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The rapid discrimination of bacteria is currently an emerging trend in the fields of food safety, medical detection, and environmental observation. Traditional methods often require lengthy culturing processes, specialized analytical equipment, and bacterial recognition receptors. In response to this need, we have developed a paper-based fluorescence sensor array platform for identifying different bacteria. The sensor array is based on three unique carbon quantum dots (CQDs) as sensing units, each modified with a different antibiotic (polymyxin B, ampicillin, and gentamicin). These antibiotic-modified CQDs can aggregate on the bacterial surface, triggering aggregation-induced fluorescence quenching. The sensor array exhibits varying fluorescent responses to different bacterial species. To achieve low-cost and portable detection, CQDs were formulated into fluorescent ink and used with an inkjet printer to manufacture paper-based sensor arrays. A smartphone was used to collect the responses generated by the bacteria and platform. Diverse machine learning algorithms were utilized to discriminate bacterial types. Our findings showcase the platform's remarkable capability to differentiate among five bacterial strains, within a detection range spanning from 1.0 × 103 CFU/mL to 1.0 × 107 CFU/mL. Its practicality is further validated through the accurate identification of blind bacterial samples. With its cost-effectiveness, ease of fabrication, and high degree of integration, this platform holds significant promise for on-site detection of diverse bacteria. [ABSTRACT FROM AUTHOR]

In this work, a low-cost and eco-friendly paper-based analytical device (PAD) method is described for the determination of phyto-cannabinoids in cannabis and oral fluids based on a simple colorimetric reaction. The PAD was able to distinguish tetrahydrocannabinol (THC)- and cannabidiol (CBD)-rich plant samples by using 4-aminophenol (4-AP) and later on to quantify total phyto-cannabinoid content (THC + CBD + CBN) in plant and oral fluids by using the Fast Corinth V reagent. The chemical and physical properties regarding paper type and reagent concentration in the PAD were optimized to achieve the best analytical performance. After that, analytical features were obtained, including a linear range of 0.01–0.1 mg mL−1, a limit of detection (LOD) of 0.003 mg mL−1, and a suitable precision, expressed as relative standard deviation (RSD) lower than 10%. Furthermore, no significant interferences were observed in colorimetric reactions when tea, herbs, and drug samples were analyzed. Additionally, the PAD proved color stability up to 1 month after the sampling at 25 °C. The developed PAD was suitable for determining total phyto-cannabinoid content in plants and oral fluids, obtaining good results compared to GC–MS. Overall, this method showed good reliability resulting in an operational on-site device for drug monitoring. [ABSTRACT FROM AUTHOR]

Uric acid (UA) is an important biomarker, as a high concentration in blood can lead to gout and further renal syndrome. Although several point-of-care testing (POCT) devices have been reported to detect UA, there are some limitations such as the requirement for uricase and the complicated pretreatment of serum/plasma samples, which restricts their use at home or in undeveloped areas. In this work, we developed an approach by applying Zn2+ to precipitate proteins and cells in whole blood to avoid interference with the chromogenic reaction. We used carboxymethylcellulose (CMC) to immobilize tetramethylbenzidine (TMB) on a nitrocellulose membrane for colorimetric detection. Using the oxidization properties of H2O2, which turns TMB into oxidized tetramethylbenzidine (TMBox) in the presence of catalyst gold nanoparticles (AuNPs), we successfully constructed an enzyme-free paper-based POCT device using the reduction reaction of UA and TMBox for simple, speedy, and cheap colorimetric detection of UA, achieving a detection time of 8 min, a linear range of 0–150 μg/mL, and an LOD of 25.79 μg/mL. The UA concentration in whole blood samples was further measured and correlated well with the clinical value (R2 = 0.8212). Thus, the proposed assay has the potential for POCT diagnosis, monitoring, and prognosis of diseases related to UA. By applying Zn2+ reagent to precipitate proteins and cells in whole blood and the reduction reaction of UA, an enzyme-free paper-based POCT assay was established. [ABSTRACT FROM AUTHOR]

Dual-emissive fluorescent carbon dots (CDs) were prepared through the solvothermal method with citric acid and urea as raw materials and dimethylformamide as the solvent. Two emission peaks were observed at 465 nm and 630 nm. Hg2+ could selectively quench the fluorescence at 630 nm, but the fluorescence intensity at 465 nm was less affected. Accordingly, a ratiometric fluorescence sensor for Hg2+ detection was developed, with a linear detection range of 0.5–40 μM and a limit of detection (LOD) of 37 nM. The dual-emissive CDs were loaded on the surface of the filter paper to fabricate Hg2+ detection test paper. The color of the test paper could be changed from pink purple to blue by the addition of Hg2+, and thus the qualitative and quantitative detection of Hg2+ could be realized. The concentration distinguishable by the naked eye reached 50 μM, and the quantitative detection range was 5–10,000 μM. This method shows excellent selectivity for Hg2+ and can be used to detect Hg2+ in real water samples, providing a highly potential sensing platform for rapid on-site detection of mercury ions. [ABSTRACT FROM AUTHOR]

This study investigated the colorimetric response of standard glucose, serum glucose, and nucleic acid assays on various paper surfaces with different wettability, including hydrophilic, hydrophobic, and nearly superhydrophobic surfaces. Water contact angles (WCA) formed by water droplets on each surface were measured using ImageJ software. The hydrophilic surface showed no contact angle, while the hydrophobic and nearly superhydrophobic surfaces exhibited contact angles of 115.667° and 133.933°, respectively. The colorimetric sensitivity of the standard glucose assay was analyzed on these surfaces, revealing enhanced sensitivity on the nearly superhydrophobic surface due to the high molecular crowding effect owing to its non-wetting behavior and eventually confined reaction product at the sample loading zone. The hydrophobic nature of the surface restricts the spreading and diffusion of the reaction product, leading to a controlled and localized concentration of the assay product leading to moderate colorimetric intensity. On the other hand, the hydrophilic surface showed the least enhancement in colorimetric sensitivity; this is attributed to the high wettability of the hydrophilic surface causing the reaction product to spread extensively, resulting in a larger area of dispersion and consequently a lower colorimetric intensity. The measured limit of detection (LOD) for nucleic acid on nearly superhydrophobic surfaces was found to be 16.15 ng/µL, which was almost four-fold lower than on hydrophilic surfaces (60.08 ng/µL). Additionally, the LODs of standard glucose and clinical serum samples were two-fold lower on nearly superhydrophobic surfaces compared to hydrophilic surfaces. Our findings clearly highlight the promising potential of utilizing superhydrophobic surfaces to significantly enhance colorimetric sensitivity in paper-based diagnostic applications. This innovative approach holds promise for advancing point-of-care diagnostics and improving disease detection in resource-limited settings. [ABSTRACT FROM AUTHOR]

A new rhodamine B derivative (RDB) was synthesized and utilized for the colorimetric detection of copper ions (Cu2+). This chemosensor utilized a paper strip as a support and a smartphone as a detector for on-site quantitative detection of Cu2+ in water samples. Silica nanoparticles (SiNPs) were investigated as the modifier nanoparticles to achieve uniform color on the paper strip and showed a color response 1.9-fold higher than the one without SiNPs. The RDB chemosensor-based paper strip provided high selectivity toward Cu2+ with a detection limit of 0.7 mg/L, and the working concentrations for Cu2+ ranged from 1 to 17 mg/L. Parallel analyses of eight drinking water samples were conducted by inductively coupled plasma optical emission spectroscopy. The results were in good agreement, indicating the practical reliability of the established method with a short assay time and high selectivity. These indicate its great potential for on-site detection of Cu2+. [ABSTRACT FROM AUTHOR]

We report the development of a competitive ELISA-based origami microfluidic paper-based analytical device (μPAD) for the detection of mycotoxins in animal feed material. The μPAD was patterned using the wax printing technique with the design of a testing pad in the middle and two absorption pads at the side. Anti-mycotoxin antibodies were effectively immobilized on chitosan–glutaraldehyde-modified sample reservoirs in the μPAD. The determination of zearalenone, deoxynivalenol, and T-2 toxin in corn flour was successfully achieved by performing competitive ELISA on the μPAD in 20 min. Colorimetric results were easily distinguished by the naked eye with a detection limit of 1 µg/mL for all three mycotoxins. The μPAD integrated with competitive ELISA holds potential for practical applications in the livestock industry for rapid, sensitive, and cost-effective detection of different mycotoxins in animal feed materials. [ABSTRACT FROM AUTHOR]

This manuscript reports on a simple paper-based bienzymatic colorimetric assay for sarcosine as an important urinary biomarker of prostate cancer. All required assay reagents are pre-deposited on hydrophilic filter paper spots surrounded by a hydrophobic barrier. Sarcosine in the sample solution is selectively oxidized in the presence of sarcosine oxidase (SOx), resulting in the formation of hydrogen peroxide, which is subsequently detected through the horseradish peroxidase (HRP)–catalyzed conversion of the colorless indicator 3,3',5,5'-tetramethylbenzidine (TMB) into its blue-colored oxidation product. By the modification of the paper with positively charged poly(allylamine hydrochloride) (PAH), a linear response to sarcosine between 0 and 10 μM and a significant lowering of the limit of detection (LOD) (0.6 μM) compared to the unmodified paper substrate (12.6 μM) has been achieved. The improvement of the LOD was attributed to the fact that the presence of the polymer limits the enzyme-driven colorimetric reaction to the surface of the paper substrate, resulting in stronger color development. In experiments in artificial urine matrix, the bicarbonate anion was identified as an inhibitor of the colorimetric reaction. This inhibition was successfully eliminated through on-device sample pH adjustments with pH-buffer components pre-deposited onto assay devices. The LOD for sarcosine achieved in artificial urine matrix (2.5 μM) is below the 5 μM threshold value for this urinary biomarker required for diagnostic purposes. Finally, good selectivity over all 20 natural amino acids and satisfactory long-term storage stability of reagent-modified paper substrates at − 20 °C for a period of 50 days were confirmed. [ABSTRACT FROM AUTHOR]

This work presents a microfluidic paper-based analytical device (μPAD) for the determination of sucrose using the Benedict's test. An asymmetric dumbbell-shaped hydrophobic barrier was produced by rubber stamping the barrier pattern onto a laboratory filter paper. Hydrochloric acid and solution containing sucrose were successively deposited onto the sample reservoir of the μPAD attached to a glass slide. The device was placed in a plastic bag and dipped into boiling water for accelerating the hydrolysis of sucrose into the reducing sugars. Then the Benedict's reagent was added at the narrow straight channel connecting the two circular zones of the μPAD, which was replaced in the plastic bag and heated again for reduction of Cu(II) by the reducing sugars. Precipitate of brick-red copper(I) oxide was formed. The image of the μPAD was recorded by a smartphone. The ratio of the red to blue intensities gave linear correlation with the concentration of sucrose in the range of 0.5–10% w/v. The relative standard deviation of the measurement was less than 5% for 2 and 4% w/v sucrose (n = 10), with limit of determination, calculated using standard deviation of regression divided by slope of calibration, of 0.26% w/v sucrose. The method was successfully validated using the dinitrosalicylic acid method for sucrose measurement. Percent recoveries of sucrose were evaluated using ten sugarcane samples. The recoveries were in the range of 89 to 101%, demonstrating that there were no significant sample matrix effects on the quantification. [ABSTRACT FROM AUTHOR]

Background noise due to nonspecific binding of biomolecules on the assay substrates is one of the most common challenges that limits the sensitivity of microarray-based immunoassays. Background signal intensity usually increases when complex biological fluids are used because they have a combination of molecules and vesicles that can adsorb onto substrate surfaces. Blocking strategies coupled with surface chemistries can reduce such nonspecific binding and improve assay sensitivity. In this paper, we conducted a systematic optimization of blocking strategies on a variety of commonly used substrates for protein measurement in complex biofluids. Four blocking strategies (BSA, non-fat milk, PEG, and a protein-free solution) coupled with four surface chemistries (3-glycidoxypropyltrimethoxysilane (GPS), poly-L-lysine (PLL), aminoalkylsilane (AAS), and nitrocellulose (NC)) were studied for their effect on background, microspot, and net signal intensities. We have also explored the effect that these blocking strategies have when proteins in complex samples (plasma, serum, cell culture media, and EV lysate) are measured. Irregular spot morphology could affect signal extraction using automated software. We found that the microspots with the best morphology were the ones printed on GPS glass surfaces for all immunoassays. On NC membrane, the protein-based blocking strategies yielded the highest net fluorescent intensity with the antigen contained in PBS, plasma, serum, and serum-free cell culture media. Differently, with EV lysate samples, Pierce™ protein-free blocker yielded the best net signal intensity on both GPS and NC surfaces. The choice of blocking strategies highly depends on the substrate. Moreover, the findings discovered in this study are not limited to microarray-based immunoassays but can provide insights for other assay formats. [ABSTRACT FROM AUTHOR]

Nowadays, in the clinical, pharmaceutical, and environmental sectors, the development of facile and sensitive analytical methods and/or innovative devices for the follow-up and detection of antibiotics and pharmaceutical formulations, in general, are urgently needed and still challenging. This work declared three vital applications for broad-spectrum nitrofurantoin (macrofuran) antibiotic detection and quantification: A colorimetric method, a coated paper strip-based nano-lanthanum complex prototype and fabrication of smart electronic color sensor device-based coated paper strips. The colorimetric method showed a significant response upon increasing the concentration of the nitrofurantoin in a range between (1.0–100.0 ng/mL) via a visual color change from orange-yellow to red colors degree with detection and quantification limits of 0.175 and 0.53 ng/mL, respectively, whereas the nano-lanthanum complex coated paper strip prototype showed qualitative on-site sensing for nitrofurantoin via naked eye color changes which can be detected anywhere. Moreover, a smart prototype for detecting macrofuran in the means of paper color change in the RGB color component extraction algorithm and the grayscale projection value processing algorithm was fabricated. The change in RGB color on the coated paper strip was detected using an electronic color sensor device. The developed colorimetric method, coated paper strip, and the electronic color sensor device prototype exhibited fast, simple, costless, and selective towards macrofuran over the competing analyzed. As well as, showed good applicability in the different real samples spiked with different concentrations of macrofuran. [ABSTRACT FROM AUTHOR]

The fast-growing healthcare demand for user-friendly and affordable analytical tools is driving the efforts to develop reliable platforms for the customization of therapy based on individual health conditions. In this overall scenario, we developed a paper-based electrochemical sensor for the quantification of iron ions in serum as a cost-effective sensing tool for the correct supplement administration. In detail, the working electrode of the screen-printed device has been modified with a nanocomposite constituted of carbon black and gold nanoparticles with a drop-casting procedure. Square wave voltammetry has been adopted as an electrochemical technique. This sensor was further modified with Nafion for iron quantification in serum after sample treatment with trifluoroacetic acid. Under optimized conditions, iron ions have been detected with a LOD down to 0.05 mg/L and a linearity up to 10 mg/L in standard solution. The obtained results have been compared with reference methods namely commercial colorimetric assay and atomic absorption spectroscopy, obtaining a good correlation within the experimental errors. These results demonstrated the suitability of the developed paper-based sensor for future applications in precision medicine of iron-deficiency diseases. [ABSTRACT FROM AUTHOR]

We developed a paper-based colorimetric sensor for facile and cost-effective detection of Pb2+ in drinking and environmental water samples. The Pb2+ ion–selective optodes are fabricated by inkjet printing of ionophore, chromoionophore, and ion exchanger on cellulose paper. Pb2+ in water samples induces deprotonation of the pH chromoionophore and changes the optode color, which is acquired and analyzed by a smartphone. The paper-based optode without any plasticizer or polymer has a dynamic range and selectivity comparable to those of traditional optodes using PVC polymer and/or plasticizer. Furthermore, the response time of the plasticizer/polymer-free paper-based optode is much shorter than those of plasticized PVC-based optodes on paper and glass (5 min vs. 15 and 50 min). Moreover, the plasticizer/polymer-free optode preserves the water-wicking capability of porous cellulose paper, allowing for the design of pump-free microfluidic devices. Chloramine, a widely used disinfectant in drinking water, was found to be a strong and generic interference species for heavy metal ion detection via ion-selective optodes. A fully inkjet-printed lateral-flow paper-based device consisting of a sodium thiosulfate–based chloramine elimination zone and a plasticizer/polymer-free sensing zone was designed for Pb2+ detection in tap water disinfected by chloramine. The dynamic range of the Pb2+ sensor may be shifted from the current 10−6 to 10−5 M to lower concentrations by using stronger ionophores, but this work lays a foundation for the design of paper-based heavy metal ion sensors without detrimental interference from disinfectants. [ABSTRACT FROM AUTHOR]

SARS-CoV-2 has mutated many times since the onset of the COVID-19 pandemic, and the omicron is currently the most dominant variant. Determining the specific strain of the virus is beneficial in providing proper care and containment of the disease. We have previously reported a novel method of counting the number of particle immunoagglutination on a paper microfluidic chip using a smartphone-based fluorescence microscope. A single-copy-level detection was demonstrated from clinical saline gargle samples. In this work, we further evaluated two different SARS-CoV-2 monoclonal antibodies to spike vs. nucleocapsid antigens for detecting omicron vs. delta and spike vs. nucleocapsid proteins. The SARS-CoV-2 monoclonal antibody to nucleocapsid proteins could distinguish omicron from delta variants and nucleocapsid from spike proteins. However, such distinction could not be found with the monoclonal antibody to spike proteins, despite the numerous mutations found in spike proteins among variants. This result may suggest a clue to the role of nucleocapsid proteins in recognizing different variants. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HClO), the core bactericidal substance of the human immune system, plays a vital role in many physiological and pathological processes in the human body. In this work, we designed and synthesized a novel deep-red fluorescent probe TCF-ClO for the determination of hypochlorous acid through theoretical analysis. The results showed that probe TCF-ClO exhibited excellent characteristics of long-wavelength emission (635 nm), fast response (< 1 min), and low detection limit (24 nM). In addition, it had been successfully used for imaging of HClO in living HeLa cells. More importantly, the TCF-ClO composited paper-based sensing material was successfully constructed. The RGB/gray value was obtained from a mobile phone and computer, which could achieve the quantitative detection of HClO, with a linear detection range of 0–50 μM and a detection limit of 1.09 μM (RGB mode)/3.38 μM (gray mode). The function of the paper-based sensor extended from qualitative to quantitative detection of HClO, and it is expected to become a portable device widely used in the environmental area. [ABSTRACT FROM AUTHOR]

High per- and polyfluorinated alkyl substance (PFAS) concentrations have been detected in agricultural soils in Southwest Germany. Discharges of PFAS-contaminated paper sludge and compost are suspected to be the cause of the contamination. Perfluorinated carboxylic acids (PFCAs) have been detected also in groundwater, drinking water, and plants in this area. Recently, previously unknown compounds have been identified by high-resolution mass spectrometry (HRMS). Major contaminants were polyfluorinated dialkylated phosphate esters (diPAPs) and N-ethyl perfluorooctane sulfonamide ethanol–based phosphate diester (diSAmPAP). In this study, HRMS screening for PFAS was applied to 14 soil samples from the contaminated area and 14 impregnated paper samples which were from a similar period than the contamination. The paper samples were characterized by diPAPs (from 4:2/6:2 to 12:2/12:2), fluorotelomer mercapto alkyl phosphates (FTMAPs; 6:2/6:2 to 10:2/10:2), and diSAmPAP. In soil samples, diPAPs and their transformation products (TPs) were the major contaminants, but also FTMAPs, diSAmPAP, and their TPs occurred. The distribution patterns of the carbon chain lengths of the precursor PFAS in soil samples were shown to resemble those in paper samples. This supports the hypothesis that paper sludge is a major source of contamination. The presence of major degradation products like PFCAs, FTSAs, or PFOS and their distribution of carbon chain lengths indicate the activity of biotic or abiotic degradation processes and selective leaching processes from the upper soil horizons. [ABSTRACT FROM AUTHOR]

The modification of an easily available resource like paper to circumvent expensive or intensive sample pretreatment could be the answer to sample analysis in resource-poor regions. Therefore, a novel on-paper device combining sample collection with affinity sample pretreatment is introduced here. Universal smart affinity samplers are produced by a simple KIO4-mediated oxidation of cellulose, which functionalizes the paper. This is followed by immobilization of streptavidin. Streptavidin serves as a universal anchor for biotinylated antibodies, enabling simple preparation of tailor-made affinity samplers. The functionality of the device was tested using a model protein (human chorionic gonadotropin, hCG) and biotinylated anti-hCG antibodies for affinity capture. In a laboratory setting, the performance was demonstrated, and a 14-fold increase of target binding compared to binding without bmAb was achieved. The recovery of hCG captured with bmAb-treated samplers was determined to be 33% and comparable to previously described affinity capture approaches. Application of the smart affinity samplers to human serum containing hCG showed an R2 of 0.98 (200–1000 pg mL−1), precision of ≤ 9.1% RSD, and estimated limit of detection of 65 pg mL−1. Although further optimization and validation are necessary prior to application to real samples in clinical settings, the potential of the device for use in determination of low abundant biomarkers in complex samples has been demonstrated. [ABSTRACT FROM AUTHOR]

Traditionally, specific bioreceptors such as antibodies have rapidly identified bacterial species in environmental water samples. However, this method has the disadvantages of requiring an additional process to conjugate or immobilize bioreceptors on the assay platform, which becomes unstable at room temperature. Here, we demonstrate a novel mix-and-match method to identify bacteria species by loading the bacterial samples with simple bacteria interacting components (not bioreceptors), such as lipopolysaccharides, peptidoglycan, and bovine serum albumin, and carboxylated particles, all separately on multiple channels. Neither covalent conjugation nor surface immobilization was necessary. Interactions between bacteria and the above bacteria interacting components resulted in varied surface tension and viscosity, leading to various flow velocities of capillary action through the paper fibers. The smartphone camera and a custom Python code recorded multiple channel flow velocity, each loaded with different bacteria interacting components. A multi-dimensional data set was obtained for a given bacterial species and concentration and used as a machine learning training model. A support vector machine was applied to classify the six bacterial species: Escherichia coli, Salmonella Typhimurium, Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus faecium, and Bacillus subtilis. Under optimized conditions, the training model predicts the bacterial species with an accuracy of > 85% of the six bacteria species. [ABSTRACT FROM AUTHOR]

Paper has been widely employed as cheap material for the development of a great number of sensors such as pregnancy tests, strips to measure blood sugar, and COVID-19 rapid tests. The need for new low-cost analytical devices is growing, and consequently the use of these platforms will be extended to different assays, both for the final consumer and within laboratories. This work describes a paper-based electrochemical sensing platform that uses a paper disc conveniently modified with recognition molecules and a screen-printed carbon electrode (SPCE) to achieve the detection of gluten in a deep eutectic solvent (DES). This is the first method coupling a paper biosensor based on aptamers and antibodies with the DES ethaline. Ethaline proved to be an excellent extraction medium allowing the determination of very low gluten concentrations. The biosensor is appropriate for the determination of gluten with a limit of detection (LOD) of 0.2 mg L−1 of sample; it can detect gluten extracted in DES with a dynamic range between 0.2 and 20 mg L−1 and an intra-assay coefficient of 10.69%. This approach can be of great interest for highly gluten-sensitive people, who suffer from ingestion of gluten quantities well below the legal limit, which is 20 parts per million in foods labeled gluten-free and for which highly sensitive devices are essential. [ABSTRACT FROM AUTHOR]

Paper has been widely employed as cheap material for the development of a great number of sensors such as pregnancy tests, strips to measure blood sugar, and COVID-19 rapid tests. The need for new low-cost analytical devices is growing, and consequently the use of these platforms will be extended to different assays, both for the final consumer and within laboratories. This work describes a paper-based electrochemical sensing platform that uses a paper disc conveniently modified with recognition molecules and a screen-printed carbon electrode (SPCE) to achieve the detection of gluten in a deep eutectic solvent (DES). This is the first method coupling a paper biosensor based on aptamers and antibodies with the DES ethaline. Ethaline proved to be an excellent extraction medium allowing the determination of very low gluten concentrations. The biosensor is appropriate for the determination of gluten with a limit of detection (LOD) of 0.2 mg L−1 of sample; it can detect gluten extracted in DES with a dynamic range between 0.2 and 20 mg L−1 and an intra-assay coefficient of 10.69%. This approach can be of great interest for highly gluten-sensitive people, who suffer from ingestion of gluten quantities well below the legal limit, which is 20 parts per million in foods labeled gluten-free and for which highly sensitive devices are essential. [ABSTRACT FROM AUTHOR]

Microfluidic-based biosensors have been developed for their precise automatic reaction control. However, these biosensors require external devices that are difficult to transport and use. To overcome this disadvantage, our group made an easy-to-use, cheap, and light pumpless three-dimensional photo paper–based microfluidic analytical device (3D-μPAD; weight: 1.5 g). Unlike conventional paper-based microfluidic analytical devices, the 3D-μPAD can be used to control fluid flow in a 3D manner, thus allowing sophisticated multi-step reaction control. This device can control fluid flow speed and direction accurately using only the capillary-driven flow without an external device like a pump. The flow speed is controlled by the width of the microfluidic channel and its surface property. In addition, fluid speed control and 3D-bridge structure enable the control of fluid flow direction. Using these methods, multi-step enzyme-linked immunosorbent assay (ELISA) can be done automatically in sequence by injecting solutions (sample, washing, and enzyme's substrate) at the same time in the 3D-μPAD. All the steps can be performed in 14 min, and data can be analyzed immediately. To test this device, thioredoxin-1 (Trx-1), a biomarker of breast cancer, is used as the target. In the 3D-μPAD, it can detect 0–200 ng/mL of Trx-1, and the prepared 3D-μPAD Trx-1 sensor displays excellent selectivity. Moreover, by analyzing the concentration of Trx-1 in real patients and healthy individuals' blood serum samples using the 3D-μPAD, and comparing results to ELISA, it can be confirmed that the 3D-μPAD is a good tool for cancer diagnosis. [ABSTRACT FROM AUTHOR]

Microfluidic paper-based analytical devices (μPADs) have been widely used in point-of-care testing owing to their simple operation, low volume of the sample required, and the lack of the need for an external force. To obtain accurate semi-quantitative or quantitative results, μPADs need to respond to the challenges posed by differences in reaction conditions. In this paper, multi-layer μPADs are fabricated by the imprinting method for the colorimetric detection of C-reactive protein (CRP). Different lighting conditions and shooting angles of scenes are simulated in image acquisition, and the detection-related performance of μPADs is improved by using a machine learning algorithm. The You Only Look Once (YOLO) model is used to identify the areas of reaction in μPADs. This model can observe an image only once to predict the objects present in it and their locations. The YOLO model trained in this study was able to identify all the reaction areas quickly without incurring any error. These reaction areas were categorized by classification algorithms to determine the risk level of CRP concentration. Multi-layer perceptron, convolutional neural network, and residual network algorithms were used for the classification tasks, where the latter yielded the highest accuracy of 96%. It has a promising application prospect in fast recognition and analysis of μPADs. [ABSTRACT FROM AUTHOR]

The existence of pesticide residues in the hydrosphere, biosphere, and anthroposphere can cause acute or chronic diseases and deteriorate the environment. Therefore, efficient detection of pesticide residues is of great significance to prevent food poisoning, control food pollution, and protect human lives by recognizing their distribution and concentration. Herein, a novel smartphone-coupled three-layered paper-based microfluidic chip is proposed as a facile platform to detect the pesticides. The stereoscopic capillary-driven fluid transport is enabled by the three-layered microfluidic chip configuration. The detection mechanism is based on the enzyme inhibition reaction and the chromatic reaction. The detection results are obtained by a smartphone and figured out by colorimetric quantitative analysis. Taking advantages of the above merits, we demonstrate the utilization of this smartphone-coupled three-layered paper-based microfluidic chip for the effective analysis of typical pesticides (profenofo and methomyl). The linear ranges of profenofo and methomyl are 0.27–2.1 μmol L−1 and 0.14–1.85 μmol L−1, respectively. The corresponding limits of detection in the chips are 55 nM and 34 nM, respectively. The paper-based chips are also highly cost-effective with a total cost of 0.082 ¥ per piece. It can be anticipated that this technique will open new avenues for the mass fabrication of paper-based microfluidic chips and provide state-of-the-art methods in the field of analytical chemistry. [ABSTRACT FROM AUTHOR]

Urinary tract infections (UTIs) make up a significant proportion of the global burden of disease in vulnerable groups and tend to substantially impair the quality of life of those affected, making timely detection of UTIs a priority for public health. However, economic and societal barriers drastically reduce accessibility of traditional lab-based testing methods for critical patient groups in low-resource areas, negatively affecting their overall healthcare outcomes. As a result, cellulose-based materials such as paper and thread have garnered significant interest among researchers as substrates for so-called frugal analytical devices which leverage the material's portability and adaptability for facile and reproducible diagnoses of UTIs. Although the field may be only in its infancy, strategies aimed at commercial penetration can appreciably increase access to more healthcare options for at-risk people. In this review, we catalogue recent advances in devices that use cellulose-based materials as the primary housing or medium for UTI detection and chart out trends in the field. We also explore different modalities employed for detection, with particular emphasis on their ability to be ported onto discreet casings such as sanitary products. [ABSTRACT FROM AUTHOR]

Bacillus cereus is one of the most common foodborne pathogens found in various kinds of staple foods such as rice and wheat. A rapid and accurate detection method for this pathogen is highly desirable for the sustainable production of relevant food products. While several classical and molecular-based detection methods are available for the identification of B. cereus, they suffered one or more limitations such as the requirement for a tedious and time-consuming process, less than ideal specificity, and the lack of portability. Herein, we developed the first paper-based sensing device that exhibits high species specificity with sufficiently low limit of detection for the visual detection of specific DNA sequences of B. cereus. The success is attributed to the strategic planning of fabrication in various dimensions including thorough bioinformatics search for highly specific genes, the use of the pyrrolidinyl peptide nucleic acid (PNA) probe whose selectivity advantage is well documented, and an effective PNA immobilization and DNA-binding visualization method with an internal cross-checking system for validating the results. Testing in rice matrices indicates that the sensor is capable of detecting and distinguishing B. cereus from other bacterial species. Hence, this paper-based sensor has potential to be adopted as a practical means to detect B. cereus in food industries. [ABSTRACT FROM AUTHOR]

Enzyme-linked immunosorbent assay (ELISA) is widely used for the detection of disease biomarkers. However, it utilizes time-consuming procedures and expensive instruments, making it infeasible for point-of-care (POC) analysis especially in resource-limited settings. In this work, a multicolorimetric ELISA biosensor integrated on a paper/polymer hybrid microfluidic device was developed for rapid visual detection of disease biomarkers at point of care, without using costly equipment. This multicolormetric ELISA platform was built on multiple distinct color variants resulted from the catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) and the etching of gold nanorods (AuNRs). The vivid color changes could be easily distinguished by the naked eye, and their red mean values allowed quantitative biomarker detection, without using any sophisticated instruments. When this multicolorimetric ELISA was integrated on a paper/polymer hybrid analytical device, it not only provided integrated processing and high portability but also enabled fast assays in about 50 min due to the unique advantages of paper/polymer hybrid devices. The limit of detection of 9.1 ng/μL of the hepatitis C virus core antigen, a biomarker for hepatitis C, was achieved using this multicolorimetric ELISA platform. This multicolor ELISA analytical device provides a new versatile, user-friendly, affordable, and portable immunosensing platform with high potential for on-site detections of various viruses, proteins, and biomarkers for low-resource settings such as at home, public venues, rural areas, and developing nations. [ABSTRACT FROM AUTHOR]

Simple and visual quantitative detection of foodborne pathogens can effectively reduce the outbreaks of foodborne diseases. Herein, we developed a simple and sensitive quantum dot (QD)-based paper device for visual and quantitative detection of Escherichia coli (E. coli) O157:H7 based on immunomagnetic separation and nanoparticle dissolution-triggered signal amplification. In this study, E. coli O157:H7 was magnetically separated and labeled with silver nanoparticles (AgNPs), and the AgNP labels can be converted into millions of Ag ions, which subsequently quench the fluorescence of QDs in the paper strip, which along with the readout can be visualized and quantified by the change in length of fluorescent quenched band. Owing to the high capture efficiency and effective signal amplification, as low as 500 cfu mL−1 of E. coli O157:H7 could be easily detected by naked eyes. Furthermore, this novel platform was successfully applied to detect E. coli O157:H7 in spiked milk samples with good accuracy, indicating its potential in the detection of foodborne pathogens in real samples. [ABSTRACT FROM AUTHOR]

Iron is an important micronutrient involved in several mechanisms in the human body and can be an important biomarker. In this work, a simple and disposable microfluidic paper-based analytical device (µPAD) was developed for the quantification of iron in urine samples. The detection was based on the colorimetric reaction between iron(II) and bathophenanthroline and the reduction of iron(III) to iron(II) with hydroxylamine. The developed µPAD enabled iron determination in the range 0.07–1.2 mg/L, with a limit of detection of 20 µg/L and a limit of quantification of 65 µg/L, thus suitable for the expected values in human urine. Additionally, targeting urine samples, the potential interference of the samples color was overcome by incorporating a sample blank assessment for absorbance subtraction. Stability studies revealed that the device was stable for 15 days prior to usage and that the formed colored product was stable for scanning up to 3 h. The accuracy of the developed device was established by analyzing urine samples (#26) with the developed µPAD and with the atomic absorption spectrometry method; the relative deviation between the two sets of results was below 9.5%. [ABSTRACT FROM AUTHOR]

Herein we report a quantitative, multiplex assay for disease markers in plasma based on an integrated setup of a portable scanner and a disposable paper-based analytical device (PAD). The quantitative analysis relies on the digital colorimetric reading of the three-layer PAD with 30 assay sites for performing respective chromogenic reactions for plasma uric acid, glucose, and triglyceride, which are considered as important risk factors for cardiovascular diseases. A portable scanner with WiFi transmission capability was used to produce high-quality color images of the PADs and wirelessly transfer them to a smartphone or other mobile devices for data processing. The concentrations of biomarkers in both standard solutions and plasma samples can be directly obtained using a custom-designed smartphone app that is also capable of constructing calibration curves. The detection limits of uric acid, glucose, and triglyceride were determined to be 0.50 mg/dL, 0.84 mmol/L, and 14 mg/dL, respectively, which are below the normal limits and adequate for clinical validation. Owing to the distinct advantages—simple, portable, and cost-effective—this mobile assay protocol can be used for point-of-care (POC) settings or resource-limited situations, and potentially for the diagnosis and prevention of infectious diseases. [ABSTRACT FROM AUTHOR]

During epidemics, such as the frequent and devastating Ebola virus outbreaks that have historically plagued regions of Africa, serological surveillance efforts are critical for viral containment and the development of effective antiviral therapeutics. Antibody serology can also be used retrospectively for population-level surveillance to provide a more complete estimate of total infections. Ebola surveillance efforts rely on enzyme-linked immunosorbent assays (ELISAs), which restrict testing to laboratories and are not adaptable for use in resource-limited settings. In this manuscript, we describe a paper-based immunoassay capable of detecting anti-Ebola IgG using Ebola virus envelope glycoprotein ectodomain (GP) as the affinity reagent. We evaluated seven monoclonal antibodies (mAbs) against GP—KZ52, 13C6, 4G7, 2G4, c6D8, 13F6, and 4F3—to elucidate the impact of binding affinity and binding epitope on assay performance and, ultimately, result interpretation. We used biolayer interferometry to characterize the binding of each antibody to GP before assessing their performance in our paper-based device. Binding affinity (KD) and on rate (kon) were major factors influencing the sensitivity of the paper-based immunoassay. mAbs with the best KD (3–25 nM) exhibited the lowest limits of detection (ca. μg mL−1), while mAbs with KD > 25 nM were undetectable in our device. Additionally, and most surprisingly, we determined that observed signals in paper devices were directly proportional to kon. These results highlight the importance of ensuring that the quality of recognition reagents is sufficient to support desired assay performance and suggest that the strength of an individual's immune response can impact the interpretation of assay results. [ABSTRACT FROM AUTHOR]

Importantly, trends and developments of this interaction found in both biosensors and bioassays have opened new perspectives in the sensing field and are therefore also of great interest to the sensor community. (i) Biosensors are chemical sensors in which the recognition system utilizes a biochemical mechanism for the interaction process in/at the recognition layer. [Extracted from the article]

A rapid in situ analytical method was developed for the detection of generated carcinogenic aromatic amines from banned azo dyes utilizing a photocatalytic reduction-based liquid microjunction surface sampling (LMJSS)–mass spectrometry (MS) system. We utilized photocatalytic reduction under UV irradiation with TiO2 as catalyst to have rapid and mild reduction of azo dyes. The reaction conditions were optimized to have complete photocatalytic reduction within 2–5 min in pure methanol at room temperature. TiO2 was immobilized in the inner wall of the capillaries in the LMJSS system to achieve in situ sampling–online rapid reduction–MS detection for aromatic amines originating from azo dyes in packaging surface. The yields of in-tube photocatalytic reduction were near 100% by delivering the azo dye extracts through the capillary at 1 μL/min under UV irradiation. With this design, in situ analysis was completed within 2 min via direct MS detection and 7 min via liquid chromatography (LC)–MS detection. The detection limits for five aromatic amines originating from four different azo dyes were in the range of 1–17 mg/kg with relative standard deviations (RSDs) < 8.5%. In the application of the new method, four carcinogenic aromatic amines were detected and identified in three commercial packaging materials, and the quantitation results were comparable with those obtained by the conventional chemical reduction–LC–MS method (relative recovery, 81–121%). Moreover, due to the spatial resolution of the present method with a flow probe, MS imaging was achieved demonstrating clear azo dye patterns of a lab-made sample. [ABSTRACT FROM AUTHOR]

The best way to understand the environmental status of a certain region involves thorough non-target analysis, which will result in a list of pollutants under concern. Arkhangelsk (64° 32′ N 40° 32′ E, pop. ~ 344,000) is the largest city in the world to the north of the 60th parallel. Several industrial enterprises and the "cold finger" effect represent the major sources of air contamination in the city. Analysis of snow with comprehensive two-dimensional gas chromatography–high-resolution mass spectrometry allows detecting and quantifying the most hazardous volatile and semivolatile anthropogenic pollutants and estimating long-term air pollution. Target analysis, suspect screening, and non-target analysis of snow samples collected from ten sites within the city revealed the presence of several hundreds of organic compounds including 18 species from the US EPA list of priority pollutants. Fortunately, the levels of these compounds appeared to be much lower than the safe levels established in Russia. Phenol and dioctylphthalate could be considered as the pollutants of concern because their levels were about 20% of the safe thresholds. ChromaTOF® Tile, MetaboAnalyst software platform, and open-source software protocols were applied to process the obtained data. The obtained clusterization results of the samples were generally similar for various tools; however, each of them had certain peculiarities. Bis(2-ethylhexyl) hexanedioate, benzyl alcohol, phthalates, aniline, dinitrotoluenes, and fluoranthene showed the strongest influence on the clusterization of the studied samples. Possible sources of the major pollutants were proposed: car traffic and pulp and paper mills. [ABSTRACT FROM AUTHOR]

The Arxula yeast bisphenol screen (A-YBS) utilizes the bioluminescent Arxula adeninivorans yeast–based reporter cells for tailored analysis of bisphenols, one of the major endocrine-disrupting compound groups. For the first time, this bioreporter has been applied on the high-performance thin-layer chromatography (HPTLC) adsorbent surface to develop a respective planar bioluminescence bioassay (pA-YBS). The goal was to combine the advantages of HPTLC with a more selective bioassay detection for bisphenols. The performance of this pA-YBS bioluminescence bioassay was demonstrated by calculating the half-maximal effective concentration (EC50) of bisphenols compared to references. The EC50 ranged from 267 pg/band for bisphenol Z and 322 pg/band for bisphenol A (BPA) to > 1 ng/band for other bisphenols (BPC, BPE, BPF, and BPS) and references (17β-estradiol and 17α-ethinylestradiol). The EC50 value of BPA was three times more sensitive in signal detection than that of 17β-estradiol. The visual or videodensitometric limit of detection of BPA was about 200 pg/zone. The higher signal intensity and sensitivity for BPA confirmed the tailored bioassay selectivity compared to the existing estrogen screen bioassay. It worked on different types of HPTLC silica gel plates. This HPTLC–UV/Vis/FLD–pA-YBS bioluminescence bioassay method was used to analyze complex mixtures such as six tin can migrates, five thermal papers, and eleven botanicals. The detected estrogenic compound zones in the tin can migrates were successfully verified via the duplex planar yeast antagonist estrogen screen (pYAES) bioassay. The two bisphenols A and S were identified in one out of five thermal papers and confirmed with high-resolution mass spectrometry. No bisphenols were detected in the botanicals investigated via the pA-YBS bioluminescence bioassay. However, the botanicals proved to contain phytoestrogens as detected via the pYAES bioassay, which confirmed the tailored bioassay selectivity. This HPTLC–UV/Vis/FLD–pA-YBS bioluminescence bioassay is suited for cost-efficient analysis of BPA in complex samples, with no need for sterile conditions due to the fast workflow. [ABSTRACT FROM AUTHOR]

Nucleotide sugars (NS) fulfil important roles in all living organisms and in humans, related defects result in severe clinical syndromes. NS can be seen as the "activated" sugars used for biosynthesis of a wide range of glycoconjugates and serve as substrates themselves for the synthesis of other nucleotide sugars. NS analysis is complicated by the presence of multiple stereoisomers without diagnostic transition ions, therefore requiring separation by liquid chromatography. In this paper, we explored weak anion-exchange/reversed-phase chromatography on a hybrid column for the separation of 17 nucleotide sugars that can occur in humans. A robust and reproducible method was established with intra- and inter-day coefficients of variation below 10% and a linear range spanning three orders of magnitude. Application to patient fibroblasts with genetic defects in mannose-1-phosphate guanylyltransferase beta, CDP-l-ribitol pyrophosphorylase A, and UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase showed abnormal levels of guanosine-5′-diphosphate-α-d-mannose (GDP-Man), cytidine-5′-diphosphate-l-ribitol (CDP-ribitol), and cytidine-5′-monophosphate-N-acetyl-β-d-neuraminic acid (CMP-Neu5Ac), respectively, in consonance with expectations based on the diagnosis. In conclusion, a novel, semi-quantitative method was established for the analysis of nucleotide sugars that can be applied to diagnose several genetic glycosylation disorders in fibroblasts and beyond. [ABSTRACT FROM AUTHOR]

Metformin (MET) and sitagliptin (STG) are widely used as the first-line and long-term oral hypoglycemic agents for managing type 2 diabetes mellitus (T2DM). However, the current lack of convenient and rapid measurement methods poses a challenge for individualized management. This study developed a point-of-care (POC) assay method utilizing a miniature mass spectrometer, enabling rapid and accurate quantification of MET and STG concentrations in human blood and urine. By combining the miniature mass spectrometer with paper spray ionization, this method simplifies the process into three to four steps, requires minimal amounts of bodily fluids (50 μL of blood and 2 μL of urine), and is able to obtain quantification results within approximately 2 min. Stable isotope-labeled internal standards were employed to enhance the accuracy and stability of measurement. The MS/MS responses exhibited good linear relationship with concentration, with relative standard deviations (RSDs) below 25%. It has the potential to provide immediate treatment feedback and decision support for patients and healthcare professionals in clinical practice. [ABSTRACT FROM AUTHOR]

At present, the National Metrology Institute of Japan provides six national primary pH buffers under the Japan Calibration Service System. Each batch of these buffers is certified by the primary pH method using a Harned cell. On the basis of these primary buffers, the designated laboratories supply the secondary and working pH standards using a high-precision pH meter. This paper provides an estimate of the batch-to-batch reproducibility of the primary pH standard production based on the history of the certification of primary carbonate buffers in NMIJ. This buffer, which was chosen as the subject of the study because of the relative difficulty of its measurements (and thus a greater dispersion of results), is nominally the 0.025 mol kg−1 equimolal solution of disodium carbonate and sodium hydrogen carbonate. As its pH value is significantly affected by the purity of the reagents used, the evaluation of their source materials is made by both pH measurements and acidimetric gravimetric back titrations. Considering the experimentally determined pH reproducibility of ca. 0.010, potential risks to the pH accuracy are discussed when using recipe-based carbonate pH standards. [ABSTRACT FROM AUTHOR]

Antarctic seaweeds are vital components of polar marine ecosystems, playing a crucial role in nutrient cycling and supporting diverse life forms. The sulfur content in these organisms is particularly interesting due to its implication in biogeochemical processes and potential impacts on local and global environmental systems. In this study, we present a comprehensive characterization of seaweed collected in the Antarctic in terms of their total sulfur content and its distribution among different classes of species, including thiols, using various methods and high-sensitivity techniques. The data presented in this paper are unprecedented in the scientific literature. These methods allowed for the determination of total sulfur content and the distribution of sulfur compounds in different fractions, such as water-soluble and proteins, as well as the speciation of sulfur compounds in these fractions, providing valuable insights into the chemical composition of these unique marine organisms. Our results revealed that the total sulfur concentration in Antarctic seaweeds varied widely across different species, ranging from 5.5 to 56 g kg−1 dry weight. Furthermore, our investigation into the sulfur speciation revealed the presence of various sulfur compounds, including sulfate, and some thiols, which were quantified in all ten seaweed species evaluated. The concentration of these individual sulfur species also displayed considerable variability among the studied seaweeds. This study provides the first in-depth examination of total sulfur content and sulfur speciation in brown and red Antarctic seaweeds. [ABSTRACT FROM AUTHOR]

Fast, simple, and low-cost on-site visualized detection of inorganic phosphate (Pi) is in great demand since phosphate is the major reason of eutrophication. In this work, a ratiometric fluorescent probe composed by green carbon dots (GCDs) and red carbon dots (RCDs) has been established for high-sensitivity and selective sensing of Pi. A trend of color change from red to green is observed for the detection of Pi under ultraviolet light and the detection limit is 0.09 μM in the range of 0 to 55 μM. Fluorescent test paper prepared from the probe solution was successfully applied to semi-quantitative visual detection of Pi in real-world water and soil samples, which shows great real-world application potentials. [ABSTRACT FROM AUTHOR]

Non-invasive blood composition analysis based on dynamic spectrum (DS) theory has gained significant attention due to its non-invasive, simple, and fast performance. However, most of the multi-wavelength photoplethysmography (PPG) detection devices used to obtain DS are composed of halogen light sources and spectrometers and cannot detect effective PPG signals in the visible light short band (400–620 nm), which limits the detection accuracy of blood components with significant absorption spectral differences in that band. Therefore, this paper designs a multi-wavelength spectral acquisition system that can measure high signal-to-noise ratio (SNR > 65 dB) PGG signals at wavelengths of 405, 430, 450, 505, 520, and 570 nm and combines this system with a halogen lamp spectrometer acquisition system for non-invasive blood component detection. Furthermore, this paper collects the DS of 272 subjects with the combined system and establishes a predictive model for DS with the content of red blood cell (RBC) and hemoglobin (HGB) components. The results show that, compared with the halogen lamp spectrometer acquisition system, the correlation coefficient (Rp) of RBC and HGB prediction model established by the combined system has increased by 0.0619 and 0.0489, respectively, and the root mean square error (RMSE) has decreased by 0.08 1e12/L and 0.85 g/L, which confirm the feasibility of the designed multi-wavelength spectrum acquisition system to enhance the accuracy of blood component detection. [ABSTRACT FROM AUTHOR]

Glutathione and 2-aminopyridine are used as carbon sources to prepare carbon dots (CDs) by a one-step hydrothermal reaction. The results show that the average particle diameter of CDs is 8.64 nm with uniform size distribution and the fluorescence quantum yield is 13.62%. We further demonstrate that novel CDs possess highly selective sensing of Fe3+ from 0.2 to 200 μM with a low detection limit (0.194 μM). Meanwhile, the fluorescence of CDs can be repeated many times by the addition of S2−. Moreover, the CDs are used for biological imaging of living cells with well cell penetrability and low toxicity. Furthermore, it is successfully applied for anti-counterfeiting and information encryption. More interestingly, it can be doped with hydrogel and filter paper to prepare solid-phase sensors exhibiting high sensitivity and fast response, demonstrating their tremendous potential for the simple, rapid, and low-cost monitoring of Fe3+ and S2−. [ABSTRACT FROM AUTHOR]

This paper describes initially the application of the Tyndall effect (TE) of metal–organic framework (MOF) materials as a colorimetric signaling strategy for the sensitive detection of pyrophosphate ion (PPi). The used MOF NH2-MIL-101(Fe) was prepared with Fe3+ ions and fluorescent ligands of 2-amino terephthalic acid (NH2-BDC). The fluorescence of NH2-BDC in MOF is quenched due to the ligand-to-metal charge transfer effect, while the NH2-MIL-101(Fe) suspension shows a strong TE. In the presence of PPi analyte, the MOFs will undergo decomposition because of the competitive binding of Fe3+ by PPi over NH2-BDC, resulting in a significant decrease in the TE signal and fluorescence restoration from the released ligands. The results demonstrate that the new method only requires a laser pointer pen (for TE creation) and a smartphone (for portable quantitative readout) to detect PPi in a linear concentration range of 1.25–800 μM, with a detection limit of ~210 nM (3σ) which is ~38 times lower than that obtained from traditional fluorescence with a spectrophotometer (linear concentration range, 50–800 µM; detection limit, 8.15 µM). Moreover, the acceptable recovery of PPi in several real samples (i.e., pond water, black tea, and human serum and urine) ranges from 97.66 to 119.15%. [ABSTRACT FROM AUTHOR]

In this paper, we establish an in situ visualization analysis method to image the spatial distribution of metabolites in different parts (sclerotium, coremium) and different microregions of Cordyceps cicadae (C. cicadae) to achieve the in situ visual characterization of tissues for a variety of metabolites such as nucleosides, amino acids, polysaccharides, organic acids, fatty acids, and so on. The study included LC–MS chemical composition identification, preparation of C. cicadae tissue sections, DEDI-MSI analysis, DESI combined with Q-TOF/MS to obtain high-resolution imaging of mass-to-charge ratio and space, imaging of C. cicadae in positive–negative ion mode with a spatial resolution of 100 μm, and localizing and identifying its chemical compositions based on its precise mass. A total of 62 compounds were identified; nucleosides were mainly distributed in the coremium, L-threonine and DL-isoleucine, and other essential amino acids; peptides were mainly distributed in the sclerotium of C. cicadae; and the rest of the amino acids did not have a clear pattern; sugars and sugar alcohols were mainly distributed in the coremium of C. cicadae; organic acids and fatty acids were distributed in the nucleus of C. cicadae more than in the sclerotium, and the mass spectrometry imaging method is established in the research. The mass spectrometry imaging method established in this study is simple and fast and can visualize and analyse the spatial distribution of metabolites of C. cicadae, which is of great significance in characterizing the metabolic network of C. cicadae, and provides support for the quality evaluation of C. cicadae and the study of the temporal and spatial metabolic network of chemical compounds. [ABSTRACT FROM AUTHOR]

Target-based drug discovery technology based on cell membrane targets has gained significant traction and has been steadily advancing. However, current methods still face certain limitations that need to be addressed. One of the challenges is the laborious preparation process of screening materials, which can be time-consuming and resource-intensive. Additionally, there is a potential issue of non-specific adsorption caused by carrier materials, which can result in false-positive results and compromise the accuracy of the screening process. To address these challenges, this paper proposes a target-based cell membrane affinity ultrafiltration technology for active ingredient discovery in natural products. In this technique, the cell membranes of human lung adenocarcinoma epithelial cells (A549) with a high expression of epidermal growth factor receptor (EGFR) were incubated with candidate drugs and then transferred to an ultrafiltration tube. Through centrifugation, components that interacted with EGFR were retained in the ultrafiltration tube as "EGFR-ligand" complex, while the components that did not interact with EGFR were separated. After thorough washing and eluting, the components interacting with EGFR were dissociated and further identified using LC–MS, enabling the discovery of bioactive compounds. Moreover, the target-based cell membrane affinity ultrafiltration technology exhibited commendable binding capacity and selectivity. Ultimately, this technology successfully screened and identified two major components from the Curcumae Rhizoma-Sparganii Rhizoma (CS) herb pair extracts, which were further validated for their potential anti-tumor activity through pharmacological experiments. By eliminating the need for laborious preparation of screening materials and the potential non-specific adsorption caused by carriers, the development of target-based cell membrane affinity ultrafiltration technology provides a simplified approach and method for bioactive compounds discovery in natural sources. [ABSTRACT FROM AUTHOR]

This paper describes the simple and label-free detection of thrombin using optical fiber surface plasmon resonance (SPR) sensors based on gold films prepared by the cost-effective method of electroless plating. The plating conditions for simultaneously obtaining gold film on cylindrical core and end surfaces of an optical fiber suitable for measurement were optimized. The fabricated sensor exhibited a linear refractive index sensitivity of 2150 nm/RIU and 7.136 (a.u.)/RIU in the refractive index of 1.3329–1.3605 interrogated by resonance wavelength and amplitude methods respectively and a single wavelength monitoring method was proposed to investigate the sensing performance of this sensor. Polyadenine diblock and thiolated thrombin aptamers were immobilized on gold nanoparticles and gold films respectively to implement a sandwich optical fiber assay for thrombin. The developed optical fiber SPR sensors were successfully used in the determination of thrombin down to 0.56 nM over a wide range from 2 to 100 nM and showed good selectivity for thrombin, which indicated their potential clinical applications for biomedical samples. [ABSTRACT FROM AUTHOR]

Accurate quantitative analyses require standardized methods to control and improve the analytical process in the laboratory. The availability of urine reference materials (RMs) may offer a feasible option to improve the accuracy of urine analysis and to control matrix effects. This paper presents the complete process of the development of matrix RMs in urine, including sample preparation, homogeneity, and stability studies, as well as uncertainty assessment. A freeze-drying process was developed, and freeze-dried human and pig urine samples were prepared and verified to have comparable homogeneity to liquid samples and higher stability than liquid human, pig, and artificial urine samples at 4℃ or room temperature and under extreme conditions. A total of 21 authentic urine samples from August 2022 were measured with freeze-dried RMs and spiked urine samples, and the reliability of the quantification of the RMs was compared. The freeze-dried human urine matrix RM appeared to be an excellent tool for daily quality control, as it showed high stability and gave the most consistent results with spiked samples. [ABSTRACT FROM AUTHOR]

The developed method for simultaneous detection of aflatoxin B1 (AFB1) and aflD genes can effectively monitor from the source and reduce the safety problems and economic losses caused by the production of aflatoxin, which can be of great significance for food safety regulations. In this paper, we constructed a sensitive and convenient fluorescent biosensor to detect AFB1 and aflD genes simultaneously based on fluorescence resonance energy transfer (FRET) between quantum dots (QDs) and a black hole quenching agent. A stable "Y" shaped aptasensor was employed as the detection platform and a double quantum dot labeled DNA fragment was utilized to be the sensing element in this work. When the targets of AFB1 and aflD genes were presented in the solution, the aptamer in the "Y" shaped probe is specifically recognized by the target. At this time, both Si-carbon quantum dots (Si-CDs) and CdTe QDs are far away from the BHQ1 and BHQ3 to recover the fluorescence. The linear range of the prepared fluorescence simultaneous detection method was as wide as 0.5–500 ng·mL−1 with detection lines of 0.64 ng·mL−1 for AFB1 and 0.5–500 nM with detection lines of 0.75 nM for aflD genes (3σ/k). This fabricated fluorescent biosensor was further validated in real rice flour and corn flour samples, which also achieved good results. The recoveries were calculated by comparing the known and found amounts of AFB1 which ranged from 88.4 to approximately 115.32% in the rice flour samples and 90.7 ~ 102.58% in the corn flour samples. The recoveries of aflD genes ranged from 84.32 to approximately 109.3% in the rice flour samples and 89.48 ~ 100.99% in the corn flour samples. Therefore, the proposed biosensor can significantly improve food safety and quality control through a simple, fast, and sensitive agricultural product monitoring and detection system. [ABSTRACT FROM AUTHOR]

A viscosity-sensitive, lysosome-targeted near-infrared fluorescent probe (PYATT) was reported in this paper. The fluorescent spectra of PYATT are strongly dependent on viscosity, resulting in a Stokes shift of about 190 nm. Given its photostability, low cytotoxicity, and high fluorescence quantum yield, PYATT is expected to be used in cell imaging. Due to the higher viscosity of tumor cells than normal cells, the fluorescence intensity of PYATT in tumor cells is higher than normal cells, which can realize the visualization of tumors. The near-infrared probe (PYATT) is viscosity-dependent in lysosomes, which is valuable in early diagnosis and treatment of tumor. [ABSTRACT FROM AUTHOR]

This document is an editorial from the journal Analytical & Bioanalytical Chemistry (ABC) announcing the publication of a topical collection entitled "Advances in (Bio-)Analytical Chemistry: Reviews and Trends." The collection features Critical Reviews and Trends Articles from the journal's Editorial Team and International Advisory Board (IAB) and covers key areas in analytical and bioanalytical chemistry such as biosensors, green chemistry, microfluidics, and multi-omics. The editorial also highlights the change in chair editorship from Adam Woolley to Antje Baeumner and discusses the accomplishments of Woolley's term, including increasing the quality of published papers and reducing the time to first decision. The document concludes by expressing excitement for future topical collections and the contributions of the scientific community. [Extracted from the article]

Microfluidic immunoassay devices are a promising technology that can quickly detect biomarkers with high sensitivity. Recently, many studies implementing this technology on paper substrates have been proposed for improving cost and user-friendliness. However, these studies have identified problems with the large volume of sample required, low sensitivity, and a lack of quantitative accuracy and precision. In this paper, we report a novel structure implemented as a cellulosic material-based microchannel device capable of quantitative immunoassay using small sample volumes. We fabricated microfluidic channels between a transparent cellophane film and water-resistant paper to facilitate loading of small-volume samples and reagents, with a 40-μm-wide immunoreaction matrix constructed in the center of the microchannel using highly precise photolithography. A fluorescence sandwich immunoassay for C-reactive protein (CRP) was successfully implemented that required only a 1-μL sample volume and a 20-min reaction time. We confirmed that the limit of detection of the device was 10–20 ng/mL with a coefficient of variation under 5.6%, which is a performance level comparable to conventional plastic-based human CRP enzyme-linked immunosorbent assay (ELISA) kits. We expect that such devices will lead to the elimination of large amounts of medical waste from the use of ubiquitous diagnostics, a result that is consistent with environmental sustainability goals. [ABSTRACT FROM AUTHOR]