Latest ArticlesWe herein proposed a sample introduction technique based on solution cathode glow discharge (SCGD) of a portable design for inductively coupled plasma-optical emission spectrometry (ICP-OES) and its application in sensitive determination of mercury. The products from SCGD containing mercury vapor, were transported by an Ar flow to ICP spectrometer for detection. A gas liquid separator (GLS) and a dryer were used to condense and remove most of the accompanying moisture, which greatly improved both the stability and sensitivity of the signal. The detection limit (DL) acquired by this developed method was 0.22 µg/L (194.1 nm), which was nearly 82 times lower than that obtained by pneumatic nebulization (PN). The relative standard deviation (RSD) was 1.4% (n = 14) for a 50 µg/L standard. Blank solution (HNO3, pH 1) can effectively elute mercury residue. Its accuracy and practicality were also demonstrated by the determination of GBW10029 (fish) certified reference material, shrimp, crawfish, soil and human hair samples. The results showed good consistency with the certified values and the values obtained using inductively coupled plasma−mass spectrometry.
Droplet-based microfluidic technology can be utilized as a microreactor to prepare novel functional monodisperse microcapsules. In this study, a droplet-based microfluidic chip with surface modification, which allowed the one-step preparation of double emulsion microcapsules. An O/W/O double emulsion using polyethylene (glycol) diacrylate (PEGDA) solution as the intermediate water phase was prepared by regulating the hydrophilicity and hydrophobicity of the chip surface, with PEGDA microcapsules prepared using UV polymerization. And then anti-tumor drug paclitaxel and neurotoxin 6-OHDA were encapsulated in microcapsules for drug and toxicology evaluation, respectively. Compared to controls, drug-loaded microcapsules caused a significant increase in the death rate of PC12 cells. This indicates that the obtained drug-loaded microcapsules could be used in drug evaluation and potentially in drug screening and delivery.
Tumor heterogeneity plays a critical role in the determination of appropriate anticancer therapy. As circulating tumor cells (CTCs) contain all tumor-related information, the genetic changes on CTCs could help us choose the appropriate treatments for different patients. Single-base mutations are very common in tumor genetic changes which may result in drug resistance. Here, we introduce a single-cell mutation detection platform based on droplet microfluidics. This platform integrates cell capsulation, cell lysis, polymerase chain reaction (PCR) and the observation process. The droplets' generation speed is over 6000 per minute and more than 600 cells could be encapsulated in one second. To verify the performance of our platform in practical use, we performed the mutation analysis of 4 kinds of cells with our platform and noted that the genetic status of each single cell was clearly discriminated. Moreover, these results agreed with those from direct sequencing. Compared with other forms of single-cell mutation detection techniques, our platform has high throughput, short experimental time and less experimental operations.
Cell migration proceeds in 3D matrices in vivo, which can naturally switch to distinct phenotypes for better invasion in confined microenvironments. The studies of important metabolites under confinement are extremely meaningful for comprehensive insights into cancer metastasis. The integration of cell confinement device and analytical techniques is a key point for in-situ analysis of significant metabolites in vitro. Herein, an electrochemiluminescence (ECL) sensing platform was designed for in-situ monitoring of cell-secreted lactate in highly confined microenvironments. The 3-µm confiner was exactly fabricated via microfabrication and microfluidics technique, and cells in high confinement and low adhesion tended to be round with contractile blebs on cell margins. Significantly, in-situ monitoring of lactate was successfully achieved on the ECL platform with the catalysis of lactate oxidase, in which the levels in different time intervals were acquired in the luminol-hydrogen peroxide system. Furthermore, the results were verified by the liquid chromatography-tandem mass spectrometry (LC-MS/MS) technology, which showed similar fluctuations with the ECL platform. This system offered an available avenue for metabolites analysis in highly confined microenvironments, which may advance deeper insights into metabolic mechanisms of cancer metastasis
Salinity tolerance of ambient electric arc ionization (AEAI) was evaluated by comparing electrospray ionization for various samples at NaCl concentrations from 0 to 1000 mmol/L. AEAI-mass spectrometry (AEAI-MS) exhibited an excellent signal intensity even at NaCl concentrations of 1000 mmol/L, while the ESI-MS had no signal because high salinity has a strong inhibitory effect on analytes. The sodium adduct was verified using LiCl instead of NaCl. AEAI-MS successfully quantified saline samples with an excellent quantitative ability (R2 ≥ 0.998). We also achieved some analytical samples in the buffer solution at a very high concentration and even in a saturated salt solution. Overall, AEAI-MS has protonated ions for most target analytes. In addition, the relationship between auxiliary temperature and the distance from the sample to the arc was investigated, and the results indicated that thermal desorption plays an important role in AEAI source.
DNA-based logic gates promote the development of molecular computing and show enormous potential in the fields of nanotechnology and biotechnology. Dumbbell oligonucleotides (DNA) with poly-thymine (poly-T) loops and a nicked random double strand have been demonstrated to be an efficient template for the formation of fluorescent copper nanoclusters (CuNCs) in our previous work. Herein, a new platform technology is presented with which to construct molecular logic gates by employing CuNCs probe as a basic output generator, coupling of functional nucleases as the inputs. Two dumbbell DNAs are used with the difference in stem length (8 bp and 16 bp, respectively). The degradation of DNA templates can be tuned by various nucleic acid enzymes, single-stranded nuclease (S1), double-stranded specific nuclease (DSN), E. coli DNA ligase, exonucleases Ⅰ and Ⅲ. Briefly, S1 can digest both DNA templates, while the cleavage ability of DSN will be resistant by the short stem of SS-DNA (short-stem DNA). Exonuclease Ⅰ and Ⅲ can degrade these two nicked DNA templates, which are inhibited due to the ligation of E. coli DNA ligase. With this novel strategy, a set of logic gates is successfully constructed at the molecular level, including "YES", "PASS 0", "OR", "INHIBIT", which take the advantages of no label, easy operation, fast speed, high efficiency and low cost. Furthermore, S1 nuclease, as the biomarker of numerous carcinogens, is selectively detected in the range of 0.05–50 U/mL with the detection limit of 0.005 U/mL (1 × 10−6 U) based on this platform.
Supraparticles (SPs), such as assembly of inorganic components with organic, have made tremendous attention in biochemical analysis, which represents a novel but challenging research orientation. Herein, a single-SPs multifunctional fluorescent sensor array has been developed for high-throughput detection of heavy metal ions in biofluids, which is based on an inorganic/organic hybrid SPs consisting of carbon dots (CDs) and an easily available porphyrin [5, 10, 15, 20-tetra(4-carboxyphenyl)porphyrin (TCPP)]. TCPP can aggregate with the CDs to form the assembly (CDs/TCPP SPs) through the electrostatic and π-π stacking interaction. There are two independent and clearly separated fluorescence emission peaks at 470 and 668 nm in the resultant CDs/TCPP SPs under 380 nm excitation. As a proof-of concept design, F470, F668, F668/F470 of SPs are chosen as three sensor components to constitute our sensor array. With the addition of metal ions, three sensor components can generate different fluorescence response patterns for discriminating 11 heavy metal ions via principal component analysis (PCA). Additionally, thiols can readily capture Cu2+ to switch the fluorescence of CDs/TCPP initially altered by Cu2+. Hence, CDs/TCPP-Cu2+ ensemble is further demonstrated to be a powerful sensor array for pattern recognition of 7 thiols and even chiral recognition of cysteine enantiomers. This novel strategy avoids the tanglesome synthesis of multiple sensing probes and dedicates an innovative method for the facile establishment of tongue-mimic sensors, which would prospectively sprout more homologous assumptions to broaden its application toward more biosensing fields.
A class of silica anchored Schiff base decorated polyamidoamine (PAMAM) dendrimers were synthesized for removing aqueous Cu(Ⅱ) and Ag(Ⅰ). The adsorption performance was investigated synthetically and the adsorption mechanism was revealed. Results indicate the adsorption capacity depends on dendrimer generation, solution pH, contact time, temperature and initial metal ion concentration. The optimum adsorption pH is 6 for both metal ion. Adsorption kinetic suggests the adsorption can achieve equilibrium at 180 and 150 min for Cu(Ⅱ) and Ag(Ⅰ). The kinetic process is found to be in good agreement with pseudo-second-order model and film diffusion is the rate-controlling step. The adsorption isotherm indicates the adsorption is proceeded by monolayer behavior with chemical mechanism. These adsorbents exhibit competitive adsorption capacity as compared with other reported adsorbents. Theoretical calculation demonstrates the participation of hydroxyl, carbonyl, and amide groups during the adsorption of Cu(Ⅱ), while hydroxyl and amide groups are mainly responsible for capturing Ag(Ⅰ).
The temperature of waste gas in refuse transfer station, airport smoking area, and RTO terminal is low, which needs deep oxidation. Catalytic ozonation is one of the most effective treatment techniques in these scenarios. In this study, we reported that catalysts were modified under the condition of magnetic field to simulate the low temperature dynamic conditions of low concentration toluene for catalytic ozonation. This paper aims to explore the relationship between oxygen vacancy and active oxygen species, and the specific pathways of toluene oxidation. The study found that citric acid can enhance the synergistic effect between Mn and Ce, and promote the generation of oxygen vacancies. The surface molecule adsorption oxygen is more conducive to catalytic oxidation than subsurface atom adsorption oxygen. Finally, we proposed the main pathways of toluene in this reaction system, which runs through the whole process of the reaction.
The compost-derived humic substances (HS) can function as electron mediators for promoting hematite bioreduction because of its redox capacity. Humification process can affect redox capacities of compost-derived HS by changing its intrinsic structure. However, the redox properties of compost-derived HS linking with hematite bioreduction during composting still remain unclear. Herein, we investigated the redox capacities of compost-derived HS, and assessed the responses of the redox capacities to the hematite bioreduction. The result showed that compost-derived HS (i.e., humic acids (HA) and fulvic acids (FA)) were able to accept electrons from Shewanella oneidensis MR-1, and the electron accepting capacity was increased during composting. Furthermore, it could be functioned as electron mediators for promoting the hematite bioreduction, achieving 1.19-2.15 times compared with the control experience. Not only the aromatic structures (quinone) but also the non-quinone structures such as nitrogen- and sulfur-containing functional moieties were served as the redox-active functional groups of compost-derived HS. Our work proved that the aromatic functional groups and the heteroatom structures (especially N) were important to the hematite bioreduction. This study highlights the redox-active properties of compost-derived HS and its impact on the microbial reduction of iron mineral. Redox capacity of compost-derived HS might mitigate the environmental risk of contaminants when the composting production was added into the contaminated soils as low-cost repair materials
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