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When dealing with infectious pathogens, the risk of contamination or infection in the process of detecting them is nonnegligible. Separation-free detection will be beneficial in operation and safety. In this work, we proposed a DNAzyme walker for homogeneous and isothermal detection of enterovirus. The DNAzyme is divided into two inactivate subunits. When the subunit-conjugated antibody binds to the target virus, the activity of the DNAzyme recovers as a result of spatial proximity. The walker propels, and the fluorescence recovers. The final fluorescence intensity of the reaction mixture is related to the concentration of the target virus. The detection limit of this proposed method is 6.6 × 104 copies/mL for EV71 and 4.3 × 104 copies/mL for CVB3, respectively. Besides, this method was applied in detection of EV71 in clinical samples with a satisfactory result. The entire experiment is easy to operate, and the proposed method has great potential for practical use.

Bioorthogonal chemistry has been considered as a powerful tool for biomolecule labeling due to its site specificity, moderate reaction conditions, high yield, and simple post-treatment. Covalent coupling is commonly used to modify quantum dots (QDs) with bioorthogonal functional group (azide or cycloalkyne), but it has a negative effect in the decrease of QDs' quantum yield and stability and increase of QDs' hydrodynamic diameter. To overcome these disadvantages, we propose a novel method for the preparation of two kinds of clickable QDs by the strong interaction of -SH with metal ions. One system involves azide-DNA-functionalized QDs, which are used for bioconjugation with dibenzocyclooctyne (DBCO)-modified glucose oxidase (GOx) to form a GOx-QDs complex. After bioconjugation, the stability of QDs was improved, and the activity of GOx was also enhanced. The GOx-QDs complex was used for rapid detection of blood glucose by spectroscopy, naked eye, and paper-based analytical devices. The second system involves DBCO-DNA-functionalized QDs, which are used for an in situ bioorthogonal labeling of HeLa cells through metabolic oligosaccharide engineering. Therefore, these clickable QDs based on DNA functionalization can be applied for rapid and effective labeling of biomolecules of interest.

Detection of viruses with high sensitivity is critical for the prevention and treatment of the related disease. Two homogeneous target-induced cascade amplification methods were proposed for the detection of enterovirus 71 and coxsackievirus B3. These methods both employ DNAzyme but differ in the way in which the DNAzyme is amplified. In the hybridization chain reaction (HCR)-based strategy, the DNAzyme is assembled by hairpin DNA strands, while in the rolling circle amplification (RCA)-based strategy, the DNAzyme is synthesized by the polymerase. On the basis of the virion structure, we investigated the effects of using only VP1-antibody or VP1-antibody and VP2-antibody on the detection. And the combination of two kinds of antibodies was found to further improve the performance of the detection. Subsequently, the simultaneous detection of EV71 and CVB3 was achieved by the RCA-based strategy. And the proposed methods were also applied in clinical samples analysis with a satisfactory result, showing great potential for applications in virus detection.

The viral capsid protein p24 of human immunodeficiency virus is expressed at different level during viral invasion. Detection of p24 is of great importance in acquired immunodeficiency syndrome monitoring and therapy. A ratiometric probe that is easily-synthesized was constructed based on self-assembled fluorescent Ce(Ⅲ) and fluorescein. Fluorescein was used as reference. Hydrogen peroxide quenches the fluorescence of the Ce(III) easily but does not quench the fluorescence of fluorescein. The mechanism of reaction was discussed. Benefiting from the sensitive response to hydrogen peroxide, this probe was applied for p24 detection in enzyme linked immunoassay. The fluorescence ratio was in a good linear relationship with the concentration of p24, and the detection limit was 1.1 pg mL−1. This proposed method has shown potential in virus detection with easy operation.

Detailed structural information on sulfur-containing aromatic compounds in heavy oils is valuable for the petroleum industry. In this work, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) combined with collision-induced dissociation (CID) was applied to study the structures of sulfur-containing aromatic compounds in vacuum gas oil (VGO) and vacuum residue (VR). The parent ions of the sulfur-containing model compounds and high-sulfur heavy oils were isolated by the quadrupole in FT-ICR MS with a narrow isolation window of 1 Da. For most of the sulfur-containing model compounds, removal of S atoms was achieved in the collision voltage range 10–30 V. On the other hand, the removal of S atoms from the sulfur-containing compounds in heavy oils was restrained by optimization of the collision voltage. The structures of VGO and VR were also studied by CID FT-ICR MS with a narrow isolation window at the optimal collision voltages. The results suggested that naphtheno-aromatic sulfur-containing compounds were components of heavy oils and that the structural diversity of the heavy oils increased significantly with an increase in molecular weight.

Petroleum asphaltene is a complex natural organic mixture which plays a crucial role in the refining processes. In this work, asphaltenes derived from petroleum vacuum residue and its hydrotreated product were characterized by high-field Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Tandem mass spectra with narrow ion isolation window were realized by increasing the value of collision RF amplitude. Tandem mass spectra with 3 Da and 1 Da isolation windows were compared, which demonstrated the advantages of applying narrow isolation window of 1 Da. The tandem mass spectra of asphaltenes were simplified due to the narrow isolation window. Moreover, a better correlation between the parent and fragment ions obtained by narrow isolation window of 1 Da was suggested by moving the isolation window. Finally, aromatic hydrocarbons with more naphthenic rings were suggested for the molecular structures of the processed asphaltene according to the results.

In this study, we presented a digital analysis with droplet-based microfluidic, which was applied for the detection of β-galactosidase (β-Gal) and AFP. The β-Gal was quantified according to the Poisson Distribution in digital analysis with droplets containing β-Gal and fluorogenic substrate fluorescein di-β-D-galactopyranoside (FDG). In our method, the lowest concentration of β-Gal we could accurately detect was 5 fM. We found that the digital detection could be applied in quantifying protein biomarkers, take AFP for model sample. The AFP was detected through indirect detection with excess streptavidin-conjugated β-galactosidase (SA-β-gal) as signal tag. To be specific, firstly SA-β-gal was conjugated to biotin-labeled AFP antibody, and then the unbounded signal tag in the reaction solution was taken out for digital detection with droplet-based microfluidic. As a result, the AFP could be also indirectly quantified at an fM level through subtraction. This experimental result demonstrated that the indirect detection with droplet-based digital analysis was able to detect biomarkers at a low level with a few samples on an ordinary flow-focusing microfluidic chip.

As the high concentration of lactate being an important indicator in clinical diagnosis, developing a rapid and effective method for the detection of lactate is of great significance. Herein, quantum dots-based hydrogel microspheres were developed for the rapid detection of lactate via a smartphone. The hydrogel microspheres (Alg@QDs-LOx MSs) were prepared by embedding CdTe quantum dots (QDs) and lactate oxidase (LOx) into alginate hydrogels (Alg). The Alg@QDs-LOx MSs with dense multi-layer network structure exhibits improved storage stability for lactate oxidase and anti-interference ability. The fluorescent microspheres can be employed to differentiate the high lactate levels (≥2.5 mM) in the human serum within 15 min. In addition, without the requirement of special large instruments, the results can be easily observed with naked eyes or monitored by smartphones, which is more convenient and low-cost. The detection limit of lactate is 1.25 μM. Furthermore, combing this method with a portable microfluidic device, the simultaneous detection of lactate and uric acid can be realized, proved the universality of this proposed method that can be expanded for simultaneous detection of multiple biomolecules.

Polycyclic Aromatic Sulfur Heterocycles (PASHs) are undesirable compounds in fuel and refined petroleum based products. The sulfur compounds in diesel are limited strictly to an ultra-low concentration according to environment protection rules. Alkyldibenzothiophenes are recalcitrant species in hydrodesulfuriztion process, speciation of dibenzothiophenes in deeply hydrodesulfurized diesel fuel, provides important information to catalyst and process improvement. However, most of the existing analytical methods are unsuitable for identification of ultra-low sulfur compounds in deeply HDS diesel because of the limits of sensitivity. A new method for direct quantitative analysis of alkyldibenzothiophenes in deeply hydrodesulfurized diesel fuel was developed by gas chromatography quadrupole time-of-flight mass spectrometry (GC-Q-TOFMS), which exhibited good linear response, high precision and sensitivity. The practicability of the method was shown by an extensive qualitative and quantitative analysis of alkyld...

A fluorometric method is described for the determination of the tumor biomarker mucin 1 (MUC1). It is based on signal amplification of the hybridization chain reaction (HCR), and the interaction between a luminescent ruthenium(II) complex and CdZnTeS quantum dots (QDs). If MUC1 bind to the biotin-labeled aptamer, it will initiate HCR with hairpins H1 and H2 to form a long-range dsDNA. The long nucleic acid chains are then linked on the surface of streptavidin-modified magnetic microparticles (MMPs) through streptavidin-biotin interaction. The luminescent ruthenium(II) complex is then embedded in the long dsDNA linked to the MMPs. Hence, there is little Ru complex in the supernatant after magnetic separation, and the fluorescence of the CdZnTeS QDs (best measured at excitation/emission wavelengths of 350/530 nm) is only slightly quenched. In the absence of target, the fluorescence of the CdZnTeS QDs is strongly quenched. Fluorescence increases linearly in the 0.2–100 ng·mL−1 MUC1 concentration range, and the LOD is 0.13 ng·mL−1 (at S/N = 3). The method was applied to the determination of MUC1 in spiked human serum samples.

In this work, a three-dimensional DNA machine based on the isothermal strand-displacement polymerase reaction (ISDPR) has been constructed. The walking behavior of a DNA walker on the obstructive surface of magnetic beads has also been studied by adding different nucleic acid blocks. The "leg" of the DNA walker could hybridize with a hairpin structure DNA named H1 and lead to the opening of it. And the newly exposed stem would interact with a primer. A strand exchange has happened with the assistance of polymerase and dNTPs, so that the "leg" has been displaced and the DNA walker could be pushed to move on the surface. But the nucleic acid blocks could increase steric hindrance and obstruct this process, which is similar to the behavior of human beings walking on craggy paths. Through changing these blocks, such as the structure, the amount, and the length of blocks, the movement of the DNA walker has been controlled. What's more, the results of its application for DNA detection are satisfactory. The limit of detection is 21.6 pM. Also, this method has been successfully applied in complex biological samples. Graphical abstract ᅟ.

The issue of quantifying trace metals in cells has drawn widespread attention but is threatened with insufficient sensitivity of the instruments, complex cellular matrix and limited cell consumption. In this study, microfluidic droplet-based liquid phase microextraction (LPME), as a miniaturized platform, was developed and combined with electrothermal vaporization (ETV)-inductively coupled plasma mass spectrometry (ICPMS) for the analysis of trace Cd, Hg, Pb, and Bi in cells. A novel and facile design of phase separation region was proposed, which made the phase separation very easily for subsequent ETV-ICPMS detection. Mechanism of the phase separation was carefully discussed using the incompressible formulation of the Navier-Stokes equations. The developed microfluidic droplet-based LPME system exhibited much higher extraction efficiency to target metals than microfluidic stratified flow-based LPME. Under the optimized conditions, the limits of detection of the proposed microfluidic droplet-based LPME-ETV-ICPMS system were 2.5, 3.9, 5.5, and 3.4 ng L

A new method for analysis of saturates in vacuum residue was developed by solid phase extraction and field desorption time-of-flight mass spectrometry. Vacuum residue was separated into saturates, aromatics, and resins by solid phase extraction. Saturates were ionized by field desorption source which produces primarily unfragmented mass spectra. This method could be applied for carbon number and compound-type distribution analysis of paraffins and 1-ring to 6-ring cycloparaffins in different vacuum residues. Molecular composition of saturates from various vacuum residue were characterized successfully by the developed method.

The boiling point distribution of petroleum samples remarkably affects the refining process and economic evaluation. The chemical composition of petroleum samples also varies with the boiling range, which is even more important for the processing procedure. In this work, a quick and convenient method was developed to build a clear relationship between boiling points and structures of organic compounds. A straight-run vacuum gas oil (VGO) and its narrow distillates were characterized by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The boiling point distribution of the main species in the petroleum samples was obtained by combining the FT-ICR MS data and the predicted boiling points of the compounds. Traditional gas chromatographic simulated distillations were also carried out to calibrate the boiling point distributions based on FT-ICR MS data. The detailed chemical composition of VGO varied as a function of the atmospheric equivalent boiling point (AEBP). Moreover, some composi...

A promising hydrogen sulfide (H2S) sensor was prepared by electrodeposition of Au nanoclusters on glassy carbon electrode (GCE) and the surface structure was characterized by SEM and EDAX. These flower-like form Au nanoclusters, which were made up of highly dense clustering Au nanorods with an average diameter of 20 nm and length up to 80 nm, had an average size about 600 nm and uniformly distributed on the GCE surface. The electrocatalytic oxidation of H2S in gasoline was performed on this modified electrode, which had a satisfactory liner response to H2S in the range of 1–80 ppm and a detection limit of 0.45 ppm (s/n = 3). This sensor was sensitive, selective and stable. Keywords: Hydrogen sulfide, Gasoline, Au, Nanocluster, Modified electrode

An analytical method for separation and identification of the saturated hydrocarbons in diesels at molecular level by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC x GC-TOF MS)was established. The saturated hydrocarbons were pre-separated from diesel samples by solid phase extraction before GC x GC-TOF MS analysis. More than 1,000 individual compounds (including paraffins, naphthenes and ole- fins) in coker diesel were tentatively identified based on NIST library search, mass spectrum resolution, boiling point distribution law and separation characteristics. Normal paraffins showed great regularity and could be identified easily through the relative position with pristane and phytane. The cyclic alkanes arranged above paraffins with the increasing number of rings. The normal alkyl cyclohexanes and cyclopentanes were well distinguished due to the difference of their polarity. Normal α-olefins which were often neglected in the past were also identified. With the support of the above-introduced identification, the distribution by structural type and carbon number were presented using peak area normalization. This analytical method was suc- cessfully used to investigate the molecular composition of saturated fractions in different diesel samples. All the results indicated that the molecular compositions of saturates in catalytic cracking diesel and coker diesel were significantly different because of the processing mechanism. This method provided technical support for the characterization of saturated hydrocar- bons in diesels and the investigation of processing mechanism.

The thermal decomposition of four alkanethiols was investigated in this paper. The test was processed in a pressure reactor at 200–400 °C. GC/MS and GC/SCD were used to detect the products of thermal decomposition. The result indicates that the alkane groups of alkanethiols have great influence on the thermal stability of alkanethiols. N-butylthiol, isobutylthiol and n-hexylthiol begin to pyrolyse at about 250 °C and more than 75% decomposes at 400 °C after being maintained for 4 h. However, tert-octylthiol can be broken down at lower temperature below 200 °C and almost 75% decomposes at 250 °C after 4 h. The main product of thermal decomposition is H2S and a free radical reaction is used to explain the decomposition mechanism.

A new ternary complex system was described. At pH 4.8 diphenylcarbazon formed ternary complexes with metal ions (Cr(VI) and V(V)) and hexadecyltrimethyl ammonium bromide (cetyltrimethyl ammonium bromide, CTAB). The ternary complex of chromate was separated from that of vanadate by means of liquid chromatography using a mobile phase of acetonitrile-acetone-water ( 85:5:20, v v ) containing 0.002 M CTAB. The analytical sensitivity of the complex of chromate could be raised further if the medium of the injection solution is transferred in methanol by solid-phase extraction.

Rutin was used as a chelating reagent to form ternary complexes with metal ions and hexadecyltrimethylammonium bromide (cetyltrimethylammonium bromide, CTAB). The retention behaviour of ternary complexes of Cr(VI) and W(VI) on a Nucleosil C18 column were examined. For chromatographic analysis the sample solution had to be changed because these ternary complexes did not give any peaks in aqueous mediu. A solid-phase extraction step with polyethylene as sorbent and methanol as eluent was introduced. Cr(VI) and W(VI) complexes in methanolic medium gave sharp peaks in the chromatogram and were separated from each other and other metal ions by using a mobile phase of 42.5% (v/v) tetrahydrofuran containing 0.003 M CTAB. The method was applied to the analysis of chromate in geological samples.

The identification of isoparaffin components in petroleum middle fractions including kerosene and diesel fuels was investigated by gas chromatography-mass spectrometry (GC/MS). The isodewaxing middle fraction and distilled diesel were selected as the objective samples for identification. It was shown that the isoparaffin components in middle fraction were well separated with their branched alkyl substituent numbers on a capillary chromatographic column in selected ion monitoring (SIM) mode of GC/MS. The identification for C10-C24 isoparaffins was realized with the technique of GC/MS, such as the fragmentation pathways of electron ionization and SIM technique, boiling point rule, published retention indices and theoretical rules about component retention behavior in GC including carbon number rule etc. Finally, the retention indices for the mono-substituted, di-substituted and multi-substituted isoparaffins from C10 to C24 were presented, which could provide an overall knowledge of isoparaffin distribution at carbon number level in fuels. Meanwhile, the peaks that could be well resolved in each isoparaffin group were also identified, and the detailed data for about 80 C10-C21 methyl-substituted isoparaffins and isoprenoid biomarkers were also given. The results showed that in isodewaxing middle fraction studied, the mono-substituted and di-substituted isoparaffins were the main paraffins, whereas in distilled diesel studies, the mono-substituted isoparaffins and isoprenoid biomarkers were the main ones.

As the increase of the remaining reserves of the heavier/sourer crude oil and the requirement of the clean energy, it is significant to sufficiently characterize the molecular composition of the petroleum for the selection of the refining processes and the realization of the economic value of the crude oil. Petroleomics, which is based on the high-resolution mass spectrometry platform, is a powerful tool to achieve this goal. In this paper, the analytical technology applied in petroleomics and its most recent development are reviewed, and the perspective of petroleomics is also discussed.