Selective fluorescence response and magnetic separation probe for 2,4,6-trinitrotoluene based on iron oxide magnetic nanoparticles

Despite the rapid development of nanomaterials and nanotechnology, it is still desirable to develop novel nanoparticle-based techniques which are cost-effective, timesaving, and environment-friendly, and with ease of operation and procedural simplicity, for assay of target analytes. In the work discussed in this paper, the dye fluorescein isothiocyanate (FITC) was conjugated to 1,6-hexanediamine (HDA)-capped iron oxide magnetic nanoparticles (FITC–HDA Fe₃O₄ MNPs), and the product was characterized. HDA ligands on the surface of Fe₃O₄ MNPs can bind 2,4,6-trinitrotoluene (TNT) to form TNT anions by acid–base pairing interaction. Formation of TNT anions, and captured TNT substantially affect the emission of FITC on the surface of the Fe₃O₄ MNPs, resulting in quenching of the fluorescence at 519 nm. A novel FITC–HDA Fe₃O₄ MNPs-based probe featuring chemosensing and magnetic separation has therefore been constructed. i.e. FITC–HDA Fe₃O₄ MNPs had a highly selective fluorescence response and enabled magnetic separation of TNT from other nitroaromatic compounds by quenching of the emission of FITC and capture of TNT in aqueous solution. Very good linearity was observed for TNT concentrations in the range 0.05–1.5 μmol?L^?1, with a detection limit of 37.2 nmol?L^?1 and RSD of 4.7 % (n?=?7). Approximately 12 % of the total amount of TNT was captured. The proposed methods are well-suited to trace detection and capture of TNT in aqueous solution.

Hollow Multilayer Microcapsules for pH‐/Thermally Responsive Drug Delivery using Aliphatic Poly(urethane‐amine) as Smart Component

Hollow multilayer microcapsules made of aliphatic poly(urethane‐amine) (PUA) and sodium poly(styrene sulfonate) (PSS), templated on PSS‐doped CaCO₃ particles, are prepared for pH‐/thermally responsive drug delivery. The electrostatic interaction and hydrogen bonding under weak‐acid conditions between aliphatic PUA and PSS contribute to the formation of multilayer microcapsules. Scanning electron microscopy (SEM) results demonstrate an obvious variation of the hollow multilayer microcapsules in response to changes in temperature and pH value. Drug‐release behaviors using DOX as a model drug demonstrate that the drug release increases on decreasing the pH value because of the interaction weakness between aliphatic PUA and PSS in acidic conditions. Moreover, the drug release is higher at 55 °C than that at 37 °C for the sake of the shrinkage of aliphatic PUA above its lower critical solution temperature (LCST).

     

Development and validation of a rapid and sensitive assay for the determination of anisodamine in 50 μL of beagle dog plasma by LC–MS/MS

A simple, rapid, high‐throughput, and highly sensitive LC–MS/MS was developed to determine anisodamine in a small volume (50 μL) of beagle dog plasma using atropine sulfate as the internal standard. The analyte and internal standard were isolated from 50 μL plasma samples after a one‐step protein precipitation using Sirocco 96‐well protein precipitation filtration plates. The separation was accomplished on a Hanbon Hedera CN column (100 × 4.6 mm, 5 μm) and the run time was 4 min. A Micromass Quatro Ultima mass spectrometer equipped with an ESI source was operated in the multiple reaction monitoring mode with the precursor‐to‐product ion transitions m/z 306.0→140.0 (anisodamine) and 290.0→123.9 (atropine) used for quantitation. The method was sensitive with a low LOQ of 0.05 ng/mL, and good linearity in the range 0.05–50 ng/mL for anisodamine (r² ≥ 0.995). All the validation data, such as accuracy, intra‐ and interrun precision, were within the required limits. The method was successfully applied to the pharmacokinetic study of anisodamine hydrochloride injection in beagle dogs.     

Fast and quantitative analysis of branched-chain amino acids in biological samples using a pillar array column

In this study, a fast and quantitative determination method for branched-chain amino acids (BCAAs), namely leucine, isoleucine, and valine, was developed using a pillar array column. A pillar array column with low-dispersion turns was fabricated on a 20?×?20-mm² microchip using multistep ultraviolet photolithography and deep reactive ion etching. The BCAAs were fluorescently labeled with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), followed by reversed-phase separation on the pillar array column. The NBD derivatives of the three BCAAs and an internal standard (6-aminocaproic acid) were separated in 100 s. The calibration curves for the NBD-BCAAs had good linearity in the range of 0.4–20 μM, using an internal standard. The intra- and interday precisions were found to be in the ranges of 1.42–3.80 and 2.74–6.97 %, respectively. The accuracies for the NBD-BCAA were from 90.2 to 99.1 %. The method was used for the analysis of sports drink and human plasma samples. The concentrations of BCAAs determined by the developed method showed good agreements with those determined using a conventional high-performance liquid chromatography system. As BCAAs are important biomarkers of some diseases, these results showed that the developed method could be a potential diagnostic tool in clinical research.     

A novel derivatization reagent possessing a bromoquinolinium structure for biological carboxylic acids in HPLC‐ESI‐MS/MS

A novel bromoquinolinium reagent, i.e. 1‐(3‐aminopropyl)‐3‐bromoquinolinium bromide (APBQ), was synthesized for the analysis of carboxylic acids. A simple and practical precolumn derivatization procedure using the APBQ in RP chromatography and MS (HPLC‐MS) has been developed using bile acids and free fatty acids, as the representative carboxylic acids in biological samples. The APBQ efficiently reacted with carboxylic acids at 60°C for 60 min in the presence of N,N‐dicyclohexylcarbodiimide and pyridine as the activation reagents. Because the APBQ possesses a bromine atom in the structure, the identification of a series of carboxylic acids was easily achieved due to the characteristic bromine isotope pattern in the mass spectra. The APBQ also has a quaternary amine structure, thus the positively charged derivatives are predominate for the highly sensitive detection of carboxylic acids. The APBQ was successfully applied to the selective determination of biological carboxylic acids in human plasma. The bile acids (chenodeoxycholic acid and deoxycholic acid) and several saturated (stearic acid and palmitic acid) and unsaturated free fatty acids (oleic acid and linoleic acid) were reasonably determined by HPLC‐MS under the proposed procedure. Based on the results of analyses of human plasma and saliva, the proposed procedure using APBQ seems to be applicable for the qualitative and quantitative analyses of a series of carboxylic acids in biological samples.     

Development and validation of HPLC coupled with triple quadrupole MS for the simultaneous determination of six phenolic acids,six flavonoids,and a lignan in Polygonum capitatum

Polygonum capitatum, a traditional Miao medicinal plant, has significant effects on the treatment of urinary system infections and pyelonephritis. However, no study about the comprehensive quality evaluation of P. capitatum has been reported. In this contribution, a rapid and validated method based on HPLC coupled with triple quadrupole MS was established for the simultaneous determination of six active flavonoids, six phenolic acids, and a lignan in extracts of P. capitatum. These compounds were separated within 10 min on a C₁₈ analytical column with gradient elution. All analyses were performed on an Agilent XDB C₁₈ column (2.1 × 100 mm, 3.5 μm) with a linear gradient elution of acetonitrile/water. The proposed method was applied to analyze 15 batches of samples with acceptable linearity (r², 0.9923–0.9992), precisions (RSD, 1.0–3.0%), repeatability (RSD, 2.0–3.2%), stability (RSD, 2.2–3.2%), and recovery (RSD, 2.1–3.6%) of the 13 compounds. These results demonstrated that this presented method was effective and reliable for the comprehensive quality evaluation of P. capitatum. Moreover, our study can provide chemical evidence to reveal the material basis of its therapeutic effects.     

Reversal of elution order of N‐(2,4‐dinitrophenyl)‐proline and N‐(2,4‐dinitrophenyl)‐serine in HPLC by BSA chiral stationary phase

N‐(2,4‐dinitrophenyl)‐proline and N‐(2,4‐dinitrophenyl)‐serine were enantiomerically resolved on the BSA chiral stationary phase by HPLC in reversed‐phase mode. Effects of chromatographic conditions on enantioseparation and elution order have been investigated in detail. For these two samples, reversal of enantiomer elution order was observed by changing buffer pH, the content of acetonitrile, or alcohol modifiers in mobile phase, which is firstly reported in the BSA chiral stationary phase studies. More interestingly, combined effect between buffer pH and the content of acetonitrile was also observed. In addition, coelution range of enantiomers varied along with the content of acetonitrile in mobile phase.     

In-situ interaction of nano-PbS with gelatin

Water-soluble gelatin–PbS bionanocomposites(BNCs)were synthesized via a facile one-pot chemical reaction method at pH7.40.The samples were characterized by transmission electron microscopy(TEM),X-ray diffraction(XRD),UV-vis absorption spectra(UV-vis),Fourier transform infrared spectra(FT-IR)and circular dichroism(CD).FT-IR data were used to envisage the binding of PbS particles with oxygen atoms of carbonyl groups of gelatin molecule.The possible integration mechanism between gelatin and PbS was discussed in detail.The effect of Pb2+and PbS on the conformations of gelatin has also been analyzed by means of UV-vis,CD and FT-IR spectra,resulting in less-helix content and more open structures(-sheet,β-turn,or expanded).A new formula to calculate the association constant was proposed according to the relationship between the absorbance of gelatin–PbS BNCs and the free concentration of PbS,and apparent association constants K(298/303/308 K:3.11/2.00/1.60×106mol/L)at three different temperatures were calculated based on this formula.Thermodynamic parameters such asΔGθ,ΔHθ andΔSθ were also determined.The results of the thermodynamic investigations indicated that the reaction was spontaneous(ΔGθ<0),and enthalpy-driven(ΔHθ<0).     

Fluorescent AIE dots encapsulated organically modified silica (ORMOSIL) nanoparticles for two-photon cellular imaging

2,3-Bis(4-(phenyl(4-(1,2,2-triphenylvinyl)phenyl)amino)phenyl) fumaronitrile (TPE-TPA-FN or TTF), which possesses aggregation-induced emission (AIE) characteristic, is doped in organically modified silica (ORMOSIL) nanoparticles. By increasing the weight ratio of TTF to the precursor of silica nanoparticles (the quantities of the precursors were kept the same), the fluorescence intensity of nanoparticles increased correspondingly, due to the formation of larger AIE dots in the cores of ORMOSIL nanoparticles. The fluorescent and biocompatible nanoprobes were then utilized for in vitro imaging of HeLa cells. Two-photon fluorescence microscopy clearly illustrated that the nanoparticles have the capacity of nucleus permeability, as well as cytoplasm staining towards tumor cells. Our experimental results may offer a promising method for fast and bright fluorescence imaging, as well as bio-molecule/drug delivery to cell nucleus.     

Chemomics and drug innovation

Chemomics is an interdisciplinary study using approaches from chemoinformatics,bioinformatics,synthetic chemistry,and other related disciplines.Biological systems make natural products from endogenous small molecules (natural product building blocks) through a sequence of enzyme catalytic reactions.For each reaction,the natural product building blocks may contribute a group of atoms to the target natural product.We describe this group of atoms as a chemoyl.A chemome is the complete set of chemoyls in an organism.Chemomics studies chemomes and the principles of natural product syntheses and evolutions.Driven by survival and reproductive demands,biological systems have developed effective protocols to synthesize natural products in order to respond to environmental changes;this results in biological and chemical diversity.In recent years,it has been realized that one of the bottlenecks in drug discovery is the lack of chemical resources for drug screening.Chemomics may solve this problem by revealing the rules governing the creation of chemical diversity in biological systems,and by developing biomimetic synthesis approaches to make quasi natural product libraries for drug screening.This treatise introduces chemomics and outlines its contents and potential applications in the fields of drug innovation.