Search Results (8,790)

Copper-modified screen-printed carbon electrodes require morphological and compositional assessment before further functionalization. This retrospective single-electrode study organizes SEM–EDX evidence into local composition, local coating interpretation, strip-region localization, and analytical traceability. The reported Phenom XL G2 record comprised three SEM fields, ten point spectra, and one 64 × 41-pixel map. Point Cu values ranged from 24.07 to 63.04 at.% in Image 1 at 15 kV and from 5.04 to 88.87 at.% in Image 2 at 10 kV; four additional points were reported for Image 3 at 10 kV without individual values in the article. The 15 kV map output contained 38.64 at.% Cu and 45.25 at.% C. These field-specific descriptors are consistent with a heterogeneous Cu-containing carbon surface, but do not isolate deposition variability from sampling and measurement effects. A matched bare-electrode control, complete quantification settings, and registered strip coordinates were not documented; manufacturing reproducibility was not evaluated. Previously published regional context was kept separate from the primary record. The contribution is a claim-bounded reporting framework that exposes these evidentiary gaps. Independent electrodes, native analytical exports, standardized acquisition, and uncertainty-based sampling are required for prospective validation. Full article

Pyrazines are the key odorants in food contributing to baked and nutty aromas. In order to improve practicality, a novel electrochemical olfactory biosensor for pyrazine analysis was developed using an olfactory receptor (OR5K1) as the recognition element and AuNPs-PB/ZIF-8@SWCNT/Ti₃C₂ MXene as the sensing matrix. The sensing application and molecular recognition mechanism of OR5K1 toward pyrazines were explored using molecular docking and in silico site-directed mutagenesis. We explored the sensing application and molecular recognition mechanism of OR5K1 toward pyrazines using molecular docking and in silico site-directed mutagenesis. The sensor achieved a linear detection range of 10⁻¹⁴ to 10⁻⁹ M with a low detection limit of 10⁻¹⁴ M. The biosensor exhibited significantly higher current responses toward pyrazine compounds compared to interfering substances, including ethanol, hexanal, acetone, and phenol, demonstrating excellent selectivity, and retained 79% of its initial signal after 12 days of storage, indicating good stability. The change in the reduction peak current (ΔI) in the presence of pyrazine was used as an analytical signal. When applied to four malt samples (pilsner, munich, crystal, and caramel malts), the biosensor showed ΔI responses ranging from 4.6 ± 0.2 µA to 108 ± 6 µA, which corresponded well with the total pyrazine contents determined by GC-TOF/MS (0.092–0.391 mg/kg), with a correlation coefficient of 0.96. Molecular docking revealed binding energies ranging from −3.9 to −6.0 kcal/mol, suggesting spontaneous interactions between OR5K1 and pyrazines, with Leu14, Met81, Asn84, Phe17, Phe85, and Lys90 identified as potential key residues and hydrogen bonds, hydrophobic interactions, and π−π stacking as primary driving forces. This work provides a sensitive and selective biosensor for pyrazine detection, and the elucidated recognition mechanism offers a molecular basis for understanding roasted aroma perception, supporting applications in food quality control and flavor analysis. Collectively, this study offers new insights for designing olfactory receptor-based electrochemical biosensors and facilitates future exploration of food aroma–receptor interaction mechanisms. Full article

Functional nucleic acids can connect molecular recognition with chemical signal generation, but their diagnostic value depends on the performance of the complete sample-to-answer pathway. This critical narrative review examines representative studies published through 31 July 2026, with emphasis on recognition, amplification, material interfaces, sample preparation, readout and clinical interpretation under realistic conditions. Hybridization and ligation probes, aptamers, DNAzymes, DNA nanostructures and CRISPR-associated systems are compared by specificity, kinetics, leakage and matrix compatibility. Rolling circle amplification, hybridization chain reaction, catalytic hairpin assembly and enzymatic isothermal amplification are evaluated as reaction networks whose products must remain accessible to the selected interface. Functional materials are classified by their actual analytical role, including transduction, signal amplification, capture/enrichment, spatial organization and reagent storage. Evidence is distinguished between mechanistic studies, spiked matrices, clinical specimens, manufactured-format reproducibility and demonstrated clinical utility. We further integrate sample-to-answer workflow, assay time, complexity, regulatory considerations and clinically relevant decision thresholds. Across the literature, reliable performance depends on selective recognition before high-gain reactions, compatibility between amplification products and interfaces, explicit controls for inhibition and leakage, and validation across independent lots and representative clinical populations. These principles define a path from analytical proof of concept to reproducible and clinically interpretable diagnostic testing. Full article

Dielectrophoretic (DEP) enrichment is a powerful strategy to enhance bacterial capture efficiency and accelerate the response of electrochemical biosensors by actively concentrating target bioparticles at the sensing interface. In this study, a combined numerical–experimental framework is developed to rationally design a DEP-assisted electrochemical biosensor with improved bacterial capture and detection performance. A finite-element modeling (FEM) approach was used to model the coupled electric field, dielectrophoretic force, and particle-transport phenomena, providing a quantitative basis for comparing bacterial trapping efficiency across different interdigitated electrode geometries. The modeling reveals that a wave-shaped interdigitated electrode (W_IDE) generates extended high-field regions and an enlarged effective capture area, resulting in an improved bacterial capture efficiency of 19% compared to 12% for the conventional rectangular interdigitated electrodes (R_IDE) under positive DEP (pDEP) conditions. Based on these insights, the W_IDE was fabricated on a printed circuit board (PCB) substrate, modified with platinum-black (Pt-black) to increase electroactive surface area, and interfaced with a custom-built 16-channel portable potentiostat unit, enabling sequential impedance measurements. The developed biosensor was applied to pDEP-assisted impedance detection of Staphylococcus aureus and Micrococcus luteus using vancomycin as the capture probe. The pDEP-assisted operation enabled rapid and highly sensitive detection down to 10 CFU/mL within 30 min with a wide linear range (10–10⁵ CFU/mL) in 0.1× PBS, outperforming passive detection (10²–10⁵ CFU/mL) for both Staphylococcus aureus and Micrococcus luteus. In skim milk, however, the linear detection ranges shifted to 10²–10⁵ CFU/mL with pDEP-assisted detection and 10³–10⁵ CFU/mL under passive detection conditions. Overall, this work highlights the significance of combining FEM-optimized electrodes with DEP-driven enrichment to achieve improved bacterial capture, sensitivity, and robustness in electrochemical biosensors. Full article

Modern clinical diagnostics require highly sensitive, rapid, and technologically simple methods for quantitatively determining biomarkers directly at the patient’s bedside. Fluorescence polarization (FP) meets these criteria, as it enables the homogeneous recording of an analytical signal based on changes in the rotational diffusion of a fluorescently labeled ligand upon binding to a target, without separation or washing steps. This comprehensive narrative review analyzes the literature over the past 10–15 years devoted to the use of FP analysis for detecting biomarkers of socially significant diseases. The fundamental principles of the method and modern analysis formats are discussed—from classical fluorescence polarization immunoassay (FPIA) with antibodies to aptamer sensors, DNAzyme-based systems, and reagent-free biosensors such as Quenchbody. Particular attention is paid to new approaches to signal amplification, including those using nanoparticles, protein aggregation, and isothermal amplification of nucleic acids. The main part of the review is devoted to practical applications of FP: diagnostics of infectious diseases (brucellosis, tuberculosis, and viral infections) demonstrating sensitivity at the level of traditional ELISA; liquid biopsy in oncology, including the detection of extracellular vesicles using aptamer FP platforms; therapeutic drug monitoring of antibiotics in whole blood on portable paper media; and the identification of biomarkers for metabolic and ophthalmological disorders. Prospects for integrating polarization detection with CRISPR/Cas systems, microfluidics, and smartphone-compatible readers are discussed, paving the way to the creation of a new generation of inexpensive devices for personalized medicine. Full article

For the diagnosis of diabetes, glycemic control, treatment modification, and the avoidance of both acute and long-term consequences, accurate glucose monitoring is crucial. This study examines the development of glucose-monitoring systems, from traditional diagnostic tests and finger-prick electrochemical glucometers to wearable, continuous, minimally invasive, and non-invasive sensing platforms. Major invasive technologies, including enzymatic and non-enzymatic electrochemical sensors, microdialysis systems, hexokinase-based photometric assays, and field-effect transistor biosensors, are critically evaluated. The ability of minimally invasive methods to access interstitial fluid with less pain is discussed, including fluorescence probes, surface-enhanced Raman spectroscopy, and microneedle arrays. Emerging non-invasive approaches are also evaluated. These include reverse iontophoresis, optical coherence tomography, infrared and photoacoustic spectroscopy, microwave resonators, smart contact lenses, and AI-assisted wearable systems. Finally, the review identifies major barriers related to sensitivity, selectivity, calibration, biofouling, biocompatibility, physiological variability, and clinical translation. It also outlines opportunities for intelligent, painless, and patient-centered glucose monitoring. Full article

Microstructured optical sensors (MOS) have emerged as transformative photonic devices offering unprecedented sensitivity, miniaturization, and multiplexing capability. This review synthesizes the state of the field for specialists in photonics and optics, covering principal design architectures—photonic crystal fibers, microresonators, plasmonic nanostructures, and integrated waveguide platforms—alongside the fabrication methodologies underpinning their realization. We examine four high-impact application domains: environmental monitoring, biomedical diagnostics, structural health monitoring, and food safety. A central argument runs through the review: the dominant bottleneck constraining MOS adoption has shifted from sensitivity—where many platforms now approach the physical detection limit—to the engineering triad of packaging difficulty, calibration drift, and manufacturing reproducibility. Against this backdrop, we provide frank comparative assessments of platform readiness for each application domain, distinguishing proof-of-concept demonstrations from deployable systems. A dedicated Critical Perspective section addresses the translation of laboratory sensitivity figures to field performance, the genuine and overstated contributions of machine learning, and a commercialization-readiness assessment for principal MOS platform families. Full article

Flexible wearable biosensors have emerged as a promising technology for continuous, noninvasive health monitoring, driven by the growing demand for personalized healthcare and an aging global population. Polymeric substrates such as polyethylene terephthalate (PET), polyimide (PI), and polydimethylsiloxane (PDMS) provide lightweight, flexible, and low-cost platforms that conform to the human body, but their practical deployment requires reliable integration with complementary metal–oxide–semiconductor (CMOS) electronics for signal acquisition, processing, and wireless communication. This review summarizes recent advances in CMOS-compatible flexible biosensors, emphasizing polymer-based sensing platforms, circuit-level integration, and system-on-chip (SoC) architectures for wearable healthcare applications. Flexible sensing mechanisms, including electrochemical, capacitive, resistive, and transistor-based devices, are discussed alongside CMOS analog front-end circuits, low-noise amplifiers, analog-to-digital converters, and ultra-low-power signal conditioning techniques. Finally, key challenges in CMOS–flexible sensor integration, including mechanical reliability, biocompatibility, signal integrity, packaging, and scalable manufacturing, are discussed, together with future directions toward highly integrated, intelligent, and energy-efficient wearable healthcare systems. Full article

Reduced nicotinamide adenine dinucleotide phosphate (NADPH) sustains reductive biosynthesis, antioxidant defense, oxidase activity, and redox signaling; nevertheless, studies framed as “NADPH imaging” often interrogate biochemically non-equivalent variables and analytically distinct endpoints. To resolve that ambiguity, this review organizes current methods by analyte-defining event, optical transduction or readout, acquisition modality, and deployment context. Extraction and enzyme-coupled assays can define recovered NADPH, oxidized nicotinamide adenine dinucleotide phosphate (NADP⁺), total NADP(H), or a derived ratio, albeit at the cost of subcellular information. By contrast, protein-based, genetically encoded, and chemigenetic systems enable reversible, compartment-addressable measurements of sensor-accessible cofactor binding, ligand-dependent assembly, relay output, or NADPH/NADP⁺ balance; however, quantitative interpretation remains contingent on affinity, sensor abundance, pH, maturation, calibration, and sensor-induced buffering. Reaction-based probes offer the broadest spectral and imaging flexibility—including ratiometric, near-infrared, two-photon, and photoacoustic formats—yet most rely on hydride-transfer chemistry shared by reduced nicotinamide adenine dinucleotide (NADH) and NADPH. Absent matched kinetics and simultaneous mixed-cofactor experiments, NAD(P)H-responsive remains the most defensible designation for these platforms. Label-free autofluorescence, fluorescence lifetime imaging microscopy (FLIM), and phasor analysis preserve native spatial context; even so, they report composite intensity, binding-state, or metabolic contrast rather than a universal absolute NADPH concentration. Across modalities, rigorous interpretation requires physiologically relevant concentration ranges, product or binding-mechanism verification, matrix- and organelle-specific controls, time-resolved calibration, and orthogonal measurements of pool size or flux. By aligning each signal-generating event with the endpoint it can legitimately support, the review establishes a mechanistic basis for platform selection and for interpreting NADPH-related optical changes across purified systems, cells, tissues, and biofluids. Full article

Early detection of cancer remains challenging due to the extremely low concentration of biomarkers present during initial disease stages. Dysregulation of key signaling pathways, including cyclin-dependent kinase (CDK) networks, drives uncontrolled cell proliferation and tumor progression, underscoring the need for highly sensitive, label-free biosensing technologies. Conventional analytical methods such as ELISA and PCR offer reliable detection but require complex sample preparation, fluorescent labeling, and long processing times, limiting their suitability for rapid diagnostics. This work introduces a novel label-free Biological Micro-Opto-Electro-Mechanical System (BioMEMS) platform based on an unbalanced Michelson interferometer with DBR mirrors to interrogate the minute spectral shifts induced by biomolecular interactions. A microcantilever is suspended above a silicon-on-insulator (SOI) waveguide, where the specific binding of biomarkers generates compressive surface stress, causing a downward deflection that reduces the cantilever-to-waveguide gap. This displacement modulates the effective refractive index of the sensing arm through enhanced evanescent-field coupling. The resulting phase variation is further detected through the high-sensitivity Michelson interferometric architecture, enabling ultrasensitive spectral interrogation. Numerical simulations using COMSOL Multiphysics demonstrate a narrow full width at half maximum (FWHM) of 27.6 nm, a quality factor (Q) of 53.34, and an overall sensitivity of 75.74 $\mathsf{\mu }$m/(N/m). These results highlight the potential of the proposed platform for early cancer detection and precise monitoring of dysregulated signaling pathways. Full article

Background: Wearable sweat biosensors have emerged as a promising non-invasive approach for monitoring inflammatory biomarkers, offering an alternative to repeated blood sampling. This systematic review evaluated the current evidence on the detection of C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in sweat for infection and inflammatory disease monitoring. Methods: Following PRISMA 2020 guidelines (PROSPERO: CRD420261371221), PubMed/MEDLINE, Scopus, Web of Science, IEEE Xplore, and Google Scholar were searched through April 2026. Human studies measuring CRP, IL-6, or TNF-α in sweat using wearable or biosensor-based platforms were included. Risk of bias and certainty of evidence were assessed using a modified Newcastle–Ottawa Scale/JBI checklist and GRADE. Results: Thirteen studies (2020–2025, 5–80 participants) were included. CRP showed the most consistent sweat-serum agreement (r = 0.844) and good diagnostic performance in one inflammatory bowel disease cohort (AUC = 0.845). TNF-α demonstrated the highest diagnostic accuracy in a single longitudinal study (AUC = 0.962), whereas IL-6 showed moderate sweat-serum correlations (R² = 0.60–0.72) but limited diagnostic discrimination. IL-6 and TNF-α were more consistently detected in passively collected eccrine sweat, although IL-6 was also successfully measured following pilocarpine iontophoresis in one study. Most studies had moderate methodological quality. Conclusions: Sweat-based measurement of CRP, IL-6, and TNF-α is analytically feasible for non-invasive inflammatory biomarker monitoring. However, current evidence remains limited by small, heterogeneous studies, underscoring the need for standardized protocols and larger prospective clinical validation. Full article

Gallium nitride (GaN) high-electron-mobility transistor (HEMT) biosensors have recently emerged as promising platforms for highly sensitive and label-free detection of biomolecules. Their exceptional electrical properties, including high carrier mobility, together with the wide bandgap and strong chemical bonds of GaN materials, provide excellent stability under high temperatures, ionizing radiation, and chemically harsh environments. Despite significant experimental progress, comprehensive analytical models capable of linking biomolecular recognition events to the electrical response of GaN biosensors remain limited. This work presents a physics-based, design-oriented analytical modeling framework for AlGaN/GaN HEMT biosensors. The model incorporates biomolecular binding kinetics, the dielectric properties of the hybrid system, and electrostatic coupling to the transistor channel conductivity. Numerical simulations are performed using COMSOL Multiphysics to validate the analytical model. The developed framework provides physical insight into the mechanisms governing biosensor operation and offers practical guidelines for the optimization and comparative assessment of HEMT/MIS-HEMT biosensor architectures. Full article

The bioluminescence of entomopathogenic bacteria of the genus Photorhabdus was considered to be constitutive. However, it has recently been shown that under heat shock conditions, lux-operon is activated in Photorhabdus temperata cells. In the present study, bioluminescence thermoactivation was investigated in two isolated strains, Photorhabdus hainanensis FV2401 and P. temperata FV2402. The luminescence of the more thermotolerant P. hainanensis cells was activated at higher temperatures than that of P. temperata. At the maximum induction temperatures of 37 °C for FV2401 and 34 °C for FV2402, higher bioluminescence activation was observed in FV2401, whereas the increase in lux-genes mRNA levels was approximately the same in both strains. In P. hainanensis, elevated temperatures also affected the expression of the hexA, madB, and csrB genes, which are indirectly involved in luminescence in Photorhabdus. The heat-activated lux-operon promoter in P. hainanensis and P. temperata was determined. This is a σ⁷⁰-dependent promoter that differs in its distance from the luxC start codon. When promoter variants with or without the 5′-UTR mRNA were transferred to the heterologous Escherichia coli system, heat activation of luminescence was retained in constructs containing only the promoter and was independent of σ³² and σ^E, whereas constructs with the 5′-UTR exhibited repression of luminescence following thermoactivation. The obtained data on the temperature-induced promoter of the lux-operon can broaden understanding of the ecological and biological functions of Photorhabdus bioluminescence under heat shock conditions and provide a basis for the development of novel biosensors. Full article

Skin-interfaced thermal sensors offer a promising, portable, and cost-effective alternative for continuous and noninvasive measurements of skin condition and blood flow. Skin condition, especially skin hydration, is reflected by the tissue thermal conductivity. Blood flow is characterized by the average flow velocity through blood vessels in skin. However, the measurement accuracy of tissue thermal conductivity and blood velocity is hindered by the coupled heat conduction and convection in the tissue containing blood vessels. To overcome this bottleneck for precise measurements of tissue thermal conductivity and blood velocity simultaneously, we design a skin-interfaced thermal sensor consisting of a resistive heater and three thermistors. The resistive heater with a diameter of 4 mm consumes a low power of 0.05 W. The three miniature thermistors measure the steady-state temperatures on skin at the middle location of the heater center, upstream flow location, and downstream flow location. Using finite element analysis (FEA) of heat transfer in vascular skin, we optimize the three-thermistor layout, placing the upstream and downstream thermistors 6.0 mm and 2.7 mm from the heater center, respectively. FEA results reveal that the middle-thermistor temperature is predominantly sensitive to tissue thermal conductivity with relatively low flow interference, whereas the temperature difference between upstream and downstream thermistors maintains high sensitivity to blood velocity, and is less affected by tissue thermal conductivity. With the FEA results, we implement a polynomial machine learning model and a physics-informed thermal-resistance reduced-order model to analyze the thermal sensor temperature measurements and jointly predict both quantities. The relative prediction errors are typically below 4% for thermal conductivity and 10% for blood velocity using the machine learning model, and below 1% and 8% using the reduced-order model. This work provides a framework for the development of skin-interfaced thermal sensors capable of intelligent and noninvasive skin and vascular assessment. Full article

Magnetoelectric materials couple magnetic and electrical order parameters and can convert remotely applied magnetic fields into localized electrical responses. At the nanoscale, this functionality is commonly pursued through core–shell architectures in which a magnetostrictive or magnetic core is mechanically coupled to a piezoelectric or ferroelectric shell. The resulting strain-mediated transduction is attractive for biomedical and bioelectronic applications because magnetic fields penetrate biological tissue with comparatively low attenuation, whereas the generated electrical signals can interact directly with charged biomolecules, cell membranes, ion channels, and electroactive tissues. This review critically evaluates magnetoelectric core–shell nanoparticles from a broad biomedical and bioelectronic perspective. The physical basis of direct and converse magnetoelectric coupling is first discussed, with emphasis on nanoscale boundary conditions, magnetic-domain state, ferroelectric polarization, interfacial strain transfer, ionic screening, and nonlinear field dependence. Representative magnetic-core/piezoelectric-shell material families, including ferrite-based, multiferroic-oxide, lead-free piezoelectric, PZT-containing, and polymer-integrated architectures, are compared in terms of magnetic response, piezoelectric activity, chemical stability, biocompatibility, toxicity, and processability. Particular attention is given to CoFe₂O₄–BaTiO₃ (CFO-BTO) as a benchmark magnetoelectric core–shell system, while alternative material combinations are comparatively discussed to reflect the broader diversity of the field. Synthesis and processing strategies, structural and physicochemical characterization, surface engineering, and local or macroscopic magnetoelectric measurement methods are examined together with the artifacts that can complicate quantitative interpretation. Particular attention is paid to particle size, shell thickness, crystallinity, aggregation, colloidal stability, surface chemistry, biomolecular functionalization, and their influence on magnetoelectric performance and biological interactions. The available literature demonstrates substantial progress in magnetically triggered drug delivery and cancer therapy, wireless neural and cardiac stimulation, tissue engineering, immunomodulation, wound healing, multimodal imaging, and related bioelectronic applications. Biosensing is also considered an important emerging direction; however, direct quantitative detection of proteins, nucleic acids, pathogens, and cancer biomarkers using isolated core–shell magnetoelectric nanoparticles remains comparatively underdeveloped. The review therefore distinguishes experimentally established biomedical and bioelectronic functionalities from less mature biosensing concepts and identifies the measurement, safety, clinically relevant magnetic-field exposure, scalable manufacturing, device-integration, and regulatory challenges that must be addressed for translation. A practical roadmap is proposed for developing reproducible, lead-free, biologically stable, and quantitatively characterized magnetoelectric nanoparticle platforms for next-generation wireless biomedical and bioelectronic technologies. Full article