A violet light-emitting diode-based gas-phase molecular absorption device for measurement of nitrate and nitrite in environmental water.

A simple and sensitive device for the detection of nitrite and nitrate in environmental waters was developed based on visible light gas-phase molecular absorption spectrometry. By integrating a detection cell (DC), semiconductor refrigeration temperature-controlling system (SRTCY), and nitrite reactor into a sequential injection analysis system, trace levels of nitrite and nitrate in complex matrices were successfully measured. A low energy-consuming light-emitting diode (violet, 400-405 nm) was coupled with a visible light-to-voltage converter (TSL257) to measure the gas-phase molecular absorption. To reduce the interference of water vapor, an SRTCY was used to condense the water vapor on-line before the gas-phase analyte entered the DC. The DC was radiatively heated by the SRTCY to avoid water vapor condensation in the light path. As a result, the obtained baseline noise reduced 3.75 times than that of without SRTCY. Under the optimized conditions, the device achieved limits of detection (3σ/k) of 0.055 and 0.36 mmol/L (0.77 and 5.04 mg N/L) for nitrite and nitrate, respectively, and the linear calibration ranges were 0.1-15 mmol/L (R2 = 0.9946) and 1-10 mmol/L (R2 = 0.9995), respectively. Precisions of 5.2 % and 9.0 % were achieved for ten successive determinations of 0.3 mmol/L nitrite and 1.0 mmol/L nitrate, and the analytical times for nitrite and nitrate determination were 5 and 13 min, respectively. This method was validated against standard methods and recovery tests, and it was applied to the measurement of nitrite and nitrate in environmental waters. Moreover, a device was designed to enable the field measurement of nitrite and nitrate in complex matrices.

A hydrodynamic-based dual-function microfluidic chip for high throughput discriminating tumor cells.

A hydrodynamic-based microfluidic chip consisted of two function units that could not only separate tumor cells (TCs) from whole blood but also remove residual blood cells was designed. The separation of TCs was achieved by a straight contraction-expansion array (CEA) microchannel on the front end of the chip. The addition of contractive structure brought a micro-vortex like Dean vortex that promoted cell focusing in the channel, while when cells entered the dilated region, the wall-induced lift force generated by the channel wall gave cells a push away from the wall. As the wall-induced lift force is proportional to the third power of the cell diameter, TCs with larger diameter will have a larger lateral migration under the wall-induced lift force, realizing the separation of TCs from blood sample. Fluorescent particles with diameters of 19.3 µm and 4.5 µm were used to simulate TCs and red blood cells, respectively, to verify the separation capacity of the proposed CEA microchannel for particles with different diameter. And a separation efficiency 98.7% for 19.3 µm particles and a removal rate 96.2% for 4.5 µm particles was observed at sample flow rate of 10 µL min-1 and sheath flow rate of 190 µL min-1. In addition, a separation efficiency about 96.1% for MCF-7 cells (stained with DiI) and removal rates of 96.2% for red blood cells (RBCs) and 98.7% for white blood cells (WBCs) were also obtained under the same condition. However, on account of the large number of blood cells in the blood, there will be a large number of blood cells remained in the isolated TCs, so a purification unit based on hydrodynamic filtration (HDF) was added after the separation microchannel. The purification channel is a size-dictated cell filter that can remove residual blood cells but retain TCs, thus achieving the purification of TCs. Combined the CEA microchannel and the purifier, the microchip facilitates sorting of MCF-7 cells from whole blood with a separation rate about 95.3% and a removal rate over 99.99% for blood cells at a sample flow rate of 10 µL min-1, sheath flow rate of 190 µL min-1 and washing flow rate of 63 µL min-1.

Multiplex Profiling of Biomarker and Drug Uptake in Single Cells Using Microfluidic Flow Cytometry and Mass Spectrometry.

To perform multiplex profiling of single cells and eliminate the risk of potential sample loss caused by centrifugation, we developed a microfluidic flow cytometry and mass spectrometry system (µCytoMS) to evaluate the drug uptake and induced protein expression at the single cell level. It involves a microfluidic chip for the alignment and purification of single cells followed by detection with laser-induced fluorescence (LIF) and inductively coupled plasma mass spectrometry (ICP-MS). Biofunctionalized nanoprobes (BioNPs), conjugating ∼3000 6-FAM-Sgc8 aptamers on a single gold nanoparticle (AuNP) (Kd = 0.23 nM), were engineered to selectively bind with protein tyrosine kinase 7 (PTK7) on target cells. PTK7 expression induced by oxaliplatin (OXA) uptake was assayed with LIF, while ICP-MS measurement of 195Pt revealed OXA uptake of the drug in individual cells, which provided further in-depth information about the drug in relation to PTK7 expression. At an ultralow flow of ∼0.043 dyn/cm2 (20 µL/min), the chip facilitates the extremely fast focusing of BioNPs labeled single cells without the need for centrifugal purification. It ensures multiplex profiling of single cells at a throughput speed of 500 cells/min as compared to 40 cells/min in previous studies. Using a machine learning algorithm to initially profile drug uptake and marker expression in tumor cell lines, µCytoMS was able to perform in situ profiling of the PTK7 response to the OXA at single-cell resolution for tests done on clinical samples from 10 breast cancer patients. It offers great potential for multiplex single-cell phenotypic analysis and clinical diagnosis.

Tracking and imaging nano-plastics in fresh plant using cryogenic laser ablation inductively coupled plasma mass spectrometry.

Tracking and imaging of nano-plastics are extremely challenging, especially in fresh biological samples. Here, we propose a new strategy in which polystyrene (PS) was doped with the europium chelate Eu (DBM)3bpy to quantify, track, and in situ image nano-plastics in fresh cucumber based on inherent metals using cryogenic laser ablation inductively coupled plasma mass spectrometry (cryo-LA-ICP-MS). The cryogenic conditions provide a stable condition for imaging fresh cucumber, suppressing the evaporation of water in fresh plants, and maintaining the original structure of plants with respect to room temperature imaging in LA-ICP-MS. The plants were cultivated in two types of nano-plastics solutions with low (50 mg/L) and high (200 mg/L) concentrations for 9 days. The results showed that nano-plastics mainly enrich the roots and have negative effects, which decrease the trace elements of Zn, Mn, and Cu in cucumber. Smaller PS particles are able to penetrate the plant more easily and inflict serious damage. Novel imaging method provides a novel insight into the tracking and imaging of nano-plastics in fresh plant samples. The results illustrated that nano-plastics deposition on plants has the potential to have direct ecological effects as well as consequences for potential health.

Interaction of Cellular Uptake of Nanosilver and Metallothionein Stress Expression Elucidated by 2D Single-Cell Analyses Based on LIF and ICP-MS.

The exploration of cytology mechanisms of nanosilver uptake, toxicity, and detoxification has become an important issue due to its widespread applications. Previous studies have shown differences in the toxic response of mammalian cells to nanosilver. However, the analysis results based on cell populations ignore the impact of cell uptake heterogeneity on the expression of associated stress proteins and cellular physiological activities. In this respect, this work investigated the interaction between silver uptake and metallothionein (MT) expression in individual cells. In addition, we have also preliminarily elucidated the sensitivity variation to AgNPs by using five cell lines, e.g., LX-2, HepG-2, SK-HEP-1, Huh-7, and MDA-MB-231, by adopting a two-dimensional (2D) high-throughput single-cell analysis platform coupling laser-induced fluorescence (LIF) and inductively coupled plasma mass spectrometry (ICP-MS). We developed a 2D data analysis method for one-to-one unification of fluorescence-mass spectrometry signals corresponding to a specific single cell. It indicated that there is no obvious correlation between cellular silver uptake and cell size, and the low MT expression of cells is more sensitive to silver nanoparticles. For each cell line, significant heterogeneity in MT expression was observed. This provides important information for understanding the potential heterogeneous effects of nanosilver on mammalian biological systems. Overall, detoxified cells are more tolerant to nanosilver and normal cells are more tolerant than cancer cells.

Single Cell Phenotypic Analysis for Cancer Stem Cell Identification by Dual-Isotope ICP-QMS.

Single cell phenotypic analysis is significant for clinical diagnosis, treatment, and prognosis of cancer. Accurate differentiation of cancer stem cell (CSC) subpopulations from a large number of cancer cells may become a cancer surveillance tool and provide important implications for the development of new CSC-targeted therapy strategies. Herein, we report a new approach based on dual-isotope inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) for single cell phenotypic analysis. High-throughput single cell sampling was achieved by a spiral channel microfluidic chip for cell focusing and alignment, and single cell analysis was performed with time-resolved ICP-QMS by identifying the highly specific probes. This enables the monitoring of two surface protein markers (EpCAM and MUC1) of three cell types, i.e., HeLa, MCF-7, and HepG2, at single cell level. The analysis of breast cancer stem cells further confirmed its capability in distinguishing rare cell phenotypes. The present study provides promising possibilities for adopting ICP-QMS in biomedical investigations in terms of cell typing, stemness identification of tumor cells, and cell heterogeneity analysis.

Two-Dimensional Multi-parameter Cytometry Platform for Single-Cell Analysis.

A 2D flow cytometry platform, known as CytoLM Plus, was developed for multi-parameter single-cell analysis. Single particles or cells after hydrodynamic alignment in a microfluidic unit undergo first-dimension fluorescence and side scattering dual-channel optical detection. They were thereafter immediately directed to ICP-MS by connecting the microfluidic unit with a high-efficiency nebulizer to facilitate the second-dimension ICP-MS detection. Flow cytometry measurements of fluorescent microspheres evaluated the performance of CytoLM Plus for optical detection. 6434 fluorescence bursts were observed with a valid signal proportion as high as 99.7%. After signal unification and gating analysis, 6067 sets of single-particle signals were obtained with 6.6 and 6.2% deviations for fluorescence burst area and height, respectively. This is fairly comparable with that achieved by a commercial flow cytometer. Afterward, CytoLM Plus was evaluated by 2D flow cytometry measurement of Ag+-incubated and AO-stained MCF-7 cells. A program for 2D single-cell signal unification was developed based on the algorithm of screening in lag time window. In the present case, a lag time window of -4.2 ± 0.09 s was determined by cross-correlation analysis and two-parameter optimization, which efficiently unified the concurrent single-cell signals from fluorescence, side scattering, and ICP-MS. A total of 495 sets of concurrent 2D signals were screened out, and the statistical analysis of these single-cell signals ensured 2D multi-parameter single-cell analysis and data elucidation.

[Impacts of Climate Change and Human Activities on NDVI Change in Eastern Coastal Areas of China].

Based on the datasets of normalized difference vegetation index (NDVI), temperature, precipitation, and solar radiation and the methods of trend, partial correlation, and residual analyses, this study explored the spatiotemporal variation in NDVI and its response to climate change from 1982 to 2019 in eastern coastal areas of China. Then, the effects of climate change and non-climatic factors (e.g., human activities) on NDVI trends were analyzed. The results showed that:① the NDVI trend varied greatly in different regions, stages, and seasons. On average, the growing season NDVI increased faster during 1982-2000 (stage I) than that during 2001-2019 (stage Ⅱ) in the study area. Moreover, NDVI in spring showed a more rapid increase than that in other seasons in both stages. ② For a given stage, the relationships between NDVI and each climatic factor varied in different seasons. For a given season, the major climatic factors associated with NDVI change were different between the two stages. The relationships between NDVI and each climatic factor showed great spatial differences in the study period. In general, the increase in growing season NDVI in the study area from 1982 to 2019 was closely related to the rapid warming. The increase in precipitation and solar radiation in stage Ⅱ also played a positive role. ③ In the past 38 years, climate change played a greater role in the change in growing season NDVI than non-climatic factors, including human activities. Whereas non-climatic factors dominated the increase in growing season NDVI during stage I, climate change played a major role during stage Ⅱ. We suggest that more attention should be paid to the impacts of various factors on vegetation cover variation during different periods to promote the understanding of terrestrial ecosystem changes.

Open flow cytometer with the combination of 3D hydrodynamic single cell focusing and confocal laser-induced fluorescence detection.

Flow cytometry is among the most powerful tools for single-cell analysis, while the high cost and mechanical complexity of the commercial instrumentation limit the applications in personalized single-cell analysis. For this issue, we hereby construct an open and low-cost flow cytometer. It is highly compact to integrate the functions of (1) single cell aligning by a lab-made modularized 3D hydrodynamic focusing device, and (2) fluorescence detection of the single cells by a confocal laser-induced fluorescence (LIF) detector. The ceiling cost of the entire hardware for the LIF detection unit and 3D focusing device is $ 3200 and $ 400 respectively. A sheath flow velocity of 150 µL/min produces a focused sample stream of 17.6 µm × 14.6 µm at sample flow of 2 µL/min, based on the LIF response frequency and the laser beam spot diameter. The assay performance of the flow cytometer was evaluated by characterizing fluorescent microparticles and acridine orange (AO) stained HepG2 cells, producing throughputs of 40.5/s and 6.2/s respectively. Favorable assay precision and accuracy were demonstrated by the agreement of frequency histogram with imaging analysis, and good Gaussian-like distributions of fluorescent microparticles and AO-stained HepG2 cells. Practically, the flow cytometer was successfully applied for the evaluation of ROS generation in single HepG2 cells.

Stellate Ganglion Block Improves Postoperative Sleep Quality and Analgesia in Patients with Breast Cancer: A Randomized Controlled Trial.

INTRODUCTION: Postoperative impaired sleep quality and pain are associated with adverse outcomes. Stellate ganglion block (SGB) has shown promising results in enhancing sleep quality and alleviating neuropathic pain. This study aimed to investigate the effects of ultrasound-guided SGB on postoperative sleep quality and pain in patients undergoing breast cancer surgery. METHODS: This study is a parallel-group randomized controlled clinical trial with two groups: SGB and control. Fifty female patients undergoing breast cancer surgery were randomized in a 1:1 ratio to receive preoperative ultrasound-guided single-injection SGB (SGB group) or just an ultrasound scan (control group). All participants were blinded to the group assignment. The primary outcome was postoperative sleep quality, assessed by the St. Mary's Hospital Sleep Questionnaire and actigraphy 2 days postoperatively. The secondary outcome was postoperative pain, measured by the visual analog scale. RESULTS: A total of 48 patients completed the study, with 23 patients in the control group and 25 in the SGB group. The postoperative St. Mary's Hospital Sleep Questionnaire scores were significantly higher in the SGB group than in the control group on 1 day postoperative (30.88 ± 2.44 versus 27.35 ± 4.12 points, P = 0.001). The SGB also increased the total sleep time and sleep efficiency (main actigraphy indicators) during the first two postoperative nights. Compared with the control group, preoperative SGB reduced postoperative pain and the incidence of breast cancer-related lymphedema (20% versus 52.2%, P = 0.02, odds ratio 0.229, 95% confidence interval 0.064-0.821). There were no adverse events related to SGB. CONCLUSION: Preoperative ultrasound-guided SGB improves postoperative sleep quality and analgesia in patients undergoing breast cancer surgery. SGB may be a safe and practical treatment to enhance the postoperative quality of life in patients with breast cancer. TRIAL REGISTRATION: The study was registered in the Chinese Clinical Trial Registry (ChiCTR2100046620, principal investigator: Kai Zeng, date of registration: 23 May 2021).

Dean-Flow-Coupled Elasto-Inertial Focusing Accelerates Exosome Purification to Facilitate Single Vesicle Profiling.

Exosomes are recognized as noteworthy biomarkers playing unprecedented roles in intercellular communication and disease diagnosis and treatment. It is a prerequisite to obtain high-purity exosomes for the comprehension of exosome biochemistry and further illustration of their functionality/mechanisms. However, the isolation of nanoscale exosomes from endogenous proteins is particularly challenging for small-volume biological samples. Herein, a Dean-flow-coupled elasto-inertial microfluidic chip (DEIC) was developed. It consists of a spiral microchannel with dimensional confined concave structures and facilitates elasto-inertial separation of exosomes with lower protein contaminants from cell culture medium and human serum. The presence of 0.15% (w/v) poly-(oxyethylene) controls the elastic lift force acting on suspended nanoscale particles and makes it feasible for field-free purification of integrity exosomes with a 70.6% recovery and a 91.4% removal rate for proteins. As a proof of concept, the technique demonstrated the individual-vesicle-level biomarker (EpCAM and PD-L1) profiling in combination with simultaneous aptamer-mediated analysis to disclose the sensibility for immune response. Overall, DEIC enables the collection of high-purity exosomes and exhibits potential in integration with downstream analyses of exosomes.

Incidence of Anti-Drug Antibodies to Monoclonal Antibodies in Asthma: A Systematic Review and Meta-Analysis.

BACKGROUND: Antidrug antibodies (ADAs) may worsen the efficacy and safety of biologics. However, little is known about the incidence of ADAs associated with the 6 biologics approved for the treatment of asthma in the United States. OBJECTIVE: To elucidate the incidence of ADAs and their impact on reported clinical outcomes. METHODS: Systematic review and meta-analyses of randomized controlled trials, open-label extension studies, and nonrandomized studies of biologics in patients with asthma indexed in PubMed, Embase, and CENTRAL between January 1, 2000, and July 9, 2022, were carried out. The primary outcomes were treatment-emergent ADAs (incidence) and ADA prevalence. RESULTS: A total of 46 studies met the eligibility criteria. ADA incidence over follow-up was 2.91% (95% CI, 1.60-4.55) and was highest in the benralizumab studies (8.35%), with a risk ratio of 4.9 (2.69-8.92) when compared with placebo, and lowest in the omalizumab studies (0.00%). Incidence was 7.61% in the dupilumab studies, 4.39% in reslizumab, 3.63% in mepolizumab, and 1.12% in the tezepelumab studies. Incidence of neutralizing antibodies was 0.00% to 10.74% and was highest for benralizumab (7.12%). Incidence of neutralizing antibodies was higher in the benralizumab every 8 weeks (8.17%) versus every 4 weeks arms (5.81%). Results were consistent in subgroup analyses by study type and length of follow-up. CONCLUSIONS: Approximately 2.9% of individuals in the included studies developed ADAs over study follow-up period. The incidence was highest in the benralizumab group and lowest in the omalizumab group. The subcutaneous route and longer dosing intervals were associated with higher ADA development.

Comparative efficacy of tezepelumab to mepolizumab, benralizumab, and dupilumab in eosinophilic asthma: A Bayesian network meta-analysis.

BACKGROUND: It is unclear how the efficacy of tezepelumab, approved for the treatment of type 2 high and low asthma, compares to the efficacy of other biologics for type 2-high asthma. OBJECTIVES: We sought to conduct an indirect comparison of tezepelumab to dupilumab, benralizumab, and mepolizumab in the treatment of eosinophilic asthma. METHODS: The investigators conducted a systematic review and Bayesian network meta-analyses. They identified randomized controlled trials indexed in PubMed, Embase, or Cochrane Central Register of Controlled Trials (CENTRAL) between January 1, 2000, and August 12, 2022. Outcomes included exacerbation rates, prebronchodilator FEV1, and the Asthma Control Questionnaire. RESULTS: Ten randomized controlled trials (n = 9201) met eligibility. Tezepelumab (relative risk: 0.63; 95% credible interval [CI]: 0.46-0.86) was associated with significantly lower exacerbation rates than benralizumab and larger improvements in FEV1 compared to mepolizumab (mean difference [MD]: 66; 95% CI: -33 to 170) and benralizumab (MD: 62; 95% CI: -22 to 150), though the 95% CI crossed the null value of 0. Mepolizumab improved the Asthma Control Questionnaire score the most, but this improvement was not significantly different from that of tezepelumab (tezepelumab vs mepolizumab; MD: 0.14; 95% CI: -0.10 to 0.38). For efficacy by clinically important thresholds, tezepelumab, mepolizumab, and dupilumab achieved a >99% probability of reducing exacerbation rates by ≥50% compared to placebo, but benralizumab had only a 66% probability of doing so. Tezepelumab and dupilumab had a probability of 1.00 of improving prebronchodilator FEV1 by ≥100 mL above placebo. Compared to mepolizumab, dupilumab had >90% chance for improving FEV1 by ≥50 mL, but none of the differences between biologics exceeded 100 mL. CONCLUSIONS: In individuals with eosinophilic asthma, tezepelumab and dupilumab were associated with greater improvements (although below clinical thresholds) in exacerbation rates and lung function than benralizumab or mepolizumab.

Lumi-HOF@Tb as Probes for Multiple Ratiometric Fluorescence and Chemiluminescence Sensing of α-Glucosidase.

The innovative assembly of luminescent hydrogen-bonded organic frameworks (HOFs) into multifunctional optical sensors is of great significance for developing advanced materials. Herein, we report a facile room-temperature synthesis strategy for the luminol HOF modified by Tb3+ (Lumi-HOF@Tb) and featuring sensitive chemiluminescence and fluorescence characteristics. Lumi-HOF@Tb is further pioneered as a dual-signal sensor for selective detection of α-glucosidase, a type of enzyme that plays a crucial role in the digestion of carbohydrates, and screening of its inhibitors. The sensor is constructed by combining the dual optical characteristics of luminol from the HOF and lanthanide ion assistance. From the hydrolysis of α-glucosidase and the 4-nitrophenyl-α-d-glucopyranoside (pNGP) substrate emerges the fluorescent luminol-p-nitrophenol (pNP) complex at 466 nm and changes the inner filter absorption to recover Tb3+ characteristic fluorescence at 546 nm; luminol also produces a chemiluminescence signal driven by H2O2 from additional glucose oxidase-catalyzed hydrolysis of α-d-glucose. Fluorescence and chemiluminescence assays for α-glucosidase activity have therefore been established and exhibit detection limits as low as 0.04 and 0.005 U L-1, respectively. This study not only presents the possibility of Ln3+-HOF-based sensors as intelligent optical materials by integration of fluorescence and chemiluminescence techniques but also demonstrates great potential for future applications in biosensing.

Intolerance of profligacy: an aptamer concentration gradient-tailored unicellular array for high-throughput biologics-mediated phenotyping.

In aptamer-based assay schemes, aptamer probes not labeled with biomarkers have to be eliminated before testing, which may lead to a tremendous waste of precious probes. We herein propose a microfluidics system integrating an aptamer concentration gradient generator (Apt-CGG) and a dual single-cell culturing array (D-SCA), termed Mi-Apt-SCA. This facilitates the precise construction of a nanoscale-gradient microenvironment and the high-throughput profiling of single-cell growth/phenotypes in situ with the minimal consumption of Apt-probe. Unlike previous snakelike mixers, the choreographed winding-ravined aptamer dual-spiral micromixer (Apt-WD-mixer) in Apt-CGG could allow thorough blending to generate linear concentration gradients of aptamer (quasi-non-Newtonian fluid) under the action of continuous fluidic wiggles and bidirectional Dean flow. In contrast to other trap-like systems, the mild vortex allows single-cell growth in an ultra-tender fluidic microenvironment using triple-jarless single-cell culture capsules (TriJ-SCCs) in D-SCA (shear stress: 3.43 × 10-5 dynes per cm2). The minimum dosage of aptamer probe required for exploring PDL1 protein expression in two hepatoma cell lines is only one-900th of that required by conventional protocols. In addition, this approach facilitated the profiling of ITF-ß/cisplatin-mediated single-cell/cell-cluster phenotypes.

Tracking cellular transformation of As(III) in HepG2 cells by single-cell focusing/capillary electrophoresis coupled to ICP-MS.

The cellular metabolism of metals is highly critical to elucidate their potential cytotoxicity or cell protection mechanism. In this work, an asymmetric serpentine microfluidic device (ASMD) with high sampling efficiency and excellent focusing performance was developed for single-cell focusing. ASMD coupling with ICP-MS ensures single-cell assay to provide the information for trivalent arsenic (As(III)) uptake by HepG2 cells, which reveals the heterogeneity of cellular arsenic distribution, and elucidates the arsenic elimination behaviors in single HepG2 cells. Further, the metabolism and transformation of As(III) in HepG2 cells was tracked by hyphenating capillary electrophoresis (CE) separation with ICP-MS. The results for single-cell analysis and arsenic elimination kinetics illustrated that the half-life of arsenic elimination is 0.9 ± 0.04 h with the elimination constant of 0.77 ± 0.03, i.e., 77% of accumulated As in HepG2 cells may be eliminated per hour. Moreover, arsenobetaine (AsB) was identified to be the main metabolite and biotransformation species of As in HepG2 cells. ASMD-ICP-MS and CE-ICP-MS are powerful for tracking the fate of metals or metal drugs in single cells to comprehensively understand their metabolic pathway and transformation behaviors.

Dual mode assay of glutathione with Tb-doped g-C3N4/MnO2 nanoconjugates as fluorescence probe and Mn as elemental target.

Glutathione (GSH) plays important roles in various physiological processes, thus highly sensitive assay of GSH and timely warning of its variation at trace level in complex biological matrixes is of great significance. However, this is challenging due to the coexisting reductive biomolecules and dynamic change of GSH levels in responding to various stimuli which remain largely unexploited. Herein, we report a dual mode protocol for the assay of GSH based on nanoconjugate g-C3N4:Tb/MnO2 between MnO2 nanosheets and terbium-doped g-C3N4 (g-C3N4:Tb) nanosheets. MnO2 moiety effectively quenches the emission at 546 nm from Tb3+ in the nanoconjugate, which is restored under the reduction of MnO2 by GSH to ensure fluorescence turn-on assay of GSH. Meanwhile, the generated Mn2+ facilitates inductively coupled plasma mass spectrometry (ICP-MS) detection to endow indirect highly sensitive assay of GSH. Fluorescence mode derived a limit of detection (LOD) of 0.17 µmol L-1 within a linear range of 0.5-160 µmol L-1, while ICP-MS resulted in a superior LOD of 0.016 µmol L-1 within 0.05-160 µmol L-1. Both detection modes provide excellent selectivity to GSH. The dual mode platform was validated by GSH assay in cell lysates. It was further demonstrated by monitoring the variation of dynamic change of GSH level under CuSO4 or cisplatin induced GSH consumption.

Cryogenic Laser Ablation in a Rapid Cooling Chamber Ensures Excellent Elemental Imaging in Fresh Biological Tissues.

Laser ablation inductively coupled plasma mass spectrometry imaging of biologically significant targets largely relies on maintaining the original structures of samples. The temperature regulation capability of the ablation cell is crucial. Herein, a rapid cooling cryogenic sample cell (RCCSC) was developed. In the RCCSC chamber, the temperature reduces to -20 °C in 4 min with a minimum 10 h variation of ±0.1 °C at -26 °C. Improvements on the precision were achieved for the elements of interest in NIST 612 and spiked agarose gel under cryogenic conditions. The limits of detection improved by up to 1.57, 1.70, 3.26, and 1.33 fold for 63Cu, 66Zn, 57Fe, and 140Ce in agarose gel, respectively, were obtained under cryogenic conditions compared with those at room temperature. In a time period of testing (10 h), the cryogenic ablation maintains the native state of biological tissues with a high water content to ensure better elemental imaging by reducing thermal effects in ablation and suppressing evaporation of water. The rapid cooling cryogenic ablation significantly improves elemental imaging, as demonstrated by the imaging of various elements in coriander leaves. The present study may provide further insights into elemental distributions in fresh biological samples.

Insights into Surface Charge of Single Particles at the Orifice of a Nanopipette.

The dynamic behaviors of particles in various physical fields are related to the physicochemical properties of particles. Herein, we focus on the relationship between surface charge and dynamic behaviors of particles at the orifice of a nanopipette. We interestingly find that angle θ, a parameter related to the asymmetric degree of current spike, exhibits a strong relationship with surface charge of the particles. Both theoretical derivation and finite element simulation validate this relationship and thus could be used for quantifying the surface charge of single particles. Moreover, the gold and silica nanoparticles with the same size but different surface charges could be well distinguished and identified based on this relationship. This study not only gives a comprehensive understanding on the dynamic behaviors of particles outside the nanopipette but also opens a new way for investigating the surface charge of single particles.