A shape-reconfigurable,light and magnetic dual-responsive shape-memory micropillar array chip for droplet manipulation

Droplet manipulation on an open surface has great potential in chemical analysis and biomedicine engineering.However,most of the reported platforms designed for the manipulation of water droplets cannot thoroughly solve the problem of droplet evaporation.Herein,we report a shape-reconfigurable micropillar array chip for the manipulation of water droplets,oil droplets and water-in-oil droplets.Water-in-oil droplets provide an enclosed space for water droplets,preventing the evaporation in an open environment.Perfluoropolyether coated on the surface of the chip effectively reduces the droplet movement resistance.The micropillar array chip has light and magnetic dual-response due to the Fe3O4 nanoparticles and the reduced iron powder mixed in the shape-memory polymer.The micropillars irradiated by a near-infrared laser bend under the magnetic force,while the unirradiated micropillars still keep their original shape.In the absence of a magnetic field,when the micropillars in a temporary shape are irradiated by the near-infrared laser to the transition temperature,the micropillars return to their initial shape.In this process,the surface morphology gradient caused by the deformation of the micropillars and the surface tension gradient caused by the temperature change jointly produce the driving force of droplet movement.

Revealing the Regulation Effect of Surface Charge at Aromatic Interface to Dynamic Conformational Changes of α-Synuclein at Early Aggregation Stage

The aggregation ofα-synuclein(α-syn)is strongly influenced by membrane interfaces,but the mechanism of transition from monomers to oligomers at early aggregation stage is not clear.Here,we investigate the adsorption and structure changes ofα-syn on oppositely charged aromatic interfaces through in-situ surface-enhanced infrared absorption(SEIRA)spectroscopy and nano-IR technique.The results show that the synergy of electrostatic and hydrophobic interactions leads to a“fast-slow”two-step aggregation pathway on negatively charged interface.Surface adsorption induces the formation of an extended helix structure and subsequently partial helix unwinding in NAC region,which enables the hydrophobic stacking between nearby NAC regions.Stable antiparallel β-sheet rich aggregates are gradually emerging as further interactions of monomers with the fast formed“first layer”.Monomers electrostatically adsorb on positively charged interface by C-terminus with NAC region and N-terminus stretched in solvent,which serve as an aggregation core and induce further adsorption and gradual formation of aggregates with C-terminus exposure.Our results demonstrate the modulation of surface charge and synergy of electrostatic and hydrophobic interactions on the interaction modes and aggregation pathways,which provide insights into dynamic conformation changes ofα-syn at early aggregation stage and imply the important role of spatial-temporal heterogeneity of membranes inα-synucleinopathies.

Rational Design of Capping Ligands of Quantum Dots for Biosensing

Quantum dots have been widely applied in biosensing due to their outstanding optical properties.The emissions of quantum dots are mainly determined by their composition and size,as described by the Brus’s equation.Somehow,in this case,their emissions are hardly regulated reversibly and responsively,which are unsuitable for biosensing and biodetection.In the last decade,capping ligands have been used for designing biosensors because of their responsive regulation on the photoluminescence of quantum dots.Here,we first summarize the advances in characterization and calculation specific for ligands,which have helped to provide insights into the photoluminescence process and energy band theory of quantum dots.We then review two ways of ligand design that influence the optical properties of quantum dots:affecting the process of photoluminescence,or the orbital/electronic structure.In the latter case,the atoms on both the ligand and the surface of the quantum dot interact to affect the energy band structure of the quantum dot core.Examples are presented of how these quantum dots that possess responsive properties due to the design of the ligands have been applied to sensing.With further exploration,we hope to see advances in the fundamental understanding of the energy band structures and practical applications of these quantum dots.

C-doped BiOCl/Bi_(2)S_(3) heterojunction for highly efficient photoelectrochemical detection and photocatalytic reduction of Cr(VI)

Novel C-BiOCl/Bi_(2)S_(3) composites are prepared by hydrothermal C doping in BiOCl and in-situ growth of Bi_(2)S_(3) on C-BiOCl.Compared with BiOCl,C-BiOCl has a larger exposed surface area and can effectively absorb visible light.The construction of a heterojunction in C-BiOCl/Bi_(2)S_(3) further promotes the separation and transfer of photogenerated carriers.With improved photoelectric properties,the optimized 5C-BiOCl/5Bi_(2)S_(3) is applied as a dual-functional composite for photoelectrochemical(PEC)detection and photocatalytic(PC)reduction of Cr(VI).The 5C-BiOCl/5Bi_(2)S_(3) shows a linear range of 0.02-80μM for PEC cathodic detection of Cr(VI)with a detection limit of 0.01628μM.Additionally,99.5%of Cr(VI)can be removed via absorption and PC reduction by 5C-BiOCl/5Bi_(2)S_(3),with the reduction rate constant(k)336 times higher than that of BiOCl.

Enzymatic Determination of Glucose by Optical-Fiber Sensor Sequential Injection Renewable Surface Spectrophotometry

On the basis of oxidative decoloration of bromopyrogallol red （BPR） with H2O2, catalyzed by horseradish peroxidase（ HRP）, and the sequential injection renewable surface technique（ SI-RST）, a highly sensitive optical-fiber sensor spectrophotometric method for the enzymatic determination of hydrogen peroxide was proposed. By coupling with a glucose oxidase（GOD）-catalyzed reaction, the method was used to determine glucose in human serum. The considerations in system and flow cell design, and factors that influence the determination performance are discussed. With 100μL of sample loaded and 0. 6 mg of bead trapped, the linear response range from 5.0 × 10^-8 to 5.2 × 10^-6 mol/L BPR with a detection limit（3σ） of 2. 5 ×10 ^-8 mol/L BPR, and a precision of 1.1% RSD（ n = 11 ） and a throughput of a 80 samples per hour can be achieved. Under the conditions of a 8. 7 × 10^ -6 mol/L BPR substrate, 0. 04 unit/mL HRP, 600 s reaction time and a reaction temperature of 37℃, the linear response range for H2O2 was from 5.0 × 10^-8 to 7.0 × 10^-6 mol/L with a detection limit（3σ） of 1.0 × 10^-8 mol/L and a precision of 3.7% RSD （ n = 11 ）. The linear response range by coupling with a GOD-catalyzed reaction was from 1.0 × 10^-7 to 1.0 × 10^-5 mol/L. The method was directly applied to determine glucose in human serum. Glucose contents obtained by the proposed procedure were compared with those obtained by using the phenol-4-AAP method, the error was found to be less than 3%.

Recent Advances in Triplet-Triplet Annihilation Upconversion for Bioimaging and Biosensing

Photon upconversion is an anti-Stokes process that converts low-energy photons into high-energy photons.The use of upconversion luminescence can avoid the autofluorescence of biological tissue and realize background-free bioimaging with a high signal-to-noise ratio at a low power density.In addition,the excitation of red or near-infrared light facilitates the reduction of photodamage in biological tissues and subsequent bioimaging of deep tissue features in vivo.Meanwhile,upconversion emission-mediated bio sensing offers both high sensitivity and low detection limits for quantitative analysis of the target substances in complicated biological samples.Due to its high upconversion quantum yield,low excitation power density,and tunable absorption and emission wavelengths,triplet-triplet annihilation upconversion(TTA-UC)has garnered considerable interest for bioimaging and biosensing.This review will introduce the fundamental concepts of TTA-UC,the factors that influence TTA-UC materials,and the methodologies for preparing TTA-UC materials.The important progress of TTA-UC in bioimaging and bio sensing in recent years will also be discussed in detail in vitro and in vivo.Furthermore,the current challenges of TTA-UC in bioimaging and biosensing will be discussed,along with potential solutions.

A new photolabeling probe for efficient enrichment and deep profiling of cell surface membrane proteome by mass spectrometry

The cell surface membrane proteome is a class of proteins encoded by ~25% of all protein-coding genes in living organisms and plays a key role in mediating communication between the cells and their surrounding environment. However, most cell surface membrane proteins(CSMPs) are naturally expressed at very low levels compared with intracellular proteins. The difficulties in their purification with high specificity further hinder the understanding of their structure and function. In this study, we developed a new photolabeling probe to achieve efficient tagging and facile enrichment of the CSMPs. The probe is composed of a lipid tail for cell surface localization, a polyethylene glycol(PEG) spacer for increased water solubility, two 4-(N-maleimido)benzophenone(MBP) groups for UV-active tagging of the CSMPs, and a biotin tag for subsequent isolation. Application of this photolabeling probe resulted in the successful enrichment and identification of 3098 annotated CSMPs in HT22 cells with close to 70% selectivity. The proposed photolabeling probe and enrichment strategy were demonstrated to be a powerful method for deep cell surface proteome profiling, representing one of the largest groups of current drug targets.

A robust and unique approach for tuning the energy level of Ag_(2)Se quantum dots via“on-surface”manipulation of nitrogencontaining groups of surface-coordinated ligands

Effects of surface chemistry on energy levels or optical properties of semiconductor nanocrystals have attracted considerable attention and show great promise in broad applications.Yet,it remains challenging to controllably tune the photoluminescence(PL)of quantum dots(QDs)by manipulating surface ligands.Herein,we investigated effects of the ligand,glutathione(GSH),on PL properties of near-infrared(NIR)Ag_(2)Se QDs by“on-surface”manipulation,that is,precisely manipulating the chelating group without dissociating the ligand from the surface.The anchoring of the amino group was found to be controlled by solution pH,whereas the binding of the thiol group to the Ag+was pH independent,maintaining the“on-surface”state of GSH.By tuning the pH-controlled binding of amino groups,the energy level or the bandgap of Ag2Se QDs could be increased by up to 140 meV.The increased bandgap resulted in the blueshift of PL spectrum,which could be reversibly tuned by up to 75 nm.The pH-mediated tunable PL properties of QDs could also be extended to other nitrogen-containing pH-sensitive groups which could coordinate to the Ag+,not limited to the amino group.Our work would facilitate the study of nanocrystal surface chemistry and our model that the binding of amino groups affected energy levels of Ag2Se QDs might facilitate new insights into the electronic structure and energy level of other QD-ligand complexes.

利用定量单病毒示踪技术探究SARS-CoV-2与细胞膜融合动态过程

Viral envelope fusion with the host plasma membrane(PM)for genome release is a hallmark step in the life cycle of many enveloped viruses.This process is regulated by a complex network of biomolecules on the PM,but robust tools to precisely elucidate the dynamic mechanisms of virus-PM fusion events are still lacking.Here,we developed a quantitative single-virus tracking approach based on highly efficient dual-color labelling of viruses and batch trajectory analysis to achieve the spatiotemporal quantification of fusion events.This approach allows us to comprehensively analyze the membrane fusion mechanism utilized by pseudotyped severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)at the singlevirus level and precisely elucidate how the relevant biomolecules synergistically regulate the fusion process.Our results revealed that SARS-CoV-2 may promote the formation of supersaturated clusters of cholesterol to facilitate the initiation of the membrane fusion process and accelerate the viral genome release.

3D时代:简单光化学方法实现无机纳米材料复杂3D结构打印

3D printing,or more formally known as additive manufacturing,is a collection of layer-by-layer approaches to assemble materials into freeform objects in 3D [1].Compared with traditional manufacturing technologies,it represents a disruptive process that benefits from the freedom in 3D structural designs and unlocks new material properties and device functionalities [1].These compelling capabilities render 3D printing attractive in fundamental research,industry,and our daily life,with applications ranging from rapid prototyping of customized products [2] to advanced engineering of biomedical implants [3],optics [4],and electronics[5].The past decade has witnessed the rapid progress of 3D printing in terms of new printing mechanism [2],more complex structures,and higher throughput [6].

Recent progress in co-detection of single-cell transcripts and proteins

Cellular heterogeneity is a universal property of living systems,and the interrogation of single cells facilitates in-depth understanding of distinct cellular states and functions in various biological processes.Co-analysis of transcripts and proteins from the same single cells opens the way to decipher complex RNA regulatory frameworks and phenotypes,facilitating the understanding of cellular fate and function regulations,discovery of novel cell types,and construction of a high-resolution cell atlas.Herein,we review the state-of-art advances in the development of methodologies for co-analysis of single-cell transcripts and proteins.First,imaging-based methods are summarized with particular emphasis on optical and mass spectrometry imaging.Next,sequencing-based approaches for high-throughput and sensitive co-analysis of single-cell transcripts and proteins are described,including droplet-,microwell-,and split-pool-based platforms.Subsequently,combined methods with more flexibility and universality are discussed.These methods commonly employ different strategies or reactions to convert transcripts and proteins of single cells into distinct signals simultaneously,which can be detected by different instruments or platforms.Lastly,some perspectives on the future challenges and development trends in this field are presented.

Intracellular redox potential-driven live-cell synthesis of CdSe quantum dots in Staphylococcus aureus

Biosynthesized semiconductor quantum dots(QDs) have bright fluorescence,adjustable particle sizes,and environmental friendliness,endowing them with convenience and potential for biological applications.Due to the unclear mechanism of the cellular environment on the live-cell synthesis of QDs,it is still difficult to regulate their optical properties.Here,the critical role of the intracellular redox environment in regulating the fluorescence properties of biosynthesized CdSe QDs in Staphylococcus aureus(S.aureus) has been elucidated.The glutathione peroxidase(GPx) activity directly affects the intracellular H_(2)O_(2) produced in the SeO_(3)^(2-) reduction,which further manipulates the glutathione redox cycle to determine the content of low-valence Seintermediates.As a result,the fluorescence intensity of the synthesized CdSe QDs increases by 60% in the GPx overexpressed cells.The cellular redox potential that is controlled by the GSH redox cycle provides the driving force for the reduction of SeO_(3)^(2-),facilitating the synthesis of CdSe QDs in S.aureus cells.The proposed mechanism of the cellular redox state provides a new perspective for regulating the synthesis of semiconductor nanomaterials in live cells.

Nitrogen-doped fluorescence carbon dots as multi-mechanism detection for iodide and curcumin in biological and food samples

Iodine ion is one of the most indispensable anions in living organisms,particularly being an important substance for the synthesis of thyroid hormones.Curcumin is a yellow-orange polyphenol compound derived from the rhizome of Curcuma longa L.,which has been commonly used as a spice and natural coloring agent,food additives,cosmetics as well as Chinese medicine.However,excess curcumin may cause DNA inactivation,lead to a decrease in intracellular ATP levels,and trigger the tissue necrosis.Therefore,quantitative detection of iodine and curcumin is of great significance in the fields of food and life sciences.Herein,we develop nitrogen-doped fluorescent carbon dots(NCDs)as a multi-mechanism detection for iodide and curcumin in actual complex biological and food samples,which was prepared by a one-step solid-phase synthesis using tartaric acid and urea as precursors without adding any other reagents.An assembled NCDs-Hg^(2+) fluorescence-enhanced sensor for the quantitative detection of I^(-) was established based on a fluorescence“turn-off-on”mechanism in a linear range of 0.3-15μM with a detection limit of 69.4 nM and successfully quantified trace amounts of I^(-) in water samples and urine sample.Meanwhile,the as-synthesized NCDs also can be used as a fluorescent quenched sensor for curcumin detection based on the synergistic internal filtration effect(IFE)and static quenching,achieving a good linear range of 0.1-20μM with a satisfactory detection limit of 29.8 nM.These results indicate that carbon dots are potential sensing materials for iodine and curcumin detection for the good of our health.

Improvement of antibacterial activity of copper nanoclusters for selective inhibition on the growth of gram-positive bacteria

In general, copper nanoclusters (CuNCs) possess very low or even virtually no bactericidal effect. Herein,we report a novel CuNCs possessing significantly high antibacterial activity, that is tannic acid (TA)capped CuNCs (TA-CuNCs). TA-CuNCs exhibit strong absorption and excitation-dependent fluorescence within pH 2-12, resulting from the functional groups of TA-CuNCs due to two prototropic equilibria,phenolphenolate and carboxyliccarboxylate. There exists synergistic effect of TA and copper nanoclusters which endows TA-CuNCs remarkable antibacterial capability as a microbicide, as characterized by the effective inhibition on the growth of gram-positive bacteria by damaging the cell membrane. By incubating 1 x 10~7 CFU/mL of gram-positive bacteria Staphylococcus aureus and Bacillus subtilis with 30 μg/mL of TA-CuNCs for 10 min, the bacteria are completely inhibited, while under same conditions the viabilities of gram-negative bacteria Escherichia coli 0157:H7 and Pseudomonas aeruginosa remain 85.0%, 72.0%, respectively. In addition, TA-CuNCs exhibit low cytotoxicity and favorable biocompatibility demonstrated by standard methyl thiazolyl tetrazolium (MTT) assay with HepG2 and 293 Tcells, giving rise to cell viability of 94.2% for HepG2 and 96.7% for 293 T by incubating 10~6 cell/mL with 200 μg/mL of TA-CuNCs for 24 h. These results make TA-CuNCs a potential alternative as bactericide for infection treatment caused by gram-positive bacteria.

A modular single-cell pipette microfluidic chip coupling to ETAAS and ICP-MS for single cell analysis

Accurate single-cell capture is a crucial step for single cell biological and chemical analysis. Conventional single-cell capturing often confront operational complexity, limited efficiency, cell damage, large scale but low accuracy, incompetence in the acquirement of nano-upgraded single-cell liquid. Flow cytometry has been widely used in large-scale single-cell detection, while precise single-cell isolation relies on both a precision operating platform and a microscope, which is not only extremely inefficient, but also not conducive to couple with modern analytical instruments. Herein, we develop a modular single-cell pipette(m SCP) microfluidic chip with high efficiency and strong applicability for accurate direct capture of single viable cell from cell suspensions into nanoliter droplets(30-1000 n L). The m SCP is used as a sampling platform for the detection of Cd Te quantum dots in single cells with electrothermal atomic absorption spectrometry(ETAAS) for the first time. It also ensures precise single-cell sampling and detection by inductively coupled plasma mass spectrometry(ICP-MS).

Exploring fluorescent covalent organic frameworks for selective sensing of Fe^3＋

Covalent organic frameworks （COFs） have been widely applied in gas capture and separation, but the fluorescent property of COFs with large n-conjugated system tends to be underexplored. Here we report the fluorescent properties of several COFs including TaTa, DhaTab, TRITER- 1 and TzDa and the effect of metal ions of Na＋, Mg2＋, K＋, Ca2＋, Cu2＋, Zn2＋, Pb2＋, Ag＋, Cd2＋ and Fe3＋ on the fluorescence of these COFs. The results show that only Fe3＋ significantly quenched the fluorescence of the studied COFs. The possibility of the four COFs for selective sensing of Fe3＋ was demonstrated. The possible mechanism of the effect of Fe3＋ on the fluorescence of the COFs was based on the absorption competition quenching.

A variable importance criterion for variable selection in near-infrared spectral analysis

Variable selection is a universal problem in building multivariate calibration models, such as quantitative structure-activity relationship(QSAR) and quantitative relationships between quantity or property and spectral data. Significant improvement in the prediction ability of the models can be achieved by reducing the bias induced by the uninformative variables. A new criterion,named as C, is proposed in this study to evaluate the importance of the variables in a model. The value of C is defined as the average contribution of a variable to the model, which is calculated by the statistics of the models built with different combinations of the variables. In the calculation, a large number of partial least squares(PLS) models are built using a subset of variables selected by randomly re-sampling. Then, a vector of the prediction errors, in terms of root mean squared error of cross validation(RMSECV), and a matrix composed of 1 and 0 indicating the selected and unselected variables can be obtained. If multiple linear regression(MLR) is employed to model the relationship between the RMSECVs and the matrix, the coefficients of the MLR model can be used as a criterion to evaluate the contribution of a variable to the RMSECV. To enhance the efficiency of the method, a multi-step shrinkage strategy was used. Comparison with Monte Carlo-uninformative variables elimination(MC-UVE), randomization test(RT) and competitive adaptive reweighted sampling(CARS) was conducted using three NIR benchmark datasets. The results show that the proposed criterion is effective for selecting the informative variables from the spectra to improve the prediction ability of models.

Mn-doped ZnS quantum dots/methyl violet nanohybrids for room temperature phosphorescence sensing of DNA

Mn-doped ZnS quantum dots/methyl violet nanohybrids were explored to develop a novel room temperature phosphorescence (RTP) sensor for the detection of DNA. Methyl violet (MV) as the electron acceptors was adsorbed on the surface of the quantum dots (QDs) to quench the RTP of the Mn-doped ZnS QDs through an electron-transfer process under excitation. The addition of DNA recovered the RTP signal of the Mn-doped ZnS QDs due to the binding of MV with DNA and the removal of MV from the surface of the Mn-doped ZnS QDs. Under the optimal conditions, the enhanced RTP intensity of the Mn-doped ZnS QDs/MV nanohybrids linearly increased with the concentration of DNA from 0.08 to 12 mg L-1 with the detection limit of 33.6 μg L-1. The relative standard deviation for eleven replicate detections of the reagent blank was 3.7%. The developed method was applied to the detection of DNA in spiked urine samples with recoveries of 96%-103% without interference from nonspecific fluorescence.

Dual functional AgNPs-M13 phage composite serves as antibacterial film and sensing probe for monitoring the corrosion of chromium-containing dental alloys

The preparation of silver nanoparticles(AgNPs)with microbe or plant tissues as bio-template offers green approach,while it suffers from low harvest and purification is needed.Herein,we propose a facile protocol for one-pot preparation of AgNPs using M13 phage as bio-template by simply mixing AgN03 solution with alkali M13 phage.In the obtained AgNPs-M13 phage composite,Cr(Ⅲ)selectively coordinates with the amino residues on phage surface and leads to the aggregation of AgNPs through the bridging of M13 phages.This makes it feasible for colorimetric sensing of Cr(Ⅲ)by measuring the absorbance ratio of AgNPs at 600 and 405 nm,which provides a LOD of 14 nmol/L.The composite also showed favorable bactericidal activity for both Gram-positive and Gram-negative bacteria,making it a promising candidate as antibacterial film in chromium-containing dental alloys and meanwhile serve as a sensing probe for monitoring the corrosion of the dental alloys.

Recent advances in flow-based sample pretreatment for the determination of metal species by atomic spectrometry

During the last few years,various flow-based separation/preconcentration methodologies have gained pertinent novel advances and exhibited powerful capability in the field of sample pretreatment and their hyphenation with detection by atomic spectrometry.The present mini-review presents and discusses the progress of flow-based sample processing approaches commonly used for the assay of trace elemental species with detection by atomic spectrometry,including preliminary sample pretreatment,solid phase extraction(including solid phase microextraction),liquid-liquid extraction,vapor generation and dialysis techniques.Special emphasis has been paid on the novel applications and analytical procedures hyphenated with atomic spectrometry.The future perspectives of flow-based sample pretreatment protocols in the determination of trace elements and their speciation are also discussed.