Preparation of a novel composite particles and its application in the fluorescent detection of proteins

A new fluorescence method for the detection of proteins with novel composite nanoparticles (CdS/PPA) has been developed. The composite nanoparticles have been prepared through an in-situ polymerization method under ultrasonic irradiation. The surface of the composite nanoparticles was covered with functional groups (-COOH). These groups may play a major role in the improving the water solubility and biocompatibility of the nanoparticles. The composite particles is combined with proteins in NaAc-HCl buffer solution (pH=1.99), which can result in strong fluorescence, and the response is linearly proportional to the concentration of proteins. In λem/λex=650 nm/365 nm place (the stoke’ shift is 285 nm), its fluorescent strength reaches the maximum. Under the optimum conditions, the linear range is 0.10–20.0 μg·ml⁻¹ with the detection limit of 41 ng·ml⁻¹ for HSA, and 0.10–15.0 μg·ml⁻¹ with the detection limit of 35 ng·ml⁻¹ for Human γ-IgG . The method has been applied to the determination of the total protein in human serum samples collected from the hospital and the results are satisfactory.     

Hollow latex particles: synthesis and applications

One of the major developments in emulsion polymerization over the last two decades has been the ability to make hollow latex particles. This has contributed many fundamental insights into the synthesis and the development of structure in particles. Hollow latex particles also enhance the performance of industrial coatings and potentially are useful in other technologies such as microencapsulation and controlled release. Ever since the publication of the initial process patents describing these particles, there has been a global R&D effort to extend the synthetic techniques and applications. One prominent synthetic approach to hollow particles is based on osmotic swelling. This dominates the literature, and usually starts with the synthesis of a structured latex particle containing an ionizable core that is subsequently expanded with the addition of base. Fundamental to this approach are a sophisticated control of transport phenomena, chemical reactivity within the particle, and the thermoplastic properties of the polymer shell. Hydrocarbon encapsulation technology has also been employed to make hollow latex particles. One approach involves a dispersed ternary system that balances transport, conversion kinetics, and phase separation variables to achieve the hollow morphology. Other techniques, including the use of blowing agents, are also present in the literature. The broad range of approaches that affords particles with a hollow structure demonstrates the unique flexibility of the emulsion polymerization process.     

The mini-review for synthesis of core@Ag nanocomposite

As common noble metal, Ag nanoparticles (Ag NPs) have unique physical and chemical properties and it is widely used in daily life, scientific research, industrial production, environment, medical and healthcare systems. Core/shell of Ag nanocomposite have attracted attention due to the significant properties and wide applications by combination with the core and shell. As a mini-review, it is emphasized the approaches for fabrication Ag shell coating on core nanoparticles as core@Ag nanocomposite, including situ growth method, phenol formaldehyde resin method, silane coupling agent method, ultrasound method, PEI method, dopamine method and other methods. The procedures and mechanism for construction of core@Ag nanocomposite are highlighted. The comparison of those approaches, including their advantages and disadvantages are described in detail. At the same time, the properties and applications of Ag NPs are briefly introduced. The current challenges and perspectives in the future for synthesis of core/shell nanocomposite is proposed. The review is very useful for quickly gaining knowledge and experience for synthesis of core@Ag nanocomposite.     

Effect of the structure of latex particles on adhesion. Part I: Synthesis and characterization of structured latex particles of acrylic copolymers and their peel adhesion behavior

This is a series of articles that deals with fundamental aspects of the effects of the structure of latex particles of acrylic copolymers on their adhesion behavior. Specifically, relationship or analogy between rheological properties and adhesion performance of the acrylic copolymers was demonstrated. The first part of this series concerns the synthesis and characterization of latex particles with desired structures and compositions, and the experimental results of peel adhesion. The second part develops an analogy between the peel adhesion performance of the adhesives and rheological properties of the corresponding copolymers. The third part addresses the generalities and particularities of three major tests for adhesion: peeling, blistering, and spontaneous peeling. Three types of structured latex particles were synthesized by three different emulsion polymerization processes: the first type had a uniform composition over the entire particles with a glass transition temperature (T_g) varying between ?40°C and 0°C, depending upon the compositions of monomers involved in the copolymer; the second type was of core-shell structure. As for the third type, the composition of monomers varied gradually across the particle radii. The glass transition behavior and the dynamic mechanical properties in the solid state of the copolymers confirmed the structures of the corresponding latex particles. On the other hand, the peel adhesion performance of the films of these latex particles varied with the dynamic mechanical properties of the corresponding copolymers. This implies that a correlation could be found between the structure of the latex particles, dynamic mechanical properties in the solid state of the corresponding copolymers, and the peel adhesion performance of the adhesive films. ©1995 John Wiley & Sons, Inc.     

The surface characterization of styrene-acrylamide copolymer latex particles and their deposition onto fibers

The surface characteristics of styrene-acrylamide (St-AAm) copolymer latex particles were investigated and their deposition onto polyamide (Nylon 6), polyester (polyethylene terephthalate) and polyacrylonitrile fibers was studied. Conductometric titrations and viscosity measurements of latex dispersions revealed the presence of a water-soluble polymer layer on the particle surface and the thickness of its polymer layer increased with increasing acrylamide fraction in a latex particle. The deposition rates of St-AAm copolymer latices onto Nylon 6 and polyester fibers increased with increasing acrylamide fraction and decreasing pH at a constant ionic strength. These deposition phenomena onto Nylon 6 and polyester fibers agreed qualitatively with prediction based on the electrokinetic data of the latices and the fibers. However, a participation of attractive interaction due to an increase in acrylamide fraction was also suggested.The deposition rate onto polyacrylonitrile fiber decreased with increasing acrylamide fraction in spite of a decrease in electrostatic repulsive interaction, and it was found that a specific large repulsive interaction acts between polyacrylonitrile fiber and St-AAm copolymer latex particles.This paper is part VIII in a series on Interfacial electrical studies on the deposition of polymer latexes onto fabrics and the removal of these deposited latexes. Part VII: Tamai H, Kimura I,Suaza T Coll Polym Sci 261: 661 (1983)     

Reactive blends of thermoplastics and latex particles

Monodisperse homogeneous and core–shell latex particles of various sized between 200 and 600 nm were synthesized by emulsion copolymerization. Some of the core–shell particles were functionalized with epoxy groups at their peripheries upon introduction of glycidyl methacrylate (GMA) during the synthesis. The core consisted of crosslinked polybutylacrylate and the shell polymethylmethacrylate. Synthesis conditions at high and low temperatures were optimized to obtain coreshell particles with a well-defined morphology. The particles were characterized by quasi-elastic light scattering, scanning electron microscopy and transmission electron microscopy. The latex particles functionalized with GMA were then dispersed into a reactive matrix (styrene and maleic anhydride copolymer) using a batch mixer to obtain blends with well-defined and stabilized morphology. 4 Dimethylaminopyridine was used as a catalyst. The reaction between the epoxy groups at the particle surface and the maleic anhydride or diacid groups of the matrix was evaluated by torque and extraction techniques. A small amount of conversion generates sufficient amounts of grafted species at the matrix and particle interfaces to ensure a good interfacial adhesion.     

Examination of dodecylpyridinium chloride as a potentially selective fluorescence quenching agent for discriminating between alternant versus nonalternant polycyclic aromatic hydrocarbons

Fluorescence behavior is reported for 13 alternant and 12 nonalternant polycyclic aromatic hydrocarbons (PAHs) dissolved in aqueous micellar cetyltrimethylammonium chloride (CTAC)+dodecylpyridinium chloride (DDPC) and sodium dodecylsulfate (SDS)+DDPC mixed surfactant solvent media. Experimental measurements indicate that the dodecylpyridinium cation selectively quenches fluorescence emission of alternant PAHs. Emission intensities of nonalternant PAHs, with a few noted exceptions, essentially remain constant, irrespective of both DDPC concentration and cosurfactant headgroup charge.     

Preparation and characterization of submicron hybrid magnetic latex particles

Micrometer magnetic hybrid particles are of great interest in biomedical field, and various morphologies have been prepared via encapsulation processes. Regarding submicron, only few processes have been investigated and the most recent one leading to highly magnetic submicron magnetic hybrid particles is based on oil in water magnetic emulsion (MES) transformation. The encapsulation of magnetic iron oxide nanoparticles forming oil in water MES was investigated using different styrene/cross‐linker divinylbenzene volume ratio in the presence of potassium persulfate initiator. The encapsulation performed in this work is basically conducted by using well‐defined oil in water MES as a seed in radical emulsion polymerization. The chemical composition, morphology, iron oxide content, magnetic properties, electrokinetic properties, particle size, and size distribution of the prepared magnetic hybrid particles were examined using various techniques. The desired perfect magnetic core and polymer shell morphology were successfully obtained, and the final magnetic hybrid particles are superparamagnetic in nature and exhibit high iron oxide content (64 wt %). Copyright © 2015 John Wiley & Sons, Ltd.     

A novel immunoassay based on the dissociation of immunocomplex and fluorescence quenching by gold nanoparticles

This study reports a novel, simple and sensitive immunoassay using fluorescence quenching caused by gold nanoparticles coated with antibody. The method is based on a non-competitive heterogeneous immunoassay of human IgG conducted by the typical procedure of sandwich immunocomplex formation. Goat anti-human IgG was first adsorbed on polystyrene microwells, and human IgG analyte was captured by the primary antibody and then sandwiched by antibody labeled with gold nanoparticles. The sandwich-type immunocomplex was subsequently dissociated by the mixed solution of sodium hydroxide and trisodium citrate, the solution obtained, which contains gold nanoparticles coated with antibody, was used to quench fluorescence. The fluorescence intensity of fluorescein at 517 nm was inversely proportional to the logarithm of the concentration of human IgG in the dynamic range of 10-5000 ng mL⁻¹ with a detection limit of 4.7 ng mL⁻¹. The electrochemical experiments and the UV-vis measurements were applied to demonstrate whether the immunoglod was dissociated completely and whether the gold nanoparticles aggregated after being dissociated, respectively. The proposed system can be extended to detect target molecules such as other kinds of antigen and DNA strands, and has broad potential applications in disease diagnosis.     

Synthesis of a sugar-functionalized iridium complex and its application as a fluorescent lectin sensor

Syntheses of two [Ir(bipy)(Ppy)₂] complexes functionalized with mannose and galactose are reported. The complexes were characterized by NMR and mass spectrometry. Fluorescence studies have shown enhanced interaction of the mannose-functionalized complex with mannose specific lectin concanavalin A whereas the galactose-functionalized complex did not show any interaction. The binding constant (2.9 × 10⁵ mol⁻¹) was determined from the fluorescence spectroscopic data.     

Fluorescence quenching method for the determination of catechol with gold nanoparticles and tyrosinase hybrid system

<正>The determination method of catechol by fluorescence quenching was developed.The assay was based on the combination of the unique property of gold nanoparticles with tyrosinase enzymatic reaction.In the presence of tyrosinase,the fluorescence of gold nanoparticles was quenched by catechol which can be employed to detect catechol.Under the optimal conditions,a linear range 5.0×10~(-7)-1.0×10~(-3) mol L~(-1) and a detection limit 1.0×10~(-7) mol L~(-1) of catechol were obtained.o-Quinone intermediate produced from the enzymatic catalyzed oxidation of catechol was considered to play the main role in the fluorescence quenching.     

The properties of covalently immobilized trypsin on soap-free P(MMA-EA-AA) latex particles

The covalent immobilization of trypsin onto poly[(methyl methacrylate)-co-(ethyl acrylate)-co-(acrylic acid)] latex particles, produced by a soap-free emulsion polymerization technique, was carried out using the carbodiimide method. The catalytic properties and kinetic parameters, as well as the stability of the immobilized enzyme were compared to those of the free enzyme. Results showed that the optimum temperature and pH for the immobilized trypsin in the hydrolysis of casein were 55 degrees C and 8.5, both of which were higher than that of the free form. It was found that K(m) (Michaelis constant) was 45.7 mg . ml(-1) and V(max) (maximal reaction rate) was 793.0 microg . min(-1) for immobilized trypsin, compared to a K(m) of 30.0 mg . ml(-1) and a V(max) of 5 467.5 microg . min(-1) for free trypsin. The immobilized trypsin exhibited much better thermal and chemical stabilities than its free counterpart and maintained over 63% of its initial activity after reusing ten times.     

Synthesis and characteristics of poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite hollow latex particles and their application as drug carriers

In this work, the poly(methacrylic acid‐co‐N‐isopropylacrylamide) thermosensitive composite hollow latex particles was synthesized by a three‐step reaction. The first step was to synthesize the poly(methyl methacrylate‐co‐methacrylic acid) (poly(MMA‐MAA)) copolymer latex particles by the method of soapless emulsion polymerization. The second step was to polymerize methacrylic acid (MAA), N‐isopropylacrylamide (NIPAAm), and N,N′‐methylenebisacrylamide in the presence of poly(MMA‐MAA) latex particles to form the linear poly(methyl methacrylate‐co‐methacrylic acid)/crosslinking poly(methacrylic acid‐co‐N‐isopropylacrylamide) (poly(MMA‐MAA)/poly(MAA‐NIPAAm)) core–shell latex particles. In the third step, the core–shell latex particles were heated in the presence of ammonia solution to form the crosslinking poly(MAA‐NIPAAm) thermosensitive hollow latex particles. The morphologies of poly(MMA‐MAA)/poly(MAA‐NIPAAm) core–shell latex particles and poly(MAA‐NIPAAm) hollow latex particles were observed. The influences of crosslinking agent and shell composition on the lower critical solution temperature of poly(MMA‐MAA)/poly(MAA‐NIPAAm) core–shell latex particles and poly(MAA‐NIPAAm) hollow latex particles were, respectively, studied. Besides, the poly(MAA‐NIPAAm) thermosensitive hollow latex particles were used as carriers to load with the model drug, caffeine. The effect of various variables on the amount of caffeine loading and the efficiency of caffeine release was investigated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5203–5214     

Interactions in mixtures of latex particles and polymers as revealed by turbidimetry

We report a turbidimetric study of the depletion forces between latex particles induced by a dissolved polyelectrolyte. The system consists of a polystyrene latex and potassium polystyrene sulfonate (PSS). Since turbidimetry is practically insensitive to multiple scattering the analysis of the mixtures of the colloid and the dissolved polymer could be extended up to latex concentrations of 50 g/l. The amount of dissolved PSS was varied between 0.025 and 0.2 wt.%. The scattering contribution of the polymer can be neglected in very good approximation and the change in scattering intensity upon addition of PSS can directly be related to the effective attraction of the latex spheres caused by the dissolved polymer. It is demonstrated that a potential based on the volume-exclusion mechanism can describe in good approximation the osmotic compressibility resulting from the turbidimetric analysis.     

卤代荧光素与西布曲明的荧光猝灭和褪色光谱及其分析应用

在弱酸性缓冲溶液中,乙基曙红(EE)、赤藓红(ET)和荧光桃红(PX)3种卤代荧光素与盐酸西布曲明(SH)形成离子缔合物,导致吸收光谱发生变化和荧光猝灭。研究了反应产物的吸收和荧光光谱特征,适宜的反应条件,据此建立了以卤代荧光素为光谱探针的灵敏、简便、快速测定SH的新方法。其中ET体系褪色反应灵敏度最高,对SH的线性范围为0.1～4.0μg/mL,检出限为0.06μg/mL;PX-SH体系的荧光猝灭法对SH的线性范围是0.2～4.6μg/mL(λex/λem=540nm/560nm),检出限为0.09μg/mL。讨论了离子缔合反应对荧光及吸收光谱的影响及卤代荧光素荧光猝灭和褪色的原因。     

Electrochemical synthesis of copper-arabinoxylan nanocomposite for applications as antimicrobial agent and CO2 conversion catalyst

This study reports the electrochemical synthesis, antimicrobial and catalytic activity of copper-arabinoxylan nanocomposite. The synthesis was achieved without use of any hazardous reducing and stabilizing agent. The spherical copper nanoparticles (size approx. 40 nm) dispersed in the arabinoxylan matrix as they formed and got stabilized. In the absence of arabinoxylan the particles rapidly converted to copper oxide suggesting a high stability for the composite. Electrolysis was carried out with copper plate as the sacrificial anode, carbon rod as the cathode and sodium nitrate (1.00 % in 1 % arabinoxylan suspension) as an electrolyte. The copper nanoparticles dispersed in arabinoxylan were characterized by surface plasmon resonance spectroscopy, X-ray diffraction, electron microscopy and zeta potential measurements. The synthesized composite exhibited good antimicrobial activity against P. aeruginosa, Staph. aureus and E. coli and a catalytic activity in conversion of CO₂ to methanol.     

Effect of quenching conditions on particle formation and growth in thermal plasma synthesis of fine powders

The vapor-phase synthesis of ultrafine powders in reactive thermal plasma systems is studied. A mathematical model is developed to determine the effect of quenching conditions on the size characteristics of powders produced. The particle nucleation is considered to be due to both condensation of product vapor and surface reaction between adsorbed reactant species. The particle growth is considered to be exclusively due to further condensation of product vapor. Numerical predictions on powder formation are explored through a case study for the synthesis of zinc oxide powders from zinc vapor and oxygen carried in argon gas. The results of the present srudy indicate that the size characteristics of plasma-produced powders can be significantly enhanced by gradual, regulated quenching, as opposed to the rapid quenching conventionally used in the past. The results further indicate that distribution of the quench gas along the reactor provides an effective means to accomplish the much desired control over the powder properties.     

Fabrication of Pt/polypyrrole hybrid hollow microspheres and their application in electrochemical biosensing towards hydrogen peroxide

Pt/polypyrrole (PPy) hybrid hollow microspheres were successfully prepared by wet chemical method via Fe₃O₄ template and evaluated as electrocatalysts for the reduction of hydrogen peroxide. The as-synthesized products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), X-ray diffraction (XRD), inductive coupled plasma emission spectrum (ICP) and Fourier-transform infrared spectra (FTIR) measurements. The results exhibited that ultra-high-density Pt nanoparticles (NPs) were well deposited on the PPy shell with the mean diameters of around 4.1 nm. Cyclic voltammetry (CV) results demonstrated that Pt/PPy hybrid hollow microspheres, as enzyme-less catalysts, exhibited good electrocatalytic activity towards the reduction of hydrogen peroxide in 0.1 M phosphate buffer solution (pH = 7.0). The composite had a fast response of less than 2 s with linear range of 1.0-8.0 mM and a relatively low detection limit of 1.2 μM (S/N = 3). The sensitivity of the sensor for H₂O₂ was 80.4 mA M⁻¹ cm⁻².     

Synthesis of magnetic polyphosphazene-Ag composite particles as surface enhanced Raman spectroscopy substrates for the detection of melamine

Magnetic polyphosphazene(MPZS) particles coated by Ag nanoparticles(MPZS-Ag) have been developed as surface enhanced Raman spectroscopy(SERS) substrates for sensitive detection of melamine in aqueous solutions and milk samples.5,5'-Dithiobis-(2-nitrobenzoic acid)(DTNB) was used as model analyte to test the SERS activity of the MPZS-Ag particles.The prepared MPZS-Ag particles possess both magnetic responsiveness and excellent SERS properties.SERS detection of different concentrations of melamine aqueous solutions and spiked milk samples were performed by the MPZS-Ag particles.The limit of detection(LOD) of the melamine in aqueous solutions was 10-7 mol/L(0.0126 mg/L) and 0.6 mg/L in real milk samples using the MPZS-Ag particles as SERS substrates.The LOD of the melamine are much lower than the safety values of Food and Drug Administration and Codex Alimentarius Commission.These results indicate that the MPZS-Ag particles have promising application prospect for SERS analysis in food safety fields.     

Effect of the structure of latex particles on adhesion. Part II: Analogy between peel adhesion and rheological properties of acrylic copolymers

This article, the second part of this series, concerns the development of an analogy between the peel behavior of pressure-sensitive adhesives and the dynamic mechanical properties of the corresponding copolymers. The adhesive copolymers used were synthesized by emulsion polymerization processes. Their physical and dynamic mechanical properties were characterized and presented in Part I of this series. In this study, an analogy was built up between the force in a peel test as a function of peel velocity, F_p(v_p), and the loss modulus of the adhesive as a function of the angular frequency in a dynamic mechanical experiment, G″(ω). This was done by superimposing the curves of F_p versus v_p and those of G″ versus ωβ₀/β, where β₀/β is a shift factor with β being a parameter in the Kaelble theory and β₀ being some reference value of the Kaelble parameter. When the curves of F_p ～ v_p and those of G″ ～ ωβ₀ were plotted together, they followed the same trend of variation. This analogy between G″(ωβ₀/β) and F_p(v_p) was further confirmed by the fact that the apparent activation energies of the primary glass transition for G″(ω) and F_p(v_p) are virtually the same, suggesting that the analogy between G″(ω) and F_p(v_p) is dictated by the glass transition. The existence of the above-mentioned analogy between G″(ω) and F_p(v_p) shows that the performance of an adhesive can be evaluated or predicted from the dynamical loss modulus of the corresponding (co)polymer. ©1995 John Wiley & Sons, Inc.