors through the signal amplification of the RAFT polymerization method were summarized. This work could provide inspiration for researchers to prepare fascinating sensing materials and develop novel detection technologies applied in various fields. Full article

Lactate is a vital biomarker for disease diagnosis and healthcare management. With the development of wearable sensors, by analyzing biofluids, such as sweat, saliva, and tears, it is possible to implement the in situ detection of lactate, which could provide clinical-grade data for early disease detection and personalized healthcare. Among them, non-enzymatic lactate electrochemical sensors (NELESs) are on the rise due to their quick response, are easily miniaturized, and have the ability to overcome the intrinsic disadvantages of enzymatic sensors. Compared with enzyme-based lactate sensors, NELESs could simplify the electrode preparation process, reduce the cost, and improve the sensing stability and service life. In this review, we introduce the significance of the real-time monitoring of lactate and highlight recent advances in wearable electrochemical sensors toward continuous lactate analysis in biofluids. In particular, metal nanomaterials have great potential in constructing NELESs due to their unique physical and chemical properties, which can be divided into four categories: bimetallic nanomaterials, transition metal chalcogenides (TMC), metal oxides, and layered double hydroxides. We discuss recent advances of these non-enzymatic lactate oxidation materials in detail, and provide some insights for the further development of NELESs through a comprehensive analysis. Full article

Molecularly imprinted polymer (MIP) biosensors offer an attractive strategy for selective biomolecule detection, yet imprinting proteins with structural fidelity remains a major challenge. In this work, we present a rationally designed electrochemical biosensor for matrix metal-loproteinase-8 (MMP-8), a key salivary biomarker of periodontal disease. By integrating graphene oxide (GO) with electropolymerized poly(eriochrome black T, EBT) films on screen-printed carbon electrodes, the partially reduced GO interface enhanced electrical conductivity and facilitated the formation of well-defined poly(EBT) films with re-designed polymerization route, while template extraction generated artificial antibody-like sites capable of specific protein binding. The MIP-based electrodes were comprehensively validated through morphological, spectroscopic, and electrochemical analyses, demonstrating stable and selective recognition of MMP-8 against structurally similar interferents. Complementary density functional theory (DFT) modeling revealed energetically favorable interactions between the EBT monomer and catalytic residues of MMP-8, providing molecular-level insights into imprinting specificity. These experimental and computational findings highlight the importance of rational monomer selection and nanomaterial-assisted polymerization in achieving selective protein imprinting. This work presents a systematic approach that integrates electrochemical engineering, nanomaterial interfaces, and computational validation to address long-standing challenges in protein-based MIP biosensors. By bridging molecular design with practical sensing performance, this study advances the translational potential of MIP-based electrochemical biosensors for point-of-care applications. Full article

A compact electrochemical sensor module for pH detection was developed for potential integration into specialized devices used for live cell or tissue incubation, for applications in highly parallelized cell culture analysis, by incorporating Organ-on-Chip devices. This research focuses on the deposition, structural and chemical analysis, and functional characterization of different titanium-oxide layers with various compositions as potentially sensitive materials for pH sensing applications. The titanium-oxide layers were deposited using vacuum sputtering and atomic layer deposition at 100 °C and 300 °C, respectively. Transmission electron microscopy and X-ray photoelectron spectroscopy were utilized to determine the specific composition and structure of different titanium-oxide layers. These TiO_x-functionalized electrodes were connected to the application-specific analog front-end chip of the low-power readout circuit for precise evaluation. The pH sensitivity of the differently modified electrodes, employing various TiO_x materials, was evaluated using pH calibration solutions ranging from pH 6 to 8. Among the various deposition solutions, such as sputtering or high-temperature atomic layer deposition, the TiO_x layer deposited using low-temperature atomic layer deposition proved more suitable for pH sensing applications, with a sensitivity of 54.8–56.7 mV/pH, which closely approximates the Nernstian response. Full article

The development of cost-effective and highly sensitive hydrogen peroxide (H₂O₂) biosensors with robust stability is critical due to the pivotal role of H₂O₂ in biological processes and its broad utility across various applications. In this work, porous ceria hollow microspheres (CeO₂-phm) were synthesized using a solvothermal synthesis method and employed in the construction of an electrochemical biosensor for H₂O₂ detection. The resulting CeO₂-phm featured a uniform pore size centered at 3.4 nm and a high specific surface area of 168.6 m²/g. These structural attributes contribute to an increased number of active catalytic sites and promote efficient electrolyte penetration and charge transport, thereby enhancing its electrochemical sensing performance. When integrated into screen-printed carbon electrodes (CeO₂-phm/cMWCNTs/SPCE), the CeO₂-phm/cMWCNTs/SPCE-based biosensor exhibited a wide linear detection range from 0.5 to 450 μM, a low detection limit of 0.017 μM, and a high sensitivity of 2070.9 and 2161.6 μA·mM⁻¹·cm⁻²—surpassing the performance of many previously reported H₂O₂ sensors. In addition, the CeO₂-phm/cMWCNTs/SPCE-based biosensor possesses excellent anti-interference performance, repeatability, reproducibility, and stability. Its effectiveness was further validated through successful application in real sample analysis. Hence, CeO₂-phm with solvothermal synthesis has great potential applications as a sensing material for the quantitative determination of H₂O₂. Full article

This work introduces 2-(azulen-1-yldiazenyl)-5-(thiophen-2-yl)-1,3,4-thiadiazole (L) as a functional monomer capable of forming stable, redox-active films with high affinity for lead in aqueous solutions. L was synthesized and characterized using physical chemical methods and electrochemistry. Polymer films of L were prepared through oxidative electro polymerization on glassy carbon electrodes in L solutions in 0.1 M TBAP in acetonitrile. They were characterized through electrochemistry. The surface of chemically modified electrodes (CMEs) prepared through controlled potential electrolysis (CPE) at variable concentrations, potentials, and electric charges was characterized through scanning electron spectroscopy, atomic force microscopy, and Raman spectroscopy, which confirmed the films’ formation. Electrochemical sensing of the films deposited on these CMEs was tested with respect to heavy metal (HM) ion analysis in aqueous solutions to obtain sensors for HMs. The obtained CMEs presented the best characteristics for the recognition of Pb among the investigated HMs (Cd, Pb, Cu, and Hg). Calibration curves were obtained for the analysis of Pb(II) in aqueous solutions, which allowed for the estimation of a good detection limit of this cation (<10⁻⁸ M) for non-optimized CMEs. The resulting CMEs show promise for deployment in portable environmental monitoring systems, with implications for public health protection and environmental safety. Full article

The rapid development of nanotechnology has significantly transformed the design and performance of glucose biosensors, leading to enhanced sensitivity, selectivity, and real-time monitoring capabilities. This review highlights recent advances in glucose-sensing platforms facilitated by nanomaterials, including metal and metal oxide nanoparticles, carbon-based nanostructures, two-dimensional materials, and metal–organic frameworks (MOFs). The integration of these nanoscale materials into electrochemical, optical, and wearable biosensors has addressed longstanding challenges associated with enzyme stability, detection limits, and invasiveness. Special emphasis is placed on non-enzymatic glucose sensors, flexible and wearable devices, and hybrid nanocomposite systems. The multifunctional properties of nanomaterials, such as large surface area, excellent conductivity, and biocompatibility, have enabled the development of next-generation sensors for clinical, point-of-care, and personal healthcare applications. The review also discusses emerging trends such as biodegradable nanosensors, AI-integrated platforms, and smart textiles, which are poised to drive the future of glucose monitoring toward more sustainable and personalized healthcare solutions. Full article

Monitoring contamination in soil and food systems remains vital for ensuring environmental and public health, particularly in agriculture-intensive regions. Existing laboratory-based techniques are often time-consuming, equipment-dependent, and impractical for rapid on-site screening. In this study, we present a portable, non-faradaic electrochemical impedance-based sensing platform capable of simultaneously detecting Salmonella Typhimurium (S. Typhi) and Aflatoxin B1 in spiked soil run-off samples. The system employs ZnO-coated electrodes functionalized with crosslinker for covalent antibody immobilization, facilitating selective, label-free detection using just 5 µL of sample. The platform achieves a detection limit of 1 CFU/mL for S. Typhi over a linear range of 10–10⁵ CFU/mL and 0.001 ng/mL for Aflatoxin B1 across a dynamic range of 0.01–40.96 ng/mL. Impedance measurements captured with a handheld potentiostat were strongly correlated with benchtop results (R² > 0.95), validating its reliability in field settings. The duplex sensor demonstrates high precision with recovery rates above 80% and coefficient of variation below 15% in spiked samples. Furthermore, machine learning classification of safe versus contaminated samples yielded an ROC-AUC > 0.8, enhancing its decision-making capability. This duplex sensing platform offers a robust, user-friendly solution for real-time environmental and food safety surveillance. Full article

Recent advances in computational tools, particularly machine learning (ML), deep learning (DL), and structure-based modeling, are transforming aptamer research by accelerating discovery and enhancing biosensor development. This review synthesizes progress in predictive algorithms that model aptamer–target interactions, guide in silico sequence optimization, and streamline design workflows for both laboratory and point-of-care diagnostic platforms. We examine how these approaches improve key aspects of aptasensor development, such as aptamer selection, sensing surface immobilization, signal transduction, and molecular architecture, which contribute to greater sensitivity, specificity, and real-time diagnostic capabilities. Particular attention is given to illuminating the technological and experimental advances in structure-switching aptamers, dual-aptamer systems, and applications in electrochemical, optical, and lateral flow platforms. We also discuss current challenges such as the standardization of datasets and interpretability of ML models and highlight future directions that will support the translation of aptamer-based biosensors into scalable, point-of-care and clinically deployable diagnostic solutions. Full article

The Centers for Disease Control and Prevention (CDC) classifies Bacillus anthracis as one of the most dangerous pathogens that may affect public health and national security. Due to its importance as a potential biological weapon, this bacteria has been classified in the highest category A, together with such pathogens as variola virus or botulinum neurotoxin. Characteristic features of this pathogen that increase its military importance are the ease of its cultivation, transport, and storage and its ability to create survival forms that are extremely resistant to environmental conditions. However, beyond bioterrorism, B. anthracis is also a naturally occurring pathogen. Anthrax outbreaks occur in livestock and wildlife, particularly in spore-contaminated regions of Africa, Asia, and North America. Spores persist for decades, leading to recurrent infections and zoonotic transmission through direct contact, inhalation, or consumption of contaminated meat. This work presents a new electrochemical method for detecting and quantifying B. anthracis in spore form using a selective immune reaction. The developed method is based on the thiol-modified electrodes that constitute the sensing element of the electrochemical system. Tests with the B. anthracis spore suspension showed that the detection limit for this pathogen is as low as 10³ CFU/mL. Furthermore, it was possible to quantify the analyte with a sensitivity of 11 mV/log (CFU/mL). Due to several features, such as low unit cost, portability, and minimal apparatus demands, this method can be easily implemented in field analyzers for this pathogen and provides an alternative to currently used techniques and devices. Full article