PS Microspheres Research Articles

Quantum dots/particle-based immunofluorescence assay: Synthesis, characterization and application

Recently, it has been proved that quantum dots (QDs) hold the potential to be used in the bioanalysis as fluorescent probes for their many unique optical properties. In this paper, immunofluorescence assay, an integration of particle-based immunoassays and fluorescent QD-probes, was constructed. Firstly, high quality CdSe/ZnS QDs were prepared. Then after being water-solubilized by amphiphilic polymer based on self-assembling, the QDs were labeled by immunoglobulin G (IgG) antibody. At the same time, both carboxyl-polystyrene (PS) and magnetic carboxyl-PS microspheres were prepared and coated by antigens. The antigen sensitized PS microspheres were specifically captured by the QD–IgG bioconjugates based on the antibody-antigen reaction, which was confirmed by the immunofluorescence test in vitro. The sensitivity of current assay was tested by sandwich immunofluorescence assay using human alpha fetoprotein (AFP) as antigen model. The detection limit of AFP antigen is 4.9 ng/mL.

Preparation and thermal decomposition of PS/Ni microspheres

Integrated and homogeneous nickel coating was achieved by electroless nickel-plating on pretreated PS microspheres. The resulting PS/Ni microspheres were characterized by SEM, EDS, XRD, and VSM. The hollow nickel microspheres were obtained by removing the PS core from the PS/Ni microspheres by a process of calcination. The thermogravimetric analysis was studied using a TGA system. The Ozawa and Coats-Redfern methods were exploited to calculate activation energy and determine thermal decomposition mechanism. The thermal decomposition mechanism of pure PS microspheres was also investigated to draw comparisons with the mechanism of PS/Ni microspheres. Although the essentials of thermal decomposition in both PS microspheres and PS/Ni microspheres is the decomposition of polystyrene, great differences in activation energies and mechanisms still exist. This may be attributed to the heat seclusion effect of nickel coating on the PS core.

Core‐Shell Nanoblends from Soy Protein/Polystyrene by Emulsion Polymerization

AbstractNovel soy protein/polystyrene nanoblends with core‐shell structures were successfully prepared by introducing nano‐sized PS into soy protein through emulsion polymerization. The nanoblends showed core‐shell structures, with the core being of PS and the shell of sodium dodecane sulfonate and soy protein polypeptides, when investigated by electron microscopy. Nanoblends containing high levels of PS (>30%) exhibited characteristic infrared spectrum bands, X‐ray diffraction peak, and glass transition, since PS microsphere aggregated to form independent PS domains. Mechanical strength and water resistance were effectively improved by introducing PS. An effective structure‐performance relationship was thereby established to describe the nanoblends.magnified image

Preparation and characterization of core‐shell PS/Ni composite microspheres

AbstractPS/Ni microspheres were prepared by electroless nickel plating on PS microspheres. Several parameters for plating were optimized in order to obtain integrated and uniform nickel coatings. The properties of obtained composite microspheres, such as chemical composition and crystal texture of the coating, mechanical property, density, and magnetism, were characterized by SEM, EDS, XRD, and VSM. It was revealed that several parameters, such as thiourea dosage, reaction temperature, and load, had significant influence on fabrication of integrated and homogeneous nickel shell. It was also demonstrated that the properties of the PS/Ni microspheres, such as nickel weight ratio, density, and magnetism, can be tuned by adjusting the load. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Chemical modification and characterization of gigaporous polystyrene microspheres as rapid separation of proteins base supports

AbstractTo overcome the disadvantages of protein denaturation and nonspecific adsorption on poly(styrene‐divinylbenzene) (PS) matrix as chromatographic supports, gigaporous PS microspheres, which we prepared in a previous study, were chemically modified with poly(vinyl alcohol) (PVA) through two‐step reaction. The microspheres were chloroacetylated through Friedel‐Crafts acetylation with chloroacetyl chloride and modified with hydrophilic PVA through Williamson reaction afterward. The modified microspheres were characterized by Fourier transform infrared (FTIR) spectra, X‐ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), mercury porosimetry measurements (MPM), BET nitrogen adsorption measurements, laser scanning confocal microscope (LSCM), and protein adsorption experiments. Results showed that PS microspheres were successfully coated with PVA, while the gigaporous structure could be maintained. Consequently, the hydrophilicity and biocompatibility of modified microspheres was greatly improved and nonspecific adsorption of proteins was significantly decreased. The coatings contained only stable chemical bonds (e.g., CC, COC) and easily derived hydroxyl moieties. The large pores of gigaporous PS microspheres also facilitated the modification by PVA. After further derivation, the coated gigaporous base supports could apply in various modes of chromatography and have great potentials in high‐speed protein chromatography. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5794–5804, 2008

Preparation of PS/Ag microspheres and its application in microwave absorbing coating

PS/Ag microspheres were prepared by electroless silver plating on PS microspheres. The PS microspheres with the average size of 1.6 μm were obtained by dispersed polymerization. Pretreatment was performed to adsorb palladium catalytic active centers on the PS surface, prior to plating. Effect of reaction temperature and loadage was studied. The proper temperature for electroless silver plating is determined to be 20 °C, and the loadage should be restricted in the range of 2.80–3.50 g to achieve ideal silver coating. It is found that the density decreases from 2.82 g/cm 3 to 2.32 g/cm 3 while the loadage increases from 2.86 g to 4.29 g. SEM, EDS, and XRD proved the successful formation of silver coating on PS microspheres. A waterborne microwave absorbing coating, based on PS/Ag microspheres and waterborne acrylic resin as binder, was developed. The result shows that nearly 70% of the incident wave is absorbed by this microwave absorbing coating in the frequency range of 10–18 GHz.

Preparation and thermal decomposition of PS/AG microspheres

AbstractPS/Ag microspheres were prepared by electroless silver plating on PS microspheres. SEM, EDS, and XRD approved the successful formation of silver coatings on PS microspheres. The thermogravimetric analysis was studied using a TGA system. The Ozawa and Coats‐Redfern methods were exploited to calculate activation energy and determine thermal decomposition mechanism. The thermal decomposition mechanism of pure PS microspheres was also investigated to draw comparisons with the mechanism of PS/Ag microspheres. It has been found that the thermal decomposition mechanism of PS/Ag microspheres and PS microspheres were both A2 model. The activation energy of PS microspheres and PS/Ag microspheres is 76.76 kJ/mol and 78.61 kJ/mol, respectively. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

In-situ synthesis of PS/(−)silica composite particles in dispersion polymerization using an (±) amphoteric initiator

Core/shell (±)PS/(−)silica nanocomposite particles were synthesized by dispersion polymerization using an amphoteric initiator, 2,2′-azobis [N-(2-carboxyethyl)-2,2-methylpropionamidine](HOOC(CH2)2HN(HN=) C(CH3)2CN=NC (CH3)2C(=NH)NH (CH2)2COOH), VA-057. Negatively charged (−6.9 mV) silica was used as the stabilizer. The effects of silica addition time and silica and initiator concentrations were investigated in terms of polymerization kinetics, ultimate particle morphology, and size/size distribution. Uniform hybrid microspheres with a well-defined, core-shell structure were obtained at the following conditions: silica content = 10−15 wt% to styrene, VA-057 content=above 2 wt% to styrene and silica addition time=0 min after initiation. The delay in silica addition time retarded the polymerization kinetics and broadened the particle size distribution. The rate of polymerization was strongly affected by the silica content: it increased up to 15 wt% silica but then decreased with further increase in silica content. However, the particle size was only marginally influenced by the silica content. The zeta potential of the composite particles slightly decreased with increasing silica content. With increasing VA-057 concentration, the PS microspheres were entirely coated with silica sol above 1.0 wt% initiator.

Homogeneous and heterogeneous binary colloidal clusters formed by evaporation-induced self-assembly inside droplets

In this paper, we report the preparation of binary clusters of colloidal particles with different sizes or species into complex structures using oil-in-water emulsion droplets as confining geometries. First, polystyrene or silica particles with bimodal size distribution were packed densely by evaporation-induced self-assembly inside oil-in-water emulsion droplets. The configurations of larger particles inside the droplets minimize the second moment of the particle locations for the ratio of large to small particle sizes less than 3. Also, the configurations of bimodal clusters were predicted by using a surface evolver simulation, and the simulation predictions were compared with the experimental results. In addition, heterogeneous colloidal clusters were produced by emulsifying the binary mixture suspension of polystyrene and silica particles in aqueous medium followed by evaporating the oil phase. A density gradient centrifugation was applied to fractionate the asymmetric binary dimers comprised of PS and silica microspheres.

Enhanced stability and bioconjugation of photo-cross-linked polystyrene-shell, Au-core nanoparticles.

Encapsulating Au nanoparticles within a shell of photo-cross-linked block copolymer surfactant dramatically improves the physical and chemical stability of the nanoparticles, particularly when they are applied as bioconjugates. Photo-cross-linkable block copolymer amphiphiles [polystyrene-co-poly(4-vinyl benzophenone)]-block-poly(acrylic acid) [(PS-co-PVBP)-b-PAA] and [poly(styrene)-co-poly(4-vinyl benzophenone)]-block-poly(ethylene oxide) [(PS-co-PVBP)-b-PEO] were assembled around Au nanoparticles ranging from 12 to 108 nm in diameter. UV irradiation cross-linked the PVBP groups on the polymer to yield particles that withstood extremes of temperature, ionic strength, and chemical etching. Streptavidin was attached to [PS-co-PVBP]-b-PAA-coated particles using the same noncovalent and covalent conjugation protocols used to bind biomolecules to divinylbenzene-cross-linked PS microspheres. We expect that these particles will be useful as plasmonic, highly light-scattering and light-absorbing analogs to fluorescently labeled PS nanospheres.

Microwave-assisted Fabrication of PS@CdS Core–Shell Nanostructures and CdS Hollow Spheres

Abstract PS@CdS core–shell nanostructures were fabricated by microwave irradiation at 70 °C from the aqueous solution of CdCl2, TAA, and PVP with PS microspheres without surface modification. The products were investigated by XRD, FE-SEM, TEM, IR, and Raman. CdS hollow spheres were easily obtained by removing the PS cores in toluene solution. The method presented here can be used for the preparation of other PS@II–VI semiconductor core–shell nanostructures and hollow spheres.

Single-Crystal ZnO Cup Based on Hydrothermal Decomposition Route

With maleic anhydride-modified PS (m-PS) microspheres as a template (core) and zinc nitrate and diethanolamine (DEA) as the starting materials, the m-PS/ZnO core−shell structure was synthesized by a wet chemical route. ZnO clusters were synthesized through controlled hydrothermal decomposition of Zn-DEA chelate at 70−90 °C and absorbed on the surface of m-PS spheres by electrostatic attraction; the preferential growth of ZnO nuclei resulted in a cup-shape shell around the m-PS core. Finally, single-crystal ZnO with a hollow and polyhedral structure was obtained after calcination at 500 °C.

TEMPO‐mediated dispersion polymerization of styrene in the presence of camphorsulfonic acid

AbstractThe TEMPO‐mediated polymerization of styrene in the presence of camphorsulfonic acid (CSA) is carried out using controlled radical dispersion polymerization. In the absence of TEMPO and CSA, 92% of conversion was achieved within 3 h of polymerization. When TEMPO is solely used, broadening of particle size with narrow PDI was observed because of the prolonged polymerization time. However, when 1:1 molar ratio of CSA/TEMPO was added, the fairly monodisperse PS microspheres having 5.83 μm average size and 3.42% CV (coefficient of variation) were successfully achieved because of the narrow molecular weight of intermediate oligomers and shortening of the polymerization time. This result obviously indicates that the addition of CSA in TEMPO‐mediated dispersion polymerization not only shortens the polymerization time but also greatly improves the uniformity of the microspheres. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 62–68, 2006

Carbon Nanotube-Adsorbed Polystyrene and Poly(methyl methacrylate) Microspheres

Monodisperse and spherical PS and PMMA microspheres, which are only conducting on the surface by the adsorption of carbon nanotubes, were used as the dispersed phase of electrorheological fluids.

The effect of camphorsulfonic acid in TEMPO-mediated bulk and dispersion polymerization of styrene

The TEMPO-mediated living free-radical bulk and dispersion polymerization of styrene in the presence of camphorsulfonic acid (CSA) are investigated. In the absence of TEMPO and CSA in the bulk polymerization, a conversion of 93% is achieved within 6 hr of polymerization. When only TEMPO is involved in this polymerization, the pseudo-living free-radical polymerization is well achieved, however, the polymerization rate becomes quite slow. This retardation of the polymerization rate is solved by the addition of a low concentration of CSA. In the TEMPO-mediated dispersion polymerization in the presence of CSA, similar trends in the conversion, kinetics, and PDI are observed as those observed in the case of bulk polymerization. When only TEMPO is used in the dispersion polymerization, the resulting particle size becomes quite broad, due to the prolonged polymerization time. However, when a 1.0 molar ratio of CSA to TEMPO is added to the TEMPO-mediated dispersion polymerization, fairly monodisperse PS microspheres having an average size of 5.83 μm and a CV of 3.4% are successfully obtained, due to the narrow molecular weight distribution of the intermediate oligomers and shortening of the polymerization time. This result indicates that the addition of CSA to the TEMPO-mediated bulk and the use of dispersion polymerization not only shortens the polymerization time, but also greatly improves the uniformity of the microspheres.

Synthesis and Characterization of Polyurethane-Derived Telechelic Macromonomer Cross-Linkable Stabilizer (TMCS)

The telechelic macromonomer cross-linkable stabilizer (TMCS) was synthesized by the reaction of isocyanate-terminated prepolymer with methacrylamide and was successfully employed as a steric stabilizer and possible cross-linking agent in the dispersion polymerization of styrene. The urethane and methyl groups in TMCS are found in the spectrum of PS microspheres, and the reactive double bonds in TMCS disappear after polymerization with styrene. The qualitative analysis reveals that the symmetric molecular structure with vinyl group in TMCS takes part in the reaction with styrene, and it is proposed that the PS microspheres are substantially cross-linked. In reality, for the 100 wt % TMCS system, the PS is not totally soluble in THF, remaining as a translucent fully-swollen gel in THF. Thus, these qualitative structural investigations suggest that the TMCS serves as a reactive stabilizer as well as a cross-linking agent.

Dithiocarbamate-incorporated monosize polystyrene microspheres for selective removal of mercury ions

Dithiocarbamate-incorporated monosize polystyrene based microspheres (2 μm in diameter) were used for selective removal of Hg(II) from aqueous solutions containing different amounts of Hg(II) (10–100 ppm). Adsorption rates were observed as high at the beginning of adsorption and then equilibrium was reached in about 30 min. The maximum Hg(II) adsorption capacity of the dithiocarbamate-incorporated PS microspheres was about 33.2 mg per gram of dry polymer, which was observed at pH 7.0. While non-specific Hg(II) adsorption onto the plain microspheres was 0.85 mg per gram of dry microsphere. The Hg(II) adsorption ability increased with increasing pH, in the range where the solubility of the Hg(II) was not affected by the pH. The preferential (i.e., competitive adsorption) binding of Hg(II) by the microspheres implies that this sorbent system might contain higher-affinity binding sites for Hg(II) than Cu(II), Cd(II) and Pb(II) ions. More than 96% of the adsorbed Hg(II) was desorbed in 15 min by using 0.1 M HNO 3 as an elution agent. The regeneration of the dithiocarbamate-incorporated PS microspheres was also sufficient.