ACS Measurement Science Au最新文献

Candidozyma auris is an emerging multidrug-resistant fungal pathogen that poses significant challenges to healthcare systems worldwide. Its ability to persist on surfaces and resist common disinfectants contributes to rapid nosocomial transmission, making early and acute detection crucial for infection control. Conventional culture-based identification methods are time-consuming and lack sensitivity, while molecular techniques are expensive and require specialized equipment and trained personnel. This study explores the use of dielectrophoresis (DEP) for the rapid detection of C. auris by quantifying its dielectric properties using the dielectric single-shell model. Furthermore, since glucose plays a fundamental role in yeast metabolism, including in C. auris, we investigate how glucose metabolism affects its dielectric behavior. Changes in ionic concentrations and enzyme activity induced by glucose metabolism can alter the electrical properties of C. auris cells, making them more responsive to external electric fields. By characterizing these dielectric shifts under glucose-rich and glucose-limited conditions, we aim to develop a DEP-based diagnostic platform for the rapid and label-free detection of C. auris. This approach could provide an effective alternative to current diagnostic methods, enhancing screening efforts and improving infection control in healthcare settings.

The development of wearable technology that is non-invasive, customizable, comfortable for the user, and able to transmit data to healthcare providers from remote and rural locations has the potential to revolutionize the healthcare sector and aligns with key United Nations Sustainable Development Goals. In this work, bespoke conductive filaments based on thermoplastic polyurethane (TPU) incorporating different ratios of carbon black (CB) and graphite (GRT) were developed, for the first time, via melt extrusion for additive manufacturing of flexible, wearable electrochemical sensors. Eight formulations were systematically evaluated in terms of morphology, electrical resistance, wettability, and electrochemical behavior. The hybrid composition containing 20 wt% CB and 20 wt% GRT demonstrated the best balance between conductivity, mechanical flexibility, printability, and electrochemical activity, while producing a 45% saving in material cost. Surface activation through (electro)-chemical treatment and mechanical polishing significantly improved the electroactive surface area and heterogeneous electron transfer rate, especially for GRT-containing electrodes. The optimized electrode exhibited the highest k ₀ and A _e values and was integrated into a fully printed three-electrode wristband for non-invasive detection of uric acid (UA) in artificial sweat. Differential pulse voltammetry enabled reliable detection of UA in the 2.5-100.0 μmol L^-1 range with a limit of detection of 1.3 μmol L^-1 and recovery rates up to 99.7%. The sensor also demonstrated high selectivity against typical sweat interferents such as urea, glucose, and tyrosine. These findings support the potential of additively manufactured carbon-based TPU electrodes for application in wearable sensing platforms for real-time biomarker monitoring.

Hydraulic properties such as porosity, water, and clay content can be inferred from electrical parameters like permittivity, conductivity, and resistivity. Spectral data enhance this analysis by revealing features such as pore size and clay type in wet particulate media. In liquid samples, electrode polarization is clearly observed, as orientational polarization occurs only at higher frequencies (MHz to sub-GHz). In contrast, particulate media exhibit electrode polarization artifacts that obscure spatial polarization peaks within the Hz-MHz range, especially in highly conductive materials like wet clayey soils, making the Cole-Cole model insufficient for distinguishing these effects. Therefore, a general circuit model using a parallel form of a resistor and a constant phase element configuration more effectively separates inherent material polarization from electrode polarization. The electrode polarization limiting frequency (f _EP) correlates with both material conductivity and electrode properties, even with low-polarization electrodes like Ag/AgCl. A novel method is introduced to estimate the effective constant phase element exponent ( $\tilde{\eta }$ ) using the slope of log permittivity vs log frequency. Finally, the chargeability of kaolinite (m = 0.83-0.86), derived from the ratio of critical frequencies between the Cole-Cole and Pelton models, aligns with its fundamental definition: m = (σ_∞ - σ₀)/σ_∞, where σ₀ is the DC conductivity and σ_∞ is the high-frequency conductivity.

Thiaminase is an enzyme that destroys thiamine (vitamin B1) and is present in various fishes, mussels, plants, and bacteria. A sensitive and versatile assay is needed to measure thiaminase activity in complex biological samples using common reagents and variable reaction conditions. We developed a simple assay that uses fluorescence spectrophotometry and a microplate reader to measure thiaminase activity in fish tissue extracts via the destruction of added thiamine over time. Thiamine concentration, cosubstrate choice and concentration, and pH can be varied according to the needs of the investigator. Using this assay, we successfully measured common enzyme kinetic constants for thiaminase from a Pacific herring extract. The enzyme exhibited Michaelis-Menten kinetics (V _max = 13.8 nmol T g^-1 min^-1, K _m = 27.4 μM) with respect to thiamine and showed positive cooperativity for nicotinic acid as a cosubstrate (Hill equation, V _max = 12.1 nmol T g^-1 min^-1, K _half = 20.3 mM, n = 3.2). The thiaminase pH optimum of a rainbow smelt extract was also successfully measured (pH = 5.06 ± 0.06). Thiaminase activities of common forage fishes from the northern Bering Sea (2024) were compared using this fluorescence-based assay and the conventional 4-nitrothiophenol assay, marking the first reported measurements of thiaminase activity in this ecosystem. This new fluorescence-based assay is a tool that can be used for studying thiaminase dynamics in specimens under a variety of reaction conditions, enabling studies that will improve the understanding of factors driving thiamine deficiency in consumers.

Diuron, a widely used herbicide, has been banned or heavily restricted in several countries due to its environmental persistence and toxicity to aquatic ecosystems. Its chemical stability allows it to remain in soil and water for extended periods, leading to long-term contamination and potential leaching into groundwater. This is particularly concerning because diuron has been classified as a possible human carcinogen and exposure through contaminated water, food, or occupational contact raises significant safety concerns. Laboratory-based instruments provide a robust methodology for the measurement of diuron, but there is an opportunity for electroanalytical based devices to provide an in-the-field approach that is comparable and, in some cases, can provide enhanced sensitivity. The low-cost and portable nature of electrochemical instruments allows one-site analysis, removing sample transportation and storage costs, and reducing the overall measurement time. In this perspective, we summarize recent advances in the measurement of diuron using electroanalytical methods, providing insights into the measurement of diuron using various sensing materials and electrochemical platforms. A wide range of electrode materials, such as carbon-based nanomaterials, metal nanoparticles, and molecularly imprinted polymers, have been explored to enhance sensitivity and selectivity in the measurement of diuron, and furthermore, we consider the use electrochemiluminescence and additive manufacturing. This overview highlights the role of material properties, electrode surface modification strategies, and signal amplification to enhance the electroanalytical detection of diuron, offering insights into current advancements and future directions in electrochemical sensing for environmental monitoring.

Rapid and ultrasensitive diagnostic tests for COVID-19 remain crucial, yet conventional lateral flow antigen kits are limited by their reliance on labeled probes and suboptimal sensitivity at low viral loads. Here, we present a label-free electrochemical antigen test kit (free-EATK) that enables one-step detection of the SARS-CoV-2 N protein without the need for conjugate pads, covalently labeled redox probes, or signal normalization schemes. The system integrates a nitrocellulose-coated electrode, a redox pad preloaded with [Ru-(NH₃)₆]³⁺, and a sample inlet. Upon sample application, the immunocomplex forms directly at the sensing zone, followed by diffusion of the redox mediator toward the electrode surface. Signal generation is achieved through direct anodic square wave voltammetry, offering sharp oxidation peaks without additional surface modification or multistep protocols. The method achieves a detection limit of 0.69 pg/mL, with high reproducibility (RSD < 10%, n = 10), sensitivity of 91.7%, and specificity of 100% across clinical samples (n = 24). The free-EATK offers a simple, robust, and reproducible alternative for early stage infectious disease screening, particularly in settings where conventional labels or complex assay formats are impractical.

Mutations in the drug-resistant gene ofMycobacterium tuberculosiscan make it challenging to use drugs in clinical practice. Traditional genetic testing for resistance requires cell culture and susceptibility testing, which take 1-2 weeks. In this study, a DNA-sensitive hydrogel (pHEAA/pMA-DNA) has been developed with nucleic acid binding ability, water retention capacity, and high-temperature resistance, allowing it to work normally at 105 °C. Molecular dynamics simulations have been used to obtain the necessary physicochemical parameters. The DNA-sensitive hydrogel acts as a novel biosensor for detecting rifampicin- and isoniazid-resistant gene mutations in Mycobacterium tuberculosis. The microarray sensor's detection range is between 10⁹ copies/ml and 10¹ copies/mL, and its stability coefficient of variation (CV) is 2.424%. The study demonstrates that there is no mutual interference in the gel lattice. In addition, experiments on actual nucleic acid samples reveal accurate detection of bacterial strains and drug-resistant gene mutations. The regression curve conforms to the kinetic characteristics of nucleic acid amplification, exhibiting a sigmoidal shape. The Four-Parameter Logistic Regression (4PL) equation was employed for fitting, achieving an excellent coefficient of determination (R² = 0.99791 > 0.99). The method enables parallel detection of microarray biosensors in multidrug-resistant Mycobacterium tuberculosis. The sensors show high efficiency in detecting resistance mutation sites of Mycobacterium tuberculosis to rifampicin and isoniazid, paving the way for researchers to design different probes in in vitro detection fields.

Electrical sensing technologies have advanced our ability to infer and evaluate the hydraulic characteristics of porous media that are otherwise inaccessible to direct measurement. Such challenges are particularly prevalent in geo-porous materials such as rocks and soils found in remote regions, harsh environments, or beneath the Earth's surface. Noninvasive sensing and characterization of these materials are indispensable preliminary steps for water-energy nexus activities, including extraction processes (e.g., desalination, groundwater utilization, fossil fuel and geothermal exploration and production) and mitigation efforts (e.g., sediment transport monitoring, contaminant management, and carbon or hydrogen capture, utilization, and storage). These electrical properties are measurable only if the material under investigation possesses an electrical charge and is polarizable. Electrical polarization refers to the relative displacement between positive and negative charges. This raises several critical questions: (i) In what ways can porous media acquire electrical charge and exhibit polarization? (ii) How can their electrical properties be measured both in laboratory and field environments? (iii) What frameworks can be used to interpret the observed electrical properties? (iv) How can we assess the reliability and validity of these interpretations in relation to the hydraulic and physical state of the porous media? This study aims to systematically investigate these questions through a comprehensive synthesis of existing literature and the integration of newly obtained experimental data.

The expanding use of microfluidic droplets and particles across disciplines, from biology to materials science, highlights the need for developing precise characterization methods. Conventional particle characterization based on light scattering typically relies on averaged data from multiple particles, which can lead to inaccuracies due to contamination from larger particles. To overcome this issue, we here present a versatile laser diffraction (LD) system for characterizing individual droplets and particles flowing in a poly-(dimethylsiloxane) (PDMS) microfluidic device. Our system, mounted on a commercial inverted microscope, facilitates the simultaneous estimation of both the diameter and the refractive index of microparticles and droplets of size 20-50 μm. The LD system captures the angular distribution of scattered light from individual droplets as they pass through the PDMS microfluidic channels. Validation experiments were performed using liquid paraffin with varying refractive indices, oil-in-water (O/W) and water-in-oil (W/O) droplets, and size-certified polystyrene beads. Results showed high accuracy, with mean diameter estimation errors under 5% and refractive index estimation errors <0.5%. This adaptable characterization system can be combined with various microfluidic systems for droplet and particle generation, mixing, and sorting, offering broad potential for applications in multiple research domains.

Ex vivo tissue culture can model tissue physiology under well-controlled conditions and is especially promising for understanding the complex mechanisms of the brain. Three-dimensional (3D) printing has immense potential to accelerate microfluidic technology development, especially for ex vivo tissue culture devices where miniaturization is ultimately limited by the physical dimensions of tissue explants. Here we describe the development of a 3D printed microfluidic perfusion device for ex vivo brain slices that utilizes media droplets segmented by oxygen bubbles, a perfusion technique we call "bubble perfusion". Device design considerations are described, including materials property challenges associated with 3D printed plastic, such as wetting behavior and thermal conductivity challenges. Integrating a heated water circulation chamber and media prewarming chambers yielded media droplets delivered to brain slice explants at a temperature of 36.8 ± 0.13 °C, with tissue experiencing a temperature drift of 0.5 ± 0.09 °C over the course of a 60 s media droplet exposure. Murine brain tissue explants containing the suprachiasmatic nucleus (SCN) or entorhinal cortex (EC) were observed to be viable within the perfusion system by fluorescence imaging of intracellular Ca²⁺ flux induced by single-droplet stimulus of 60 mM KCl. Robust Ca²⁺ flux was observed for perfusion experiments lasting up to 12 h, with sequential droplet observations indicating the temporal dynamics of Ca²⁺ responses. End-point propidium iodide staining was used to characterize the health of EC and SCN tissue, with ca. 60% of cells in both regions showing no sign of membrane damage after 12 h of perfusion. The utility of the perfusion system toward pharmacological studies was demonstrated by comparing the Ca²⁺ flux induced by stimulus with 50 μM cannabidiol (CBD) vs 50 μM anandamide (AEA). Interestingly, similar magnitude and temporal dynamics of Ca²⁺ flux were observed for both CBD and AEA stimuli despite differential proposed mechanisms of action with respect to the CB1 receptor. These studies demonstrate the utility of the 3D printed bubble perfusion system toward the study of receptor-binding ligands that induce relatively modest magnitudes of Ca²⁺ flux.