Removal of lipopolysaccharide and reactive oxygen species using sialic acid immobilized polysulfone dialyzer

Sialic acid (N‐acetylneuraminic acid, NANA) was covalently immobilized onto the surface of a polysulfone (PSF) hollow fiber membrane. Prior to the immobilization, the surface of PSF was treated with ozone, followed by grafting with acrylic acid, and then the esterification of NANA. The surface concentration of NANA was determined by 2‐thiobarbituric acid (TBA) test. Hemocompatibility, the capability of suppressing oxidative stress, and clearance of lipopolysaccharide (LPS) from the resulting hollow fiber membrane were evaluated. The results show that by immobilizing NANA onto PSF hollow fiber, the adhesion of platelet was reduced, while both APTT and PT were little affected. Furthermore, oxidative stress was suppressed by NANA‐immobilized PSF hollow fibers. The level of LPS was also greatly reduced. Copyright © 2009 John Wiley & Sons, Ltd.     

The reduction of oxidative stress,anticoagulation of platelets,and inhibition of lipopolysaccharide by conjugated linoleic acid bonded on a polysulfone membrane

Conjugated linoleic acid (CLA) was covalently bonded onto the surface of a polysulfone (PSF) membrane via esterification. The surface was characterized with contact angle measurement and FT‐IR spectrometery. The capability of bonded CLA on the suppression of oxidative stress was evaluated. The level of reactive oxygen species (ROS) was measured by the chemiluminescence (CL) method to evaluate the oxidative stress. Furthermore, the removal of bacterial endotoxin (lipopolysaccharide, LPS) by CLA‐bonding PSF was measured with enzyme‐linked immunosorbent assay (ELISA). The reduction in the platelet adhesion on the PSF surface was evaluated using a SF‐3000 automated hematology analyzer. The result indicates that CLA‐bonding PSF can reduce the adhesion of platelets by 73%. The concentration of LPS can be reduced by CLA‐bonding PSF 1.6 times more than unmodified PSF membrane. In addition, the level of ROS against CLA‐bonding PSF membrane was 23% of that against unmodified PSF membrane. Therefore CLA‐bonding PSF membrane could offer protection for patients against oxidative stress and could also inhibit LPS for clinical applications. Copyright © 2007 John Wiley & Sons, Ltd.     

Electrochemical Determination of Salivary N‐Acetylneuraminic Acid by Miniaturized Capillary Electrophoresis Coupled with Sample Stacking

Due to their important biological role as markers for different pathologies, sialic acid (SA) analyses are important for clinical research. In this work, a miniaturized capillary electrophoresis with amperometric detection (mini‐CE‐AD) was developed for the determination of N‐acetylneuraminic acid (NANA), which is the most widespread form of SAs. NANA was first oxidized by periodic acid in an acidic solution, and then the oxidation product β‐formyl pyruvic acid was derivatized with electroactive 2‐thiobarbituric acid (TBA) to form an electroactive NANA‐TBA adduct, which could be readily determined by mini‐CE‐AD. The limit of detection (LOD) of NANA‐TBA could achieve 0.50 µg/mL (1.6 µmol·L^?1, S/N=3) based on an online enrichment approach of moving chemical reaction boundary. The proposed method was successfully applied to the analysis of NANA in human saliva, and the recoveries were in the range of 91.8% –109% with RSDs of 1.8% –3.9%. Due to its simple design and construction, low cost and portability, the mini‐CE‐AD device will possess more practicability in more field work as an alternative to conventional and microchip CE approaches.     

Biofunctional properties of polyester fibers grafted with chitosan and collagen

Poly(ethylene terephthalate) (PET) fiber was treated with ⁶⁰Co-γ-ray and grafted with acrylic acid (AA). The resulting fibers were further grafted with chitosan (CS) via esterification. Afterward collagen (COL) was immobilized onto CS-grafting fibers. The antibacterial activity of CS against Staphylococus aureus, Escherichia coli, and Pseudomonas aeruginosa was preserved after COL-immobilization. After immobilizing COL, the L929 fibroblasts cell proliferation was promoted than CS-grafting PET fiber. The results indicate that by grafting with CS and immobilizing with COL, PET fibers exhibited both antibacterial activity against four pathological bacteria and improvement in the proliferation of fibroblast. Copyright © 2007 John Wiley & Sons, Ltd.     

Label‐Free and Ultra‐Low Level Detection of Salmonella enterica Serovar Typhimurium Using Electrochemical Impedance Spectroscopy

An immunosensor for rapid and low level detection of the bacterial pathogen Salmonella enterica Serovar Typhimurium was designed and developed based upon label‐free electrochemical impedance spectroscopy and correlated to viable cell counts. The immunosensor was fabricated by electroplating gold onto a disposable printed circuit board (PCB) electrode by immobilizing monoclonal antibody (MAb) specific against Salmonella typhimurium cell surface lipopolysaccharide (LPS) onto the surface of the electrode. Use of mass‐fabricated and electroplated PCB electrodes allowed for disposable, highly sensitive, and rapid detection of Salmonella in an aqueous environment. Results demonstrate that in purified solution, Salmonella can be detected as low as 10 CFU in a 100 μL volume and label‐free and rapid manner in fewer than 90 s. The cost effective approach described here can be used for detection of pathogens with relevance for healthcare, food, and environmental applications.     

Graft copolymerization kinetics of acrylic acid onto the poly(ethylene terephthalate) surface by atmospheric pressure plasma inducement

After one atmospheric pressure plasma treatment of poly(ethylene terephthalate) (PET) film, acrylic acid (AAc) in aqueous solution was successfully graft‐copolymerized onto PET films. The effects of reaction time, AAc monomer concentration and reaction temperature on grafting behavior of AAc were systematically studied. Possible reaction kinetics of plasma‐induced graft copolymerization, starting from initial hydroperoxide decomposition, were proposed. Through the Arrhenius analysis about graft copolymerization kinetics of AAc monomers on PET surface, it was revealed that the activation energies of decomposition, propagation and termination were 98.4, 63.5, and 17.5 kJ/mol, respectively. The temperature around 80 °C was favorable not only for the formation of oxide radicals through the thermal decomposition of hydroperoxide on PET surface but also for the extension of graft copolymer chain through direct polymer grafting. Poly(acrylic acid) (PAAc) grains grafted onto PET surfaces possessed relatively uniform size and both PAAc grain size and surface roughness increased with increasing the grafting degree of AAc. The increase of grain size with increasing grafting degree results from the possibility of forming long chain graft copolymers and their shielding of reactive sites. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1594–1601, 2008     

聚氯乙烯表面共价键合肝素及抗凝血性的研究

采用Ar等离子体引发聚乙二醇(PEG)在聚氯乙烯(PVC)表面固定化,进一步对固定PEG后的PVC进行肝素化处理,以改善PVC材料的抗凝血性能。探讨了PEG浓度对Ar等离子体固定化反应效果的影响。通过X射线光电子能谱(XPS)、衰减全反射红外光谱(ATR-FTIR)、扫描电镜(SEM)和接触角测定研究了固定PEG前后PVC的表面性能和表面形貌的变化。XPS分析证实肝素已成功地共价键合于PVC表面。采用体外凝血时间测定和血小板粘附实验对材料的抗凝血性能进行评价,结果表明,被修饰PVC材料的抗凝血性能显著提高。     

A novel ternary GO@SiO2‐HPW nanocomposite as an efficient heterogeneous catalyst for the synthesis of benzazoles in aqueous media

A new solid acid catalyst, consisting of 12‐phosphotungstic heteropoly acid (HPW) supported on graphene oxide/silica nanocomposite (GO@SiO₂), has been developed via immobilizing HPW onto an amine‐functionalized GO/SiO₂ surface through coordination interaction (GO@SiO₂‐HPW). The GO@SiO₂‐HPW nanocomposite was characterized by Fourier transform infrared (FT‐IR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and powder X‐ray diffraction (XRD). The prepared nanocomposite could be dispersed homogeneously in water and further used as a heterogeneous, reusable, and efficient catalyst for the synthesis of benzimidazoles and benzothiazoles by the reaction of 1,2‐phenelynediamine or 2‐aminothiophenol with different aldehydes.     

QCM‐Based Immunosensor for the Determination of Ochratoxin A

Abstract

A piezoelectric immunosensor based on a competitive format was developed for determination of ochratoxin A (OTA) concentration. Surface modifications via two self‐assembled monolayers (SAMs) were investigated respectively and a better result was obtained with the SAM of 16‐mercaptohexadecanoic acid (16‐MHDA). The quartz crystal microbalance (QCM)‐based immunosensor was fabricated by immobilizing anti‐OTA antibodies onto the surface of the 16‐MHDA‐modified electrode, and allowing competition between free OTA and that conjugated with BSA to occur. The assay exhibited a working range of 50–1000 ng/mL and a detection limit of 16.1 ng/mL. Studies of interference and matrix effects were performed to evaluate the feasibility of the developed immunosensor for the direct analysis of OTA in real samples. Recoveries were conducted at 50, 200, and 1000 ng/g and were determined to be in the range of 142%–76%. The OTA assay is specific. No cross‐reactivates were observed with citrinin.     

Voltammetric Characterization of 2‐Methoxy‐4‐Nitrophenyl Derivatized Carbon Powder

Carbon powder has been functionalized with 2‐methoxy‐4‐nitrophenyl groups by the reduction of 2‐methoxy‐4‐nitrobenzenediazonium‐1,5‐naphthalenedisulfonate salt in presence of hypophosporous acid as a reducing agent. This provides an easy and inexpensive methodology to modify the carbon particle surface. This derivatization is carried out in the presence of 2‐methoxy‐4‐nitrobenzenediazonium 1,5‐naphthalenedisulfonate salt along with the carbon powder and hypophosporous acid. The electrochemical behavior of the resulting 2‐methoxy‐4‐nitrophenyl functionalized carbon powder was characterized by immobilizing it onto basal plane pyrolytic graphite (bppg) electrode and studying its voltammetric behavior. The surface morphology of derivatized carbon powder has been examined by SEM studies which revealed that the size of the functionalized carbon particles are larger than bare carbon particles The effect of pH on peak potentials, scan rate and stability of the functionalized carbon particles has revealed that they are surface bound species.     

Reflection–absorption infrared spectroscopy investigation of the crystallization kinetics of poly(ethylene terephthalate) ultrathin films

Reflection–absorption infrared spectroscopy was used to study the crystallization behavior of poly(ethylene terephthalate) (PET) ultrathin films. The crystallinity of ultrathin films was estimated by the fraction of trans conformers of PET. The isothermal and nonisothermal crystallization kinetics of ultrathin films with different thicknesses were investigated. The thinner PET film showed slower kinetics during isothermal crystallization than the thicker film. Moreover, the final crystallinity of films with various thicknesses were reduced with decreasing thickness. An Avrami equation was used to fit the acquired results. The Avrami exponents decreased with the film thickness. As for the nonisothermal crystallization, the cold‐crystallization starting temperature shifted to a lower temperature as the film thickness increased. The influence of the substrate on the crystallization kinetics of the films was also studied. The half‐crystallization times and final crystallinities of ultrathin films adsorbed onto a self‐assembled‐monolayer‐treated surface and an untreated substrate were clearly different, although their thickness dependence was similar. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4440–4447, 2004     

Molecularly Imprinted Polymer Coated Quantum Dots for Multiplexed Cell Targeting and Imaging

Advanced tools for cell imaging are of great interest for the detection, localization, and quantification of molecular biomarkers of cancer or infection. We describe a novel photopolymerization method to coat quantum dots (QDs) with polymer shells, in particular, molecularly imprinted polymers (MIPs), by using the visible light emitted from QDs excited by UV light. Fluorescent core–shell particles specifically recognizing glucuronic acid (GlcA) or N‐acetylneuraminic acid (NANA) were prepared. Simultaneous multiplexed labeling of human keratinocytes with green QDs conjugated with MIP‐GlcA and red QDs conjugated with MIP‐NANA was demonstrated by fluorescence imaging. The specificity of binding was verified with a non‐imprinted control polymer and by enzymatic cleavage of the terminal GlcA and NANA moieties. The coating strategy is potentially a generic method for the functionalization of QDs to address a much wider range of biocompatibility and biorecognition issues.     

Functionalization of multi‐walled carbon nanotubes by the baclofen drug to immobilize palladium nanoparticles and catalyze Sonogashira coupling reactions

The baclofen‐MWCNTs‐Pd nanocatalyst was synthesized through covalent grafting of baclofen molecules onto surface‐modified carbon nanotubes and immobilizing Pd nanoparticles by the baclofen ligands. The chemical structure of the produced nanocatalyst was studied by Raman spectroscopy, Fourier transform‐infrared spectroscopy, energy‐dispersive spectroscopy (EDS), elemental mapping and inductively coupled plasma analysis. Also, its surface morphology was determined using the scanning and transmission electron microscopy techniques. Furthermore, the obtained baclofen‐MWCNTs‐Pd nanocatalyst is demonstrated to exhibit very high activity as a heterogeneous phosphine‐free catalyst in Sonogashira cross‐coupling of aryl halides by giving good to excellent yields of different products. In addition, the nanocatalyst can be reused four times without any significant leaching or loss of activity.     

Chelator‐Free Radiolabeling of Nanographene: Breaking the Stereotype of Chelation

Macrocyclic chelators have been widely employed in the realm of nanoparticle‐based positron emission tomography (PET) imaging, whereas its accuracy remains questionable. Here, we found that ⁶⁴Cu can be intrinsically labeled onto nanographene based on interactions between Cu and the π electrons of graphene without the need of chelator conjugation, providing a promising alternative radiolabeling approach that maintains the native in vivo pharmacokinetics of the nanoparticles. Due to abundant π bonds, reduced graphene oxide (RGO) exhibited significantly higher labeling efficiency in comparison with graphene oxide (GO) and exhibited excellent radiostability in vivo. More importantly, nonspecific attachment of 1,4,7‐triazacyclononane‐1,4,7‐triacetic acid (NOTA) on nanographene was observed, which revealed that chelator‐mediated nanoparticle‐based PET imaging has its inherent drawbacks and can possibly lead to erroneous imaging results in vivo.     

Selective Voltammetric Determination of Uric Acid in the Presence of Ascorbic Acid at Ordered Mesoporous Carbon Modified Electrodes

A novel chemically modified electrode was fabricated by immobilizing ordered mesoporous carbon (OMC) onto a glassy carbon (GC) electrode. The electrocatalytic behavior of the OMC modified electrode towards the oxidation of uric acid (UA) and ascorbic acid (AA) was studied. Compared to a glassy carbon electrode, the OMC modified electrode showed a faster electron transfer rate and reduced the overpotentials greatly. Furthermore, the OMC modified electrode resolved the overlapping voltammetric responses of UA and AA into two well‐defined voltammetric peaks with peak separation of ca. 0.38 V. All results show that the OMC modified electrode has a good electrocatalytic ability to UA and AA, and has an excellent response towards UA even in the presence of high concentration AA.     

Functionalization of Poly[Ethylene Terephthalate) by Means of Glow-Discharge-Initiated Polymerization of Acrylic Acid

Glow-discharge-initiated polymerization of acrylic acid incorporated in poly(ethylene terephthalate) (PET) films was investigated. An increase in polymerization yield with plasma treatment duration and power was found. Polymerization was not confined to the film surface. At high power and long treatment time, polymerization in the bulk of the PET also took place. Water regain and contact angle of the PET-treated films were affected by the presence of poly(acrylic acid) (PAA). The carboxyl groups of the PAA chains incorporated in the PET matrix were utilized for further chemical modification of the PET film. Poly(ethylene glycol) (PEG) was grafted onto PAA by esterification. DSC studies showed the presence of both PAA and PEG in the PET matrix and shed light on the morphology of the multicomponent polymeric system. Free isocyanate groups were introduced into the PET matrix by reacting PAA carboxyl groups with hexamethylene diisocyanate.     

Immobilization of capsaicin onto silica nanoparticle surface and stimulus properties of the capsaicin‐immobilized silica

To prepare silica nanoparticle having biorepellent activity, the immobilization of capsaicin onto hyperbranched poly(amidoamine) (PAMAM)‐grafted silica was investigated. Grafting of PAMAM onto a silica surface was achieved in a solvent‐free dry system using PAMAM dendrimer synthesis methodology. The immobilization of capsaicin was achieved by the reaction of hydroxyl groups of capsaicin with isocyanate groups of Silica‐PAMAM, which were introduced by the reaction of terminal amino groups of Silica‐PAMAM with hexamethylene diisocyanate. The immobilization of capsaicin was confirmed by thermal decomposition GC‐MS. The amount of capsaicin immobilized onto PAMAM‐grafted silica was determined to be 0.10 mmol/g. Capsaicin‐immobilized Silica‐PAMAM (Silica‐PAMAM‐Cap) was dispersed uniformly in water and Tyrode solution. Stimulus activity of Silica‐PAMAM‐Cap was estimated using two stimulus tests, that is a magnus test and a paw licking test, to sensory nerve of mice. As the result of magnus test, it was found that the Silica‐PAMAM‐Cap shows stimulus activity. It was found that elution of capsaicin could be depressed by immobilizing capsaicin onto Silica‐PAMAM from the result of paw licking test. In addition, the stimulus property of Silica‐PAMAM‐Cap to the human skin could be observed and it was found that Silica‐PAMAM‐Cap had acrid taste. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1800–1805, 2010     

Surface modification of titanium by using plasma‐induced graft‐polymerization

Plasma‐induced graft‐polymerization (PIGP) method was utilized in this study to improve corrosion behavior and biocompatibility of titanium (Ti) surface. Bioactive molecule polyacrylamide (PAM) was immobilized onto Ti surface by introducing silanederivatized spacer arms as an intermediary for the covalent linkage. Ti was firstly activated by O₂ plasma, and oxygen‐containing groups were introduced on its surface consequently. The intermediary mercapto silane spacer molecules were then covalently linked to the oxidated surface, followed by the covalent binding of PAM and the sulfhydryl‐terminal groups via PIGP. Surface analyses following modification process included water contact angles (CA), SEM, attenuated total reflection‐Fourier transform infrared spectroscopy (ATR‐FTIR), XPS and atomic force microscope (AFM). The results revealed the effectiveness of this method on immobilizing PAM to Ti surface, and the hydrophilicity of modified surface improved remarkably. In addition, potentiodynamic polarization and cellular proliferation tests were implemented to validate the enhanced corrosion‐resistance and biocompatibility of modified Ti surface, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

Label‐Free Detection of Bisphenol A Using a Potentiometric Immunosensor

A potentiometric immunosensor for the label‐free detection of bisphenol A (BPA) was developed by covalently immobilizing a polyclonal antibody (PAb) onto the surface of a carboxylated poly(vinyl chloride) (PVC‐COOH) membrane. The immunosensor was characterized using scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy. The immobilization of PAb and its interaction with antigen (Ag) and BPA were also confirmed by quartz crystal microbalance (QCM) studies. Experimental parameters affecting the immuno‐interaction between PAb and its Ag or BPA were examined in terms of pH, antibody concentration, and temperature. The immunosensor showed a specific recognition of BPA with less interference than 4.8% from other common phenolic compounds. A calibration plot was obtained between 1.0 and 30.0 ng/mL and the detection limit was determined to be 0.6 ng/mL. The proposed immunosensor was applied for a real water sample spiked with BPA and the recoveries were in the range between 102.5 and 105.7%.     

Reactive compatibilization of polyolefin/PET blends by melt grafting with glycidyl methacrylate

The melt free radical grafting of glycidyl methacrylate (GMA) onto high‐density polyethylene (HDPE) was carried out in Brabender internal mixer. The GMA content of the grafted HDPE (HDPE‐g‐GMA) was determined through FTIR by means of a calibration curve. The influence of reaction procedure, radical initiator concentration and addition of a co‐monomer (styrene) on the grafting efficiency was examined. Blends of poly(ethylene terephthalate) (PET) with HDPE and HDPE‐g‐GMA (75/25 w/w) were prepared by melt mixing in internal mixer. The morphology of the blends was then analysed by SEM microscopy. PET/HDPE‐g‐GMA blends displayed improved phase dispersion and interfacial adhesion as compared to unfanctionalized PET/HDPE blend.