Natural flavonols as probes for direct determination of borax: From conventional fluorescence analysis to paper-based smartphone sensing

Borax is strictly regulated in the food processing and pharmaceutical industry due to its physiological toxicity, and the development of a direct analytical method is essential for effectively monitoring the borax abuse. In this work, the fluorescence properties of flavonoids, including flavones, isoflavones and flavonols, were systematically investigated from aqueous to borax solutions, and it was found that the weak intrinsic fluorescence of flavonols could be pervasively sensitized by borax. A natural flavonol, morin, was subsequently chosen as a representative probe to develop a turn-on fluorescence sensing method for borax analysis, which achieved a linear response spanning four orders of magnitude with a detection limit of 1.07 μM (0.22 μg mL-1 in terms of Na2B4O7 content). Furthermore, a smartphone-assisted paper-based test device was designed and constructed by 3D printing technology. Using morin-impregnated test strips as the carrier, the borax could be visually detected by the RGB signals of the captured images, with a detection limit of 0.13 mM (27.05 μg mL-1 for Na2B4O7). Combining ion exchange treatment for food samples and sodium periodate oxidation for drug samples, the developed methods were successfully applied for the direct analysis of borax in various products with the recoveries of 86.9-106.3% for traditional fluorescence analysis and 82.7-108.8% for smartphone-assisted fluorescence sensing. The fluorescence property of the morin-borax system was studied using time-dependent density functional theory, and the sensing mechanism was discussed in conjunction with experimental research.

Assessing the Redox Toxicity of 2D Nanosheets Based on Their Redox Effect on Cytochrome c in Microchannels

2D nanosheets (NSs) have been widely used in drug-related applications. However, a comprehensive investigation into the cytotoxicity mechanism linked to the redox activity is lacking. In this study, with cytochrome c (Cyt c) as the model biospecies, the cytotoxicity of 2D NSs was evaluated systematically based on their redox effect with microfluidic techniques. The interface interaction, dissolution, and redox effect of 2D NSs on Cyt c were monitored with pulsed streaming potential (SP) measurement and capillary electrophoresis (CE). The relationship between the redox activity of 2D NSs and the function of Cyt c was evaluated in vitro with Hela cells. The results indicated that the dissolution and redox activity of 2D NSs can be simultaneously monitored with CE under weak interface interactions and at low sample volumes. Both WS2 NSs and MoS2 NSs can reduce Cyt c without significant dissolution, with reduction rates measured at 6.24 × 10-5 M for WS2 NSs and 3.76 × 10-5 M for MoS2 NSs. Furthermore, exposure to 2D NSs exhibited heightened reducibility, which prompted more pronounced alterations associated with Cyt c dysfunction, encompassing ATP synthesis, modifications in mitochondrial membrane potential, and increased reactive oxygen species production. These observations suggest a positive correlation between the redox activity of 2D NSs and their redox toxicity in Hela cells. These findings provide valuable insight into the redox properties of 2D NSs regarding cytotoxicity and offer the possibility to modify the 2D NSs to reduce their redox toxicity for clinical applications.

Calibration of the oscillation amplitude of quartz tuning fork-based force sensors with astigmatic displacement microscopy

Quartz tuning forks and qPlus-based force sensors offer an alternative approach to silicon cantilevers for investigating tip-sample interactions in scanning probe microscopy. The high-quality factor (Q) and stiffness of these sensors prevent the tip from jumping to the contact, even at sub-nanometer amplitude. The qPlus configuration enables simultaneous scanning tunneling microscopy and atomic force microscopy, achieving spatial resolution and spectroscopy at the subatomic level. However, to enable precise measurement of tip-sample interaction forces, confidence in these measurements is contingent upon the accurate calibration of the spring constant and oscillation amplitude of the sensor. Here, we have developed a method called astigmatic displacement microscopy with picometer sensitivity.

Nanozyme-Mediated Catalytic Signal Amplification for Microfluidic Biosensing of Foodborne Bacteria

Early detection of foodborne bacteria is urgently needed to ensure food quality and to avoid the outbreak of foodborne bacterial diseases. Here, a kind of metal-organic framework (Zr-MOF) modified with Pt nanoparticles (Pt-PCN-224) was designed as a peroxidase-like signal amplifier for microfluidic biosensing of foodborne bacteria. Taking Escherichia coli (E. coli) O157:H7 as a model, a linear range from 2.93 × 102 to 2.93 × 108 CFU/mL and a limit of detection of 2 CFU/mL were obtained. The whole detection procedure was integrated into a single microfluidic chip. Water, milk, and cabbage samples were successfully detected, showing consistency with the results of the standard culture method. Recoveries were in the range from 90 to 110% in spiked testing. The proposed microfluidic biosensor realized the specific and sensitive detection of E. coli O157:H7 within 1 h, implying broad prospects of MOF with biomimetic enzyme activities for biosensing.

Non-destructive distinction of single seed for Medicago sativa and Melilotus officinalis by capillary electrophoresis with laser-induced fluorescence detection

Flavonoids are a class of natural polyphenolic compounds with great health benefits, and the development of methods for their analysis is of continuing interest. In this work, apigenin, kaempferol and formononetin were selected as the typical representatives of flavone, flavonol and isoflavone, three subclasses of flavonoids. Fluorescence studies revealed that tetraborate complexation could significantly sensitize the weak intrinsic fluorescence of flavonoids in solution, with a maximum of 137-fold for kaempferol. Subsequently, an integrated strategy of derivatization and separation was proposed for the universal analysis of flavonoids by capillary electrophoresis (CE) with 405 nm laser-induced fluorescence (LIF) detection. Using a running buffer consisting of 20 mM sodium tetraborate, 10 mM SDS and 10% methanol (pH 8.5), the dynamic derivatization was realized in the capillary, and the baseline separation was achieved within 10 min, with the detection limits of 0.92-35.46 nM (S/N=3) for the total of 9 flavonoids. The developed CE-LIF method was employed to the quantitative analysis of some flavonoids in Medicago sativa (alfalfa) plants and granulated alfalfa with the recoveries of 80.55-94.25%. Combined with the principal component analysis, the developed method was successfully applied to the non-destructive distinction of single seed for alfalfa and Melilotus officinalis (sweet clover), two forage grass seeds with very similar apparent morphology. Furthermore, this method was used to continuously monitor the substance metabolism during the soaking process at the level of single seed.

Three-in-One Detector by 3D Printing: Simultaneous Contactless Conductivity, Ultraviolet Absorbance, and Laser-Induced Fluorescence Measurements for Capillary Electrophoresis

We describe a 3-in-1 detector for simultaneous contactless conductivity (C⁴D), ultraviolet absorbance (UV-AD), and laser-induced fluorescence (LIF) measurements on a single detection point for capillary electrophoresis (CE). A key component of the detector was a rectangular detector head that was assembled with four 3D-printed parts. Two parts covering the detector head to function as a Faraday cage were fused deposition modeling printed using an electrically conductive material. The other two parts in between the conductive parts were stereolithography (SLA) printed with high-resolution (50 μm) constructions on the surface. After assembling the two SLA printed parts, several cavities were built with the surface constructions. Two electrodes and a Faraday shield for C⁴D were cast by injecting molten Wood's metal into the cavities. For UV-AD, a slit (100 μm width) was created by putting together two grooves (50 μm depth) on the surface of the SLA printed parts. A 255 nm UV-LED was used as the light source. The effective path length and stray light for a 50 μm id capillary were 39 μm and 13%, which were superior to those of other reported 3D-printed AD detectors. Confocal LIF detection was conducted by using an objective lens to focus the laser on the capillary via a through-hole. The detector was used to detect model analytes, including inorganic and organic ions, and fluorescein isothiocyanate labeled amino acids in a signal-run CE separation. In detecting fluorescein, LODs were 1.3 μM (C⁴D), 2.0 μM (UV-AD), and 1 nM (LIF). The calibration ranges covered from 0.01 μM to 500 μM.

Zwitterionic surfactant as an additive for efficient electrophoretic separation of easily absorbed rhodamine dyes on plastic microchips

Plastic microchips possess the advantages of easy fabrication and low-cost, but their surface properties are frequently incompatible with electrophoretic separation without proper surface modification. Meanwhile, the separation microchannels on typical microchips are usually only a few centimeters long, the pressurized flow may significantly affect the electrophoretic separation if their inner diameters (id) are relatively larger (approximately > 50 μm), viscous separation medium is therefore required for efficient separation. Herein, a zwitterionic surfactant, N-hexadecyl-N,N-dimethyl-3-ammonio-1-propane sulfonate (HDAPS), was used as a multifunctional additive to inhibit the analyte adsorption, improve the surface status, control Joule heating and modulate the resolution on cyclic olefin copolymer microchips with 80 μm id, 5 cm long separation microchannels, eliminating the necessity of viscous polymeric additives. The effectiveness of HDAPS was compared with an ionic polymeric additive, poly(diallydimethylammonium chloride). The streaming potential and electroosmotic flow measurements indicated an effective inhibition of the adsorption of rhodamine B and a stable negative surface charge with zwitterionic HDAPS. Using 15 mmol/L HDAPS, 40% (v/v) methanol, and 10 mmol/L boric acid (pH 3.2) as the running buffer, rapid separation of four rhodamines was achieved within 90 s under a separation electric field of 520 V/cm. The theoretical plate numbers were in a range of 5.0×10⁵-6.9×10⁵/m. The relative standard deviations were no more than 0.9% for retention time and 1.5% for peak area. The proposed system was verified by the determination of rhodamines in eyeshadow and wolfberry, with standard recoveries in a range of 98.2%-101.4%.

NaCl Micro-Crystal as a Molecular Mold for Enhanced Synthesis of Planar Phenazines and Their Applications on Chemosensing and a Full-Color Fluorescent Material

NaCl has been successfully used as a template for the synthesis of 2D nanomaterials, but it is seldom used for the construction of flat small organic molecules. Herein, a simple, low-cost, and highly efficient synthesis of phenazines with planar main frames, such as 5-phenyl-5,14-dihydro-5,7,12,14-tetraazapentacene, in the presence of NaCl micro-crystal as a kind of molecular mold is described. The reactants were mixed with NaCl powder and heated to 320 °C for 5 min. Yields >90% were readily achieved after a simple precipitation in water. The effectiveness of NaCl crystal as a mold with HCl was confirmed by comparison with common inorganic salts, SiO₂, and γ-Al₂O₃ with HCl together with combinations including NaNO₃ + HNO₃, Na₂SO₄ + H₂SO₄, NaH₂PO₄ + H₃PO₄, and NaH₂PO₄ + polyphosphoric acid. The mechanism was deduced with the aid of computer simulation, which confirms the stabilization of 5,14-dihydro-5,7,12,14-tetraazapentacene by the NaCl surface. DMSO solution of a product, 1,3-dihydro-imidazo[4,5-b]phenazin-2-one, showed enhanced fluorescence in H₂O, and it was used as a fluorescent probe for pH and Hg²⁺. A full-color material was prepared by mixing precursors of epoxy resin and phenazines, and its fluorescent color could be adjusted by the ratio of phenazines.

High-Resolution Micro-object Separation by Rotating Magnetic Chromatography

The development of new technologies for the separation, selection, and isolation of microparticles such as rare target cells, circulating tumor cells, cancer stem cells, and immune cells has become increasingly important in the last few years. Microparticle separation technologies are usually applied to the analysis of disease-associated cells, but these procedures often face a cell separation problem that is often insufficient for single specific cell analyses. To overcome these limitations, a highly accurate size-based microparticle separation technique, herein called "rotating magnetic chromatography", is proposed in this work. Magnetic nanoparticles, placed in a microfluidic separation channel, are forced to move in well-defined trajectories by an external magnetic field, colliding with microparticles that are in this way separated on the basis of their dimensions with high accuracy and reproducibility. The method was optimized by using fluorescein isothiocyanate-modified polystyrene particles (chosen as a reference standard) and then applied to the analysis of cancer cells like Hep-3B and SK-Hep-1, allowing their fast and high-resolution chromatographic separation as a function of their dimensions. Due to its unmatched sub-micrometer cell separation capabilities, RMC can be considered a break-through technique that can unlock new perspectives in different scientific fields, that is, in medical oncology.

Circular Nonuniform Electric Field Gel Electrophoresis for the Separation and Concentration of Nanoparticles

A circular nonuniform electric field strategy coupled with gel electrophoresis was proposed to control the precise separation and efficient concentration of nano- and microparticles. The circular nonuniform electric field has the feature of exponential increase in the electric field intensity along the radius, working with three functional zones of migration, acceleration, and concentration. The distribution form of electric field lines is regulated in functional zones to control the migration behaviors of particles for separation and concentration by altering the relative position of the ring electrode (outside) and rodlike electrode (inner). The circular nonuniform electric field promotes the target-type and high-precision separation of nanoparticles based on the difference in charge-to-size ratio. The concentration multiple of nanoparticles is also controlled randomly with the alternation of radius, taking advantage of vertical extrusion and concentric converging of the migration path. This work provides a brand new insight into the simultaneous separation and concentration of particles and is promising for developing a versatile tool for the separation and preparation of various samples instead of conventional methods.

[Emulation pulmonary nodules localization model:a novel non-invasive localization technique in resection of pulmonary nodules]

Objective: To explore the accuracy and efficiency of a novel 3D-printed emulation localization model of small pulmonary nodules in lung surgery. Methods: From April 2020 to April 2021, a total of 66 patients were selected in the study, who underwent localization and resection of pulmonary nodules with video-assisted thoracoscopic surgery (VATS) guided by the 3D-printed emulation localization model at Department of Thoracic Surgery, West China Hospital of Sichuan University. There were 13 males and 53 females, aged from 25 to 79 (52.7±11.4) years. Of all patients, 24 (36.4%) had single pulmonary nodule, and 42 (63.6%) had synchronous multiple pulmonary nodules. The chest high-resolution CT image data were utilized for digital reconstruction and 3D printing to make a tailored life-size emulation pulmonary nodules localization model, which was used to navigate real-time intraoperative localization of nodules. Clinical data including operative parameters, localization information, resection types and pathological findings of nodules were analyzed. The pulmonary nodules that doctors planned to resect were categorized into two categories:major nodules and additional nodules, according to their presence of invasion and radiological risk factors. The accuracy of localization and resection efficiency of nodules were evaluated in accordance with the categories of the nodules respectively. Results: On the basis of preoperative evaluation, there were 71 major nodules with median maximal diameter of 0.9 (0.6-1.3) cm, and 77 additional nodules with median maximal diameter of 0.5 (0.4-0.7) cm. All patients underwent VATS surgery, 52 of them (78.8%) were treated with uniportal VATS and 14 (21.2%) with triportal VATS. Among the patients with single nodule, 18 segmentectomies and 6 wedge resections were performed; whereas among the patients with multiple nodules, 5 segmentectomies, 14 wedge resections, and 23 combined pulmonary resections (including 2 cases of lobectomy+segmentectomy, 7 cases of lobectomy+wedge resections, and 14 cases of segmentectomy+wedge resections) were achieved. The median operative time was 93 (45-240) min, and the median resection time for all nodules was 51.4 (6.7-147.0) min. All major nodules were successfully resected and visibly dissected after removal, and all additional nodules were successfully resected with 85.7%(66/77) nodules visibly dissected. The accuracy rate of localization of both types of nodules was 100%. All major nodules were malignant, and the malignancy rate of additional nodules was 21.2%(14/66). Conclusion: This novel 3D-printed emulation localization model of small pulmonary nodules proved to be a non-invasive, accurate and efficient technique. Not only that, it has a unique advantage in localization of synchronous multiple pulmonary nodules.

A polysaccharide from Lycium barbarum L.: Structure and protective effects against oxidative stress and high-glucose-induced apoptosis in ARPE-19 cells

Lycium barbarum polysaccharides (LBPs) are beneficial for vision; however, relevant research has mainly focused on entire crude polysaccharides, with the basis and exact structure of the polysaccharide rarely explored. In this study, LICP009-3F-2a, a novel polysaccharide from Lycium barbarum L., was separated and then purified using anion-exchange and size-exclusion chromatography. Structural characteristics were investigated using chemical and spectroscopic methods, which revealed that LICP009-3F-2a has an Mw of 13720 Da and is an acidic heteropolysaccharide composed of rhamnose (39.1%), arabinose (7.4%), galactose (22.5%), glucose (8.3%), galacturonic acid (13.7%), and glucuronic acid (4.0%). Linkage and NMR data revealed that LICP009-3F-2a has the following backbone: →2)-α-L-Rha-(1→2,4)-α-L-Rha- (1→4)-α-D-GalAp-(1→3,6)-β-D-Galp-(1→3,6)-β-D-Galp-(1→6)-β-D-Galp-(1→, with three main branches, including: α-L-Araf-(1→5)-α-L-Araf-(1→6)-β-D-Glcp-(1→2,4)-α-L-Rha-(1→, β-D-Glcp-(1→4)-β-D-Glcp-(1→3,6)-β-D-Galp-(1→, and β-D-Galp-(1→3)-β-D-Galp-(1→3,6) -β-D-Galp-(1→. Differential scanning colorimetry and thermogravimetric analysis showed that LICP009-3F-2a is thermally stable, while X-ray diffractometry showed that LICP009-3F-2a has a semi-crystalline structure. In addition, LICP009-3F-2a protects ARPE-19 cells from H₂O₂-induced oxidative damage by regulating the expression of antioxidant SOD1 and CAT enzymes and down-regulating MMP2 expression. Moreover, LICP009-3F-2a promotes the proliferation of ARPE-19 cells in a concentration-dependent manner, and protects ARPE-19 cells from hyperglycemia by inhibiting apoptosis.

A Reverse Transcription Recombinase-Aided Amplification Method for Rapid and Point-of-Care Detection of SARS-CoV-2, including Variants

The worldwide pandemic caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and its emergence of variants needs rapid and point-of-care testing methods for a broad diagnosis. The regular RT-qPCR is time-consuming and limited in central laboratories, so a broad and large-scale screening requirement calls for rapid and in situ methods. In this regard, a reverse transcription recombinase-aided amplification (RT-RAA) is proposed here for the rapid and point-of-care detection of SARS-CoV-2. A set of highly conserved primers and probes targeting more than 98% of SARS-CoV-2 strains, including currently circulating variants (four variants of concerns (VOCs) and three variants of interest (VOIs)), was used in this study. With the preferred primers, the RT-RAA assay showed a 100% specificity to SARS-CoV-2 from eight other respiratory RNA viruses. Moreover, the assay here is of a high sensitivity and 0.48 copies/μL can be detected within 25 min at a constant temperature (42 °C), which can be realized on portable equipment. Furthermore, the RT-RAA assay demonstrated its high agreement for the detection of SARS-CoV-2 in clinical specimens compared with RT-qPCR. The rapid, simple and point-of-care RT-RAA method is expected to be an appealing detection tool to detect SARS-CoV-2, including variants, in clinical diagnostic applications.

Low-cost devices with fluorescence spots brightness and size dual-mode readout for the rapid detection of Cr(VI) based on smartphones

Sensitive, convenient and rapid detection devices for toxic Cr(VI) suitable for filed use are required. Smartphone can be used as the detector, but the quality of images taken with a smartphone may depend on the ambient light and the operator. In this work, two types of low-cost and portable smartphone-based devices used for fluorescence spots brightness and size dual-mode detection of Cr(VI) were constructed with the aid of the 3D printing, which avoids the effect of ambient light and maintains a fixed position of the phone camera relative to the samples. Based on the brightness reflected by the blue channel of RGB values of the images of carbon nanodots, a linear relationship between quenching efficiency and concentration of Cr(VI) in a range of 0.2-150 μM with a limit of detection of 0.058 μM was attained, which is comparable to or better than that from fluorescence spectrometers. With the size variation of fluorescence spots, a linear range of 10-350 μM was acquired and it is more intuitive for direct naked-eye estimation of the concentration of Cr(VI). The applicability of the proposed devices for the detection of Cr(VI) was verified with water and soil samples with recoveries ranging in 95.0-108.2%.

Controlled synthesis of fluorescent carbon materials with the assistance of capillary electrophoresis

Carbon nanodots (CNDs) have been widely applied in variety of fields, while some evidences indicate their components may be complicated. In this work, capillary electrophoresis (CE) was used to evaluate the effect of synthetic conditions of fluorescent CNDs prepared through the hydrothermal method using citric acid (CA) and Triaminoguanidinium chloride (TG_Cl) as the starting materials. The results indicated that the fluorescent components of the products were affected by the ratio of the starting materials, the reaction temperature and reaction time. Under selected conditions, a ratio of TG_Cl to CA of 1:6, the reaction at 180 °C for 3 h, the product contains more than 4 fluorescent components with similar optical properties. CNDs were used for the determination of Cr(VI) in environmental samples with recoveries ranging in 95.3-107%, and the mechanism was also confirmed.

Visually precise, low-damage, single-cell spatial manipulation with single-pixel resolution

The analysis of single living cells, including intracellular delivery and extraction, is essential for monitoring their dynamic biochemical processes and exploring intracellular heterogeneity. However, owing to the 2D view in bright-field microscopy and optical distortions caused by the cell shape and the variation in the refractive index both inside and around the cells, achieving spatially undistorted imaging for high-precision manipulation within a cell is challenging. Here, an accurate and visual system is developed for single-cell spatial manipulation by correcting the aberration for simultaneous bright-field triple-view imaging. Stereo information from the triple view enables higher spatial resolution that facilitates the precise manipulation of single cells. In the bright field, we resolved the spatial locations of subcellular structures of a single cell suspended in a medium and measured the random spatial rotation angle of the cell with a precision of ±5°. Furthermore, we demonstrated the visual manipulation of a probe to an arbitrary spatial point of a cell with an accuracy of <1 pixel. This novel system is more accurate and less destructive for subcellular content extraction and drug delivery.

We achieved the low-damage spatial puncture of single cells at specific visual points with an accuracy of <65 nm.

Quick stabilization of capillary for rapid determination of potassium ions in the blood of epilepsy patients by capillary electrophoresis without sample pretreatment

Mutations in the potassium channel genes may be linked to the development of epilepsy and affect the blood potassium levels. Therefore, accurate determination of potassium in the blood will be critical to diagnose the cause of epilepsy. CE is a competent technique for the fast detection of multiple ions, but complicated matrices of a blood sample may cause significant variation of migration times and the peak shape. In this work, a procedure for rapid stabilization of the capillary inner surface through preflushing of a blood sample was employed. The process takes only 40 min for a capillary and then it can be used for more than 2 weeks. No pretreatment of the blood sample or other surface modification of the capillary is needed for the analysis. The RSDs of the migration time and peak area were reduced to 1.5 and 5.1% from 12.6 and 14.5%, respectively. The proposed method has been successfully applied to the determination of the potassium contents in the blood sample of patients with epilepsy at different stages. The recoveries of potassium ions in these blood samples are in a range from 86.5 to 104.5%.

Wavelength selective photoactivated autocatalytic oxidation of 5,12-dihydrobenzo[b]phenazine and its application in metal-free synthesis

Photochemical stability of 5,12-dihydrobenzo[b]phenazine (DHBP) was investigated with LEDs with central emission wavelengths in a range of 365 to 595 nm. Photochemical conversion of DHBP to benzo[b]phenazine (BP) was observed with wavelengths upto 516 nm. Light of 490 and 516 nm is not absorbed by DHBP, but photoactivated autocatalytic oxidation of DHBP to BP with these wavelengths was confirmed. The reaction rate is in a range of 111-208 μg min^-1 with these LEDs. The mechanism of the reaction was examined and the experimental results exclude the intermolecular interaction such as the Förster resonance energy transfer, the intermolecular charge transfer, the photoinduced electron transfer and the formation of an exciplex. The formation of the reactive oxygen species was verified with electron paramagnetic resonance, which indicates its potential in the synthesis. When sunlight was used as the light source, the oxidation rate of 1 mg mL^-1 DHBP was 393 μg min^-1. Same autocatalytic oxidation was also observed on similar compounds and it can be used for producing metal-free organic substances for semiconductors.

Electric Field-Driven On-Request Instant in Situ Formation/Removal of Solid Hydrogel within Microchannels for Efficient Electrophoretic Separation

Electrophoretic separation in short microchannels is a promising way for rapid analysis of biomolecules, but the pressurized laminar flow may compromise the separation efficiency. In this work, through an electric field, instant formation and removal of a solid chitosan/β-glycerol phosphate (CS/β-GP) hydrogel within microchannels of microchips were realized. In a typical cross-type microchip, the CS/β-GP hydrogel was precisely formed in the separation microchannel within 15 s of the application of a voltage of 2000 V. Highly efficient separation of peptides and proteins was achieved, and theoretical plate numbers of 0.6 to 1.5 × 10⁶/m were attained for proteins in 120 s. The used hydrogel could be swiftly removed also with an electric field, and the whole procedure was achieved on a standard microchip electrophoresis device with no extra accessory or special operation required.

Visual and real-time imaging focusing for highly sensitive laser-induced fluorescence detection at yoctomole levels in nanocapillaries

We developed a highly sensitive laser-induced fluorescence detection system, involving visual and real-time imaging focusing instead of the use of fluorescent reagents, for the detection of analytes in nanocapillaries.

Facile Evaluation of Nanoparticle-Protein Interaction Based on Charge Neutralization with Pulsed Streaming Potential Measurement

Exploration of simple and universal methods to quantitatively measure nanoparticle (NP)-protein interaction is of great importance. In this work, pulsed streaming potential (SP) measurement has been used to evaluate the interaction between NPs and proteins within microchannels. Graphene oxide (GO) and SiO₂ NPs were selected to represent two kinds of NPs. Lysozyme and common blood proteins, including albumin V, γ-globulins, and fibrinogen, were used as model proteins. The linear relationship between the initial adsorption rate (S = dE_r/dt) and the concentration of proteins was observed. Combined with the Hill equation, the microscopic dissociation constant (K_D) and the Hill coefficient (n) between NPs and proteins were calculated based on the relationship between S and the concentration of each protein. The concentration of free proteins which have not interacted with the NPs in the NPs-protein mixture could also be measured. The influence of pH, conductivity, and ionic strengths of the incubation buffer on the interaction between GO and lysozyme was evaluated based on the constant K_D. The interaction intensity between NPs and proteins was defined as charge neutralization efficiency Q_C, which could be calculated from the value of S. It takes only 150 s to get the whole set of data under the optimized experiment parameters. The measurement solely depends on the surface charge, no intrinsic fluorescence is required for either the NPs or the proteins, and no labeling or immobilization process is involved as well.

Interference-Free Determination of Trace Levels of Gold and Palladium in Geological and Metallurgical Samples by Flame Atomic Absorption Spectrometry Coupled with a Flow Injection On-Line Microcolumn Preconcentration and Separation System

A simple and highly selective method was developed for the routine determination of trace or ultratrace amounts of gold and palladium in geological and metallurgical samples. The method uses flow injection on-line preconcentration and separation with determination by flame atomic absorption spectrometry. Au and Pd in the sample are adsorbed on a 2-mercaptopyrimidine chemically modified silica gel (MPMSG) packed microcolumn in a 0.50M HCl medium and then eluted with 0.5 or 1.0% thiourea solution. The eluates are introduced into the flame atomic absorption spectrometer directly. With the use of a 0.85 mL microcolumn (about 0.14 g MPMSG packed), the present system tolerated concentrations of common base metal ions up to 25.0 mg/mL and concentrations of anions up to 100.0 mg/mL when Au(III) at 0.100 μg/mL and Pd(II) at 0.200 μg/mL were preconcentrated for 60 s with a sample flow rate of 5.0 mL/min. The limits of detection were 3.1 ng/mL for Au(III) and 6.1 ng/mL for Pd(II) with relative standard deviations of ≤2.5%. The analytical results obtained by the proposed method for geological and metallurgical samples were in good agreement with the certified values.

Thiol-ene Click Derivatization for the Determination of Acrylamide in Potato Products by Capillary Electrophoresis with Capacitively Coupled Contactless Conductivity Detection

The development of analytical methods for acrylamide formed during food processing is of great significance for food safety, but limited by its inherent characteristics, the analysis of acrylamide is a continuing challenge. In this study, an efficient derivatization strategy for acrylamide based on thiol-ene click reaction with cysteine as derivatization reagent was proposed, and the resulting derivative was then analyzed by capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C⁴D). After systematic investigation including catalyst dosage (0-20 mM), reaction temperature (30-90 °C) and time (1-60 min), and cysteine concentration (0.2-3.6 mM), acrylamide could be efficiently labeled by 2.0 mM cysteine at 70 °C for 10 min using 4 mM n-butylamine as catalyst. Application of 10 mM triethylamine as separation buffer, the labeled acrylamide was analyzed within 2.0 min, and the relative standard deviations of migration time and peak area were less than 0.84% and 5.6%, indicating good precision. The C⁴D signal of acrylamide derivative showed a good linear relationship with acrylamide concentration in the range of 7-200 μM with the correlation coefficient of 0.9991. The limit of detection and limit of quantification were calculated to be 0.16 μM and 0.52 μM, respectively. Assisted further by the QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample pretreatment, the developed derivatization strategy and subsequent CE-C⁴D method were successfully applied for the determination of acrylamide in potato products.

Distinct correlation between (CN2)x units and pores: a low-cost method for predesigned wide range control of micropore size of porous carbon

Flexible control of the micropore size of carbon was achieved in a cost-efficient way by predesigned quantitative correlation between the sizes of extendable (CN₂)_x nanosized modulators and the generated micropore sizes ranged from 0.2 to 2.3 nm, with effectiveness for boosting the electrochemical performance systematically.

Advancement of electroosmotic pump in microflow analysis: A review

This review (with 152 references) covers the progress made in the development and application of electroosmotic pumps in a period from 2009 through 2018 in microflow analysis. Following a short introduction, the review first categorizes various electroosmotic pumps into five subclasses based on the materials used for pumping: i) open channel EOP, 2) packed-column EOP, iii) porous monolith EOP, iv) porous membrane EOP, and v) other types of EOP. Pumps in each subclass are discussed. A next section covers EOP applications, primarily the applications of EOPs in micro flow analysis and micro/nano liquid chromatography. Other scattered applications are also examined. Perspectives, trends and challenges are discussed in the final section.

Fast screening of aflatoxins in dairy cattle feeds with CE-LIF method combined with preconcentration technique of vortex assisted low density solvent-microextraction

Aflatoxin contamination in agricultural products poses a great threat to humans and livestock. The aim of this study was to establish a simple, rapid, highly sensitive, and inexpensive method for the simultaneous detection of aflatoxin B₁ , B₂ , G₁ , and G₂ in agricultural products. We used a vortex assisted low density solvent-microextraction (VALDS-ME) technique for sample preconcentration and sample detection was achieved with a CE-LIF method. Aflatoxins were separated in an uncoated fused-silica capillary with the MEKC mode and were excited by a 355 nm UV laser to produce native fluorescence for detection. The obtained LOD and LOQ for the four aflatoxins were in the range of 0.002-0.075 and 0.007-0.300 μg/L, respectively, and the analysis time was within 6.5 min. Using the established method, aflatoxins were screened in naturally contaminated dairy cattle feed samples including alfalfa, bran, and corn kernel. The result shows that the alfalfa and bran samples were contaminated with aflatoxins to varying degrees. Compared with other analytical techniques for aflatoxin screening in agricultural products, this CE-LIF method combined with VALDS-ME preconcentration technique is simple, rapid, highly efficient, and inexpensive.

Rapid quantitation of multiple ions released from HeLa cells during emodin induced apoptosis by low-cost capillary electrophoresis with capacitively coupled contactless conductivity detection

Change in cation concentration, including that of potassium and sodium, is characteristic of apoptosis, therefore it is significant to detect cation concentration changes.

HMPA-Catalyzed One-Pot Multistep Hydrogenation Method for the Synthesis of 1,2,3-Trisubstituted Indolines

A convenient and facile method was developed for the synthesis of 1,2,3-trisubstituted indolines. Starting from indole derivatives and ketones/aldehydes, the corresponding indoline products could be obtained with high yield by the hexamethylphosphoramide (HMPA) catalyzed indole Friedel–Crafts reaction, reduction and direct reductive amination process.

[Strategies for the prevention and control of bleeding due to vascular injury in thoracoscopic lung surgery]

The technique of thoracoscopic lung surgery has gradually matured. Nowadays, thoracoscope is recommended as the most preferred approach for surgical treatment of early stage non-small cell lung cancer in different guidelines. However, there are still some cases of accidential major bleeding due to vascular injury during thoracoscopic lung surgery. The wall of the hilum vessels is relatively thin. These vessels often involve a great portion of the cardiac output blood flow. Once the injury happened, the emergent condition may be life-threatening due to massive blood loss. Therefore, this became an important factor which hindered the development of thoracoscopic lung surgery. In this review, details of the vascular injury in thoracoscopic lung surgery were summarized, including the incidence of vascular injury, commonly injured sites and reasons of the injuries. Among all the cases of thoracoscopic major pulmonary resection, 2.9% to 9.2% may suffer from vascular injury during the operation. The most commonly injuried sites are pulmonary artery and the branches, and this is also the most critical situation during thoracoscopic lung surgery. Hilum adhesion is the most important risk factor for vascular injury. On the one hand, the suction-compressing angiorrhaphy technique was developed for bleeding control and angioplasty. On the other hand, the strategies like pre-control of the pulmonary, cut the bronchus in advance, and fire the bronchus and pulmonary artery together may decrease the incidence of vascular injury in patients with risk factors.

Confocal laser-induced fluorescence detector for narrow capillary system with yoctomole limit of detection

Laser-induced fluorescence (LIF) detectors for low-micrometer and sub-micrometer capillary on-column detection are not commercially available. In this paper, we describe in details how to construct a confocal LIF detector to address this issue. We characterize the detector by determining its limit of detection (LOD), linear dynamic range (LDR) and background signal drift; a very low LOD (~70 fluorescein molecules or 12 yoctomole fluorescein), a wide LDR (greater than 3 orders of magnitude) and a small background signal drift (~1.2-fold of the root mean square noise) are obtained. For detecting analytes inside a low-micrometer and sub-micrometer capillary, proper alignment is essential. We present a simple protocol to align the capillary with the optical system and use the position-lock capability of a translation stage to fix the capillary in position during the experiment. To demonstrate the feasibility of using this detector for narrow capillary systems, we build a 2-μm-i.d. capillary flow injection analysis (FIA) system using the newly developed LIF prototype as a detector and obtain an FIA LOD of 14 zeptomole fluorescein. We also separate a DNA ladder sample by bare narrow capillary - hydrodynamic chromatography and use the LIF prototype to monitor the resolved DNA fragments. We obtain not only well-resolved peaks but also the quantitative information of all DNA fragments.

Use of Pulsed Streaming Potential with a Prepared Cationic Polyelectrolyte Layer to Detect Deposition Kinetics of Graphene Oxide and Consequences of Particle Size Differences

The deposition kinetics of graphene oxide (GO) onto poly(ethylene imine) (PEI) layer was characterized in situ with pulsed streaming potential (SP) measurement, and it was found that the initial rate constant (k_i) was dependent on the size of GO with same surface charge density at a fixed concentration under controlled experimental conditions. Assuming the deposition was controlled by diffusion at the initial stage, k_i is proportional to R_h^-2/3, where R_h is the hydrodynamic radius. By flushing a GO solution through a capillary coated with PEI, the initial change rate of relative SP (dE_r/dt) was obtained in 20 s and k_i was measured with five different concentrations in about 2 min. Three GO samples of different sizes obtained from the same batch of raw material were characterized with pulsed SP to get k_i values, and their sizes were verified with atomic force microscopy and dynamic light scattering. The experimental results are consistent with the predicted effects of the size of NPs on their deposition kinetics.

HBV-induced ROS accumulation promotes hepatocarcinogenesis through Snail-mediated epigenetic silencing of SOCS3

Interleukin-6 (IL-6) has been demonstrated to be involved in Hepatitis B virus (HBV)-associated hepatocarcinogenesis through activation of the STAT3 pathway. The sustained activation of the IL-6/STAT3 pathway is frequently associated with repression of SOCS3, which is both a target gene and a negative regulator of STAT3. However, the silencing mechanism of SOCS3 in hepatocellular carcinoma (HCC) remains to be elucidated. Here, we showed that the repression of SOCS3 and sustained activation of IL-6/STAT3 pathway in HBV-producing HCC cells were caused by HBV-induced mitochondrial ROS accumulation. Mechanistic studies revealed that ROS-mediated DNA methylation resulted in the silencing of SOCS3. Decreased SOCS3 expression significantly promoted the proliferation of HCC cells and growth of tumor xenografts in mice. Further studies revealed that HBV-induced ROS accumulation upregulated the expression of the transcription factor, Snail, which bound to the E-boxes of SOCS3 promoter and mediated the epigenetic silencing of SOCS3 in association with DNMT1 and HDAC1. In addition, we found that the expression of Snail and SOCS3 were inversely correlated in HBV-associated HCC patients, suggesting that SOCS3 and/or Snail could be used as prognostic markers in HCC pathogenesis. Taken together, our data show that HBV-induced mitochondrial ROS production represses SOCS3 expression through Snail-mediated epigenetic silencing, leading to the sustained activation of IL-6/STAT3 pathway and ultimately contributing to hepatocarcinogenesis.

Minimally invasive surgery for congenital diaphragmatic hernia: a meta-analysis

Objectives

To compare the safety and efficacy of minimally invasive surgery (MIS) with traditional open surgical approach for congenital diaphragmatic hernia (CDH).

Methods

A literature search was performed using the PubMed database, Embase, and the Cochrane central register of controlled trials using a defined set of criteria. The outcomes, which include post-operative mortality, incidence of hernia recurrence, rates of patch use and complications, were analyzed.

Results

We investigated nine studies, which included 507 patients. All studies were non-randomized historical control trials. The MIS group had a significantly lower rate of post-operative death with a risk ratio of 0.26 [95 % confidence interval (CI) 0.10–0.68; p = 0.006] but a greater incidence of hernia recurrence with a risk ratio of 3.42 (95 % CI 1.98–5.88; p < 0.00001). Rates of prosthetic patch use were similar between the two groups. Fewer cases of surgical complications were found in the MIS group with a risk ratio of 0.66 (95 % CI 0.47–0.94; p = 0.02).

Conclusions

MIS for CDH repair is associated with lower post-operative mortality and morbidity compared with traditional open repair. Although rate of patch use appears to be comparable, the increased risk of CDH recurrence should not be ignored. The lack of well-controlled prospective trials still limits strong evaluations of the two surgical techniques.

Facile real-time evaluation of the stability of surface charge under regular shear stress by pulsed streaming potential measurement

The applicability of the pulsed streaming potential measurement for real-time evaluation of stability of assembled layers based on the relative zeta potential change rate S_R was demonstrated.

Microchip electrophoresis for fast and interference-free determination of trace amounts of glyphosate and glufosinate residues in agricultural products

Fast screening of herbicide residues is becoming important to ensure food safety, but traditional chromatographic methods may not be suitable for rapid on-site analysis of samples with complicated matrices. Here, we describe a method for rapid and sensitive determination of glyphosate (GLYP) and glufosinate (GLUF) residues in agricultural products by electrophoresis on disposable microchips with laser-induced fluorescence detection. With this method, quantitative analysis of trace amounts of GLYP and GLUF can be achieved with relatively simple sample preparation.

High-pressure open-channel on-chip electroosmotic pump for nanoflow high performance liquid chromatography

Here, we construct an open-channel on-chip electroosmotic pump capable of generating pressures up to ∼170 bar and flow rates up to ∼500 nL/min, adequate for high performance liquid chromatographic (HPLC) separations. A great feature of this pump is that a number of its basic pump units can be connected in series to enhance its pumping power; the output pressure is directly proportional to the number of pump units connected. This additive nature is excellent and useful, and no other pumps can work in this fashion. We demonstrate the feasibility of using this pump to perform nanoflow HPLC separations; tryptic digests of bovine serum albumin (BSA), transferrin factor (TF), and human immunoglobulins (IgG) are utilized as exemplary samples. We also compare the performance of our electroosmotic (EO)-driven HPLC with Agilent 1200 HPLC; comparable efficiencies, resolutions, and peak capacities are obtained. Since the pump is based on electroosmosis, it has no moving parts. The common material and process also allow this pump to be integrated with other microfabricated functional components. Development of this high-pressure on-chip pump will have a profound impact on the advancement of lab-on-a-chip devices.

Microwave-assisted derivatization for fast and efficient analysis of saccharides on disposable microchips

A domestic microwave oven was used to achieve rapid derivatization of saccharides for their microchip electrophoresis analysis.