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This study introduces the development of a photothermal-based microfluidic paper analytical device (PT-µPAD) integrated with near-field communication (NFC) technology and smartphone readout for enzyme-free glucose quantification in human samples. With the properties of gold nanoparticles (AuNPs) both as a nanozyme and as a photothermal substrate, there is no need for costly reagents like enzymes or a readout instrumentation for the selective and sensitive detection of glucose. In PT-µPADs, AuNPs are etched by hydrogen peroxide (H 2 O 2 ) generated from glucose catalysis. Photothermal detection from the plasmonic heating of these AuNPs when illuminated by a 533nm LED light source is achieved by inserting the PT-µPAD sensor into a portable NFC platform suitable for smartphone readout. Temperature variation is directly proportional to the glucose concentration. After optimization, we acquired a linear range between 5.0 and 20.0 µmol L -1 ( R 2 = 0.9967) and a limit of detection (LOD) of 25.0 nmol L -1 for glucose. Additionally, while our sensor does not utilize any enzyme, it is remarkably selective to glucose with no effects from interferences. Recovery studies in various human control samples indicated a range of 99.73-102.66% with the highest RSD of 3.53%, making it highly accurate and precise. Moreover, our method is more sensitive than other methods relying on conventional µPADs for glucose sensing. By integrating the potential benefits of microfluidics, nanomaterials as nanozymes, and NFC technology for wireless readout, our sensor demonstrates great promise as an accessible, affordable, and shelf-stable device for glucose quantification. Moreover, this concept can be extended to detect other molecules of interest as a point-of-care (POC) diagnostics device.

A new analytical method for chronic kidney disease (CKD) detection utilizing paper spray mass spectrometry (PS-MS) combined with machine learning is presented. The analytical protocol is rapid and simple, based on metabolic profile alterations in urine. Anonymized raw urine samples were deposited (10 μL each) onto pointed PS-MS sample strips. Without waiting for the sample to dry, 75 μL of acetonitrile and high voltage were applied to the strips, using high resolution mass spectrometry measurement (15 s per sample) with polarity switching to detect a wide range of metabolites. Random forest machine learning was used to classify the resulting data. The diagnostic performance for the potential diagnosis of CKD was evaluated for accuracy, sensitivity, and specificity, achieving results >96% for the training data and >91% for validation and test data sets. Metabolites selected by the classification model as up- or down-regulated in healthy or CKD samples were tentatively identified and in agreement with previously reported literature. The potential utilization of this approach to discriminate albuminuria categories (normo, micro, and macroalbuminuria) was also demonstrated. This study indicates that PS-MS combined with machine learning has the potential to be used as a rapid and simple diagnostic tool for CKD.

Paper-based ratiometric fluorescence sensors are normally prepared using two or more types of fluorescent materials on a paper chip for simple, low-cost and fast detection. However, the choice of multi-step and one-step modifications on the paper chip affects the analytical performance. Herein, a novel paper-based dual-emission ratiometric fluorescence sensor was designed for the selective detection of tetracycline (TC). Carbon dots (CDs) modified with Eu3+ were combined with a sealed paper-based microfluidic chip by two methods: one-step grafting of CDs-Eu3+ on paper and step-by-step grafting of CDs and Eu3+ on paper. The analytical performance was studied and optimized respectively. The red fluorescence of Eu3+ at 450 nm is enhanced and the blue fluorescence of CDs at 617 nm is quenched by energy transfer in the presence of TC. Under optimal conditions, TC is selectively determined in the linear range from 0.1 μM to 100 μM with a detection limit of 0.03 μM by the step-by-step grafting method. In addition, the sealed paper chip could effectively prevent pollution and volatilization from the reagent. This technique has been used to analyze TC in seafood aquaculture water with satisfactory results. [ABSTRACT FROM AUTHOR]

Plastic pollution at the nanoscale continues to pose adverse effects on environmental sustainability and human health. However, the detection of nanoplastics (NPLs) remains challenging due to limitations in methodology and instrumentation. Herein, a "green approach" for surface-enhanced Raman spectroscopy (SERS) was exploited to detect polystyrene nanospheres (PSNSs) in water, employing untreated filter paper and a simple syringe-filtration set-up. This SERS protocol not only enabled the filtration of nano-sized PSNSs, which are smaller than the pore size of the ordinary filter paper, but also offered SERS enhancement by utilizing quasi-spherical-shaped silver nanoparticles (AgNPs) as the SERS-active substrate. The filtering of NPLs was accomplished by adding an aggregating agent to the nanoparticle mixture, which caused the aggregation of NPLs and AgNPs, resulting in a larger cluster and more hot spots for SERS detection. The optimal aggregating agent and its concentration, as well as the volume ratio between the AgNPs and NPLs, were also optimized. This SERS method successfully detected and quantified PSNSs of various sizes ( i.e. , 100, 300, 460, 600, and 800 nm) down to a limit of detection (LOD) of about 0.31 μg mL -1 . The method was also validated against the presence of several interferents ( i.e. , salts, sugars, amino acids, and surfactants) and was proven practical, as evidenced by the detection of 800nm PSNSs in drinking and tap water (LODs of 1.47 and 1.55 μg mL -1 , respectively).

Paper-based microfluidics combined with potentiometric measurement has emerged as an attractive approach for detecting various chemical ionic moieties. Detection of heavy metal ions, using paper substrates as solution sampling and delivery systems remains challenging despite efforts to introduce several physico-chemical paper substrate modifications to stop adsorption of ions onto the paper substrates. This study quantitatively investigates the adsorption of heavy metal ions on the paper substrates during paper-based potentiometric measurements and explains the super-Nernstian response of potentiometric sensors through local depletion of heavy metal ions from the solution. Consequently, based on the investigated ion adsorption, a corrective potential protocol was established for the electrodes coupled with paper-based solution sampling by predicting interference free sensor response from paper-based measurement. Furthermore, the ion adsorption was also recorded for mixed metal ion solutions to understand competitive primary/interfering ions adsorption onto the paper substrates and establish corrective measures to predict interference free sensor response. In this method, no modifications of the paper substrates are necessary before actual potentiometric measurements. The proposed corrective protocol allows prediction of sensor response based on the paper-based solution sampling potentiometric measurement, providing a simple methodological approach based on correction of potential readout of the potentiometric sensor, thus completely resigning from the need of modifying paper substrate for measurements of heavy metal ions.

Nowadays, kidney dysfunction is a common health issue due to the modernized lifestyle. Even though medications are commercially available to treat kidney diseases, early diagnosis is crucial and challenging. Clinically, measuring urine creatinine and pH has gained significant interest as a way to diagnose kidney diseases early. In the present work, we attempted to develop a low-cost, robust, accurate and naked-eye colorimetric method to determine both creatinine levels and pH variations in artificial urine samples using a simple 3D-printed hybrid microfluidic device. Creatinine was detected by the incorporation of the traditional Jaffe test onto the hybrid paper-PMMA microfluidic device and pH (4-8) was measured by a simple anthocyanin test. Notably, the tests were established without employing any sophisticated or costly instrument clusters. The developed 3D-printed microfluidic probe showed a limit of detection (LOD) of 0.04 mM for creatinine over a concentration range of 1-10 mM, with a regression coefficient ( R 2 ) of 0.995 in laboratory conditions. Interestingly, the experimental data obtained with artificial urine exhibited a wide linear range from 0.1 mM to 5 mM under different pH values ranging from 4 to 8 in the presence of matrices commonly found in urine samples other than proteins, indicating the potential use of this method in pre-clinical analysis. Since the wide linear range of urine creatinine in artificial urine samples falls well below the clinically relevant concentrations in humans (0.07-0.27 mM), the developed lab-on-chip device is further suitable for clinical evaluation with proper ethical clearance. This 3D-printed hybrid microfluidic colorimetry-based creatinine detection and pH indicator platform can be beneficial in the healthcare sector due to the on-site testing capability, cost-effectiveness, ease of use, robustness, and instrument-free approach.

Paper-based electrochemical sensors have the characteristics of flexibility, biocompatibility, environmental protection, low cost, wide availability, and hydropathy, which make them very suitable for the development and application of biological detection. This work proposes electrospun cellulose acetate nanofiber (CA NF)-decorated paper-based screen-printed (PBSP) electrode electrochemical sensors. The CA NFs were directly collected on the PBSP electrode through an electrospinning technique at an optimized voltage of 16 kV for 10 min. The sensor was functionalized with different bio-sensitive materials for detecting different targets, and its sensing capability was evaluated by CV, DPV, and chronoamperometry methods. The test results demonstrated that the CA NFs enhanced the detection sensitivity of the PBSP electrode, and the sensor showed good stability, repeatability, and specificity (p < 0.01, N = 3). The electrochemical sensing of the CA NF-decorated PBSP electrode exhibited a short detection duration of ∼5–7 min and detection ranges of 1 nmol mL−1–100 μmol mL−1, 100 fg mL−1–10 μg mL−1, and 1.5 × 102–106 CFU mL−1 and limits of detection of 0.71 nmol mL−1, 89.1 fg mL−1, and 30 CFU mL−1 for glucose, Ag85B protein, and E. coli O157:H7, respectively. These CA NF-decorated PBSP sensors can be used as a general electrochemical tool to detect, for example, organic substances, proteins, and bacteria, which are expected to achieve point-of-care testing of pathogenic microorganisms and have wide application prospects in biomedicine, clinical diagnosis, environmental monitoring, and food safety. [ABSTRACT FROM AUTHOR]

Exosomal microRNAs (miRNAs) play a pivotal role in intercellular communication, regulating gene expression in target cells, and hold significant promise as cancer biomarkers for early detection and screening. However, achieving precise and viable detection of exosomal miRNAs remains a challenge. This paper proposes an all-in-one detection strategy for breast cancer-derived exosomal miRNA-21 on a pen-based paper chip (PPC). The PPC is constructed using a modified automatic pen and lateral flow assay (LFA), which results in a cost-effective fabrication process. The user only needs to add the sample and trigger the top of the self-contained PPC after a period of time to complete the entire detection process. To enhance the sensitivity of exosomal miRNA testing, an enzyme-free catalyzed hairpin assembly (CHA) is further introduced, enabling highly sensitive detection of miRNA-21 with a limit of detection (LOD) of 25 fmol. Additionally, the detection of miRNAs in differentially-expressed cells and clinical samples has also been successfully achieved with high specificity. Overall, the proposed PPC provides an effective tool for detecting early cancer, monitoring diseases, and establishing point of care testing (POCT). [ABSTRACT FROM AUTHOR]

A new method utilizing fluorescent ratiometry is proposed for detecting putrescine and spermidine. The method involves the use of a fluorescent probe comprising a 2D halide perovskite synthesized from octadecylamine-iodine and PbI 2 via a grinding-sonicating technique, along with a Eu 3+ -complex. Upon excitation at 290 nm, the probe fluoresces at two distinguishable wavelengths. The addition of putrescine and spermidine significantly decreases the emission of the 2D halide perovskite at 496 nm, while the emission of the Eu 3+ -complex at 618 nm remains stable. The color changes of the probe depend on the concentration of putrescine and spermidine, and the assay offers linearity over a wide concentration range (30-4000 ng mL -1 ), a low detection limit (4 ng mL -1 for spermidine), and a quick response time. Furthermore, a portable device based on a smartphone can be used to record the color change of the paper test strip using the prepared fluorescent materials. The fluorescence quenching mechanism of the probe is explained as dynamic quenching.-1 for spermidine), and a quick response time. Furthermore, a portable device based on a smartphone can be used to record the color change of the paper test strip using the prepared fluorescent materials. The fluorescence quenching mechanism of the probe is explained as dynamic quenching.

MicroRNAs (miRNAs) have emerged as a promising class of biomarkers for early detection of various cancers, including ovarian cancer. However, quantifying miRNAs in human blood samples is challenging owing to the issues of sensitivity and specificity. In this study, hsa-miR-200a-3p of the miR-200a sub-family, which is a biomarker of ovarian cancer, was used as the analyte to demonstrate the analytical capability of an integrated biosensing platform using an extremely sensitive surface-enhanced Raman scattering (SERS) nanotag-nanoaggregate-embedded beads (NAEBs), magnetic nanoparticles (MNPs), a pair of highly specific locked nucleic acid (LNA) probes, and a semi-automated paper-based electrowetting-on-dielectric (pEWOD) device to provide labor-less and thorough sample cleanup and recovery. A sandwich approach where NAEBs are modified by one LNA-1 probe and MNPs are modified by another LNA-2 probe was applied. Then, the target analyte miRNA-200a-3p was introduced to form a sandwich nanocomplex through hybridization with the pair of LNA probes. The pEWOD device was used to achieve short cleanup time and good recovery of the nanocomplex, bringing the total analysis time to less than 30 min. The detection limit of this approach can reach 0.26 fM through SERS detection. The versatility of this method without the need for RNA extraction from clinical samples is expected to have good potential in detecting other miRNAs.

Paper-based ratiometric fluorescence sensors are normally prepared using two or more types of fluorescent materials on a paper chip for simple, low-cost and fast detection. However, the choice of multi-step and one-step modifications on the paper chip affects the analytical performance. Herein, a novel paper-based dual-emission ratiometric fluorescence sensor was designed for the selective detection of tetracycline (TC). Carbon dots (CDs) modified with Eu 3+ were combined with a sealed paper-based microfluidic chip by two methods: one-step grafting of CDs-Eu 3+ on paper and step-by-step grafting of CDs and Eu 3+ on paper. The analytical performance was studied and optimized respectively. The red fluorescence of Eu 3+ at 450 nm is enhanced and the blue fluorescence of CDs at 617 nm is quenched by energy transfer in the presence of TC. Under optimal conditions, TC is selectively determined in the linear range from 0.1 μM to 100 μM with a detection limit of 0.03 μM by the step-by-step grafting method. In addition, the sealed paper chip could effectively prevent pollution and volatilization from the reagent. This technique has been used to analyze TC in seafood aquaculture water with satisfactory results.

Albuminuria is a clinical condition associated with poor kidney function, diagnosed by determining the ratio of albumin to creatinine concentrations in patient urine samples. We present a high-throughput paper spray mass spectrometry (PS-MS) method for simultaneous quantitation of urinary albumin and creatinine for potential diagnosis of albuminuria. Minimal (urine dilution) or no sample preparation is required. The analytical performance of the method was evaluated, achieving linear calibration curves ( R 2 > 0.99) with little inter-day variability in the slope ( N = 5 days), exhibiting coefficient of variation (CV) of 8% and 3% for albumin and creatinine, respectively. LOD and LOQ for albumin were 2.1 and 7.0 mg L -1 , and for creatinine were 0.01 and 0.03 mmol L -1 , respectively. Intra- and inter-day ( N = 5) precisions (%CV) and accuracies (%bias) were <10% and ±11%, respectively, for both analytes. The method was applied to determine albumin-to-creatinine ratios in anonymous human patient urine samples ( N = 56), and a correlation of R 2 = 0.9744 was achieved between the PS-MS results and validated clinical method results. This work demonstrates the utility of PS-MS to simultaneously quantify a large (albumin) and a small (creatinine) molecule directly in patient urine samples, and its potential as a tool for clinical albuminuria diagnostics.

A new method utilizing fluorescent ratiometry is proposed for detecting putrescine and spermidine. The method involves the use of a fluorescent probe comprising a 2D halide perovskite synthesized from octadecylamine-iodine and PbI2via a grinding-sonicating technique, along with a Eu3+-complex. Upon excitation at 290 nm, the probe fluoresces at two distinguishable wavelengths. The addition of putrescine and spermidine significantly decreases the emission of the 2D halide perovskite at 496 nm, while the emission of the Eu3+-complex at 618 nm remains stable. The color changes of the probe depend on the concentration of putrescine and spermidine, and the assay offers linearity over a wide concentration range (30–4000 ng mL−1), a low detection limit (4 ng mL−1 for putrescine, and 7 ng mL−1 for spermidine), and a quick response time. Furthermore, a portable device based on a smartphone can be used to record the color change of the paper test strip using the prepared fluorescent materials. The fluorescence quenching mechanism of the probe is explained as dynamic quenching. [ABSTRACT FROM AUTHOR]

Fast detection of contaminants of emerging concern (CECs) in water resources is of great environmental interest. Ideally, sustainable materials should be used in water quality monitoring technologies implemented for such purposes. In this regard, the application of bio-based materials aimed at the fabrication of analytical platforms has become of great importance. This research merges both endeavors by exploring the application of chitosan-coated paper, decorated with silver nanoparticles (AgNPs), on surface-enhanced Raman scattering (SERS) spectroscopy studies of two distinct types of CECs dissolved in aqueous samples: an antibiotic (ciprofloxacin) and a pesticide (thiram). Our results indicate the superior SERS performance of biocoated substrates compared to their non-coated paper counterparts. The detection limits achieved for thiram and ciprofloxacin using the biocoated substrates were 0.024 ppm and 7.7 ppm, respectively. The efficient detection of both analytes is interpreted in terms of the role of the biopolymer in promoting AgNPs assemblies that result in local regions of enhanced SERS activity. Taking advantage of these observations, we use confocal Raman microscopy to obtain Raman images of the substrates using ciprofloxacin and thiram as molecular probes. We also demonstrate that these biobased substrates can be promising for on-site analysis when used in conjunction with portable Raman instruments. [ABSTRACT FROM AUTHOR]

More than 65% of bacterial infections are caused by biofilms. However, standard biofilm susceptibility tests are not available for clinical use. All conventional biofilm models suffer from a long formation time and fail to mimic in vivo microbial biofilm conditions. Moreover, biofilms make it difficult to monitor the effectiveness of antibiotics. This work creates a powerful yet simple method to form a target biofilm and develops an innovative approach to monitoring the antibiotic's efficacy against a biofilm-associated infection. A paper-based culture platform can provide a new strategy for rapid microbial biofilm formation through capillary action. A combined electrical-electrochemical technique monitors bacterial metabolism rapidly and reliably by measuring microbial extracellular electron transfer (EET) and using electrochemical impedance spectroscopy (EIS) across a microbe-electrode interface. Three representative pathogens, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus, form their biofilms controllably within an hour. Within another hour their susceptibilities to three frontline antibiotics with different action modes (gentamicin, ciprofloxacin, and ceftazidime) are examined. Our antibiotic susceptibility testing (AST) technique provides a quantifiable minimum inhibitory concentration (MIC) of those antibiotics against the in vitro biofilm models and characterizes their action mechanisms. The results will have an important positive effect because they provide immediately actionable healthcare information at a reduced cost, revolutionizing public healthcare. [ABSTRACT FROM AUTHOR]

Rapid, sensitive, and quantitative detection of biomarkers is needed for early diagnosis of disease and surveillance of infectious outbreaks. Here, we exploit a plasmonic syringe filter and surface-enhanced Raman spectroscopy (SERS) in the development of a rapid detection system, using human IgG as a model diagnostic biomarker. The novel assay design facilitates multiple passages of the sample and labeling solution through the detection zone enabling us to investigate and maximize sampling efficiency to the capture substrate. The vertical flow immunoassay process in this study involves the utilization of filter paper embedded with gold nanoparticles (AuNPs) to form a plasmonic substrate. Capture antibody (anti-human IgG) is then immobilized onto the prepared plasmonic paper and inserted into a vertical flow device (syringe filter holder). Sample solution is passed through the filter paper and the target antigen (human IgG) is selectively captured by the immobilized antibody to form an antibody–antigen complex. Next, functionalized AuNPs as extrinsic Raman labels (ERLs) are passed through the filter paper to label the captured biomarker molecules forming a layered structure. This sandwiched geometry enhances plasmonic coupling and SERS signal to provide highly sensitive detection of biomolecules. Systematic studies to investigate the impact of multiple infuse/withdraw cycles of the sample and labeling solutions reveal that antigen and ERL binding are maximized with 10 and 20 cycles, respectively. The optimized assay achieves a detection limit of ∼0.2 ng mL−1 for human IgG with a total assay time of less than 5 minutes, meeting the demands for rapid point of care diagnostics. Additionally, the optimized platform was implemented in the quantitative analysis of the SARS-CoV-2 nucleocapsid protein, the typical target in commercial, FDA-approved rapid antigen tests for COVID-19. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal "Analyst" published by the Royal Society of Chemistry. It includes a range of articles and papers on various topics in the field of chemistry. Some of the topics covered include bacterial transglycosylation, nanozyme kinetics, fiber optic cadmium ion sensors, and electrochemical biosensors. The journal aims to connect the global chemistry community and reinvest its profits back into the field. [Extracted from the article]

The document is a contents list for the journal "Analyst" published by the Royal Society of Chemistry. It includes a range of papers on various topics such as nanomaterial-induced hepatotoxicity, pH-dependent complex formation, ultrasensitive detection of circulating miRNA, and determining chromosomal instability in breast cancer cells. The journal covers a wide range of scientific research and aims to connect the world with the chemical sciences. [Extracted from the article]

A portable and non-invasive sensor presents an innovative way to measure inflammation biomarkers in exhaled breath condensate (EBC). This research is focused on developing a miniaturized bipolar electrochemical sensor that can be connected to a smartphone app. This device will be able to detect adding known amounts of nitrite (spikes) to a salt solution and small amounts of nitrite ions in collected real samples in EBC. The sensor was fabricated and tested for its rapid electron transfer capability and ability to detect nitrite ions even at very low concentrations and low real sample levels. In the proposed setup, when the required potential was applied by using a direct power supply, the nitrite ions were oxidized electrocatalytically at amine-functionalized graphene oxide (AGO) decorated with gold nanoparticles on a carbon paper anodic pole. On the other hand, the reduction reaction of Prussian blue occurred at the cathodic pole of the bipolar electrode simultaneously. This strategy led to a change in color from blue to white as a result of the reduction process and the color change is proportional to the concentration of nitrite ions in the analytical solution. The combination of smartphones with the colorimetric method has resulted in a platform for the detection of test strips that is more visual and convenient. The amperometry and voltammetric methods of nitrite detection showed a linear range of up to 1230 μM. The bipolar electrochemical sensor was able to detect the clinically relevant range of nitrite from 0.5 to 85 μM in a buffer with an ultralow detection limit (LOD) of 250 nM (S/N = 3), fast response and excellent selectivity. It was benchmarked by utilizing pre-characterized real EBC samples to differentiate patients with respiratory diseases from healthy volunteers. By tracking the results of nitrite measurements over time, it has become possible to detect trends and changes in an individual's nitrite ion concentration and to potentially identify lung inflammation earlier. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal "Analyst" published by the Royal Society of Chemistry. It includes various articles and papers on topics such as physical and chemical MEMS sensors, alternative tumor models, electrochemiluminescence detection, and bacterial identification. The journal aims to connect the world with the chemical sciences and invest profits back into the chemistry community. [Extracted from the article]

The document is a contents list for the journal "Analyst" published by the Royal Society of Chemistry. It includes information about articles and papers featured in the journal, as well as details about an upcoming symposium on chromatography and allied techniques. The document provides a range of topics related to chemistry research, including uremic toxin detection, fluorescent imaging, and spectroscopy. It also includes information about keynote speakers and the venue for the symposium. [Extracted from the article]

Electrical insulators used in transmission lines and outdoor substations are exposed to severe environmental pollution, which significantly increases the risk of power system failure, especially when the pollution layer is highly humid due to adverse weather conditions. The focus of this paper is to establish an effective method for assessing the moisture content (MC) in pollution layers as it serves as a crucial indicator for evaluating the risk of failure in insulators. Hyperspectral imaging (HSI) technology with a spectral range of 371.08–1037.89 nm was applied to determine significant changes in reflectance spectral characteristics in insulators during dynamic wetting and drying periods. Partial least squares regression (PLSR) models were utilized to evaluate the data presentation enhancement abilities of spectral transformation models and the data dimensionality reduction abilities of characteristic band selection methods. Furthermore, PLSR models were developed to calculate the MC along the pixel dimension to visually retrieve the dynamic wetting and drying processes of the pollution layer. The R-squared and root-mean-square error (RMSE) results in the cross-verification set and prediction set of the RE-RF(70%)-PLSR model with two characteristic bands with a wavelength of 543.28 nm and 848.01 nm were as follows: RCV2 = 0.9824, RMSECV = 0.0367, RP2 = 0.9818, RMSEP = 0.0369, respectively. This research contributes towards the visualization retrieval of the MC and offers an important technique for analyzing flashover evolution, optimizing insulator design, and preparing coating materials for insulators. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal "Analyst" published by the Royal Society of Chemistry. It includes information about articles and papers featured in the journal, as well as details about upcoming events and conferences. The journal covers a wide range of topics in the field of chemistry and provides a platform for scientific research and advancements. [Extracted from the article]

The document is a contents list for the journal "Analyst" published by the Royal Society of Chemistry. It includes a range of papers and articles on various topics in the field of chemistry, such as analytical applications of Raman spectroscopy, pH detection in cancer cells, and monitoring sphingomyelin synthase activity. The journal aims to connect the global chemistry community and reinvest its profits back into the field. [Extracted from the article]

The document is a contents list for the journal "Analyst" published by the Royal Society of Chemistry. It includes a range of articles on various topics related to chemistry and bioanalytical research. Some of the topics covered include advances in biosensing, virus testing, and surface-enhanced Raman spectroscopy. The journal aims to connect the global chemistry community and invest its profits back into the field. [Extracted from the article]

In this paper, we present Raman imaging as a non-invasive approach for studying changes in mitochondrial metabolism caused by cardiolipin–cytochrome c interactions. We investigated the effect of mitochondrial dysregulation on cardiolipin (CL) and cytochrome c (Cyt c) interactions for a brain cancer cell line (U-87 MG). Mitochondrial metabolism was monitored by checking the intensities of the Raman bands at 750 cm−1, 1126 cm−1, 1310 cm−1, 1337 cm−1, 1444 cm−1 and 1584 cm−1. The presented results indicate that under pathological conditions, the content and redox status of Cyt c in mitochondria can be used as a Raman marker to characterize changes in cellular metabolism. This work provides evidence that cardiolipin–cytochrome c interactions are crucial for mitochondrial energy homeostasis by controlling the redox status of Cyt c in the electron transport chain, switching from disabling Cyt c reduction and enabling peroxidase activity. This paper provides experimental support for the hypothesis of how cardiolipin–cytochrome c interactions regulate electron transfer in the respiratory chain, apoptosis and mROS production in mitochondria. [ABSTRACT FROM AUTHOR]

NMR spectroscopy is one of the most potent methods in analytical chemistry. NMR titration experiments are particularly useful since they measure molecular binding affinities and other concentration-dependent effects. These experiments, however, require a long series of measurements. An alternative to these serial measurements has recently been presented, exploiting a pH (or generally – a concentration) gradient along the NMR tube. The proposed experiment, although efficient, was based on the sensitivity- and hardware-demanding chemical shift imaging (CSI) method. Thus, it is practically limited to high-resolution NMR spectrometers. This paper proposes modifying and adapting the approach to the popular and cost-efficient benchtop NMR machines. Instead of CSI, we use a device that shifts the NMR tube vertically to measure the spectra of different sample volumes, which have different pH values due to the established gradient along the tube. We demonstrate the potential of the method on the test samples of L -tyrosine and 2,6-lutidine, and two real samples from the food industry – an infant formula and an energy drink. The proposed method boosts spectral resolution and allows for the sampling of a broader range of pH values when compared to the original approach. [ABSTRACT FROM AUTHOR]

Understanding the influence of oxygen tension on cellular functions and behaviors is crucial for investigating various physiological and pathological conditions. In vitro cell culture models, particularly those based on hydrogel extracellular matrices, have been developed to study cellular responses in specific oxygen microenvironments. However, accurately characterizing oxygen tension variations with great spatiotemporal resolutions, especially in three dimensions, remains challenging. This paper presents an approach for rapid time-lapse 3D oxygen tension measurements in hydrogels using a widely available inverted fluorescence microscope. Oxygen-sensitive fluorescent microbeads and widefield frequency-domain fluorescence lifetime imaging microscopy (FD-FLIM) are utilized for oxygen tension estimation. To incorporate the third dimension, a motorized sample stage is implanted that enables automated image acquisition in the vertical direction. A machine learning algorithm based on K-means clustering is employed for microbead position identification. Using an upside-down microfluidic device, 3D oxygen gradients are generated within a hydrogel sample, and z-stack images are acquired using the FD-FLIM system. Analyses of the acquired images, involving microbead position identification, lifetime calculation, and oxygen tension conversion, are then performed offline. The results demonstrate the functionality of the developed approach for rapid time-lapse 3D oxygen tension measurements in hydrogels. Furthermore, the 3D oxygen tension adjacent to a tumor spheroid within a hydrogel during media exchange is characterized. The results further confirm that the 3D spatiotemporal oxygen tension profiles can be successfully measured quantitatively using the established setup and analysis process and that the approach may have great potential for investigating cellular activities within oxygen microenvironments. [ABSTRACT FROM AUTHOR]

Glucose is an important biomarker for diagnosing and prognosing various diseases, including diabetes and hypoglycemia, which can have severe side effects, symptoms, and even lead to death in patients. As a result, there is a need for quick and economical glucose level measurements to help identify those at potential risk. With the increase in smartphone users, portable smartphone glucose sensors are becoming popular. In this paper, we present a disposable microfluidic glucose sensor that accurately and rapidly quantifies glucose levels in human urine using a combination of colorimetric analysis and computer vision. This glucose sensor implements a disposable microfluidic device based on medical-grade tapes and glucose analysis strips on a glass slide integrated with a custom-made polydimethylsiloxane (PDMS) micropump that accelerates capillary flow, making it economical, convenient, rapid, and equipment-free. After absorbing the target solution, the disposable device is slid into the 3D-printed main chassis and illuminated exclusively with Light Emitting Diode (LED) illumination, which is pivotal to color-sensitive experiments. After collecting images, the images are imported into the algorithm to measure the glucose levels using computer vision and average RGB values measurements. This article illustrates the impressive accuracy and consistency of the glucose sensor in quantifying glucose in sucrose water. This is evidenced by the close agreement between the computer vision method used by the sensor and the traditional method of measuring in the biology field, as well as the small variation observed between different sensor performances. The exponential regression curve used in the study further confirms the strong relationship between glucose concentrations and average RGB values, with an R-square value of 0.997 indicating a high degree of correlation between these variables. The article also emphasizes the potential transferability of the solution described to other types of assays and smartphone-based sensors. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal "Analyst" published by the Royal Society of Chemistry. It includes a range of articles on various topics related to chemistry and analysis. Some of the articles featured in this issue include recent advances in nanopore technique in single-cell analysis, recent advances in biological molecule detection based on a three-dimensional graphene structure, and the design and application of dual-emission metal-organic framework-based ratiometric fluorescence sensors. The journal aims to connect the world with the chemical sciences and reinvest its profits back into the chemistry community. [Extracted from the article]

Norfloxacin (NOX), a broad spectrum fluoroquinolone (FQ) antibiotic, is commonly detected in environmental residues, potentially contributing to biological drug resistance. In this paper, an aptamer recognition probe has been used to develop a label-free liquid crystal-based biosensor for simple and robust optical detection of NOX in aqueous solutions. Stimuli-receptive liquid crystals (LCs) have been employed to report aptamer–target binding events at the LC–aqueous interface. The homeotropic alignment of LCs at the aqueous–LC interface is due to the self-assembly of the cationic surfactant cetyltrimethylammonium bromide (CTAB). In the presence of the negatively charged NOX aptamer, the ordering changes to planar/tilted. On addition of NOX, the aptamer–NOX binding causes redistribution of CTAB at the LC–aqueous interface and the homeotropic orientation is restored. This results in a bright-to-dark optical transition under a polarized optical microscope (POM). This optical transition serves as a visual indicator to mark the presence of NOX. The devised aptasensor demonstrates high specificity with a minimum detection limit of 5 nM (1.596 ppb). Moreover, the application of the developed aptasensor for the detection of NOX in freshwater and soil samples underscores its practical utility in environmental monitoring. This proposed LC-based method offers several advantages over conventional detection techniques for a rapid, feasible and convenient way to detect norfloxacin. [ABSTRACT FROM AUTHOR]

A restriction endonuclease (RE) is an enzyme that can recognize a specific DNA sequence and cleave that DNA into fragments with double-stranded breaks. This sequence-specific cleaving ability and its ease of use have made REs commonly used tools in molecular biology since their first isolation and characterization in 1970s. While artificial REs still face many challenges in large-scale synthesis and precise activity control for practical use, searching for new REs in natural samples remains a viable route to expanding the RE pool for fundamental research and industrial applications. In this paper, we propose a new strategy to search for REs in an efficient manner. We constructed a host bacterial cell to link the genotype of REs to the phenotype of β-galactosidase expression based on the bacterial SOS response, and used a high-throughput microfluidic platform to isolate, detect and sort the REs in microfluidic drops at a frequency of ∼800 drops per second. We employed this strategy to screen for the XbaI gene from the constructed libraries of varied sizes. In a single round of sorting, a 90-fold target enrichment was achieved within 1 h. Compared to conventional RE-screening methods, the direct screening approach that we propose excels at efficient search of desirable REs in natural samples – especially unculturable samples – and can be tailored to high-throughput screening of a wide range of genotoxic targets. [ABSTRACT FROM AUTHOR]

The contamination of environmental sites due to the presence of persistent species represents an important issue to be tackled. In particular, the presence of high levels of metals in soil and surface water is more frequent. One of the metals that sometimes exceeds the permissible limit set by regulatory authorities is copper. For instance, copper-based fungicides are widely used in viticulture. However, copper ions remain in soil and can enter the food chain, posing threats to human health and environmental safety. Although the rapid detection of copper ions using portable sensors is effective in enhancing early warning, it sometimes solves only half of the problem as remediation is not considered. In this paper, we present a novel integrated/portable approach that merges the remediation and sensing of metals by proposing a remediate-and-sense concept. In order to realize this concept, alginate beads were coupled with printed electrochemical strips for on-site copper detection. Within the same architecture, alginate beads were used to remove copper ions from the soil, and printed electrochemical strips were used to evaluate the efficacy of remediation at the point of need. The concept was applied towards soil containing copper ions at the parts per billion level; with few alginate beads and in the absence of additional species, copper ions were quantitatively removed from the matrix; and 3D printing allowed us to combine the printed strips and spheres within a unique tool. The architecture was optimized and the results were compared to inductively coupled plasma-mass spectrometry (ICP-MS) measurements with a recovery percentage of 90%–110%. It should be noted that this novel portable approach may be applied to other pollutants, opening new possibilities for integrated remediation and sensing. [ABSTRACT FROM AUTHOR]

Antimicrobial resistance poses a serious threat to human health due to the high morbidity and mortality caused by drug-resistant microbial infections. Therefore, the development of rapid, sensitive and selective identification methods is key to improving the survival rate of patients. In this paper, a sandwich-type electrochemical DNA biosensor based on a polyadenine-DNA tetrahedron probe was constructed. The key experimental conditions were optimized, including the length of polyadenine, the concentration of the polyadenine DNA tetrahedron, the concentration of the signal probe and the hybridization time. At the same time, poly-avidin-HRP80 was used to enhance the electrochemical detection signal. Finally, excellent biosensor performance was achieved, and the detection limit for the synthetic DNA target was as low as 1 fM. In addition, we verified the practicability of the system by analyzing E. coli with the MCR-1 plasmid and realized multi-channel detection of the drug resistance genes MCR-1, blaNDM, blaKPC and blaOXA. With the ideal electrochemical interface, the polyA-based biosensor exhibits excellent stability, which provides powerful technical support for the rapid detection of antibiotic-resistant strains in the field. [ABSTRACT FROM AUTHOR]

Microparticle rotation is an important process in biomedical engineering, such as biosensors, cell injection or cell morphology. Single particle rotation has been widely investigated, while rotation of particle chains has gained rare attention. In this paper, we utilize a noncontact manipulation method to rotate microparticle chains via electrorotation by designing an octuple-electrode array (OEA). Finite element simulations were conducted for analyzing the desired electrode field and optimizing the structure of microelectrode pairs. The direction of the electric field in the workspace is investigated with different voltage signal inputs through specially designed circuits. In the experiment, microparticles are driven to form several chains in the proposed electrode fields. With the rotation of the electric field, particle chains could be rotated synchronously. Automated rotation and detection of polystyrene microspheres and yeast cell chains are achieved using machine vision technology. Results show that the proposed method could be utilized to rotate ordered microparticles with an appropriate input signal. [ABSTRACT FROM AUTHOR]

Small extracellular vesicles (sEVs), a form of extracellular vesicles, are lipid bilayered structures released by all cells. Large-scale studies on sEVs from clinical samples are necessary, but a major obstacle is the lack of rapid, reproducible, efficient, and low-cost methods to enrich sEVs. Acoustic microfluidics have the advantage of being label-free and biocompatible, which have been reported to successfully enrich sEVs. In this paper, we present a highly efficient acoustic microfluidic trap that can offer low and large volume compatible ways of enriching sEVs from biological fluids by flexible structure design. It uses the idea of pre-loading larger seed particles in the acoustic trap to enable sub-micron particle capturing. The microfluidic chip is actuated using a piezoelectric plate transducer attached to a silicon-glass bonding plate with circular cavities. Each cavity works as a resonant unit, excited at the frequency of both the half wave resonance in the main plane and inverted quarter wave resonance in the depth direction, which has the ability to strongly trap seed particles at the center, thereby improving the subsequent nanoparticle capture efficiency. Mean trapping efficiencies of 35.62% and 64.27% were obtained using 60 nm and 100 nm nanobeads, respectively. By the use of this technology, we have successfully enriched sEVs from cell culture conditioned media and blood plasma at a flow rate of 10 µL min-1. The isolated sEV subpopulations are characterized by NTA and TEM, and their protein cargo is determined by WB. This acoustic trapping chip provides a rapid and robust method to enrich sEVs from biofluids with high reproducibility and sufficient quantities. Therefore, it can serve as a new tool for biological and clinical research such as cancer diagnosis and drug delivery. [ABSTRACT FROM AUTHOR]

Cell migration is known to be a fundamental biological process, playing an essential role in development, homeostasis, and diseases. This paper introduces a cell tracking algorithm named HFM-Tracker (Hybrid Feature Matching Tracker) that automatically identifies cell migration behaviours in consecutive images. It combines Contour Attention (CA) and Adaptive Confusion Matrix (ACM) modules to accurately capture cell contours in each image and track the dynamic behaviors of migrating cells in the field of view. Cells are firstly located and identified via the CA module-based cell detection network, and then associated and tracked via a cell tracking algorithm employing a hybrid feature-matching strategy. This proposed HFM-Tracker exhibits superiorities in cell detection and tracking, achieving 75% in MOTA (Multiple Object Tracking Accuracy) and 65% in IDF1 (ID F1 score). It provides quantitative analysis of the cell morphology and migration features, which could further help in understanding the complicated and diverse cell migration processes. [ABSTRACT FROM AUTHOR]

A europium-functionalized, dual-emissive, metal–organic framework-based fluorescence sensor (EuUCNDA) was constructed via post-synthetic modification of an UiO-66-type precursor through coordination interactions. EuUCNDA exhibited extremely high selectivity and sensitivity for malachite green (MG) with a low detection limit of 13.01 nM, a wide linear concentration range (0.05–50 μM), excellent anti-interference properties, a rapid response (<1 min), and the possibility of recycling. The good sensing performance of EuUCNDA enables the practical detection of MG in fish pond water and grass carp with good recoveries. Moreover, EuUCNDA can be reused for sensing MG and over 90% of fluorescence intensity can be restored after 7 cycles. Furthermore, EuUCNDA-embedded paper-based sensors combined with smartphone imaging afford portable and visual monitoring of MG in real samples. Notably, besides good sensing performance, EuUCNDA could efficiently remove MG from water. Hence, this work provides a recyclable and sensitive fluorescence sensor for portable, visual, rapid detection and efficient removal of MG. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPs) are extensively used in cellular imaging, single-particle tracking, disease diagnosis, studying membrane protein interaction, and drug delivery. Understanding the dynamics of AuNP uptake in live cells is crucial for optimizing their efficacy and safety. Traditional manual methods for quantifying AuNP uptake are time-consuming and subjective, limiting their scalability and accuracy. The available fluorescence-based techniques are limited to photobleaching and photoblinking. Optical microscopy techniques are limited by diffraction limits. Electron microscopy–based imaging techniques are destructive and unsuitable for live cell imaging. Furthermore, the resulting images may contain hundreds of particles with varied intensities, blurring, and substantial occlusion, making it difficult to manually quantify AuNP uptake. To overcome this issue and measure AuNP uptake by live cells, we annotated a dataset of dark-field images of 50 nanometer–radius AuNPs at different incubation durations. Then, to count the number of particles present in a cell, we created a customized multi-column convolutional neural network (MC-CNN). The customized MC-CNN outperformed typical particle counting architectures when compared to spectroscopy-based counting. This will allow researchers to gain a better understanding of AuNP behavior and interactions with cells, paving the way for advancements in nanomedicine, drug delivery, and biomedical research. The code for this paper is available at the following link: https://github.com/Namerlight/LabelFree_AuNP_Quantification. [ABSTRACT FROM AUTHOR]

This paper describes the electrochemical behavior of five β-blockers at the polarized liquid–liquid interface formed between aqueous solution (sodium chloride solution or Britton–Robinson buffers) and bis(triphenylphosphoranylidene)ammonium tetrakis(4-chlorophenyl)borate (BTPPATPBCl) dissolved in 1,2-dichloroethane (the organic phase). All measurements reported in this work were conducted using cyclic voltammetry (CV). The effects of the concentration of analytes, the pH of the aqueous phase, and applied electrochemical parameters on the analytical performance of the studied system are studied and discussed. The linear dynamic ranges (LDRs) of the studied β-blockers were in the range of 5–200 μmol L−1 and the lowest limit of detection (LOD) value was determined for pindolol (LOD = 1.96 μM μmol L−1). The highest LOD value was 4.96 μmol L−1 found for nebivolol. In addition, physicochemical parameters such as the formal Galvani potential difference (Δ aqorg φ), formal Gibbs free energies of the ion transfer reaction (Δ aqorg G′) and partition coefficients (log P′aq/org) for all studied molecules were determined. The latter were compared and correlated with the available literature values of log Poctanol. Finally, a standard addition method was used to determine the concentration of nebivolol in pharmaceutical preparations using a platform based on the electrified liquid–liquid interface. [ABSTRACT FROM AUTHOR]

Cadmium poisoning is a chronic accumulation process, and long-term drinking of even low cadmium content water will cause kidney damage, so an ultra-low detection limit is particularly important. However, at the present stage, the traditional detection method cannot reach a sufficiently low detection limit, the response time is too long, and the cost of detection is very high, so that real-time measurement cannot be realized. Therefore, the traditional cadmium ion detection method has a slow response and an insufficient detection limit. This paper presents a fiber optic cadmium ion sensor functionalized based on an Fe3O4@SiO2@CS magnetic ion imprinting polymer (M-IIP). The sensor is based on the coupling characteristics of the optical microfiber coupler (OMC) cone region to achieve a highly sensitive response to the change in the cadmium ion concentration. M-IIP materials were prepared by surface imprinting polymerization to achieve low cross-sensitivity and thus improve the detection limit of the sensor. The results show that the developed fiber sensor has high specificity and a rapid response to cadmium ions. The experimental limit of detection (LOD) reached 0.051 nM within 0–1 μM with a response time of less than 50 s. Moreover, the proposed fiber cadmium ion sensor exhibits excellent performance in terms of sensitivity, stability, repeatability and biocompatibility. [ABSTRACT FROM AUTHOR]

Droplet microfluidics is a highly sensitive and high-throughput technology extensively utilized in biomedical applications, such as single-cell sequencing and cell screening. However, its performance is highly influenced by the droplet size and single-cell encapsulation rate (following random distribution), thereby creating an urgent need for quality control. Machine learning has the potential to revolutionize droplet microfluidics, but it requires tedious pixel-level annotation for network training. This paper investigates the application software of the weakly supervised cell-counting network (WSCApp) for video recognition of microdroplets. We demonstrated its real-time performance in video processing of microfluidic droplets and further identified the locations of droplets and encapsulated cells. We verified our methods on droplets encapsulating six types of cells/beads, which were collected from various microfluidic structures. Quantitative experimental results showed that our approach can not only accurately distinguish droplet encapsulations (micro-F1 score > 0.94), but also locate each cell without any supervised location information. Furthermore, fine-tuning transfer learning on the pre-trained model also significantly reduced (>80%) annotation. This software provides a user-friendly and assistive annotation platform for the quantitative assessment of cell-encapsulating microfluidic droplets. [ABSTRACT FROM AUTHOR]

The issue of preserving carbonatic stones of cultural heritage (CH) restored in the past that have undergone new decay phenomena is strongly emerging and conservation science has not yet found a reliable solution. In this paper, we propose the application of synchrotron radiation X-ray diffraction computed tomography (XRDCT) to explore the effects of using inorganic-mineral products (ammonium oxalate; ammonium phosphate) in sequence as a novel, compatible and effective re-treatment approach to consolidate decayed carbonatic stones already treated with inorganic-mineral treatments. High-quality XRDCT datasets were used to qualitatively/quantitatively investigate and 3D localize the complex mixture of crystalline phases formed after the conservation re-treatments within a porous carbonatic stone substrate. The XRDCT reconstruction images and the structural refinements of XRD patterns with the Rietveld methods showed that the phase composition of reaction products, their volume distribution, and weight fraction vary as a function of the treatment sequence and penetration depth. The high potential of XRDCT allows (i) assessment of peculiar trends of each treatment/treatment sequence; (ii) exploration of the reaction steps of the sequential treatments and (iii) demonstration of the consolidating effect of inorganic re-treatments, non-destructively and at the micron scale. Above all, our study (i) provides new analytical tools to support the conservation choices, (ii) showcases new analytical possibilities for XRDCT in conservation science, including in investigations of CH materials and decay processes, and (iii) opens up new perspectives in analytical chemistry and material characterisation for the non-destructive and non-invasive analysis of reactions within heterogeneous polycrystalline systems. [ABSTRACT FROM AUTHOR]

New electrochemical probes offer the opportunity to investigate new systems. A dual barrel electrode can be laser pulled to produce micron-sized platinum disk electrodes. Here, we detail several important considerations for both the fabrication process and for experimental implimentation of the probe. We provide parameters for a Sutter P-2000 laser puller, methods for optical and electrochemical characterization, tips for how to successfully bevel the microelectrodes, and how salt concentrations and electrostatic discharge affect the voltammetry. This paper serves as a guide for how to successfully implement dual barrel electrodes from fabrication to experimentation. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal "Analyst" published by the Royal Society of Chemistry. It includes articles on various topics such as the separation and purification of fluorescent carbon dots, the effects of nucleotide mutations on loop-mediated isothermal amplification, and the combinatorial effect of calcium chloride and polyethylene glycol on the isolation of small extracellular vesicles. The journal covers a range of research in the field of chemistry and is open to everyone. [Extracted from the article]

The electrochemical detection method of cytotoxicity using intracellular purines as biomarkers has shown great potential for in vitro drug toxicity evaluation. However, no electrochemical detection system based on an in vitro drug metabolism mechanism has been devised. In this paper, electrochemical voltammetry was used to investigate the effect of the S9 system on the electrochemical behavior of HepG2 cells, and benzo[a]pyrene, fluoranthene, and pyrene were employed to investigate the sensitivity of electrochemical signals of cells to the cytotoxicity of drugs metabolized by the S9 system. The results showed that, within 8 h of exposure to the S9 system, the electrochemical signal of HepG2 cells at 0.7 V did not alter noticeably. The levels of xanthine, guanine, hypoxanthine, and adenine in the cells were not significantly altered. Compared with the absence of S9 system metabolism, benzo[a]pyrene and fluoranthene processed by the S9 system decreased the electrochemical signal of the cells in a dose-dependent manner, while pyrene did not change it appreciably. HPLC also revealed that benzo[a]pyrene and fluoranthene metabolized by the S9 system decreased the intracellular purine levels, whereas pyrene had no effect on them before and after S9 system metabolism. The cytotoxicity results of the three drugs examined by electrochemical voltammetry and MTT assay showed a strong correlation and good agreement. The S9 system had no effect on the intracellular purine levels or the electrochemical signal of cells. When the drug was metabolized by the S9 system, variations in cytotoxicity could be precisely detected by electrochemical voltammetry. [ABSTRACT FROM AUTHOR]

Selectivity improvement by the frequency tuning of Mg@ZnO–TiO2 nanoflake-based heterojunction devices under exposure to different volatile organic compounds is the prime focus of the present paper. The synthesis of Mg@ZnO–TiO2 nanoflakes was carried out using a solution process followed by a low-cost hydrothermal method. A capacitive measurement approach was used to find the resonant frequencies of the device in 2-butanone, acetone, 2-propanol, ethanol, and methanol environments in the frequency range from 0.001 to 220 kHz. A Cole–Cole plot derived from impedance measurements suggested that the device impedance consisted of capacitance (Cz = 2.01 pF and CT = 2.17 pF) and resistance (Rz = 13 552.2 kΩ and RT = 3500.574 kΩ) from the ZnO nanoflake layer and TiO2 thin film layer, respectively. The maximum capacitive responses to 2-butanone (C4H8O), acetone (C3H6O), 2-propanol (C3H8O), ethanol (C2H5OH), and methanol (CH3OH) were recorded at resonant frequencies of 1.000 kHz, 0.791 kHz, 0.702 kHz, 0.319 kHz and 0.103 kHz, respectively, at the corresponding temperature of 125 °C, 100 °C, 100 °C, 75 °C, and 75 °C, respectively. The device offered optimum capacitive responses of 221.32%, 242.65%, 317.09%, 373.96%, and 401.24% to 100 ppm of 2-butanone, acetone, 2-propanol, ethanol, and methanol, respectively. Experimental observation confirmed that the capacitive response inversely varied with the resonant frequency. Such an inverse relation was correlated with the dielectric variation at the junction interface, change in the molecular weights of VOCs, and their sticking coefficient. An equivalent circuit diagram with the help of adsorption–desorption isotherms and an energy band model is illustrated to correlate the device optimum capacitive response at the tuned frequencies under different VOC media. [ABSTRACT FROM AUTHOR]

The advancement of point-of-care diagnostics is crucial to improving patient outcomes, especially in areas with low access to hospitals or specialized laboratories. In particular, rapid, sensitive, and multiplexed detection of disease biomarkers has great potential to achieve accurate diagnosis and inform high quality care for patients. Our Coulter counting and immunocapture based detection system has previously shown its broad applicability in the detection of cells, proteins, and nucleic acids. This paper expands the capability of the platform by demonstrating multiplexed detection of whole-virus particles using electrically distinguishable hydrogel beads by demonstrating the capability of our platform to achieve simultaneous detection at clinically relevant concentrations of hepatitis A virus (>2 × 103 IU mL−1) and human parvovirus B19 virus like particles (>106 IU mL−1) from plasma samples. The expanded versatility of the differential electrical counting platform allows for more robust and diverse testing capabilities. [ABSTRACT FROM AUTHOR]