Notes

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A simple and robust integrated handheld optical fiber dissolved oxygen (DO) sensor was developed based on a compact optical structure and phase shift measurement principle. In this device, a 1 × 4 multi-mode optical fiber bundle structure was used for the transmission of excitation light and the collection and transmission of fluorescence. The fiber optode was fabricated by coating an O2 sensing foil on the end of the optical fiber bundle. This elegant optical design significantly improved the optical transmission efficiency, miniaturization, portability, and stability of the entire sensor system. A low-cost photodetector (PD) was applied for simultaneous detection of the fluorescence signal and reference light signal based on the time-resolved effect. Rapid and accurate measurement of the phase shift between the fluorescence and reference light signals was achieved using phase measurement electronics and signal processing system. Based on a proposed theoretical model with temperature compensation calibration, this DO sensor was used for rapid, accurate, and reproducible detection of DO concentrations with long-term stability and low drift. The results of in-situ/on-line detection for various water samples were highly consistent with those of commercial optical oxygen sensors. The proposed DO sensor has the potential to be a powerful alternative to traditional oxygen sensors in laboratory or in field.The global public health crisis and economic losses resulting from the current novel coronavirus disease (COVID-19) pandemic have been dire. The most used real-time reverse transcription polymerase chain reaction (RT-PCR) method needs expensive equipment, technical expertise, and a long turnaround time. Therefore, there is a need for a rapid, accurate, and alternative technique of diagnosis that is deployable at resource-poor settings like point-of-care. This study combines heat deactivation and a novel mechanical lysis method by bead beating for quick and simple sample preparation. Then, using an optimized reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay to target genes encoding the open reading frame 8 (ORF8), spike and nucleocapsid proteins of the novel coronavirus, SARS-CoV-2. The test results can be read simultaneously in fluorometric and colorimetric readouts within 40 min from sample collection. We also calibrated a template transfer tool to simplify sample addition into LAMP reactions when pipetting skills are needed. Most importantly, validation of the direct RT-LAMP system based on multiplexing primers S1ORF8 in a ratio (10.8) using 143 patients' nasopharyngeal swab samples showed a diagnostic performance of 99.30% accuracy, with 98.81% sensitivity and 100% selectivity, compared to commercial RT-PCR kits. Since our workflow does not rely on RNA extraction and purification, the time-to-result is two times faster than other workflows with FDA emergency use authorization. Considering all its strengths speed, simplicity, accuracy and extraction-free, the system can be useful for optimal point-of-care testing of COVID-19.Reported herein is a novel detection method for sulfur dioxide in aqueous solutions, in which the presence of sulfur dioxide leads to color changes of filter paper modified with both β-cyclodextrin and manganese. This detection method is rapid (less than 5 min required for complete color change), sensitive (limits of detection as low as 33 ppm), broadly applicable (tolerant of a range of pH values), and practical (color changes can be observed via naked eye detection and quantified via straightforward color analysis). Extensive optimization of each component provides insight into the unique stabilizing effect of cyclodextrin in preventing the filter paper from permanganate-induced degradation, and mechanistic analysis points to an oxidation-reduction reaction as responsible for the observed color changes. Overall, these results lay the groundwork for the development of practical sulfur dioxide sensors for use in the food and beverage industry, and provide precedent for the use of cyclodextrin as a stabilizing force in paper-based chemical sensors.The high-efficiency separation and extraction of short fragments of cell-free DNA (cfDNA) remain challenging due to their low abundance and short lengths. This study presents a method for separating short cfDNA fragments, with lengths ranging from about 100 to 200 base pairs, from liquid human plasma samples into separable and extractable bands as solid agarose gel slabs. To achieve this, a novel millimeter-scale fluidic device is used for sample handling, transient isotachophoresis, and extraction. The device features open-to-atmosphere liquid chambers that define and manually actuated (i.e., movable) agarose-made gate valve structures. The agarose gates then define discrete zones for buffers, sample injection, DNA pre-concentration via isotachophoresis, size-based gel separation, and DNA-band extraction. As a demonstration of its efficacy, the device is applied to the enrichment and purification of M. tuberculosis genomic DNA fragments spiked in human plasma samples. This purified cfDNA is analyzed using the quantitative polymerase chain reaction (qPCR) of the IS6110 repetitive sequence in the M. tuberculosis genome. The data from this study demonstrates that high sensitivity can be achieved in cfDNA detection, as shown by the comparison with a typical solid-phase extraction method and buffer spiked with cfDNA. Evidence is presented that suggests plasma peptides generated by treatment of the sample with proteinase K acts as endogenous spacer molecules, which improve the resolution and purification of DNA relative to the marker dye and other contaminants that decrease the signal level in qPCR.It seems to be well received that nonlinear electrospray ionization (ESI) distorts the signal distribution in mass spectrometry (MS) analysis, thus leading to diminished statistical power for t-test. However, the exact consequence and possible solutions to this quantitative issue have not been systematically explored. In this work, using a serial diluted urine metabolomics dataset, we demonstrated that over 80% of the metabolic features present nonlinear ESI response patterns, causing either left-skewed or right-skewed MS signal distributions. Among them, right-skewed MS distributions cannot be rescued using conventional data transformation (e.g., log transformation, power transformation). Furthermore, using a Monte Carlo simulation, we quantitatively assessed the reduced statistical power for t-test calculated using MS signal data in various sample sizes and effect sizes. In all these comparisons, t-test using MS signal data has consistently lower statistical power than t-test using metabolic concentration data. To address this statistical issue, we proposed a bioinformatic workflow, termed PowerU, to minimize the diminished statistical power caused by both the nonlinear ESI response and the intrinsic non-normal distribution of metabolic concentrations. The PowerU workflow is composed of two steps. The first step is to convert MS signals to quality control (QC) sample injection amounts to solve the skewed MS signal distributions. The second step is to perform a Shapiro-Wilk test to determine data normality and then use the normality results to guide the application of t-test and Mann-Whitney U test for the best statistical outcome. PowerU was tested using a metabolomics study of mouse cecum samples. Results demonstrate that the PowerU workflow can significantly boost statistical power for t-test and facilitate the discovery of significantly altered metabolites for downstream biological interpretation.Small cell lung cancer (SCLC) is highly associated with the risk of early metastasis. Neuron-specific enolase (NSE), a biomarker of SCLC, is directly related to tumor burden and early diagnosis. This biomarker exists in nerve tissue and neuroendocrine tissue. read more In this study, an electrochemical NSE immunosensor based on gold nanoparticles modified molybdenum disulfide and reduced graphene oxide (AuNPs@MoS2/rGO) as the electrode platform and CoFe2O4@Ag nanocomposite as the signal amplification was developed. The immobilization of anti-NSE capture antibody was successfully performed on AuNPs@MoS2/rGO modified electrode surface by amino-gold affinity and the conjugation of anti-NSE secondary antibody on CoFe2O4@Ag nanocomposite was successfully completed by the strong esterification reaction. The final immunosensor was designed by the specific interactions of electrode platform and signal amplification. The fabricated nanocomposites and electrochemical immunosensor were characterized by both physicochemical characterization techniques including transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR), and electrochemical methods such as cyclic voltammetry (CV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy (EIS). The quantification limit (LOQ) and the determination limit (LOD) were computed to be 0.01 pg mL-1 and 3.00 fg mL-1, respectively. In brief, it can be speculated that the constructed electrochemical NSE immunosensor can be successfully utilized in the early diagnosis for lung cancer.Bioluminescence, that is the emission of light in living organisms, has been extensively explored and applied for diverse bioanalytical applications, spanning from molecular imaging to biosensing. The unprecedented technological evolution of portable light detectors opened new possibilities to implement bioluminescence detection into miniaturized devices. We are witnessing a number of applications, including DNA sequencing, reporter gene assays, DNA amplification for point-of care and point-of need analyses relying on BL. Several photon detectors are currently available for measuring low light emission, such as photomultiplier tubes (PMT), charge-coupled devices (CCD), complementary metal oxide semiconductors (CMOS), single photon avalanche diodes (SPADs), silicon photomultipliers (SiPMs) and smartphone-integrated CMOS. Each technology has pros and cons and several issues, such as temperature dependence of the instrumental specific noise, the power supply, imaging capability and ease of integration, should be considered in the selection of the most appropriate detector for the selected BL application. These issues will be critically discussed from the perspective of the analytical chemist together with relevant examples from the literature with the goal of helping the reader in the selection and use of the most suitable detector for the selected application and to introduce non familiar readers into this exciting field.In this work, a hollow zirconium-porphyrin-based metal-organic framework (HZ-PMOF) was prepared as a coating for solid-phase microextraction (SPME) fiber to determine two naphthols. HZ-PMOF coating provided good extraction performance for naphthols because of the rich forces including π-π interactions, hydrogen bonding, and electrostatic interaction between the materials and targets. Furthermore, due to the special shape of the hollow structure, HZ-PMOF coating showed time-saving SPME equilibrium time and higher extraction capacity than zirconium-porphyrin-based metal-organic framework (Z-PMOF) coating without hollow structure. Combining with gas chromatography-tandem mass spectrometry (GC-MS/MS), an analytical method of naphthols with low detection limit (1.0 ng L-1), wider linear range (3.0-1000.0 ng L-1) and good reproducibility (RSD ≤8.6%) was established. Subsequently, naphthols in water samples from five cities in China were successfully detected by this developed method with satisfactory recoveries (81.
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