Colloidal stability of dextran-modified latex particles toward adsorption of concanavalin A

The colloidal stability of the dextran-modified poly(methyl methacrylate) (PMMA) latex particles toward adsorption of a carbohydrate-binding protein, concanavalin A (Con A), is primarily controlled by the charge neutralization mechanism. Formation of a crosslinked network structure via the specific affinity interactions between the dimeric Con A molecules and the dextran molecules anchored onto different latex particles may also have an impact on the coagulation kinetics. Judging from the data of coagulation kinetics, the colloidal stability of the latex particles toward added Con A in the decreasing order is: latex particles without dextran modification>latex particles with a dextran content of 2.15%>latex particles with a dex-tran content of 1.24% based on total polymer weight (PMMA+grafted dextran). The coagulation mechanisms involved in the adsorption of Con A onto the latex particles have been proposed to explain these experimental data. Charge neutralization of the negatively charged latex particles by adsorption of the positively charged Con A is the predominant destabilization mechanism. The ratio of the number of dextran active sites to that of Con A molecules plays an important role in the formation of the crosslinked network structure. The electrolytes in water cause a reduction in the electrostatic repulsion force among the interactive latex particles, but this ionic strength effect is not significant in comparison with charge neutralization. Received: 22 October 1997 Accepted: 24 December 1997     

Isothermal equilibrium adsorption of concanavalin A on dextran-modified poly(methyl methacrylate) latex particles

Isothermal equilibrium adsorption experiments were carried out to study the adsorption of concanavalin A (Con A) on dextran-modified poly(methyl methacrylate) (PMMA) latex particles. Three PMMA particles with various levels of dextran modification were selected for study: 0% (designated as D0), 1.24% (D20), and 2.45% (D75) based on total polymer weight. The Langmuir model is applicable to both D0 and D20 systems, although the data for the D20 system are somewhat scattered. On the other hand, the amount of Con A adsorbed per gram polymer particles (q*) versus the Con A concentration in water (c*) curve for the D75 system cannot be described by the Langmuir model. The deviation is attributed to the formation of a crosslinked network structure, caused by specific binding of the dimeric Con A molecules onto two neighboring particles with grafted dextran. The ratio of the initial number of Con A molecules to the initial number of active binding sites on the dextran-modified particle surface plays an important role in determining the structure of flocs formed. The maximum amount of Con A adsorbed on the particle surface (q _max) is of the order of 10⁻¹ μmol per gram particles and q _max in decreasing order is D75 > D20 > D0. The dissociation constant of the Con A-D20 (or Con A-D75) pair is of the order of 10⁻¹ μmol dm⁻³ which is 1 order of magnitude smaller than that of the Con A-D0 pair. Thus, the electrostatic interaction between Con A and D0 is much weaker than the affinity interaction between Con A and D20 (or D75). An empirical model is proposed to qualitatively explain the q* versus c* data. Received: 18 June 1998 Accepted in revised form: 24 December 1998     

Distribution-analyzing latex immunoassay (DALIA): methods for determination of antigen and for elimination of non-specific reaction induced by rheumatoid factor

A highly sensitive distribution-analyzing latex immunoassay method (DALIA), which is based on analysis of the volume distribution of latex particles including both the agglutinates and the residual non-agglutinating particles, has been established. Numbers of latex particles, which are sensitized with specific antibodies, are counted by using an electric particle counter with a personal computer and simultaneously the extent of agglutination was quantified by analyzing the volume distribution of the reacted latex particles. It was found that ultramicrospheres coated with normal goat immunoglobulin G can completely eliminate non-specific reactions induced by human serum containing rheumatoid factor (RF) in this DALIA method. The degree of absorption of RF activity by these ultramicrospheres was associated with the diameters of the ultramicrospheres. Moreover, by use of the combination of ultramicrospheres and latex particles coated with monoclonal antibodies against alpha-fetoprotein (AFP) or with polyclonal antibody specific to C-reactive protein, specific DALIA systems were able to be developed. Both DALIA systems exhibited the high sensitivity (1 to 7 ng/ml). The correlation coefficient (gamma) of the results of DALIA with those of enzyme-linked immunoadsorbent assay in measuring AFP was 0.994.     

乳胶凝集法快速检测猪圆环病毒2型

发展了一种简单、快速、灵敏的乳胶凝集法用于猪圆环病毒2M的检测.合成了带有磺酸基的三元聚合物乳胶微球,通过静电相互作用,将猪圆环病毒2型单克隆抗体吸附到乳胶微球表面,形成乳胶抗体复合物诊断试剂.乳胶抗体复合物诊断试剂表面抗体与病毒表面抗原发生特异性反应,促使分散的乳胶微球凝集在一起,出现肉眼可见的凝集现象,而与去离子水...     

Chemical Modifications on Polystyrene Latex: Preparation and Characterization for Use in Immunological Applications

Polystyrene latex microspheres are efficient supports for immunological reactions. In the presence of suitable functional groups these microspheres may react by covalent binding with antigens or antibodies and have been extensively used in immunoassay technique. By using the emulsion polymerization and diazotization methods, a kind of functionalized latex was prepared. The preparation of this latex consisted of six syntheses of polystyrene followed by nitration, amination and diazotization. A narrow distribution of particle size was obtained in all the cases. The synthesis that presented 98% of monomer conversion and the largest particle size diameter 0.2 ± 0.05 μm was chosen for the subsequent chemical treatments. The chemical characterizations of every step were performed by Fourier transform infrared and Raman spectroscopies. The particle size was determined by a submicrometer particle analyzer and scanning electron microscopy. The polydiazostyrene latex obtained was sensitized using bovine serum albumin (BSA) and when it was submitted to agglutination assay in the presence of a rabbit serum containing specific antibodies to BSA demonstrated efficient results. © 1997 John Wiley & Sons, Ltd.     

Interactions between dextran-modified poly(methyl methacrylate) latex particles and concanavalin A

The electrostatic and affinity interactions between concanavalin A (Con A) and dextran-modified latex particles were investigated. The ratio of the initial number of dextran active sites to that of Con A molecules plays an important role in determining the structure of flocs formed during adsorption and, thereby, has an influence on the amount of adsorbed Con A and the subsequent elution yield. NaCl and d-glucose, used successively in the two-step desorption of Con A, were employed to study the relative importance of electrostatic and affinity interactions involved in the Con A adsorption process. A significant fraction of adsorbed Con A is attributed to the electrostatic interaction mechanism. The feasibility of using the dextran-modified latex products to purify Con A from Jack bean meal was demonstrated. Received: 22 February 2000 Accepted: 19 September 2000     

Grafting of amino functional monomer onto initiator-modified polystyrene particles

Polystyrene nanoparticles with grafted chains of an amino functionalized polymer were prepared by a two-step polymerization process. In the first step, the polystyrene seed particles were synthesized by the conventional batch emulsion polymerization using terpolymer HAS (hydroperoxide monomer, acrylic acid, and styrene) as a surface-active initiator. The surface of the obtained particles contains carboxyl groups, which are responsible for the latex stability, and residual undecomposed hydroperoxide groups. Therefore, in the second step, an amino functional monomer was grafted onto the hydroperoxide modified polystyrene particles by a "grafting from" approach. X-ray photoelectron spectroscopy, NMR, and scanning electron microscopy were used to examine the surface of the amino functionalized particles. The amount of incorporated amino groups onto the particles was determined by fluorescenometric titration. In general, the number of amino groups on the particle surface increased with the increase of the functional monomer content in the reaction mixture. The incorporation of the functional monomer was also confirmed by electrophoretic measurements. Final particles possess amphoteric character due to the presence of amino and carboxyl groups on the surface. Adsorption of human immunoglobulins G onto the amino functionalized particles was studied as a function of pH and ionic strength. The covalent binding of human IgG was performed using the glutaraldehyde preactivation method. The immunoreactivity of the latex-IgG complex was examined by the latex agglutination test.     

Effect of depletion interactions on transport of colloidal particles in porous media

The influence of depletion interactions on the transport of micrometer-sized, negatively charged polystyrene latex particles through porous media was studied by analysis of particle breakthrough curves as a response to short-pulse particle injections to the inlet of a packed column of glass beads. The column outlet latex particle concentration profiles and the total amount of particles exiting the column were determined as a function of the concentration of small, silica nanoparticles in the solution and the bulk flow rate. Because of similar charges, the silica particles do not adsorb to either the latex particles or glass beads and thus induce an attractive depletion force between the latex particles and glass bead collectors. The total column outlet latex particle amount was calculated by integrating the measured breakthrough concentration curve and compared to the known amount of injected particles at the column inlet. It was found that the particle recovery was a decreasing function of the silica nanoparticle concentration and the carrier fluid residence time, and an increasing function of the velocity in the bed. In addition, removing the silica nanoparticles from the flowing solution caused a second outlet peak to appear, suggesting that some of the polystyrene particles were captured in secondary energy wells. The experimental data were interpreted using the predicted potential energy profile between a single particle and a glass bead, which was assumed to consist of electrostatic, van der Waals, and depletion components. The results indicate that secondary energy wells significantly affect particle transport behavior through porous media.     

苝酰亚胺功能化聚苯乙烯乳胶粒水凝胶膜

将带有硼酸基团的苝酰亚胺荧光分子引入聚苯乙烯共聚乳胶粒表面,再将其嵌入聚丙烯酰胺水凝胶膜内,合成了对葡萄糖敏感的水凝胶膜。通过扫描电子显微镜、激光粒径分析仪对微球的外观形貌、单分散性进行表征,并用原子吸收光谱法间接测定了微球表面苝酰亚胺的含量,研究了苝酰亚胺功能化聚苯乙烯乳胶粒的紫外-可见吸收光谱图及其水凝胶膜的荧光性能。结果表明:苝酰亚胺功能化聚苯乙烯乳胶粒水凝胶膜经浓度逐渐增大的葡萄糖溶液浸泡后,其荧光强度降低,但发射峰位置不变。当葡萄糖浓度达到200 mmol/L时,其荧光淬灭效率为0.34。     

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.     

Electrostatic interactions between amphoteric latex particles and proteins

The electrostatic interactions between amphoteric polymethyl methacrylate latex particles and proteins with different pI values were investigated. These latex particles possess a net positive charge at low pH, but they become negatively charged at high pH. The nature and degree of interactions between these polymer particles and proteins are primarily controlled by the electrostatic characteristics of the particles and proteins under the experimental conditions. The self-promoting adsorption process from the charge neutralization of latex particles by the proteins, which have the opposite net charge to that of the particles, leads to a rapid reduction in the zeta potential of the particles (in other words colloidal stability), and so strong flocculation occurs. On the other hand, the electrostatic repulsion forces between similarly charged latex particles and the proteins retard the adsorption of protein molecules onto the surfaces of the particles. Therefore, latex particles exhibit excellent colloidal stability over a wide range of protein concentrations. A transition from net negative charge to net positive charge, and vice versa (charge reversal), was observed when the particle surface charge density was not high enough to be predominant in the protein adsorption process.     

Electromagnetophoretic force measurement of a single binding interaction between lectin and yeast cell surfaces.

A novel measurement method of the binding force between a micrometer-sized particle and a solid surface in an electrolyte solution has been established by using the electromagnetophoretic buoyancy on the particle. By this method, we investigated the binding force between a yeast cell surface and an oligosaccharide-binding protein, concanavalin A (Con A), fixed on a silica capillary wall. The force measurement was carried out up to 60 pN. In a lower surface concentration of Con A, yeast cells could be desorbed by a force less than 60 pN. However, in a higher surface concentration after treated by 1 mg ml(-1) solution, yeast cells were adsorbed with a force stronger than 60 pN. In this case, the addition of 10 mg ml(-1) D-mannose solution to the medium reduced the binding force to less than 60 pN. The observed adsorption force of yeast cells ranged within 30 - 40 pN, regardless of the interfacial amount of Con A. This force was thought to be the single binding force between a mannose group of the cell surface and an active site of Con A. Moreover, the dissociation rate constant of the single binding of yeast cell and Con A complex was determined as 4.6 x 10(-3) s(-1) and the increment of the binding distance at the transition state as 0.33 nm from the desorption kinetic experiments of yeast cell under the constant pulling conditions of 10, 20 and 30 pN. Such satisfactory results demonstrate the novel advantages of the present method.     

The effect of metallic cations on the electrophoretic properties of a pretreatedHevea latex

High-ammonia latex concentrate prepared from doubly-centrifuged fieldHevea latex was exhaustively dialysed to remove any residual water-soluble non-rubber constituents. The electrophoretic mobilities of the dialysed latex in the presence of various metallic cations were investigated as a function of electrolyte concentration. The mobility decreased with increasing concentration of the cations Na⁺, Ba²⁺, Mg²⁺ and Ca²⁺ in a manner consistent with the effect of simple electrolyte on compression of the electric double layer. Anomalous behaviour was noted for the divalent ion copper, in that it reversed the charge of the latex particles at a concentration even lower than that of uranyl ions. Multivalent cations (lanthanum, cerium and thorium) had a profound influence on the latex particles where very low charge reversal concentrations were observed. It is believed that strong adsorption of hydrolysed species from the metallic ions was responsible for reversing the charge of the originally negative latex particles. These experiments indicated that the efficiency with which the cations reversed the charge of the latex particle surface was in the order: lanthanum > cerium > copper > thorium > uranyl > calcium > magnesium > barium > sodium. The number of cation binding sites on the latex particle surface and the chemical free energies of cation adsorption were calculated. It was found that the interaction of the latex particle with the hydrolysable metallic cations was much more stronger than that with the simple divalent cations and that this intercation was comparable to that of biological surfaces.     

SANS and SAXS analysis of charged nanoparticle adsorption at oil-water interfaces

A systematic study of the adsorption of charged nanoparticles at dispersed oil-in-water emulsion interfaces is presented. The interaction potentials for negatively charged hexadecane droplets with anionic polystyrene latex particles or cationic gold particles are calculated using DLVO theory. Calculations demonstrate that increased ionic strength decreases the decay length of the electrostatic repulsion leading to enhanced particle adsorption. For the case of anionic PS latex particles, the energy barrier for particle adsorption is also reduced when the surface charge is neutralized through changes in pH. Complementary small-angle scattering experiments show that the highest particle adsorption for PS latex occurs at moderate ionic strength and low pH. For cationic gold particles, simple DLVO calculations also explain scattering results showing that the highest particle adsorption occurs at neutral pH due to the electrostatic attraction between oppositely charged surfaces. This work demonstrates that surface charges of particles and oil droplets are critical parameters to consider when engineering particle-stabilized emulsions.     

Controlling deposition and release of polyol-stabilized latex on boronic acid-derivatized cellulose

Poly(glycerol monomethacrylate)-stabilized polystyrene (PGMA-PS) latex particles undergo specific, pH-dependent adsorption onto regenerated cellulose film bearing surface phenylboronic acid groups (cellulose-PBA). Deposition occurs at pH 10 and is driven by the boronate ester formation with the polyol latex surface coating. In contrast, no deposition occurs at pH 4, and previously deposited particles can be readily desorbed at this lower pH. In control experiments, conventional anionic sulfate-stabilized polystyrene latex did not deposit onto the hydrophilic cellulose surface. The distribution of boronate groups in the cellulose was determined by exposure to Alizarin Red S dye, which forms a fluorescent complex with phenylboronic acid; confocal microscopy was used to determine a surface density of 3 nm(2) per boronic acid group on the cellulose surface. Although the boronic acid binding constant with PGMA is relatively low (5.4 L/mol), the cooperative interactions between multiple PBA surface sites and the many PGMA chains per latex particle are sufficient to induce specific latex adsorption, providing a convenient new tool for controlling nanoparticle deposition on surfaces.     

Preparation and characterization of biotinylated and enzyme‐immobilized heterobifunctional latex particles as nanobio devices

A novel biotinylated and enzyme‐immobilized nanobio device was prepared with heterobifunctional composite latex particles. Hemispherical poly(glycidyl methacrylate‐co‐divinylbenzene)/polystyrene [P(GMA‐DVB)/PSt] particles with epoxy and hydroxyl groups were prepared by soap‐free seeded emulsion polymerization with P(GMA‐DVB) seed particles. Hydroxyl groups were introduced to PSt chain terminals in the seeded stage by adding 2‐mercaptoethanol as a chain‐transfer agent. To obtain the desired hemispherical structure particles, we studied the effects of the preswelling process, the type and amount of solvents added in the seeded polymerization step, the weight ratio of the secondary monomer (styrene) to the seed particle (M/P), and the type of initiators. Under suitable conditions, heterobifunctional P(GMA‐DVB)/PSt was obtained, which was confirmed by observing the binding of streptavidin–colloidal gold with transmission electron microscopy (TEM). To obtain biotinylated and enzyme‐immobilized particles, 5‐(N‐succinimidyloxycarbonyl)pentyl D‐biotinamide was first reacted with the hydroxyl group on the PSt domain of the particle. Pyruvate kinase (PK) was then directly immobilized to the biotinylated particles through a reaction with the epoxy group in the PGMA domain. The monolayer of PK on the latex particle surface was considered to be formed by covalent binding. The activity of immobilized PK was almost conserved, even after being stored at 4 °C for 48 days. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 562–574, 2005     

Crosslinking network structure governing particle shape and size distribution by one-step emulsion polymerization in the presence of particle coagulation

In this study, sub-200?nm, crosslinked latex particles with a narrow particle size distribution were prepared by one-step emulsion polymerization in the presence of particle coagulation. The relationship between the particle shape and particle coagulation was investigated by varying the time of crosslinking network structure formation and particle coagulation. Particles with irregular shapes such as doublet, triplet, and ellipsoid were obtained using divinylbenzene (DVB) and ethylene glycol dimethacrylate (EGDMA) as the crosslinking agents, because the crosslinking network structure of particles was formed before the particle coagulation. In contrast, latex particles with a uniform spherical shape were also prepared using triallyl isocyanurate (TAIC) or dihydrodicyclopentadienyl acrylate (DCPA) as the crosslinking agents by delaying the time of crosslinking network structure formation. Alternatively, uniform spherical latex particles were prepared by bringing forward the particle coagulation time using cationic initiator, 2, 2′-azobis (2-methylpropionamidine) dihydrochloride (AAPH). This study presents a new idea that would further broaden the application of particle coagulation in emulsion polymerization.     

Composite natural rubber–polychloroprene latex particles produced by the heterocoagulation technique

Composite natural rubber (NR) based latex particles were prepared using the heterocoagulation technique. A nonionic surfactant (Tween 80) whose molecules bear poly(ethylene oxide) (PEO) was adsorbed on polychloroprene (CR) latex particles and allowed to form complexes between PEO and indigenous surfactant (protein–lipid) on the NR particle surface. The heterocoagulated NR/CR–Tween particles produced were characterised by particle size, zeta-potential and glass-transition temperature measurements and the data indicated the presence of CR–Tween on the outer layer of the composite polymer particles. The results agreed well with the better oil resistance of films cast from heterocoagulated latex when compared with that of the NR film. Received: 22 August 2000 Accepted: 8 January 2001     

Porous latex composite membranes: fabrication and properties

A new class of microfiltration (MF) and ultrafiltration (UF) membranes has been developed. By placing latex particles onto the surface of a microporous substrate and stabilizing the porous array, voids are formed between the particles which provide narrowly distributed pores that serve as separation channels. The size of the interstitial voids in the array is governed by the diameter of the latex particle. This aqueous based technology has advantages relative to other membrane fabrication processes in terms of the high asymmetry of the membranes, the facile adjustment of pore sizes, and the ability to easily modify pore surfaces during the synthesis of particles.A number of approaches were examined for placement of particles and stabilization of latex composite membranes (LCMs). Filtration of particles with reactive surface groups that provide covalent linkages at the contact points in the particle array proved most effective in obtaining stable membranes. These membranes had narrow size distributions in both the UF and MF range and were capable of being cleaned and backflushed. The membranes were characterized in terms of gas permeabilities, pure water permeabilities and electron microscopy. The rejection properties of LCMs were also examined during filtration of monodispersed latex particles and a broadly dispersed dextran mixture.     

Effect of pressure on electrophoretic mobility of polystyrene latex particles

A capillary electrophoresis system that can apply arbitrary helium gas pressures at both inlet and outlet reservoirs was constructed. The system was used to investigate the effect of pressure on electrophoretic behavior of polystyrene latex particles. The electrophoretic mobility of latex particles was increased with the application of pressure (< 3.0 kgf/cm2). The shrinkage of particle diameter under pressurization was observed using a microscope, however, the magnitude of shrinkage was not enough to explain the increase in electrophoretic mobility. Therefore, the application of pressure might increase the electric charge of the latex particle. Since methanol inhibited the enhancement in the electrophoretic mobility of the latex particles, water might play an important role in increasing mobility.