Qingzhong Guo

Magnetic solid-phase extraction of hydrophobic analytes in environmental samples by a surface hydrophilic carbon-ferromagnetic nanocomposite.

A new sorbent of carbon-ferromagnetic nanocomposite was proposed for the extraction of polycyclic aromatic hydrocarbons (PAHs) in environmental samples. The sorbent was specially designed with a hydrophobic sublayer and a hydrophilic surface, which endows the sorbent some unique features. The former shows high extraction capability for the PAHs and the latter provides benign compatibility with the sample matrix. The sorbent can be easily dispersed in aqueous solutions for extraction and no additional stirring or shaking was necessary to facilitate the dispersion, which may bring operational convenience especially for on-site sampling and extraction. Parameters affecting the extraction efficiency were investigated in detail. The optimal conditions were as follows: 10mg of nanoparticles, 40mmol/L of sodium chloride, 30min of extraction time without shaking, hexane as the desorption solvent and 15min as the desorption-sonication time. The results demonstrate that enrichment factors ranging from 35- to 133-fold were obtained for the analytes. The limits of detection and the limits of quantification are in the range of 0.015-0.335ng/mL and 0.05-1.14ng/mL, respectively. Finally, the new sorbent was successfully used for the extraction of PAHs in lake water samples.

Preparation of polyaniline-metal composite nanospheres by in situ microemulsion polymerization

Nanosized metal and polyaniline (PANi) composite spheres have been prepared via the polymerization of aniline using PdCl(2) or HAuCl(4) as the oxidant in a microemulsion system. The oxidization of aniline and the reduction of metal ion happened together during the reaction, yielding PANi and elemental metal simultaneously. The results of FTIR spectra suggested that the oxidation degree of PANi was affected by the initial ratio of metal ions to monomer in the microemulsion system. The PANi-metal nanospheres were characterized using X-ray photoelectron spectroscopy and the conductivity of the composite nanospheres was measured by conventional four-probe method. Scanning and transmission electron microscopy were used to show the morphology of the composites.

Synthesis of penetrable macroporous silica spheres for high-performance liquid chromatography.

Silica microspheres have been synthesized by phase separation and sol-gel transition coupled with emulsion method. The as-obtained material is characterized by scanning electron microscopy, nitrogen sorption, elemental analysis and particle size distribution measurements. The results demonstrated that the material featured with hierarchically porous structure, possessing both mesopores and penetrable macropores. The mesopores provide large surface area while the macropores traverse the silica particles, which may facilitate fast mass transfer as well as guarantee low backpressure when such materials are used for packed high-performance liquid chromatography (HPLC) column. Therefore, their preliminary applications as HPLC packings in fast separation and low-pressure separation have been attempted in the present study. Benzene, benzaldehyde and benzyl alcohol were separated within two minutes on the silica column at a flow rate of 7 mL min(-1). Vitamin E mixtures can also be baseline separated at a high flow rate of 8 mL min(-1). In addition, thirteen aromatic hydrocarbons were well separated on the octadecyl-bonded silica (ODS) column. In comparison with a commercial Kromasil ODS column, the pressure of the proposed column is much lower (<1/2) under the same chromatographic conditions, while comparable separation efficiency can be achieved.

Dextran Gadolinium Complexes as Contrast Agents for Magnetic Resonance Imaging to Sentinel Lymph Nodes

ABSTRACTPurposeThe aim was to investigate three dextran gadolinium complexes Dextran-DTPA-Gd as the potential MRI contrast agents in lymphatic system.MethodsThree dextran gadolinium complexes Dextran-DTPA-Gd containing differing amounts of Gd-DTPA were synthesized by the incorporation of Gd-DTPA to the hydroxyl groups of dextran. These dextran ligands and gadolinium complexes were characterized, and their properties in vitro and in vivo were also evaluated.ResultsDextran-DTPA-Gd demonstrated obviously higher relaxation effectiveness than that of Gd-DTPA. The result of in vitro cytotoxicity assay showed that these macromolecular ligands and their corresponding gadolinium complexes had low cytotoxicity to HeLa cells. Dextran-DTPA-Gd greatly enhanced the contrast of MR images of normal politeal lymph nodes and reactive hyperplasia of politeal lymph nodes in rabbits and provided prolonged duration in lymphatic system with lower injection doses than that of Gd-DTPA. However, Dextran-DTPA-Gd displayed low signal enhancements in MR images of politeal lymph nodes with VX2 carcinoma in rabbits during the detection time.ConclusionsThese dextran gadolinium complexes Dextran-DTPA-Gd can be taken up selectively by lymphatic system and showed the potential as MRI contrast agents in lymphatic system.

Surface-initiated Atom-transfer Radical Polymerization from Polyimide Films and Their Anti-fouling Properties

A simple one-step method for the chloromethylation of polyimide (PI) under mild conditions was used to introduce benzyl chloride groups into PI film surface. Covalently tethered hydrophilic polymer brushes of poly(ethylene glycol) monomethacrylate (PEGMA) and glycidyl methacrylate (GMA) were prepared via surface initiated atom-transfer radical polymerization (ATRP) from the chloromethylated PI surfaces using benzyl chloride groups as the active ATRP initiators. A kinetics study indicated that the chain growth from the films was in agreement with a controlled process. The dormant chain ends of the grafted polymer on the PI films could reinitiate the consecutive surface-initiated ATRP to prepare surface-functionalized diblock copolymer brushes on the PI films. The modified surface was characterized by X-ray photoelectron spectroscopy (XPS) after each modification stage. Protein adsorption experiments indicated that the PI-P(PEGMA) membrane exhibited substantially improved anti-fouling properties compared to the pristine PI surface.

Surface-initiated atom-transfer radical polymerization from polyethersulfone membranes and their use in antifouling

Abstract A simple one-step method for the chloromethylation of polyethersulfone (PES) under mild conditions provided surface benzyl chloride groups as the active initiators for the surface-initiated atom-transfer radical polymerization (ATRP) to tailor the functionality of the PES membrane. Functional hydrophilic polymer brushes of poly(ethylene glycol)monomethacrylate (PEGMA) and sodium 4- styrenesulfonate (NaStS), as well as their block copolymer brushes, were prepared via surface initiated ATRP from the chloromethylated PES surfaces. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to characterize the surface-modified membranes. The PEGMA-grafted PES membranes showed great protein resistance to protein adsorption compared to the pristine PES surface.

Functionalization of Poly(ether imide) Membranes via Surface-Initiated Atom-Transfer Radical Polymerization and their Use in Antifouling

Poly(ether imide) (PEI) was chloromethylated by a simple one-step method under mild conditions to provide surface benzyl chloride groups as the active initiators for the surface-initiated atom-transfer radical polymerization (ATRP). Functional hydrophilic polymer brushes of poly(ethylene glycol) monomethacrylate and sodium 4-styrenesulfonate, as well as their block copolymer brushes, were synthesized via surface-initiated ATRP from the chloromethylated PEI membrane surfaces. The surface-modified membranes were studied by X-ray photoelectron spectroscopy. Using the bovine serum albumin solution adsorption test, the grafted PEI membranes showed great antifouling properties compared to the pristine PEI surface. Thus, the chloromethylated PEI membranes with the active ATRP initiators opens up opportunities for the functionalization of membranes via surface molecular design.

Polyaspartamide spin probes containing isoindoline nitroxide and porphyrin groups

Water-soluble polyaspartamide isoindoline nitroxides 5-(4′-aminophenyl)-10,15,20-tris (4′-sulfonatophenyl) porphyrin, trisodium salt–poly[α,β-N-(2-hydroxyethyl)-l-aspartamide]–5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl were synthesized by the incorporation of 5-(4′-aminophenyl)-10,15,20-tris(4′-sulfonatophenyl) porphyrin, trisodium salt, as a tumor-targeting group, and 5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl into poly[α,β-N-(2-hydroxyethyl)-l-aspartamide]. These compounds were characterized, and the in vitro properties were evaluated. The polyaspartamide isoindoline nitroxides had higher relaxation effectiveness and had greater toxicity to HeLa cells than that of 5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl. The polyaspartamide isoindoline nitroxides retained similar electrochemical properties and redox reaction mechanisms as the parent nitroxides. The electron paramagnetic resonance spectra of polyaspartamide isoindoline nitroxides exhibited characteristic hyperfine electron paramagnetic resonance spectra of tetramethyl isoindoline nitroxides, with typical nitroxide g-values and nitrogen isotropic hyperfine coupling constants. Therefore, the water-soluble 5-(4′-aminophenyl)-10,15,20-tris(4′-sulfonatophenyl) porphyrin, trisodium salt–poly[α,β-N-(2-hydroxyethyl)-l-aspartamide]–5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl is considered to be a novel potential spin probe for electron paramagnetic resonance.

Dextran gadolinium complex containing folate groups as a potential magnetic resonance imaging contrast agent

Folate-containing dextran ligand (FA-Dextran-DTPA) was synthesized by the incorporation of diethylenetriaminepentaacetic acid (DTPA) and folate (FA) as a tumor-targeting group into dextran as a polymer carrier. This ligand was further reacted with gadolinium chloride to make a dextran gadolinium complex FA-Dextran-DTPA-Gd. The ligand and its gadolinium complex were characterized by 1H-NMR, FTIR, UV-Vis, average particle sizes and zeta potential, as well. In vitro properties including relaxivity, cytotoxicity assay, cellular uptake assay, and magnetic resonance imaging (MRI) were also evaluated. Compared with Gd-DTPA, FA-Dextran-DTPA-Gd possessed obviously higher relaxation effectiveness and lower cytotoxicity to HeLa cells. FA-Dextran-DTPA-Gd had a high affinity to the H460 and MDA-MB-231 tumor cells and can be taken up selectively by these tumor cells. Moreover, FA-Dextran-DTPA-Gd showed enhanced signal intensities (SI) of MRI and enhanced the contrast of MR images of tumor cells. These results indicated that FA-Dextran-DTPA-Gd showed the potential as a tumor-targeting contrast agent in MRI.

Determination of polycyclic aromatic hydrocarbons in water samples by hollow fiber extraction coupled with GC-MS

An octadecyl silica hollow fiber (OSHF) was prepared by a template method. The characteristics of the OSHF were evaluated by scanning electron microscopy, elemental analysis and a pore size analyzer. It was an ideal material for solid phase microextraction. The performance of it was thus studied by extracting polycyclic aromatic hydrocarbons (PAHs) in water samples. The results demonstrated that under the optimal extraction conditions, the linearities were 0.6–60, 1–60 and 2–60 ng mL−1 for different PAHs with all regression coefficients higher than 0.976. The limits of detection were in the range of 31.5 to 97.9 pg mL−1 for these analytes.