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A ratiometric fluorescent probe based on a “dual-key-and-lock” design was reported for the imaging of vicinal dithiol proteins in living cells.

Despite the great potential of microplasma optical emission spectrometry (OES) for on-site analysis, it remains a challenge to achieve the fast, sensitive, batch, and multielement analysis of trace heavy metals in a complex matrix. Herein, a novel ultrasonic nebulization-accelerated gas-phase enrichment (GPE) following in situ microplasma desorption sampling approach is employed for the determination of trace heavy metals by a miniature dielectric barrier discharge (DBD)-OES device. The volatile heavy metal species obtained by hydride generation (HG) can be quickly separated from the complex matrix under the action of ultrasonic nebulization, adsorbed on the surface of the activated carbon electrode tip for GPE, and then in situ desorbed and excited by DBD microplasma to achieve multielement OES analysis. With an array nebulizer plate, a batch of 10 samples can be handled for GPE in 40 s, and DBD-OES analysis is maintained at a rate of 6 s per sample. Under the optimized conditions, the detection limits for simultaneous determinations of Hg, Cd, Cu, and Sn are 0.005, 0.01, 0.03, and 0.04 μg L

Lysosomal polarity is considered a key indicator of lysosomal function due to its significant impact on membrane fluidity and enzymatic reactions in lysosomes. Monitoring lysosomal polarity can gain insight into the related physiological and pathological processes and develop new diagnostic methods. However, current fluorescent probes with lysosomal polarity response suffer from narrow linear range, photobleaching and complicated preparation. Herein, a ratiometric fluorescent probe (r-bCDs) for intracellular lysosomal polarity imaging is designed and constructed by amide bond assembly of polarity-sensitive red fluorescent carbon dots (rCDs) and referenced blue fluorescent carbon dots (bCDs). r-bCDs show a much wider linear range of polarity response (orientation polarizability Δf from 0.020 to 0.315) than other probes, and the interference of uneven distribution and instrument factors can be effectively eliminated by ratiometric fluorescent sensing. Imaging of intracellular lysosomal polarity with r-bCDs is implemented to observe the polarity variation caused by the change of cell state and the difference between cancer cells and normal cells. This work provides a promising tool for studying the related physiological and pathological processes and developing new diagnostic methods.

A machine learning-based colorimetric sensor array enables simple and accurate identification of pathogens in household refrigerators.

Point-of-care testing (POCT) with the advantages of simplicity, rapidity, portability, and low-cost is of great importance to improve healthcare, especially in resource-limited settings and home healthcare settings. Moreover, it is a great challenge to quantitative POCT of multiplexed biomarkers within a single accessible assay but provides enhanced diagnostic accuracy and improved diagnostic efficiency. Herein, a smartphone optical device has been designed for POCT of glucose and cholesterol in metabolic syndrome patients using a ratiometric fluorescent sensor. The sensing system of Ag NPs/UiO-66-NH2 and o-phenylenediamine presents a dual-emission response to H2O2 (the main product of glucose and cholesterol catalyzed by glucose oxidase and cholesterol oxidase) on account of the inner filter effect, resulting in an increase in the response of the fluorescence intensity ratio (F555 nm/F425 nm) accompanied by a distinguishable color transition from blue to yellow green. After compositing probes with a flexible substrate, the obtained test strip can be integrated with a smartphone-based portable platform to read RGB values for accurate testing of glucose and cholesterol with both detection limits of 10 μmol L-1, which are hundreds of times lower than their concentrations in human serum. With the advantages of low-cost, ease of operation, and broad adaptability, this smartphone optical device holds great potential for portable detection of numerous targets in personalized healthcare and clinical diagnosis.

Discrimination of glycoproteins and cell types is a significant but difficult issue. Herein, we presented a novel fluorescence sensor array for the detection and identification of glycoproteins and cancer cells based on the specific affinity between boronic acid-containing carbon dots (BA-CDs) and cis-diol residues of polysaccharides. The differential binding affinity of three BA-CDs to various glycoproteins resulted in a different fluorescence turn-on signal pattern caused by aggregation-enhanced emission (AEE), along with negligible response from other proteins. Therefore, BA-CDs encompassing sensing elements and signal indicator into one can enable a fast and accurate discrimination of glycoproteins with simple and easy operation. Seven glycoproteins could be well discriminated at a very low concentration of 10 nmol/L. The discriminating capability of glycoproteins is not sacrificed in both human urine and serum. Notably, different glycoprotein compositions of cancer cells provide more recognizable features for identification of cancer cells, comparing to the total protein. Five cell types could be identified in 15 min at a low concentration of 1000 cells/mL. This method is fast, accurate, and easy operation, and has a potential application in cancer diagnosis.

Quantification of exosomal multi-miRNA can reveal the initiation, progression, and metastasis of tumors, which is conducive to the noninvasive early diagnosis of cancer. However, low-sensitivity and single-plex detection characteristics of traditional methods seriously hinder the accuracy and specificity of exosomal miRNAs in cancer diagnosis. Herein, we design an ultramultiplexing strategy that enables simultaneous and sensitive detection of multiple exosomal miRNAs by nanosatellites (magnetic beads (MBs) @ NaLnF

As typical transition metal dichalcogenides (TMDC), tungsten selenide (WSe

Mercury (Hg) is harmful to the environment and human health. The gut plays important roles as the biological, chemical, mechanical, and immune barriers in animals and human beings. It has been known that Hg can be absorbed and methylated/demethylated in the gut, on the other hand, the impacts of Hg to the gut (especially the gut microbiota) is less studied. This review paper summarizes the impacts of inorganic Hg (IHg) and methyl Hg (MeHg) on gut barriers and the extraintestinal effects (damage to other organs such as the liver and brain). Both IHg and MeHg were found to cause intestinal microbial disorders, abnormal metabolites production, tight junction damage, and immune responses in the gut. The damage to the gut also contributed to the extraintestinal effects like the hepatotoxicity by IHg and the neurotoxicity by MeHg. In all, it is proposed that the gut should be considered as an important target tissue of Hg exposure, and the regulation of gut microbiota may have the potential for the prevention and control of the toxicity of Hg.

Azodicarbonamide (ADA) is widely used as a flour additive due to its oxidizing and bleaching properties, but it reacts with wet flour during heat processing and is easily decomposed into semicarbazide with genotoxicity and carcinogenicity. In order to improve the efficiency of food safety supervision and expand the scope of food safety control, it is of great significance to develop a facile method for point-of-care testing (POCT) of ADA. Herein, a field-portable and universal smartphone-based photoacoustic (PA) integration device is constructed for quantitative POCT of ADA in flour. The recognition probe Prussian blue with favorable stability is loaded on a flexible substrate for fabricating a portable test strip. In the presence of target ADA, the PA signal changes driven by a modulated 808 nm laser beam can be conveniently collected through the recording application (Audio Lab) of the smartphone. By combining the economic test strip and portable PA device with smartphone readout, it not only greatly simplifies the operation steps but also dramatically reduces the size and cost of the instrument. There is a favorable linear relationship between the PA signal and ADA concentration in the range of 10-200 μmol L

Speciation analysis of arsenic in blood is essential for identifying and quantifying the exposure of arsenic and studying the metabolism and toxicity of arsenic. Herein, a novel pretreatment device is rationally designed and used for speciation analysis of arsenic in whole blood by ion chromatography-inductively coupled plasma-mass spectrometry (IC-ICP-MS). The sample centrifuge tubes containing blood, reagents, and a magnetic stir bar are placed on the fidget spinner of the pretreatment device. When flicking the fidget spinner rotation with the finger, the magnetic stir bar in the tube rotates in three dimensions under the magnetic field, thereby assisting dispersive extraction of arsenic species by the mixing of blood with reagents. Afterward, the arsenic extract is separated in situ from the blood matrix using an ultrasonic spray sheet covered with a filter and ultrafiltration membrane, which is directly used for subsequent IC-ICP-MS analysis. For 100 μL of blood, the whole pretreatment operation can be completed within 10 min. With As(III), As(V), MMA, and DMA in blood as analytes, the use of the present pretreatment device will hardly lead to the loss and transformation of arsenic species, and the extraction efficiency of the total arsenic is more than 96%. When the pretreatment device is coupled to IC-ICP-MS, the detection limits of four arsenic species in whole blood are 0.017-0.023 μg L-1, and precisions are within 2.3-4.2%. This pretreatment device provides a simple, fast, efficient, and low-cost tool for extraction and separation of arsenic species in whole blood, opening a new idea for the pretreatment of complex samples.

Tumor exosomes with molecular marker-proteins inherited from their parent cells have emerged as a promising liquid biopsy biomarker for cancer diagnosis. However, facile, robust, and sensitive detection of exosomal proteins remains challenging. Therefore, a nanozyme sensor array is constructed by using aptamer-modified C3N4 nanosheets (Apt/C3N4 NSs) together with a solvent-mediated signal amplification strategy for ratiometric fluorescence detection of exosomal proteins. Three aptamers specific to exosomal proteins are selected to construct Apt/C3N4 NSs for high specific recognition of exosomal proteins. The adsorption of aptamers enhances the catalytic activity of C3N4 NSs as a nanozyme for oxidation of o-phenylenediamine (oPD) to 2,3-diaminophenazine (DAP). In the presence of target exosomes, the strong affinity between aptamer and exosome leads to the disintegration of Apt/C3N4 NSs, resulting in a decrease of catalytic activity, thereby reducing the production of DAP. The ratiometric fluorescence signal based on a photoinduced electron transfer (PET) effect between DAP and C3N4 NSs is dependent on the concentration of DAP generated, thus achieving highly facile and robust detection of exosomal proteins. Remarkably, the addition of organic solvent-1,4-dioxane can sensitize the luminescence of DAP without affecting the intrinsic fluorescence of C3N4 NSs, achieving the amplification of the aptamer-exosome recognition events. The detection limit for exosome is 2.5 × 103 particles/mL. In addition, the accurate identification of cancer can be achieved by machine learning algorithms to analyze the difference of exosomal proteins from different patients' blood. We hope that this facile, robust, sensitive, and versatile nanozyme sensor array would become a promising tool in the field of cancer diagnosis.

On-site and sensitive analysis of phytoavailable heavy metals is the key to fast evaluate the pollution incidents, while the development of convenient and efficient sample introduction approaches against matrix interference is crucial to improve the performances of field-deployable instruments. Herein, trace phytoavailable heavy metals in soil are first extracted by 0.1 M NaNO

Exosomes are expected to be used as cancer biomarkers because they carry a variety of cancer-related proteins inherited from parental cells. However, it is still challenging to develop a sensitive, robust, and high-throughput technique for simultaneous detection of exosomal proteins. Herein, three aptamers specific to cancer-associated proteins (CD63, EpCAM, and HER2) are selected to connect gold nanoparticles (AuNPs) as core with three different elements (Y, Eu, and Tb) doped up-conversion nanoparticles (UCNPs) as satellites, thereby forming three nanosatellite assemblies. The presence of exosomes causes specific aptamers to recognize surface proteins and release the corresponding UCNPs, which can be simultaneously detected by inductively coupled plasma-mass spectrometry (ICP-MS). It is worth noting that rare earth elements are scarcely present in living systems, which minimize the background for ICP-MS detection and exclude potential interferences from the coexisting species. Using this method, we are able to simultaneously detect three exosomal proteins within 40 min, and the limit of detection for exosome is 4.7 × 103 particles/mL. The exosomes from seven different cell lines (L-02, HepG2, GES-1, MGC803, AGS, HeLa, and MCF-7) can be distinguished with 100% accuracy by linear discriminant analysis. In addition, this analytical strategy is successfully used to detect exosomes in clinical samples to distinguish stomach cancer patients from healthy individuals. These results suggest that this sensitive and high-throughput analytical strategy based on ICP-MS has the potential to play an important role in the detection of multiple exosomal proteins and the identification of early cancer.

The miniaturized optical emission spectrometry (OES) devices based on various microplasma excitation sources provide reliable tools for on-site analysis of heavy metal pollution, while the development of convenient and efficient sample introduction approaches is essential to improve their performances for field analysis. Herein, a small activated carbon electrode tip is employed as solid support to preconcentrate heavy metals in water and subsequently served as an inner electrode of the coaxial dielectric barrier discharge (DBD) to generate microplasma. In this case, heavy metal analytes in water are first adsorbed on the surface of the activated carbon electrode tip via a simple liquid-solid phase transformation during the sample loading process, and then, fast released to produce OES during the DBD microplasma excitation process. The corresponding OES signals are synchronously recorded by a charge-coupled device (CCD) spectrometer for quantitative analysis. This activated carbon electrode tip provides a new tool for sample introduction into the DBD microplasma and facilitates "insert-and-go" in subsequent DBD-OES analysis. With a multiplexed activated carbon electrode tip array, a batch of water samples (50 mL) can be loaded in parallel within 5 min. After drying the activated carbon electrode tips for 5 min, the DBD-OES analysis is maintained at a rate of 6 s per sample. Under the optimized conditions, the detection limits of 0.03 and 0.6 μg L-1 are obtained for Cd and Pb, respectively. The accuracy and practicability of the present DBD-OES system have been verified by measuring several certified reference materials and real water samples. This analytical strategy not only simplifies the sample pretreatment steps but also significantly improves the sensitivity of the DBD-OES system for heavy metal detection. By virtue of the advantages of high sensitivity, fast analysis speed, simple operation, low cost, and favorable portability, the upgraded DBD-OES system provides a more powerful tool for on-site analysis of heavy metal pollution.

Lipid droplets (LDs) are intracellular lipid-rich organelles, which not only serve as neutral lipid reservoirs but also involve in many physiological processes and are associated with a variety of metabolic diseases and cancers. Long-term tracking of the state and behavior of LDs is of great significance but challenging. The difficulty is largely due to the lack of low cytotoxicity, high photobleaching resistance, and long intracellular retention probes that are capable of long-term tracking LDs. Herein, we report the discovery of two amphiphilic LD-targeting carbon nanoparticles (CNPs, i.e., CPDs and CDs) prepared by one-step room-temperature and hydrothermal methods. Their high lipid-water partition coefficient (log P > 2.13) and strong positive solvatochromism property ensure the quality of LD imaging. Especially, CDs exhibit favorable biocompatibility (2 mg mL-1, cell viability >90%), excellent photostability (after continuous laser irradiation on a confocal microscope for 2 h, relative FL intensity >85%), and superior intracellular retention ability, thereby enabling long-term tracking of LDs in hepatocytes for up to six passages. Based on the excellent long-term tracking ability, CDs are successfully applied to observe autophagy in a typical catabolic process and to evaluate the effect of a commonly used lipid-lowering drug atorvastatin on hepatocyte lipid uptake.

Butyrylcholinesterase (BuChE), the primary source of serum cholinesterase activity, is an indispensable biochemical marker for clinical diagnosis of liver function and organophosphorus poisoning. The requirement for bulky and expensive instruments represents a huge hindrance for point-of-care testing (POCT) of BuChE, especially in resource-limited settings. Herein, an easy-operated, economic, and portable photothermal (PT) biosensing platform for high-throughput BuChE detection was rationally designed. BuChE could "light up" the PT signal through in situ generation of Prussian blue (PB) by MIL-53 (Fe), which allowed us to translate biological signals into temperature signals. Such temperature change signals could be monitored at high throughput (six samples for a single measurement) by a miniature self-made integrated PT device via combining separable 96-well plates, a three-dimensional (3D) printed sample bracket, 808 nm lasers, and thermometers, satisfying the requirement for rapid on-site detection in a large batch with low cost. In addition, the large specific surface area, 3D network structure, and high porosity of MIL-53 (Fe) offered a beneficial platform for its reaction with enzymatic hydrolysate, resulting in high sensing sensitivity and low detection limit (0.3 U L-1), which was at least 20 000 times lower than the normal human serum BuChE activity. This facile, affordable, and broad applicability PT sensing platform provides a beneficial reference for the rational design of other disease diagnostic approaches suitable for POCT.

It is still a high challenge to develop a simple, sensitive and portable approach for bioassay in strong scattering medium. Herein, a photoacoustic (PA) device is developed for the detection of alkaline phosphatase (ALP) in serum with silver nanoparticles (AgNPs) as signal probe, without any requirements for expensive equipment, professional operation and pre-processing of real samples. ALP as an important disease marker could catalyze the breakdown of sodium L-ascorbyl-2-phosphate (AAP) into ascorbic acid (AA), thereby reducing Ag+ to AgNPs. AgNPs could generate strong PA signal under the irradiation of modulated 638-nm laser due to their localized plasmon resonance, and detected by the self-made portable PA device. Under the optimized experimental conditions, the present PA device exhibits excellent photostability and reproducibility with the relative standard deviation (RSD) of 2.2% at the concentration of 25 U L−1 ALP. Linear calibration graph is obtained within 5–70 U L−1 for ALP, along with a detection limit of 1.1 U L−1. This portable PA device is applied to detect ALP in serum samples, providing satisfactory spiking recoveries and competitive analytical performances with the current techniques. The PA-based analytical strategy obviously opens up a new avenue to the detection of disease-correlated biomarker in practice.

Herein, novel carbon dots (CDs) with efficient antibacterial activity are prepared by a simple cyclization reaction of 4-formylbenzoic acid and pyrrole and cross-linking with p-phenylenediamine at room temperature. The CDs exhibit the fluorescence property of red emission, greatly reducing the noise interference from bacterial autofluorescence in fluorescence imaging. At the same time, the CDs with the feature of red absorption facilitate the achievement of light excitation of deep tissues in the living body. Owing to the introduction of the porphyrin ring structure as a photosensitizer, the CDs are able to trigger the generation of singlet oxygen. When excited by a 638 nm laser and irradiated for 20 min, 10 μg mL−1 CDs can achieve complete bacterial extinction. Laser confocal microscopy imaging further demonstrates that the CDs act on the outside of bacteria and generate reactive oxygen species under red light irradiation, providing a non-multidrug resistant sterilization method.

A microplasma-based optical emission spectrometry (OES) system has emerged as a potential tool for field analysis of heavy metal pollution due to its features of portability and low energy consumption, while the development of an efficient sample introduction approach against matrix interference is crucial to meet the requirements of complex sample analysis. Herein, a MoS

Single-cell-based genomics and transcriptomics analysis have revealed substantial cellular heterogeneity among seemingly identical cells. Knowledge of the cellular heterogeneity at multiomics levels is vital for a better understanding of tumor metastasis and drug resistance, stem cell differentiation, and embryonic development. However, unlike genomics and transcriptomics studies, single-cell characterization of metabolites, proteins, and post-translational modifications at the omics level remains challenging due to the lack of amplification methods and the wide diversity of these biomolecules. Therefore, new tools that are capable of investigating these unamplifiable "omes" from the same single cells are in high demand. In this work, a microwell chip was prepared and the internal surface was modified for hydrophilic interaction liquid chromatography-based tandem extraction of metabolites and proteins and subsequent protein digestion. Next, direct electrospray ionization mass spectrometry was adopted for single-cell metabolome identification, and a data-independent acquisition-mass spectrometry approach was established for simultaneous proteome profiling and phosphoproteome analysis without phosphopeptide enrichment. This integrated strategy resulted in 132 putatively annotated compounds, more than 1200 proteins, and the first large-scale phosphorylation data set from single-cell analysis. Application of this strategy in chemical perturbation studies provides a multiomics view of cellular changes, demonstrating its capability for more comprehensive investigation of cellular heterogeneity.

A two-dimensional cytometry platform (CytoLM) with high sensitivity and high temporal resolution is developed for single-particle and single-cell sampling and analysis. First, a Dean flow-assisted vortex capillary cell sampling (VCCS) unit confines the sample stream in curved flow and drives to focus and align the particles or cells in a small probe volume. By coupling VCCS to a laser-induced fluorescence (LIF) detector with data acquisition and processing capability, a high-throughput single-particle/cell analysis system (VCCS-LIF) was established. The particle analysis throughput of 119.42/s and a detection recovery of 78.20 ± 1.75% were achieved at a density of 9.16 × 104/mL for fluorescent particles, and the cell analysis throughput is 48.20/s at a density of 1.5 × 105/mL. Second, the CytoLM platform is constructed by hyphenating VCCS-LIF with inductively coupled plasma mass spectrometry (ICP-MS). In the analysis of HepG2 cells by Ag+ incubation and AO staining, 10,760 fluorescence bursts and 3068 MS events were observed in 240 s. Invalid signals due to undispersed cells were controlled at 3.80% for LIF and 1.01% for MS, with a proportion of effective signal of >96.20%. After peak identification and integral processing of the original data, the statistical results including peak area, height, width, and spacing are obtained concurrently and the information on concentration and elemental quantification of single cells is evaluated. CytoLM facilitates high-throughput, multi-dimensional, and multi-parameter characterization of particles and cells, and it may provide vast potential in life science analysis.

Selective isolation and enrichment of phosphoproteins play critical roles for identification of biomarkers in biological applications. Herein, a kind of polyoxometalate (P5W30)/polydopamine (PDA) composite microspheres is readily synthesized via an in situ polymerization way, followed by immobilization of Ti4+ on the surface of the microspheres to obtain P5W30/PDA-Ti4+. Due to metal affinity and π stacking interaction, this novel material exhibits high selectivity to β-casein (β-ca), and the theoretical maximum adsorption capacity is as high as 1250 mg g-1, fitting well with the Langmuir model. The captured β-ca can be collected by using Britton-Robinson (B-R) buffer at pH 7.0, and a recovery of 81.5% is acquired. The enrichment factor is over 150 at a mass ratio of BSA/β-ca = 100:1, indicating that phosphoproteins can be purified by P5W30/PDA-Ti4+. Moreover, the application of P5W30/PDA-Ti4+ as sorbent in real biological samples has been investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, and the consequences show that this kind of material is able to selectively isolate phosphoproteins from complex samples such as drinking milk and chicken egg white.

In this study, a crystal porous organic framework (POF) belonging to ctn topology (POFct-1) is synthesized to selectively scavenge Hg(II) and Cu(II) ions. The maximum adsorption capacities of 167.1...

Long-term and multipoint monitoring is very important to evaluate the safety of water environment. Atomic fluorescence spectrometer (AFS) is generally used for analyzing metals or metalloids in water quality monitoring. In the present work, for the first time, AFS is employed for sensitive monitoring of nitrogen nutrients, i.e., NO2−, NO3− and NH4+, with nitric oxide (NO) vapor generation. By taking advantage of the different vapor generation conditions for NO2−, NO3− and NH4+, a unit integrating with sampling, heating, cooling, gas-liquid separation and moisture removal is employed for controlling the vapor generation process, by reacting with either iodide or titanium (III). An antimony hollow cathode lamp is used for the excitation of NO to produce fluorescence emission at 193–320 nm. Linear calibration graphs are obtained within 0.02–2, 0.1–20, 0.2–1 mg L−1 for NO2−, NO3− and NH4+, along with detection limits of 0.006, 0.03, 0.06 mg L−1, respectively. The new analytical strategy obviously broadens the application of AFS, and it is well demonstrated by the determination of NO2−, NO3− and NH4+ in certified reference materials as well as various real water samples, providing competitive sensitivity with the current techniques for nutrient monitoring in environmental water.

Highly sensitive metal ion discrimination and detection are of great value in environmental monitoring. However, it is still a challenge to obtain multidimensional information from a single material by applying various transduction principles to realize high-order sensing. Herein, a kind of yellow luminescent sub-10 nm carbon-based nanoparticles (CNPs) was prepared by chemically oxidative polymerization. The synthesis process involves only mixing the o-phenylenediamine (o-PD) and ammonium persulphate (APS) aqueous solutions together and allowing to stand at room temperature for 24 h without any external heating or additional energy input. Due to the rich aromatic diamine groups, these room-temperature carbon-based nanoparticles (RT-CNPs) can chelate various metal ions, leading to the changes in absorption and fluorescence as well as further change of fluorescence with the addition of 3,3′,5,5′-tetramethylbenzidine (TMB). Base on this phenomenon, a lab-on-RT-CNPs sensing platform for discrimination of metal ions has been developed. In both the triple-channel and double-channel modes, eight metal ions, including Cr3+, Cu2+, Fe3+, Hg2+, Cd2+, Pb2+, Co2+, and Ni2+, can be discriminated at a low concentration of 0.5 μM. In addition, the sensing platform was also validated by 100% accurate identification of 48 unknown samples and spiked Lake waters.

The discrimination of various sulfur -containing species helps us to deeply understand how sulfur affects cellular signaling and other physiological events. Herein, we present a three-dimensional sensor array based on simultaneous variation of the optical properties (fluorescence, light scattering, and UV–vis absorption) of gold–silver alloy nanocluster (AuAgNCs)–gold nanoparticle (AuNPs) composite for the rapid identification of 13 sulfur-containing species and sulfur-oxidizing bacteria. The sensor array is fabricated based on the strong coordination interactions between sulfur-containing compounds and AuAgNCs on the surface of AuNPs. The sulfur species of interest exhibit different affinities toward AuAgNCs and generate unique optical properties. These response patterns could divide the analytes into three categories including organic sulfide, inorganic sulfide, and thiols. Thirteen types of sulfur species including cystine, methionine, GSSG, S2–, SO32–, S2O32–, S2O72–, S2O82–, S4O62–, GSH, N-acetyl-l-c...

In view of the high toxicity of Cr(VI), simple and rapid on-site analytical approaches are in high demand for environment monitoring. Herein, an innovative chemosensor is developed for on-site sensitive detection of Cr(VI) in minutes by the naked eye. The chemosensor consists of gallic acid-capped gold nanoparticles (GA-Au NPs), methylene blue (MB), and NaBH4. In the presence of Cr(VI) ions, the reduction of MB by NaBH4 is able to greatly accelerate due to the Cr(VI)-stimulated catalytic activity of GA-Au NPs, resulting in a color switching of MB from blue to colorless for the quantitative detection of Cr(VI). The chemosensor in solution exhibits excellent selectivity and ultrahigh sensitivity to Cr(VI), with the detection limits of 0.05 nM by UV-vis spectroscopy and 0.1 nM by the naked eye. Similarly, a paper-based chemosensor is obtained by immobilization of GA-Au NPs and MB onto a piece of filter paper, offering a more convenient approach for rapid on-site detection of Cr(VI). In addition, H2O2 as an oxidizing agent is employed to convert Cr(III) into Cr(VI), thus achieving speciation analysis of Cr. The applicability of a chemosensor is also validated by the detection of Cr speciation in water samples with satisfactory recoveries.

Fluorescence imaging of cellular metals is widely reported. However, the quantification of intracellular metals with fluorescence imaging is so far not feasible and highly challenging. In this work, a ratiometric probe with two fluorescently labeled complementary DNA strains is designed for intracellular zinc quantification via fluorescence imaging, based on fluorescence resonance energy transfer (FRET) from carbon dots (CDs) to fluorescein (FAM). The donor CDs are modified with a Zn2+ aptamer, whereas the receptor FAM is conjugated with the complementary DNA sequence to ensure selectivity. MCF-7 cells are cultured sequentially with Zn2+ (20, 40, 55, 70, 85, and 100 μmol L–1) and CDs–FAM (100 μg mL–1), which is used for fluorescence imaging (at λex = 405 nm and λem = 440–490 nm for CDs, λem = 500–550 nm for FAM) to provide a relative fluorescence ratio ((F – F0)/F0, F = ICDs/IFAM), followed by quantifying intracellular zinc with ICPMS. A linear correlation is achieved between the relative fluorescence rat...

Flow over a fish-like airfoil is numerically investigated to elaborate the hydrodynamics of the undulatory braking locomotion for an elongated eel-like body or long-based fin. For undulation with low frequency, we find that boundary layer separation occurs in a parameter region with wakes in which two vortex pairs are formed per undulatory period. The physical mechanism of separation is governed by the slip (the ratio of swimming-to-body-wave speed), and the critical value of the slip in an inertial flow regime is approximately 4/3 rather than 1, which is independent of steepness (or amplitude). The relationship between pressure drag and relative velocity (between phase speed and free stream velocity) changes from linear to quadratic, corresponding to two different flow structures; this happens due to boundary layer separation, and the piecewise scaling relationship between pressure drag and relative velocity is explicitly clarified. Considering the viscosity effects, the separation criterion and the scaling relationship in the case of an undulatory brake are both synthetically modified using the Reynolds number, with all the required parameters clearly expressed. The results of this study provide physical insight into understanding the flow structures and hydrodynamics of the undulatory braking locomotion, which has instructional significance to brake design.

Robust and sensitive cell-based enzyme-linked immunosorbent assay (CELISA) is of great significance in the diagnosis and screening of cancer. However, the method is limited by the high rate of negative results attributed to the instability of horseradish peroxidase (HRP), H2O2, and antibody. Here, we construct a folic acid-functionalized in situ-grown MnO2 nanosheet/graphene oxide hybrid (FA-MnO2/GO) with oxidase-like activity instead of the anti-folate receptor antibody in traditional CELISA to resist the possible negative interference arising from unstable HRP, H2O2, and antibodies for more robust colorimetric detection of cancer cells. The functionalization of FA enables the selective binding between hybrid and cancer cells through the over-expressed folate receptor, and then the binding events are converted into quantitative colorimetric signals though the oxidation of the chromogenic substrate TMB catalyzed by MnO2, allowing the detection of cancer cells with colorimetric method. Moreover, the construction of MnO2/GO hybrid can synergistically enhance the oxidase-like activity of MnO2 and promote its dispersion in water, further ensuring the accuracy and sensitivity of the detection. A detection limit of 20 cancer cells is obtained by a plate reader, which is lower than those obtained by most reported CELISA methods for cancer cell detection, and as few as 75 cancer cells can be identified by the naked eye. This study not only provides a multifunctional sensing platform for robust and sensitive cancer cell detection, but also offers a promising oxidase-like mimic in the field of bioanalysis.

Robust and sensitive cell-based enzyme-linked immunosorbent assay (CELISA) is of great significance in the diagnosis and screening of cancer. However, the method is limited by the high rate of negative results attributed to the instability of horseradish peroxidase (HRP), H

Mercury (Hg) is one of the most toxic heavy metals. It can migrate around the globe and magnify through the food chain, ultimately harming human health. Urinary Hg reflects recent exposure of Hg, which reflects the status of environmental contamination by Hg. This review summarized the levels and presented temporal trends of urinary Hg in Chinese people (both the general public and the occupationally exposed people) reported from 1970s to 2010s. It was found that urinary Hg levels in 92.3% of the reported population were less than the reference value (10.0 µg/L) recommended by Chinese health authority, while 76.9% were less than the reference value (4.0 µg/L) recommended by World Health Organization (WHO) in the general public in China. For the temporal trend from 1970s to 2010s, the urinary Hg levels in the general public in China were found to decrease gradually. In the occupationally exposed people, the urinary Hg levels generally exceeded the reference value (10.0 µg/L) for the general public, and about half of them were higher than the occupational exposure limit (35.0 µg/g creatinine) set by Chinese Occupational Health Standard (WS/T 265 - 2006). From 1970s to 2010s, the urinary Hg levels in occupationally exposed population increased first and then decreased slowly. Hg miners in Guizhou were found to have the highest urinary Hg levels, while workers in Anhui, Chongqing, Qinghai and Shanxi also had high levels of urinary Hg. In all, the urinary Hg levels in both the general public and the occupationally exposed people decreased from 1970s to 2010s, especially in recent decades. Attention should be paid to occupationally exposed people since high levels of urinary Hg were found in them. The message provided in this review can help better understand the situation of Hg burden in Chinese people and lay a basis for the coming effectiveness evaluation on the implementation of Minamata Convention on Mercury. Capsule abstract: The urinary Hg levels in both the general public and the occupationally exposed people in China are decreasing.

Real-time and rapid detection of various biomarkers in body fluids has important significance for early disease diagnosis, efficient monitoring of treatment, and evaluation of prognosis. However, traditional detection methods not only require bulky and costly instruments but also are not suitable for the analysis of heterogeneous samples (e.g., serum and urine), limiting their applications in point-of-care testing (POCT). Herein, an integrated photoacoustic (PA) device with a smartphone as the acoustic signal readout has been constructed, greatly reducing the volume and cost of the instrument, and providing a potential miniature platform for POCT of clinical samples. By exploiting the electron transfer product of 3,3',5,5'-tetramethylbenzidine (TMB) (i.e., TMB++) as the PA probe and hemin-graphene oxide (H-GO) complex as the peroxidase, quantitative analysis of uric acid was successfully performed by using only 30 μL of a sample solution. Due to the favorable stability of artificial enzymes, reaction reagents could be effectively embedded in agar gel to make a portable "test strip". Therefore, operators just need to drop clinical samples on the "test strip" for PA analysis, which is user friendly without requiring complex sample preparation steps. In addition, since the acoustic change mainly comes from the PA effect, it has a lower background signal than UV-vis and fluorescence analysis, greatly improving the analytical performance. The simplicity, low cost, and broad adaptability make this miniature PA device attractive for on-site detection, particularly in resource-limited settings.