Investigation of the surface confinement effect of copper nanoclusters: construction of an ultrasensitive fluorescence turn-on bio-enzyme sensing platform.

Copper nanoclusters (CuNCs) have attracted considerable research interest due to their good physicochemical properties, ease of preparation, and low price. However, the low quantum yield and poor stability in aqueous solutions have greatly limited their applications. In order to improve the fluorescence properties and stability of CuNCs, in this paper, the surface confinement effect of CuNCs based on 2D layered double hydroxide (LDH) was proposed to prepare the fluorescent composites of glutathione protected CuNCs and LDH (GS-CuNCs/LDH) with excellent quantum yield and long fluorescence lifetime. Moreover, a novel, simple, and ultrasensitive fluorescence assay for the detection of hyaluronidase was proposed based on the surface confinement effect. The limit of detection for hyaluronidase was as low as 0.014 U mL-1. For the first time, this work developed a bio-enzyme sensing platform based on the surface confinement effect, which can serve as a promising candidate in biosensing.

A modulation approach for covalent organic frameworks: Application to solid phase microextraction of phthalate esters.

A modulation approach with 4-hydroxybenzhydrazide as the modulating agent was designed for constructing 2,4,6-triphenoxy-1,3,5-benzene-based covalent organic frameworks (COFs). The COFs materials were employed as solid phase microextraction (SPME) coatings for the extraction of phthalate esters (PAEs). Various experimental conditions including extraction temperature, extraction time, salt concentration, and desorption time were investigated and optimized. The introduction of modulating agent into the synthesis of fibers significantly enhanced the extraction efficiency towards PAEs. The linear range was 1-100 µg L‒1 and the detection limits in the range of 0.032-0.451 µg L‒1 were achieved with good linearity ranged from 0.9904 to 0.9970. Inter-batch and intra-batch relative standard deviations were in the ranges of 0.83-4.67% and 3.08-9.73%, respectively. Moreover, the developed coating fibers were used for the extraction of PAEs in water samples and satisfactory recoveries were achieved.

Electrostatically controlled fluorometric assay for differently charged biotargets based on the use of silver/copper bimetallic nanoclusters modified with polyethyleneimine and graphene oxide.

An electrostatically controlled fluorometric assay is described that is based on the use of silver/copper bimetallic nanoclusters. The nanoclusters were coated with polyethyleneimine (PEI-Ag/CuNCs). At pH 7.4, these particles are positively charged. Their blue fluorescence (with excitation/emission peaks at 341/464 nm) depends on local pH values and temperature. If graphene oxide (which is negatively charged at pH 7.4) is introduced, the fluorescence of the PEI-Ag/CuNCs is quenched. Based on various electrostatic interactions, three kinds of biomacromolecules were detected by fluorometry. These include (negatively charged) heparin, (positively charged) protamine, and (virtually uncharged) trypsin. Heparin is detected by using GO/PEI-Ag/CuNCs, protamine by using GO/heparin/PEI-Ag/CuNCs, and trypsin by using GO/protamine/heparin/PEI-Ag/CuNC. The detection limits and linear ranges are 4.8 nM and 10-450 nM for heparin, 0.09 µg·mL-1 and 0.25-5 µg·mL-1 for protamine, and 0.03 µg·mL-1 and 0.05-1 µg·mL-1 for trypsin. Zeta potentials of the various substances in the system were determined to elucidate the detection mechanism. Comceivably, the method provides a widely applicable approach for electrostatically controlled biomolecular assays. Graphical abstract Schematic presentation of electrostatically controlled fluorometric assay for the detection of heparin, protamine, and trypsin based on the silver/copper bimetallic nanoclusters modified with polyethyleneimine and graphene oxide.

Cobalt Phthalocyanine Tetracarboxylic Acid Functionalized Polymer Monolith for Selective Enrichment of Glycopeptides and Glycans.

In this study, poly(glycidyl methacrylate-ethyleneglycol dimethacrylate) monolith functionalized with cobalt phthalocyanine tetracarboxylic acid is prepared. The polymer monolithic material is used for glycopeptides enrichment coupled with MALDI-TOF MS. By taking advantage of cobalt phthalocyanine including hydrogen bonds between isoindole subunits of phthalocyanine and glycans, coordination interaction between cobalt and glycopeptides, the monolithic material is successfully applied to the enrichment of glycopeptides efficiently and selectively. With IgG and horse radish peroxidase as the model glycoproteins, 28 and 17 glycopeptides could be identified respectively after enrichment with the monolith, only four and three glycopeptides could be obtained for direct analysis. The monolith is also employed to the digests mixture of BSA and IgG (50:1, m/m), indicating the high enrichment selectivity of glycopeptides even in the presence of a large interference ratio. The detection limit is determined to be 6.7 fmol, implying that the present method had great potential for trace sample analysis. In addition, the monolith was successfully applied to the enrichment of N-linked glycans in human serum samples, demonstrating its great potential for the analysis of glycoproteins.

[Preparation of cobalt phthalocyanine functionalized polymer monolith and application to enrichment of transferrin glycopeptides].

Poly(glycidyl methacrylate-ethyleneglycol dimethacrylate) (Poly(GMA-EDMA)) monolith functionalized with cobalt phthalocyanine tetracarboxylic acid (CoPcTc) was prepared. The monolith was used for transferrin (Tf) glycopeptide enrichment. By taking advantage of hydrogen bonds between isoindole subunits of phthalocyanine and glycans and coordination interaction between cobalt and glycopeptides, the monolithic material was efficient and selective. After enrichment of transferrin through the functionalized monolith, 17 glycopeptides were identified by electrospray ionization quadrupole time-of-flight mass spectrometry. When the concentration of transferrin was reduced to 8.8×10-10mol/L, three glycopeptides could still be obtained. The present method has great potential for trace sample analysis.

Preparation of carboxylatocalix[4]arene functionalized magnetic polyionic liquid hybrid material for the pre-concentration of phthalate esters.

In this work, we designed a novel hybrid material based on the polymerization of an ionic liquid on a magnetic core and further functionalized with carboxylatocalix[4]arene. Scanning electron microscope, transmission electron microscope, Fourier transform infrared spectroscopy, thermal gravimetric-derivative thermogravimetric analysis, energy dispersive X-ray spectroscopy, X-ray diffractometer, and vibrating sample magnetometer were utilized to examine the physicochemical properties of the hybrid material obtained. The material was used as the adsorbent for magnetic solid-phase extraction of phthalate esters. To obtain the maximum pre-concentration efficiency, a series of parameters influencing the extraction efficiency, including sample pH, adsorbent amount, adsorption time, eluent type as well as salt addition, was examined systematically. Under the optimum conditions, a fast and feasible pre-concentration protocol for phthalate esters was established with satisfactory enrichment factors between 158.7 and 191.3. The limits of detection from high-performance liquid chromatographic analysis for the target analytes were in the range of 0.02-0.31 ng mL-1. The wide linear ranges varying from 0.1 to 100 ng mL-1 were achieved with correlation coefficients greater than 0.9977. To evaluate the feasibility of this method, it was successfully applied to analyse phthalate esters in multiple kinds of real samples including tap water, lake water, drinks, tonic lotions, and human serum samples. The results obtained demonstrated that the synthesized magnetic material had potential as a candidate in the pre-concentration field for phthalate esters due to the special properties stemming from its structure and components.

Anchoring ß-cyclodextrin modified lysine to polymer monolith with biotin: specific capture of plasminogen.

Plasminogen (Plg) is a kind of glycoprotein which plays an important role in cell migration. The determination of Plg content can directly reflect the abnormal manifestation of fibrinolytic system dysfunctions. In the present work, lysine (Lys)-based adsorbents were prepared for the specific capture of Plg through the covalent binding of Lys with a polymer monolithic substrate. Lys was modified with ß-cyclodextrin (ß-CD) via a click reaction and anchored to the substrate with biotin by host-guest interaction. The biotin-Lys-CD based monolithic material was employed for the specific capture of Plg. Combining with mass spectrometry (MS) determinations, the method exhibited a low detection limit of 1.0 fmol with relative standard deviations below 10.0% for Plg. Considering the advantages of simplicity, sensitivity, and high specificity, the developed approach was successfully applied to the determination of Plg in human plasma samples and opened a gallery for testing Plg as a biomarker for the diagnosis of fibrinolytic system dysfunctions.

Highly selective enrichment of phosphopeptides by on-chip indium oxide functionalized magnetic nanoparticles coupled with MALDI-TOF MS.

Selective and efficient preconcentration is indispensable for low concentration of phosphopeptides in phosphorylated protein-related samples prior to MS-based analysis. Herein, an on-chip system coupled magnetic SPE with MALDI-TOF MS was designed. A metal oxide affinity chromatography material, indium oxide, was coated on the surface of Fe3 O4 magnetic nanoparticles to prepare the adsorbent, spatially confined with an applied magnetic field. The adsorbent exhibited high selectivity for phosphopeptides in tryptic digests of the mixture of ß-casein and BSA (1:1000) and the mixture of ß-casein, BSA, and ovalbumin (1:100:100). Thanking to the enrichment ability and specificity for phosphopeptides with the adsorbent, the on-chip magnetic SPE-MALDI-TOF MS approach showed high sensitivity with a low detection limit of 4 fmol. In addition, the developed approach was used to analyze phosphopetides in non-fat milk digests and human serum successfully.

[Synthesis of Magnetic Metal Organic Framework Fe3O4@NH2-MIL-53 (Al) Materials and Application to the Adsorption of Lead].

Metal organic framework, a novel class of organic inorganic hybrid functional materials, has been widely used in the fields of gas adsorption, catalysis, separation, and biological medicine due to its large specific surface area, diverse structural, and adjustable channel. In this work, a new amine-functionalized magnetic metal-organic framework material was synthesized. Nano-Fe3O4 was prepared by a solvothermal method, after which polyvinyl pyrrolidone was employed to modify Fe3O4. Finally, amino groups were introduced to prepare Fe3O4@NH2-MIL-53(Al). The crystal structure and functional groups of the material were characterized by means of X-ray diffraction (XRD) and Fourier transform infrared spectrometry (FT-IR). Combined with flame atomic absorption spectroscopy (FAAS), the adsorption of lead by the magnetic adsorbent was investigated. The magnetic adsorbent possesses high adsorption capacity because of the large specific surface area of Fe3O4@NH2-MIL-53(Al) and the coordination between amino group and lead. Experimental conditions affecting the adsorption percentage were discussed and the experimental operation parameters were optimized (pH value of 6.0 and adsorption time of 120 min). Kinetics and thermodynamics studies were conducted for the adsorption process. Langmuir/Freundlich and pseudo-first-order/pseudo-second-order models were applied to analyze the experimental data. Thermodynamic functions, i. e., changes of Gibbs energy, entropy, and enthalpy, were calculated from temperature experiments. In addition, the regeneration of the adsorbent was considered with hydrochloric acid as the desorption solution. Several adsorption and desorption experiments were carried out, illustrating that the Fe3O4@NH2-MIL-53(Al) adsorbent can be used repeatedly.