Preparation of fluorinated covalent organic polymers at room temperature for removal and detection of perfluorinated compounds.

Covalent organic polymers (COPs) are promising adsorbents for the removal and detection of various types of pollutants. However, the preparation of COPs that exhibit uniform dispersion and good appearance at room temperature is challenging. Herein, fluorinated covalent organic polymers (F-COPs) with different morphologies were synthesized through the Schiff base reaction of 4,4-diamino-p-terphenyl (DT) and 2,3,5,6-tetrafluoroterephthalaldehyde (TFA). The as-prepared F-COPs could selectively adsorb perfluorinated compounds (PFCs) owing to their fluoro-affinity, hydrophobicity, hydrogen bonding, and electrostatic attraction. The adsorption kinetics and isotherm simulation results showed that the adsorption process conformed to the second-order kinetics and the Langmuir model. The saturated adsorption capacity calculated by the Langmuir model was found to be 323-667 mg/g. The F-COPs were applied to the treatment of simulated fluorine industrial wastewater, and the PFC removal efficiencies of 92.3-100.0% were achieved. Moreover, ultra-high-performance liquid chromatography-mass spectrometry (UPLC-MS) was conducted for the detection of trace-level PFCs using F-COPs as dispersive solid-phase extraction (DSPE) adsorbents. The limits of detection were 0.05-0.13 ng/L and the limits of quantification were 0.17-0.43 ng/L. This study facilitates the synthesis of COPs at room temperature and extends the application of COPs as pretreated materials for environmental remediation and detection.

A magnetic fluorinated multi-walled carbon nanotubes-based QuEChERS method for organophosphorus pesticide residues analysis in Lycium ruthenicum Murr.

In order to meet the requirements of pesticide residues' detection in complex matrix samples, the magnetic fluorinated multi-wall carbon nanotubes (M-F-MWCNTs) were prepared and applied as new QuEChERS clean-up materials. Combined with GC-MS, an improved QuEChERS method was successfully developed for the detection of organophosphorus pesticide residues. The results showed that the M-F-MWCNTs could effectively remove the interfering substances in Lycium ruthenicum Murr. (L. ruthenicum) samples. The recoveries of 10 tested targets were 74.9% to 113.5% with the relative standard deviations (RSDs) of 3.9-14.7%. The experiment results pointed out that the M-F-MWCNTs were qualified as QuEChERS clean-up materials and expected to be applied to other complex matrix samples and pesticide targets.

A Light-Up Strategy with Aggregation-Induced Emission for Identification of HIV-I RNA-Binding Small Molecules.

Fluorescence methods are important tools to identify RNA-binding small molecules and further employed to study RNA-protein interactions. Most reported fluorescence strategies are based on covalent labeling of ligand or RNA, which can impede the binding between them to some extent, or light-off fluorescent indicator displacement methods, which ask for particular indicators. Herein, a label-free fluorescence strategy based on the light-on aggregation-induced emission (AIE) feature of tetraphenylethene (TPE) derivative to screen RNA-binding small molecules is presented. As a result of electrostatic interaction, the selected peptides can induce self-assembly of the TPE derivative to produce strong fluorescent emission; when the peptides are bound to RNA molecules, the TPE derivative is in the deaggregated form and shows no or minimum fluorescence. Based on the phenomenon, a competitive displacement assay combined with the TPE reporter was employed to characterize selected small molecules for their binding abilities to HIV-I RNAs. This AIE feature enables the fluorescence-off state of the TPE derivative in the presence of RNA-peptide complex to be "lightened up" quickly as the RNA-binding molecule is introduced and the peptide is competitively released. This strategy was carried out to test several small molecule binders, and the results are consistent with previous reports. This report gives an inspiring example of AIE-based fluorescent assay for HIV-I RNA-binding molecule screening, which may further be explored to build a drug screening platform for RNA-protein interference.

Ligand-RNA interaction assay based on size-selective fluorescence core-shell nanocomposite.

The application of the dye-labeled fluorescence method in a ligand-RNA interaction assay is a complex and costly process prone to steric hindrance. Fluorescent nanomaterials offer an attractive alternative due to their simple, low-cost synthesis and effective screening properties. Here, CdTe@ZIF-8 core-shell nanocomposites were used as fluorescence signal transducer in the ligand-TAR RNA interaction assay. Different experimental strategies were developed based on the size-selective nature of the CdTe@ZIF-8 nanocomposites. When ligands can quench fluorescence, two assays of fluorescence recovery with TAR RNA and Tat peptide competitive displacement are carried out successively, which can not only distinguish ligands binding to TAR RNA but also screen potential Tat protein antagonists. When ligands cannot quench fluorescence, the mitoxantrone-TAR RNA complex is used in the competitive displacement assay. Ligands that displaced mitoxantrone from the mitoxantrone-TAR RNA complex signaled the interaction with TAR RNA. Eight ligands, including known and unknown TAR RNA-binding ligands, were tested via the above strategies. The results showed that this method was effective at distinguishing the known RNA-binding partner and screening the Tat antagonist from the test ligands. This simple and effective strategy is expected to be suitable for actual drug screening. Graphical abstract.

Enhanced biochemical characteristics of ß-glucosidase via adsorption and cross-linked enzyme aggregate for rapid cellobiose hydrolysis.

With proper design, immobilization can be useful tool to improve the stability of enzymes, and in certain cases even their activity, selectivity, productivity and economic viability. An immobilized ß-glucosidase (BGL, EC 3.2.1.21) through matrix adsorption and cross-linked enzyme aggregate (ad-CLEA) technology is presented in this work. After adsorption and precipitation, BGL was immobilized to poly(glycidyl methacrylate-co-ethylenedimethacrylate) (PGMA/EDMA) microparticles using glutaraldehyde as the cross-linker. Immobilized BGL exhibits lower apparent Km but much higher Vmax than that of the soluble enzyme, suggesting greater enzyme-substrate affinity and rapid velocity. Besides, ad-CLEA-BGL presents better thermostability retaining activity nearly 70% for 3 h and approximately 50% for 5 h at 70 °C, high operational reusability remaining more than 90% activity after nine uses and excellent storage stability holding about 95% activity after 45 days. Furthermore, the cellobiose is completely hydrolyzed within 1 h with ad-CLEA-BGL, which is significantly more efficient than soluble enzyme (about 4 h). Therefore, BGL was successfully immobilized on PGMA/EDMA microparticles with an ad-CLEA technology and the immobilization greatly enhances the biochemical characteristics. This work indicates promising application for ad-CLEA-BGL in utilizing agricultural remnants, bio-converting cellobiose to fermentable reducing sugar and ethanol production.

3-Aminophenyl Boronic Acid Functionalized Quantum-Dot-Based Ratiometric Fluorescence Sensor for the Highly Sensitive Detection of Tyrosinase Activity.

Using the commercially available and economical 6-hydroxycoumarin (6-HC) as the substrate, a dual-emission ratiometric fluorescence sensor was developed to detect tyrosinase (TYR) activity based on 3-aminophenyl boronic acid functionalized quantum dots (APBA-QDs). TYR can catalyze 6-HC, a monohydroxy compound, to form a fluorescence-enhancing o-hydroxy compound, 6,7-dihydroxycoumarin. Owing to the special covalent binding between the o-hydroxyl and boric acid groups, APBA-QDs react with 6,7-dihydroxycoumarin to form a five-membered ring ester dual-emission fluorescence probe for TYR. With an increase in TYR activity, the fluorescence at 675 nm originating from the QDs is gradually quenched, whereas that at 465 nm owing to 6,7-dihydroxycoumarin increases. Referencing the decreasing signal of the dual-emission probe at 675 nm to measure the increasing signal at 465 nm, a ratiometric fluorescence method was established to detect the TYR activity with high sensitivity and selectivity. Under the conditions optimized via response surface methodology, a linear range of 0-0.05 U/mL was obtained for the TYR activity. The detection limit was as low as 0.003 U/mL. This sensing strategy can also be adopted for the rapid screening of the TYR inhibitors.

Preparation of a fluorinated metal-organic framework and its application for the dispersive solid-phase extraction of perfluorooctanoic acid.

A fluorinated metal-organic framework material (F-MOF) was successfully prepared using tetrafluoroterephthalic acid (H2tfbdc) as the ligand and Zn(II) as the central metal ion. The F-MOF exhibited excellent adsorption performance for perfluorooctanoic acid (PFOA), with a maximum adsorption capacity of 419.8 mg g-1. A sensitive dispersive solid-phase extraction using the F-MOF as an adsorbent, coupled with GC-MS analysis, was developed for detecting trace PFOA with a limit of detection as low as 2.6 ng L-1. This method was applied to detect PFOA in environmental water samples, yielding satisfactory results.

Solidification of a Switchable Solvent-Based QuEChERS Method for Detection of 16 Pesticides in Some Fruits and Vegetables.

n-Octadecylamine was adopted as a cleanup agent to develop a novel solidification of a switchable solvent-based QuEChERS method. At higher temperatures (such as 55 °C), n-octadecylamine can melt into a liquid, allowing effective extraction of matrix interferences in acetonitrile solution (i.e., in dispersive liquid-liquid microextraction). At lower temperatures, n-octadecylamine carrying matrix interferences can rapidly solidify and easily separate from the acetonitrile solution. The results demonstrated that n-octadecylamine possessed a better ability to remove matrix interferences and reduce matrix effects than those of traditional solid-phase dispersive extraction cleanup agents of primary secondary amine and octadecyl bonded silica gel. By coupling it with gas chromatography-mass spectrometry, the proposed method was applied to the detection of 16 pesticides in cucumber. The recoveries were from 80.9 to 112.6% with relative standard deviations less than 12.9%. Satisfactory results were also obtained for the detection of 16 pesticides in pear, orange, apple, pepper, lettuce, and tomato.

A nanoporous carbon derived from bimetallic organic-framework for magnetic solid-phase extraction of bisphenol analogs.

Taking Zn-Fe bimetallic organic-framework as both template and precursor, and furfuryl alcohol (FA) as secondary carbon source, a high-surface-area magnetic nanoporous carbon (MNPC) material was successful prepared. The MNPC exhibits excellent adsorption performance for bisphenol analogs (BPs). The maximum adsorption capacity achieved 439.0 mg g-1 for bisphenol AF, 423.7 mg g-1 for bisphenol S, 330.4 mg g-1 for tetrabromobisphenol A and 252.5 mg g-1 for bisphenol A. A sensitive magnetic solid-phase extraction with MNPC as adsorbent coupled with HPLC-UV analytical method was developed for the detection of trace BPs. The limits of detection for BPs were as low as 0.03-0.07 ng mg-1 with the RSDs of less than 4.6%. This method was applied to detection of four BPs in environmental water samples and the satisfactory results were obtained.

High uptake carboxyl-functionalized porous ß-cyclodextrin polymer for selective extraction of lysozyme from egg white.

Lysozyme is widely used in medical, food and industrial fields due to its bacteriolytic effect and thus it is significant to design and develop a specific adsorbent with high adsorption capacity and selectivity for lysozyme. Inspired by the high uptake capacity of tetrafluoroterephthalonitrile-crosslinked porous ß-cyclodextrin polymers (P-CDPs) and the noncovalent interaction between lysozyme and carboxyl groups, the carboxyl-functionalized P-CDPs (P-CDP-COO-) were synthesized by base-catalysed hydrolysis of nitrile group in P-CDPs to carboxyl. Porous structure, large extent of carboxylic functional groups, cyclodextrin's preventing aggregation, and negatively charged make P-CDP-COO- possess an outstanding adsorption capability for lysozyme. The maximum saturated adsorption capacity reaches 1520 mg g-1, which is much better than the parent polymer and other reported materials. The as-prepared material was successfully utilized for the selective extraction of lysozyme from egg white.

A magnetic hyperbranched polyamide amine-based quick, easy, cheap, effective, rugged and safe method for the detection of organophosphorus pesticide residues.

Magnetic hyperbranched polyamide amine (MHPA) was successfully prepared and applied as a QuEChERS adsorbent to the gas chromatograph-mass spectrometer (GC-MS) detection of organophosphorus pesticides (OPPs) in orange juice. Abundant in amino types and the structure of hyperbranched organic chains make MHPA to possess the clean-up function integrating classic clean-up agent primary secondary amine (PSA) with C18 modified silica, and the magnetic property makes the operation easier and more time-saving. Compared the performance with classical clean-up agents of PSA and C18, better results were obtained with MHPA as adsorbent for the detection of 11 OPPs. Recoveries ranged from 75.2 to 116.2% with the relative standard deviation (RSD) of 4.1-18.9% and the limit of detection (LOD) of 0.74-8.16 ng/g. Results showed that using MHPA as adsorbent for QuEChERS sample preparation is an effective alternative with simplicity and rapidity.

Selective adsorption and separation of illegal cationic dyes from foodstuffs with anionic polyelectrolyte functionalised metal-organic frameworks.

A novel adsorbent, poly(sodium 4-styrenesulfonate) modified MIL-101(Cr)-NH2, was successfully prepared. Owing to its high surface area and degree of negative surface charge, it enables effective adsorption and separation of illegal cationic dyes, such as rhodamine B, pararosaniline, and auramine O, from foodstuffs prior to high performance liquid chromatography analysis. Under optimised conditions, good linearity was obtained over 1.0-80.0 or 1.0-120 ng mL-1 with a correlation coefficient (R2) > 0.999. Limits of detection and limits of quantification of the three dyes were 0.28-0.65 and 0.94-2.13 µg kg-1, respectively. The recoveries of the three dyes in shrimp powder, chili powder, tofu sheets, and tomato sauce were in the range of 86.8-119.3%, suggesting that the developed method is a promising tool for accurate quantification of the three dyes at trace levels in foodstuffs.