[Determination of five veterinary drug residues in milk by ultra-high performance liquid chromatography-quadrupole/electrostatic field orbitrap mass spectrometry based on modified chitosan membrane purification].

Milk is an important consumer product with high nutritional value. The presence of veterinary drug residues in milk owing to the indiscriminate use of veterinary drugs may affect consumer health. In the mass spectrometric analysis of trace compounds, chromatographic co-eluting components easily interfere with the mass spectral signals obtained, affecting the accuracy of qualitative and quantitative analyses. Matrix purification is a promising method to reduce the matrix effect. Chitosan is a natural biopolymer with numerous active functional groups such as amino, acetyl, and hydroxyl groups; these groups can adsorb lipids through hydrophobic and electrostatic interactions. Chitosan also has the advantages of low production cost, stable chemical properties, and convenient modification. Novel chitosan-based materials are promising candidates for lipid purification. In this study, a chitosan membrane was modified with trimethoxyoctadecylsilane (C18-CSM). C18-CSM was prepared through one-step hydrolysis and used as a dispersive solid phase extraction (DSPE) adsorbent to purify the matrix during milk pretreatment. We combined C18-CSM with ultra-high performance liquid chromatography-quadrupole/electrostatic field orbitrap mass spectrometry (UHPLC-Q/Exactive Orbitrap MS) to develop an effective method for the extraction and determination of ofloxacin, enrofloxacin, ciprofloxacin, diazepam, and metronidazole in milk. C18-CSM was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and water contact angle testing. The results indicated that the material has a rough surface and uniformly dense cross-section. The water contact angle of C18-CSM was 104°, indicating its good hydrophobicity. The pretreatment conditions (extraction solvent, dosage of NaCl, extraction frequency, and dosage of C18-CSM) that influenced the recoveries of the five veterinary drugs were investigated in detail. The optimal conditions were established as follows: 5% formic acid in acetonitrile, 1 g NaCl, extraction 1 time, 20 mg C18-CSM. Separation was performed on a Hypersil GOLD VANQUISH column (100 mm×2.1 mm, 1.9 µm). The mobile phase consisted of 0.1% formic acid aqueous solution and 0.1% formic acid in acetonitrile, and was flowed at a rate of 0.3 mL/min. The sample injection volume was 1 µL, and the column temperature was maintained at 25 ℃. Mass spectrometric analysis was performed in positive electrospray ionization mode. To verify the necessity of the purification material, the matrix effect was investigated using the matrix-matched standard curve method. The use of C18-CSM reduced the matrix effects of the five necessity drugs from the range of -22%-8.8% to the range of -13%-3.6%, indicating that C18-CSM is a highly efficient DSPE material. Under optimal conditions, the developed method showed good linearities within the range of 0.5-100 µg/L, with correlation coefficients (r2)≥0.9970. The limits of detection(LODs) and quantification (LOQs) were 0.2 µg/L and 0.5 µg/L, respectively. To assess the accuracy and precision of the method, we prepared milk samples with three spiked levels (low, medium, and high). The recoveries of the five veterinary drugs were ranged from 79.5% to 115%, and the intra-day and inter-day relative standard deviations were 7.0%-13% (n=6) and 1.3%-11% (n=3), respectively. This study provides a simple, accurate, and reliable method for the rapid and simultaneous determination of the five veterinary drug residues in milk.

Integrated single-nucleus sequencing and spatial architecture analysis identified distinct injured-proximal tubular types in calculi rats.

BACKGROUND: Urolithiasis with high prevalence and recurrence rate, has impacts on kidney injury in patients, becomes a socioeconomic and healthcare problem in worldwide. However, the biology of kidney with crystal formation and proximal tubular injury remains essentially unclear. The present study aims to evaluate the cell biology and immune-communications in urolithiasis mediated kidney injury, to provide new insights in the kidney stone treatment and prevention. RESULTS: We identified 3 distinct injured-proximal tubular cell types based on the differentially expression injury markers (Havcr1 and lcn2) and functional solute carriers (slc34a3, slc22a8, slc38a3 and slc7a13), and characterized 4 main immune cell types in kidney and one undefined cell population, where F13a1+/high/CD163+/high monocyte & macrophage and Sirpa/Fcgr1a/Fcgr2a+/high granulocyte were the most enriched. We performed intercellular crosstalk analysis based on the snRNA-seq data and explored the potential immunomodulation of calculi stone formation, and founded that the interaction between ligand Gas6 and its receptors (Gas6-Axl, Gas6-Mertk) was specifically observed in the injured-PT1 cells, but not injured-PT2 and -PT3 cells. The interaction of Ptn-Plxnb2 was only observed between the injured-PT3 cells and its receptor enriched cells. CONCLUSIONS: Present study comprehensively characterized the gene expression profile in the calculi rat kidney at single nucleus level, identified novel marker genes for all cell types of rat kidney, and determined 3 distinct sub-population of injured-PT clusters, as well as intercellular communication between injured-PTs and immune cells. Our collection of data provides a reliable resource and reference for studies on renal cell biology and kidney disease.

[Ultra-high performance liquid chromatography-orbitrap high-resolution mass spectrometry for rapid screening and identification of 32 illegally added drugs in slimming and anti-impotence health foods].

A novel method based on ultra-high performance liquid chromatography-orbitrap high-resolution mass spectrometry (UHPLC-Orbitrap HRMS) was developed for the rapid screening and confirmation of 32 illegally added drugs in slimming and anti-impotence health foods. In addition, the key points of the database establishment and application are summarized. This research focused on the derivatives of illegally added drugs. An HRMS database was established by comparing the response intensity of each compound in the positive and negative modes. The experimental conditions such as the type of extraction solvent and chromatographic column temperature were explored in detail. The analytes were separated on a Hypersil gold vanquish column (100 mm×2.1 mm, 1.9 µm) by gradient elution with acetonitrile/water (containing 0.1%(v/v) formic acid) as the mobile phase at a flow rate of 0.3 mL/min. Positive and negative ion full scanning/data-dependent secondary scanning mode was used to collect the 32 target compounds within 17 min, and TraceFinder software was used to screen the fragment ions. All the 32 compounds could be well separated within 17 min. The measured and theoretical values of the exact mass of the 32 compounds in the two matrix-spiked solutions were within an error of 5×10-6, and the MS2 fragment ions were within an error of 1×10-5. All the compounds showed an excellent linear relationship, with correlation coefficients (r2) above 0.99. Except dapoxetine, hydroxythiohomo sildenafil, thiohomo sildenafil, thiosildenafil, desmethyl thiosildenafil, the recoveries ranged from 50.5% to 84.5% in the solid matrix, with the relative standard deviations (RSDs) ranging from 1.2% to 13%. The recoveries were 60.4% to 109.3% in the liquid matrix, with the RSDs ranging from 0.77% to 8.2%. The matrix effect (ME) values of the 32 compounds ranged from 0.61 to 0.95 in the solid matrix and from 0.73 to 1.09 in the liquid matrix. Thiohomo sildenafil, desmethyl thiosildenafil, and chlorpretadalafil exhibited strong matrix inhibitory effects in the solid matrix. Therefore, solid and liquid negative matrix extracts were used to prepare a series of mixed standard solutions in order to reduce the ME values. The limits of detection (LODs) were 0.02 mg/kg for the 32 drugs in the liquid sample and 0.02 mg/kg for 29 compounds in the solid sample; the LODs for chlorothalidone, udenafil, and desmethyl thiosildenafil in the solid sample were 0.04 mg/kg. When the retention time in the self-built database matches the sample collection method, it should be used as one of the screening conditions. As for the selection of the matching mode, if the identify mode is selected, the retention time is a necessary condition for compound confirmation. When the retention time does not meet the requirements, subsequent screening of the fragment ions and isotope abundance ratios will not be performed. If the confirm mode is selected, the retention time is the optional condition for compound confirmation. When the retention time does not meet these requirements, subsequent matching of other conditions such as fragment ions and isotope information is required. Isotope information is very important in HRMS and is an effective supplement to the first-order extracted mass. Therefore, its use is recommended, but the isotope abundance ratio will be even lower when the target content is very low in the complex matrix, which may affect isotope matching. In addition, if the fragment ions are not detected in the screening results of the TraceFinder software but can be extracted in the data browser, their intensity threshold in the screening conditions can be further reduced to find the corresponding fragment ions. One positive sample was detected among 48 healthy food samples, with a detection rate of 2.08%. This method has the advantages of simple operation and high accuracy. It can be used for the rapid screening and confirmation of 32 illegally added drugs in slimming and anti-impotence health foods.

NanoPOP: Solution-Processable Fluorescent Porous Organic Polymer for Highly Sensitive, Selective, and Fast Naked Eye Detection of Mercury.

Fluorescence-based detection is one of the most efficient and cost-effective methods for detecting hazardous, aqueous Hg2+. We designed a fluorescent porous organic polymer (TPA-POP-TSC), with a "fluorophore" backbone and a thiosemicarbazide "receptor" for Hg2+-targeted sensing. Nanometer-sized TPA-POP-TSC spheres (nanoPOP) were synthesized under mini-emulsion conditions and showed excellent solution processability and dispersity in aqueous solution. The nanoPOP sensor exhibits exceptional sensitivity (Ksv = 1.01 × 106 M-1) and outstanding selectivity for Hg2+ over other ions with rapid response and full recyclability. Furthermore, the nanoPOP material can be easily coated onto a paper substrate to afford naked eye-based Hg2+-detecting test strips that are convenient, inexpensive, fast, highly sensitive, and reusable. Our design takes advantage of the efficient and selective capture of Hg2+ by thiosemicarbazides (binding energy = -29.84 kJ mol-1), which facilitates electron transfer from fluorophore to bound receptor, quenching the sensor's fluorescence.

Induced-fit adsorption of diol-based porous organic polymers for tetracycline removal.

Adsorption is recognized as one of the most efficient approaches for antibiotics removal from water. Inspired by the enzyme-substrate interaction model, we proposed induced-fit adsorption (IFA) model, and rationally designed and fabricated diol-based porous organic polymers (POPs) as adsorbents for tetracycline (TC) removal. For 2,3-naphthalenediol-based POP (NTdiol-POP), the preferable geometry of diol-groups contributed to the high binding energy with TC species and flexible methylene linkages between neighboring rigid naphthalene rings gave rise to precisely matching between TC species and adsorbents, that is, the induced-fit conformation change. As a result, NTdiol-POP exhibited a high saturated adsorption capacity of 155.8 mg g-1. More importantly, NTdiol-POP exhibited excellent TC removal efficiencies in both concentrated solution (96% for 4 p.p.m) and trace level solution (97% for 250 p.p.b).

Interfacial Growth of TiO2-rGO Composite by Pickering Emulsion for Photocatalytic Degradation.

A 2D sandwich-like TiO2-rGO composite was fabricated by the Pickering emulsion approach to improve the photocatalytic efficiency. Through an in situ growth of antase-TiO2 nanoparticles on the interface of O/W type GO Pickering emulsion, TiO2 nanoparticles were closely and densely packed on the surface of well-exfoliated rGO sheets; meanwhile, many mesoporous voids acting as the adsorption chamber and microreactor were produced. Evaluated by methylene blue (MB) degradation, its photocatalytic activity was prominent compared with the common TiO2-based photocatalyst, with the rate constants 5 and 3.1 times higher under visible light and xenon lamp, respectively. When we applied it in the photocatalytic degradation of tetracycline hydrochloride (TCH, such as 10 ppm) under the visible light without adding any oxidants, the total removal efficiency was as high as 94% after 40 min. The mechanism of this good photocatalytic efficiency was illustrated by the scavenger trapping tests, which showed that this unique structure of TiO2-rGO composite induced by the Pickering emulsion can significantly enhance the light absorption ability, accelerate the separation rate of electron-hole pairs, increase the adsorption capacity of organic pollutants, and hence improve the photocatalytic efficiency.

Interfacial Growth of Metal Organic Framework/Graphite Oxide Composites through Pickering Emulsion and Their CO2 Capture Performance in the Presence of Humidity.

We proposed an in situ interfacial growth method induced by the Pickering emulsion strategy to produce metal organic framework (MOF)/graphite oxide (GO) composites of Cu3(BTC)2/GO, in which GO was demonstrated to be a promising stabilizer for producing the Pickering emulsion and provided a large interfacial area for the in situ growth of Cu3(BTC)2 nanoparticles. When Cu3(BTC)2/GO composites were used as adsorbents for CO2 capture from the simulated humid flue gas, they showed both significantly improved thermodynamic and dynamic properties. Because most of the H2O molecules were adsorbed on the highly exfoliated GO sheets in Cu3(BTC)2/GO-m, CO2 uptake reached 3.30 mmol/g after exposure to the simulated flue gas for 60 min and remained unchanged for up to 120 min. This highlighted its potential application for real CO2 capture. More importantly, the in situ interfacial growth of nanoparticles induced by Pickering emulsions would be a promising strategy for designing and fabricating nanocomposites.