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Microalgae metabolite analysis is fundamental for the rational design of metabolic engineering strategies for the biosynthesis of high-value products. Mass spectrometry (MS) has been utilized for single-cell microalgae analysis. However, limitations in the detection throughput and polarities of detectable substances make it difficult to realize high-throughput screening of high-performance microalgae. Herein, a plasma-assisted label-free mass cytometry, named as PACyESI-MS, was proposed combining the advantages of orthogonal hybrid ionization and high-throughput MS analysis, which realized rapid metabolite detection of single microalgae. The cell detection throughput of PACyESI-MS was up to 52 cells/min. Dozens of the critical primary and secondary metabolites within single microalgae were detected simultaneously, including pigments, lipids, and energy metabolites. Furthermore, metabolite changes of Chlamydomonas reinhardtiiand Haematococcus pluvialisunder nitrogen deficiency stress were studied. Discrimination of Chlamydomonas under different nutrient conditions was realized using single-cell metabolite profiles obtained by PACyESI-MS. The relationships between the accumulation of bioactive astaxanthin and changes in functional primary metabolites of Haematococcus were investigated. It was demonstrated that PACyESI-MS can detect the flexible change of metabolites in single microalgae cells under different nutritional conditions and during the synthesis of high-value products, which is expected to become an important tool for the design of metabolic engineering-based high-performance microalgae factories.

Disulfide bonds are a class of important post-translational modifications that play important roles in modulating the structures and functions of proteins. Therefore, the mapping of disulfide linkages in peptides and proteins is indispensable for complete structure characterization and functional studies. As disulfide bonds in protonated ions do not dissociate readily under low-energy collision-induced dissociation (CID), they are usually chemically cleaved or activated prior to mass spectrometry (MS) or tandem MS (MS/MS) analysis. In this study, we report a new method that allows the mapping of disulfide linkages in peptides and proteins through meta-chloroperoxybenzoic acid (mCPBA)-based disulfide oxidation and MS/MS. Upon oxidation, the disulfide bond is converted to a thiosulfinate group, i.e., S(═O)–S, in a rapid (>60% yield in 1 min) and highly specific approach in an aqueous phase. The thiosulfinate group is then preferentially cleaved by MS/MS. For interchain disulfide linkages, this leads to a facile peptide chain separation and the identification of disulfide-linked peptides. For intrachain disulfide linkages, collisional activation of the thiosulfinate leads to disulfide cleavage and fragmentation of the peptide backbone constrained by the disulfide loop, enabling a near-complete peptide sequencing. The mCPBA oxidation-based disulfide mapping strategy can be readily integrated with bottom-up or top-down protein analysis for comprehensive protein structure elucidation, e.g., digested lysozyme and intact human insulin.

The tool box of site-specific cleavage for nucleic acid has been an increasingly attractive subject. Especially, the recent emergence of the orthogonally activatable DNA device is closely related to the site-specific scission. However, most of these cleavage strategies are based on exogenous assistance, such as laser irradiation. Endogenous strategies are highly desirable for the orthogonally regulatable DNA machine to explore the crucial intracellular biological process and cell signal network. Here, we found that the accurate site-specific cleavage reaction of phosphorothioate (PT) modified DNA by using myeloperoxidase (MPO). A scissors-like mechanism by which MPO breaks PT modification through chloride oxidation has been revealed. Furthermore, we have successfully applied the scissors to activate PT-modified hairpin-DNA machines to produce horseradish peroxidase (HRP)-mimicking DNAzyme or initiate hybridization chain reaction (HCR) amplification. Since MPO plays an important role in the pathway related to oxidative stress in cells, through the HCR amplification activated by this tool box, the oxidative stress in living cells has been robustly imaged. This work proposes an accurate and endogenous site-specific cleavage tool for the research of biostimuli and the construction of DNA molecular devices.

Discriminating various leukocyte subsets with specific functions is critical due to their important roles in the development of many diseases. Here, we proposed a general strategy to unravel leukocytes heterogeneity and screen differentiated metabolites as biomarker candidates for leukocyte subtypes using the label-free mass cytometry (CyESI-MS) combined with a homemade data processing workflow. Taking leukemia cells as an example, metabolic fingerprints of single leukemia cells were obtained from 472 HL-60, 416 THP-1, 313 U937, 356 Jurkat, and 366 Ramos cells, with throughput up to 40 cells/min. Five leukemia subtypes were clearly distinguished by unsupervised learning t-SNE analysis of the single-cell metabolic fingerprints. Cell discrimination in the mixed leukemia cell samples was also realized by supervised learning of the single-cell metabolic fingerprints with high recovery and good repetition (98.31 ± 0.24%, −102.35 ± 4.82%). Statistical analysis and metabolite assignment were carried out to screen characteristic metabolites for discrimination and 36 metabolites with significant differences were annotated. Then, differentiated metabolites for pairwise discrimination of five leukemia subtypes were further selected as biomarker candidates. Furthermore, discriminating cultured leukemia cells from human normal leukocytes, separated from fresh human peripheral blood, was performed based on single-cell metabolic fingerprints as well as the proposed biomarker candidates, unveiling the potential of this strategy in clinical research. This work makes efforts to realize high-throughput single-leukocyte metabolic analysis and metabolite-based discrimination of leukocytes. It is expected to be a powerful means for the clinical molecular diagnosis of hematological diseases.

Existing structured illumination microscopy (SIM) allows super-resolution live-cell imaging in few color channels that provide merely morphological information but cannot acquire the sample spectrum that is strongly relevant to the underlying physicochemical property. We develop hyperspectral SIM which enables high-speed spectral super-resolution imaging in SIM for the first time. Through optically mapping the three-dimensional (x, y, and λ) datacube of the sample to the detector plane, hyperspectral SIM allows snapshot spectral imaging of the SIM raw image, detecting the sample spectrum while retaining the high-speed and super-resolution characteristics of SIM. We demonstrate hyperspectral SIM imaging and reconstruct a datacube containing 31 super-resolution images of different wavelengths from only 9 exposures, achieving a 15 nm spectral resolution. We show time-lapse hyperspectral SIM imaging that achieves an imaging speed of 2.7 s per datacube—31-fold faster than the existing wavelength scanning strategy. To demonstrate the great prospects for further combining hyperspectral SIM with various spectral analysis methods, we also perform spectral unmixing of the hyperspectral SIM result while imaging the spectrally overlapped sample.

Understanding the spatiotemporal dynamics of particles in a complex biological environment is crucial for the study of related biological processes. To analyze the complicated trajectories recorded from single-particle tracking (SPT), we have proposed a method named SEES based on historical experience vector analysis, which allows both the global patterns and local state continuities of a trajectory to emerge by themselves as color segments without predefined models. This method implements a data-driven strategy and thus uncovers the hidden information with less prior knowledge or subjective bias. Here, we demonstrate its efficiency by comparing its performance with the Hidden Markov model (HMM), one of the most widely used methods in time series processing. The results demonstrated that the SEES operator was more sensitive in identifying rare events and could utilize multivariable observations in the dynamic processes to uncover more details. We applied the method to analyze the dynamics of nanoparticles interacting with live cells expressing programmed death ligand 1 (PD-L1) on the membrane. The results showed that the SEES operator can successfully pinpoint the transmembrane rare events, visualize the on-membrane “Brownian searching” motion, and evaluate different dynamics among multiple trajectories. Furthermore, we found that the PD-L1 expression level on the cell membrane affected the rotation behavior of the nanoparticle as well as the cellular uptake efficiency. These findings enabled by SEES could potentially help the rational design of highly efficient nanocargoes.

The formation of biomolecular condensates is driven by liquid–liquid phase separation, which is prevalent in cells to govern crucial cellular functions. However, understanding the properties of phase-separated condensates remains very challenging for the lack of suitable techniques. Here, we report a photoluminescence lifetime imaging method for real-time monitoring of phase-separated condensates, both in vitro and in living cells, using a microsecond-scale photoluminescence lifetime probe based on iridium complex. The probe has a large Stokes shift, excellent cell permeability, and minimal cell autofluorescence interference. With this method, the dynamic process of phase separation of fused in sarcoma protein has been well explored, showing high spatiotemporal resolution and high throughput. Beginning with initial formation, the protein droplets get bigger and more viscous, and then a final maturation to solidified aggregates has been characterized. This study paves the path for a deeper understanding of the properties of phase-separated biomolecular condensates.

Chemoresistance to triple-negative breast cancer (TNBC) is a critical issue in clinical practice. Lipid metabolism takes a unique role in breast cancer cells; especially, unsaturated lipids involving cell membrane fluidity and peroxidation are highly remarked. At present, for the lack of a high-resolution molecular recognition platform at the single-cell level, it is still hard to systematically study chemoresistance heterogeneity based on lipid unsaturation proportion. By designing a single-cell mass spectrometry workflow based on CyESI-MS, we profiled the unsaturated lipids of TNBC cells to evaluate lipidomic remodeling under platinum stress. Profiling revealed the heterogeneity of the polyunsaturated lipid proportion of TNBC cells under cisplatin treatment. A cluster of cells identified by polyunsaturated lipid accumulation was found to be involved in platinum sensitivity. Furthermore, we found that the chemoresistance of TNBC cells could be regulated by fatty acid supplementation, which determinates the composition of unsaturated lipids. These discoveries provide insights for monitoring and controlling cellular unsaturated lipid proportions to overcome chemoresistance in breast cancer.

Comprehensive analysis of single-cell metabolites is critical since differences in cellular chemical compositions give rise to specialized biological functions. Herein, we propose a label-free mass cytometry by coupling flow cytometry to ESI-MS (named CyESI-MS) for high-coverage and high-throughput detection of cellular metabolites. Cells in suspension were isolated, online extracted by sheath fluid, and lysed during gas-assisted electrospray, followed by real-time MS analysis. Hundreds of metabolites, including nucleotides, amino acids, peptides, carbohydrates, fatty acyls, glycerolipids, glycerophospholipids, and sphingolipids, were detected and identified from one single cell. Discrimination of four types of cancer cell lines and even three subtypes of breast cancer cells was readily achieved using their distinct metabolic profiles. Furthermore, we screened out 102 characteristic ions from 615 detected peak signals for distinguishing breast cancer cell subtypes and identified 40 characteristic molecules which exhibited significant differences among these subtypes and would be potential metabolic markers for clinical diagnosis. CyESI-MS is expected to be a new-generation mass cytometry for studying cell heterogeneity on the metabolic level.

5-Carboxylfluorescein (FAM) is a conventional pH-responsive fluorophore widely used in fluorescence labeling and imaging. Because of its nonfluorescent structure under acidic conditions, FAM has long been limited to pH determination in a neutral–basic environment. Here, we modified the optical properties of FAM with cationic arginine-rich cell-penetrating peptides (CPPs), tuning the pKavalue of FAM to adapt well to pH measurement under diverse pH conditions. With increasing length of polyarginine, the pKavalue of FAM was tuned from 6.20 ± 0.06 to 5.17 ± 0.05. The key mechanism for pKavariations was attributed to intramolecular electrostatic attraction and the positive charge of cationic CPPs tend to stabilize the fluorescent dianionic form of FAM. Apart from tunable pKa, arginine-rich CPPs also improved the water solubility, membrane permeability, and organelle-specific localization of FAM. Two conjugated probes FAM-R12and FAM-(Fxr)3were selected to monitor intracellular pH fluctuations. Compared to FAM-(Fxr)3, highly positively charged FAM-R12was more effective in lower pH condition and realized targeted visualization of lysosomal pH changes. The arginine-rich CPP-based strategy offers a promising approach to obtain optimized fluorescent pH probes with adjustable pKavalues for organelle-specific pH measurement.

Multiplex biomolecular analysis with inductively coupled plasma mass spectrometry (ICP-MS) becomes increasingly important in clinical diagnosis and single cell analysis. However, the sensitivity of ICP-MS-based immunoassay is only comparable or lower than those of fluorescence methods at the present stage. Therefore, designing elemental tags with a large number of metal atoms is necessary to achieve high-sensitive detection. In this work, we proposed a new strategy to build up elemental tag loading with hundreds of rare earth ions by coupling alkyne-DNA chains with rare earth element (REE)-DOTA complexes a click chemistry reaction. There are about 2 orders of magnitude improvement in sensitivity compared with single metal-ion tags. DNA chains with multialkynyl groups were facilely prepared by PCR synthesis. Moreover, the DNA-based elemental tags own excellent water-solubility and biocompatibility. The tags would be potentially applied to mass cytometry and clinical diagnosis.

Changes of metabolite concentrations in single cells are significant for exploring the dynamic regulation of important biological processes, such as cell development and differentiation. Accurate quantitation of metabolites is essential for single cell analysis. In this work, we proposed a quantitative method for single-cell metabolites by combining microwell array with droplet microextraction-mass spectrometry. The microwell can confine both single cells and extraction solvent in defined space, avoiding the irregular spread of trace internal standard solution during microextraction, which was the key to improve the precision and accuracy of quantification in extremely small-volume single-cell samples. Glucose-phosphate as a crucial metabolite in glycolysis was detected and quantified in single cells at this work. The calibration curve of glucose-phosphate was obtained with a linear range from amol (10–18mol) to fmol (10–15mol), providing the foundation of metabolite quantitation of single cells. We applied this method to investigate the changes of metabolites including glucose-phosphate, 2-deoxy-d-glucose-phosphate, and ribose-phosphate in single K562 cells stimulated by 2-deoxy-d-glucose. With the robust quantitative capabilities, the developed method holds great potential for studying a drugs’ mechanism of action and resistance at single cell level.

Hypoxia is a common characteristic of solid tumors, which is caused by the imbalance of oxygen supply and consumption. As the expression level of nitroreductase (NTR) increases in hypoxic solid tumors, NTR is one of the common biomarkers of hypoxia and widely used to evaluate the degree of tumor hypoxia. In this study, we designed and synthesized a highly water-soluble chemiluminescent probe, CL-NTR, for the detection of NTR activity in hypoxic tumors. It was found that the probe could be used to detect NTR with high sensitivity, and the total light photons increased tremendously with 6000-fold after the probe was treated with NTR. The chemiluminescence total light photons emission was directly proportional to the concentration of nitroreductase in the range of 3–55 ng/mL, with a detection limit of 0.947 ng/mL. Finally, the probe was successfully used to evaluate NTR activity in living mice by chemiluminescent imaging. In general, this probe has a remarkable response to NTR, which provides a promising method for the determination of NTR activity in vivo.

Chemical warfare agents (CWAs) are highly toxic compounds that have been used in wars or terrorist attacks. There is an urgent need to develop fast, inexpensive and sensitive on-site CWA inspection techniques. In this study, a low-temperature plasma (LTP) probe was directly coupled with a metal needle tip where sample molecules were desorbed and ionized in the ambient environment for subsequent analysis using mass spectrometry (MS). We found that metal needles greatly increased the ionization efficiencies compared with non-conductive sample substrates. Based on this finding, a method for rapid and highly sensitive detection and quantification of CWA-related compounds, including dimethyl methylphosphonate (DMMP), isopropyl methylphosphonic acid (IMPA), methylphosphonic acid (MPA) and thiodiglycol (TDG) was established. The whole workflow was completed in 10 s with a dynamic range of 1–500 μg L−1, and the limit of detection (LOD) was 500–980 ng L−1. Analytes were spiked in real-world water samples and quantified using this approach with satisfactory recoveries. Our results indicated that metal needle-enhanced LTP-MS will be a useful technique for the highly sensitive detection of CWAs.

While studies of collective cell migration and bacteria swarming have tremendously promoted our fundamental knowledge of the complex systematic phenomena, the quantitative characterization of the collective organelles movement at subcellular level is yet to be fully explored. Here we tagged the lysosomes in live cells with fluorescent probe and imaged their spatial motion with wide field microscopy. To quantitatively characterize the collective lysosomal behavior with high spatiotemporal heterogeneity dynamics, we developed the particle collective analysis (PECAN) method based on the single particle tracking techniques. Thousands of trajectories were detected and analyzed in each single cell. The reliability was validated by comparing with traditional PIV method, simulated and experimental data sets. We show that the lysosomes in live cells move collectively with spatial heterogeneous and temporal long-term correlated dynamics. Furthermore, the continuous wavelet analysis suggested the existence of collective lysosomal oscillation in mouse neural cells. Generally, our method provides a practical workflow for characterizing the collective lysosomal motions which can benefit related areas such as organelles mediated drug delivery and cell activity profiling.

We have combined droplet extraction and a pulsed direct current electrospray ionization mass spectrometry method (Pico-ESI-MS) to obtain information-rich metabolite profiling from single cells. We studied normal human astrocyte cells and glioblastoma cancer cells. Over 600 tandem mass spectra (MS2) of metabolites from a single cell were recorded, allowing the successful identification of more than 300 phospholipids. We found the ratios of unsaturated phosphatidylcholines (PCs) to saturated PCs were significantly higher in glioblastoma cells compared to normal cells. In addition, both isomeric PC (17:1) and (phosphatidylethanolamine) PE (20:1) were found in glioblastoma cells, whereas only PC (17:1) was observed in astrocyte cells. Our method paves the way to characterize the chemical contents of single cells, providing rich metabolome information. We suggest that this technique is general and can be applied to other life science studies such as differentiation and drug resistance of individual cells.

Mass spectrometry imaging (MSI) is a crucial label-free method to distinguish the localization patterns in single cells. MALDI-TOF MS and ToF-SIMS are now bearing the responsibility. However, MALDI-TOF MS is limited to micron spatial resolution and ToF-SIMS suffers from severe molecular fragmentation. Here, we proposed a new MSI methodology of vacuum ultraviolet laser desorption/ionization (VUVDI) with high spatial resolution, achieving higher ion yields and less fragmentation compared with ToF-SIMS at submicron level. The fluorescence image and mass spectrum of VUVDI were obtained simultaneously. In addition, the adjustable laser fluence acquired selective detection for different molecular and fragmental ions, thus realizing molecular identification. Furthermore, MSIs of single cells with submicron craters were presented. These results suggest VUVDI is a potential mass spectrometry method that provides a soft ionization source and submicron spatial resolution for molecular analysis in life science.

A novel kind of quantum dots, sulfur quantum dots (S dots), is synthesized by simply treating sublimated sulfur powders with alkali using polyethylene glycol-400 as passivation agents. The synthesized S dots exhibit excellent aqueous dispersibility, eminent photostability and temperature dependent photoluminescence (PL). An “assemble–fission” mechanism is proposed for the S dots formation in which “assembling” and “fission” are involved and contest each other. The ultimate morphologies of the S dots are dependent on the balance of the two forces. Guided by the assemble–fission mechanism, weakening the assembling effect is beneficial for obtaining monodisperse S dots, which can be achieved by pretreating of sulfur powder with nitric acid. PL wavelength of the S dots has been successfully tuned between green and blue light (from 550 to 440 nm) by simply controlling reaction time. A satisfactory quantum yield of 3.8% is obtained. Significant electrochemiluminescence of the S dots is observed in an annihilation reaction. Chemiluminescence from the S dots has been observed by direct oxidation. Taking advantage of unique and inherent antimicrobial activity of the sulfur particles, it is believed that this new emerging luminescent nanomaterial is highly promising in the development of new types of optoelectronic devices and tracer for live cells, in vivo imaging and diagnostics.

Plasma-based ambient mass spectrometry (AMS) exhibits great potential in the direct analysis of raw samples with minimum pretreatment. A variety of plasma-based ionization sources have emerged and presented favorable advantages of their high sensitivity, fast analysis speed, and promising qualitative and quantitative abilities for a wide range of applications. Successive efforts have been made to further improve the plasma-based sources for reliable practical applications. Herein, the instrumentation, mechanisms, novel configurations, and applications of versatile plasma-based AMS techniques have been overviewed, and further perspectives have been discussed in the end.

ICP-MS-based multiplex immunoassays have the advantages of low sample consumption and minimized repetitions of tedious procedures. However, this technique is seldom used in clinical tests because of the complicated matrix effect in clinical samples and the discrimination effect to the target proteins. In this work, we developed an ICP-MS-based magnetic immunoassay by using magnetic beads as highly efficient affinity probes and optimizing the magnetic immunoassay parameters. We applied this method to the simultaneous determination of three crucial gynecological tumor biomarkers that are vital in the prognosis and monitoring of the recurrence of breast cancer and ovarian cancer. The measurable ranges of HER-2, HE4 and CA15-3 were 12–1000 ng mL−1, 8–2000 pmol L−1and 5–200 U mL−1, with detection limits (3σ) of 3.94 ng mL−1, 2.59 pmol L−1and 1.62 U mL−1, respectively. The relative standard deviations (RSDs) were 2.61% for HER-2 at 15 ng mL−1, 4.90% for HE4 at 25 pmol L−1and 6.68% for CA15-3 at 10 U mL−1, indicating good accuracy of the method. The spiking test indicated that the present method had a low matrix effect. Under optimized conditions, the simultaneous detection of HER-2, HE4, and CA15-3 in clinical serum samples was performed and the values correlated well with those obtained by the time resolved fluorescence immunoassay (r2= 0.9568 for HER-2, 0.9485 for HE4, 0.9133 for CA15-3). The present work shows that the ICP-MS-based magnetic immunoassay meets the requirements for the quantification of three crucial gynecological tumor biomarkers in real clinical tests.

Rapid and sensitive quantification of peptides plays an important role in clinical diagnosis. Fluorescence assay is one of the most promising peptide detection tools, but it relies on intrinsic fluorescence or additional derivatization, resulting in poor versatility. Covalent organic frameworks (COFs) have shown a good application prospect in the field of fluorescence detection, but their application scope is limited to heavy metal ions and some small polar organic molecules. Herein, we report the application of COFs nanosheet for fluorescence detection of peptides. Fluorescent sp2acrylonitrile-linked COFs nanosheets (TTAN-CON) were prepared by water-assisted ultrasonic exfoliation which performed with excellent fluorescence properties with Stokes shifts of 146 nm and fluorescence quantum yield of up to 24.45%. Compared to the bulk fluorescent COFs, exfoliated CONs films performed with better stability of fluorescence signal in solution. We found the fluorescence of TTAN-CON can be effectively quenched by hydrophobic peptides at a very rapid rate (less than 5 min per sample). TTAN-CON presented good sensitivity and selectivity for hydrophobic peptides detection via the static and dynamic joint quenching mechanism. TTAN-CON was further used to detect NLLGLIEAK and ProGRP31–98, two target peptide fragments of lung cancer biomarker ProGRP. The fluorescence intensities of TTAN-CON were negative linearly correlated with the amounts of hydrophobic NLLGLIEAK over the range of 5–1000 ng/mL with the correlation coefficients over 0.99, and the limit of detection was 1.67 ng/mL, displaying higher sensitivity and convenience than traditional optical methods. What’s more, the quantification of ProGRP31–98was achieved by the quantification of hydrophobic peptides in its enzyme hydrolysis products. We anticipate COFs nanosheets to be a universal fluorescence detection work-box for peptides biomarkers with clinical significance.

A new “turn-on” fluorescent probe, composed of a protected phenol group with a p-nitrobenzyl moiety that functions as a latent donor and conjugated with two benzo[f]indolinium acceptors, was developed and applied for imaging nitroreductase (NTR) in hypoxic tumor cells. Nitrobenzyl moieties on the substrate can be conveniently converted into aminobenzyl groups with a nitroreductase-catalyzed reaction in the presence of reduced nicotinamide adenine dinucleotide (NADH). This is followed by a cleavage reaction and the release of the free phenol moiety, which is manifested in enhanced fluorescence intensity during the detection process. Our experimental results show that the NTR detection ability is over 100 equivalents of other biological reductants (1 mM), whereas the confocal fluorescence imaging of tumor cells indicates the possibility of its application in biomedical research fields for tumor hypoxia diagnosis.

Staying single: A DNA hybridization assay employs gold‐nanoparticle (AuNP) probes and single‐particle inductively coupled plasma spectrometry (ICP‐MS; see picture). The degree of aggregation of AuNPs is characterized by simultaneous measurement of decreased concentrations of the AuNP population and increased individual sizes.

Eins, zwei, drei: Ein DNA‐Hybridisierungsassay nutzt Goldnanopartikel(AuNP)‐Sonden und Massenspektrometrie einzelner Partikel mithilfe eines induktiv gekoppelten Plasmas (ICP‐MS; siehe Bild). Der Aggregationsgrad der AuNPs wird durch simultane Messung der Größe der einzelnen Partikel und der Verringerung der AuNP‐Konzentration bestimmt.

Existing nucleic acid and antigen profiling methods for COVID-19 diagnosis fail to simultaneously meet the demands in sensitivity and detection speed, hampering them from being a comprehensive way for epidemic prevention and control. Thus, effective screening of COVID-19 requires a simple, fast, and sensitive method. Here, we report a rapid assay for ultrasensitive and highly specific profiling of COVID-19 associated antigen. The assay is based on a binding-induced DNA assembly on a nanoparticle scaffold that acts by fluorescence translation. By binding two aptamers to a target protein, the protein brings the DNA regions into close proximity, forming closed-loop conformation and resulting in the formation of the fluorescence translator. Using this assay, saliva nucleocapsid protein (N protein) has been profiled quantitatively by converting the N protein molecule information into a fluorescence signal. The fluorescence intensity is enhanced with increasing N protein concentration caused by the metal enhanced fluorescence using a simple, specific, and fast profiling assay within 3 min. On this basis, the assay enables a high recognition ratio and a limit of detection down to 150 fg mL–1. It is 1–2 orders of magnitude lower than existing commercial antigen ELISA kits, which is comparative to or superior than the PCR based nucleic acid testing. Owing to its rapidity, ultrasensitivity, as well as easy operation, it holds great promise as a tool for screening of COVID-19 and other epidemics such as monkey pox.

Ag2S nanospheres were synthesized by a hydrothermal reaction using l-cysteine as the sulfur source and chelating reagent. The X-ray diffraction patterns and X-ray photoelectron spectra confirmed that the products were monoclinic -Ag2S. The optical absorption spectra of the Ag2S nanospheres showed very broad absorption peaks centered at about 515 nm in wavelength. Photoluminescence spectra exhibited emission peaks centered at ∼637 nm in wavelength accompanied by weaker shoulder peaks at ∼590 nm in wavelength when the sample was excited with a wavelength of 490 nm. In addition, the formation mechanism of the Ag2S nanospheres was also determined. The l-cysteine-assisted hydrothermal route using l-cysteine as the sulfur source and chelating reagent provides an alternative approach to generate sulfide nanocrystals.

Trace amounts of explosives on solid surfaces were detected by mass spectrometry at ambient conditions with a new technique termed dielectric barrier discharge ionization (DBDI). By the needle–plate discharge mode, a plasma discharge with energetic electrons was generated, which could launch the desorption and ionization of the explosives from solid surfaces. Hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX), 2,4,6‐trinitrotoluene (TNT), and pentaerythritol tetranitrate (PETN) were desorbed directly from the explosives‐contaminated surface by DBDI, forming the typical anions of [TNT]−, [TNT − H]−, [RDX + NO2]−, [PETN + ONO2]−, and [RDX + ONO2]−. The ions were transferred into the MS instrument for analysis in the negative ion mode. The detection limit of present method was 10 pg for TNT (m/z 197, S/N 8 : 1), 0.1 ng for RDX (m/z 284, S/N 10 : 1), and 1 ng for PETN (m/z 260, S/N 12 : 1). The present method allowed the detection of trace explosives on various matrices, including paper, cloth, chemical fiber, glass, paints, and soil. A relative standard deviation of 5.57% was achieved by depositing 100 pg of TNT on these matrices. The analysis of A‐5, a mixture of RDX and additives, has been carried out and the results were consistent with the reference values. The DBDI‐MS method represents a simple and rapid way for the detection of explosives with high sensitivity and specificity, which is especially useful when they are present in trace amounts on ordinary environmental surfaces. Copyright © 2007 John Wiley & Sons, Ltd.

A flow injection chemiluminescence (CL) method is described for the determination of five newly synthesized N-tetrahydrobenzothiazolyl imines (N-THBTIs) based on their sensitizing effect on the CL reaction of cerium(iv) and sulfite. The fluorescence, CL and absorption spectra are studied. The CL is deduced to originate from the excited sulfur dioxide, which is formed in a free radical reaction initiated by the free radical of N-THBTI. The relationship between the CL intensity and the concentration of N-THBTI is linear in the range of 2.0 × 10⁻⁷ to 8.0 × 10⁻⁵ mol l⁻¹ with a detection limit of 8.0 × 10⁻⁸ mol l⁻¹. The relative standard deviation (RSD) for seven independent determinations of N-THBTI (1.0 × 10⁻⁶ mol l⁻¹) is 1.2%. Most metal ions and some organic compounds do not interfere with the determination, except for Fe(iii), Fe(ii), Mn(ii), Tl(i) and Bi(iii). The method has been successfully applied to the determination of N-THBTI in synthetic samples.

Microplastics (MPs) are universally present in the ecosystem and pose great threats to the environment and living organisms. Research studies have shown that small MPs (<50 μm in diameter) are especially toxic and account for more than half of all MPs collected in the Atlantic Ocean. Nevertheless, current methods for the detection and analysis of MPs are incapable of achieving rapid and in situanalysis of small MPs in the biota to ultimately enable the study of their biological effects. In this work, we report a method that allows rapid in situidentification and spatial mapping of small MPs directly from paramecia with high accuracy by acquiring chemical composition information using secondary-ion mass spectrometry (SIMS) imaging. Specifically, six types of common MPs (polymethyl methacrylate, polyvinyl chloride, polypropylene, polyethylene terephthalate, polyglycidyl methacrylate, and polyamide 6) with a diameter of 1–50 μm were simultaneously imaged with high chemical specificity at a spatial resolution of 700 nm. In situspatial mapping of a group of MPs ingested by paramecia was performed using SIMS fragments specific to the plastic composition with no sample pretreatment, revealing the aggregation of MPs in paramecia after ingestion. Compared with existing methods, one additional advantage of the developed method is that the MPs and the organism can be analyzed in the same experimental workflow to record their fingerprint spectra, acquiring biochemical information to evaluate MP fate, toxicity, and the MP–biota interaction.

Here we report a cataluminescence-based method in the combinatorial discovery of active catalysts for NO reduction by C3H6. This method is based on the fact that NO reduction generates cataluminescence emission on the surface of various metal catalysts supported on BaO/Al2O3, whose intensity is correlated to the activity of the catalyst. The catalytic activities of the catalysts were evaluated in parallel by both the cataluminescence method and a micro-reactor evaluation system. The correlation coefficients are in the range of 0.676–0.9236 for the two methods and all above 0.632 at the confidence level 95% in the temperature region of 250–500 °C, indicating that the cataluminescence method can be applied to the evaluation of the catalytic activity of de-NOxcatalysts.

No Abstract

Welch ein Bild!Siegelmuster auf Gemälden und Kalligraphien wurden mit einer massenspektrometrischen Technik abgebildet. Dabei kam eine Niedertemperatur‐Plasmasonde zum Einsatz, die eine gute räumliche Auflösung liefert. Mit dieser Methode kann zwischen echten und gefälschten Siegeln unterschieden werden.