PS latex beads

Another interesting example of well-structured 3D ECPs is provided by Bartlett et al., who used PS latex beads as colloidal templates to electrosynthesize highly ordered macroporous PPy, PANI, and poly(bithiophene) [304]. 

Early work in this field for fiow cytometric applications was suggested by Mack Fulwyler. Seminal publications were followed by the work of Thomas Russell and coworkers, which gave rise to a series of patents describing the use of adsorbed antibodies on PS latex beads in bead assays for subpopulations of WBCs. 

Fig. 1 Wright s stain smears (air dried and mounted) of EDTA stabilized whole blood mixed with CD4 antibody-conjugated PS latex beads of 2.13 im diameter...

Fig. 2 Median angle light scatter (DF8) versus Coulter volume histograms for whole blood mixed with various sizes (2.13, 2.40, 3.20, and 4.00pm diameter left to right, top to bottom) of CD3 antibody-conjugated PS latex beads...

The flow cytometric investigation of cells in whole blood with soluble, fluorescent antibodies and native, unlabeled antibodies in competitive binding has in one instance led to the conception of a new generalized immunoassay that can be done with analyte bound to the surface of formed bodies and unknown amount of analyte in solution. The formed bodies could be biological cells or colloidal particles such as PS latex beads. It was first demonstrated for CD 16 antigen on neutrophils and soluble CD16 in whole blood. ... 

The first field of application for SdFFF were latex beads, which were used either to test the channels or to produce separation results alternative to other separation techniques. PS nanoparticles used as model surfaces for bioanalytical work have been analyzed by SdFFF [39]. The appealing feature of SdFFF is its ability to characterize particle adlayers—by direct determination of the mass increase performed by observing the differences in retention between the bare and coated particles—with high precision and few error sources the mass of the coating is determined advantageously on a per particle basis. 

Polystyrene beads (PS) are employed as physical templates for macropore. The emulsifier-tee emulsion polymerization method used here allows for the synthesise of nearly monodisperse latex beads of PS in the size of ca. 100 nm [10]. PS beads were prepared using 700 ml degassed water, 54 ml styrene monomer, 0.65 g potassium persulhite as initiator, and 20 ml divinylbenzene as cross-linkmg agent. PS beads were obtained at 70°C and 350 rpm, and dried under ambient condition. Aluminum fec-butoxide and stearic acid were separately dissolved in parent alcohol,. rec-butyl alcohol, at room tempature, and then the two solutions were mixed. Appropriate amount of HNO solution was dropped into the mixture at a rate of I ml/min to acidify and hydrolyze the aluminum precursor. PS beads were added into aluminum hydroxide solution after stirring for 10 h. The final pH of the reactant was approximately 7. Organic templates, both stearic acid and PS bead, were easily removed tern dried aluminum hydroxide by calcination. The overall synthetic procedure is as shown in Fig. 1. 

Formation of Steady-State Density Gradient in TLF Experiments. The formation of the density gradient by the effect of electric field on Percoll was evidenced by the appearance of distinct focused zones of density marker beads in TLF cell (13). A similar experiment was performed by using PS latex standard particles suspended in Percoll. Narrow steady-state focused zone was formed, thus indicating that focusing FFF of these particles should appear in the separation channel as well. 

Fig. 1 Fractograms of the polystyrene latex beads of 0.357 pm (PSl) obtained by the direct injection of 1 pi of PS 1 (a) and by the concentration procedure of the PS 1 sample diluted in 10 ml of the carrier solution (b) using the conventional SdFET technique, as well as of the a-Fe2Q3 sample with nominal particle diameter of 0.271 pm diluted in 6 ml of the carrier solution obtained by the PBSdFFF concentration methodology (Ic).

Latex cation exchangers were introduced by Dionex Corp. 10 years later than latex-agglomerated anion exchangers. These types of cation exchangers consist of a weakly sulfonated PS-DVB substrate with latex beads with a very small diameter agglomerated on its surface by both electrostatic and van der Waals interactions. 

Syntheses of different types of latex particles by emulsion polymerization that differ in particle size, polymer hydrophificity, and surface coverage with functional groups were presented by Paulke et al. [51 ]. The particles were equipped with intensive fluorescence. Concentrated particle suspensions were injected into the brain tissue of mice and the effect of two kinds of beads is shown in brain sections. The same research group [52] presented a very different work on electrophoretic three-dimensional (3D)-mobility profiles of latex particles with different surface groups. In particular, hydroxyl functions were studied in different surroundings. The latexes gave model colloids with different electrophoretic behavior in comparison with classical anionic monodisperse PS latex particles. 

A further class of ion exchange materials have been developed [85] which employ a highly sulphonated impervious core formed from an extensively cross-linked styrene-divinylbenzene (PS DVB) polymer which has a particle diameter of some 10-25 pm. For anion exchangers these beads are then layered with completely aminated latex particles (Figure 6.42). 

A special type of peculiar anion exchanger was first introduced in 1975. These stationary phases, which are called latex-based anion exchangers, have been further developed by Dionex.They comprise a surface-sulfonated PS-DVB substrate with particle diameters between 5 and 25 p,m and are fuUy aminated, high-capacity, porous polymer beads made of poly(vinylben-zyl chloride) or polymethacrylate, which are called latex... 

A similar technique was used for the preparation of polystyrene (PS)-Si02 nanohybrids, where colloidal silica solutions were mixed with PS solutions by means of ultrasonic homogenization [60]. Also, latex-silica nanohybrid films were synthesized upon mixing aqueous colloidal suspensions of silica and nanolatex polymer beads [61-63], Other silica-based nanohybrid systems with poly(ethylene oxide) (PEO) [64, 65], polyfvinyl alcohol) (PVA) [66], PS [67], polybutylacrylate [68], or PMMA [69] can be prepared by using the same suspension blending method. 

Anion-exchange stationary phases described in Section 3.4.1.4 are based on colloidal anion-exchange particles (the so-called nanobeads or latex particles) that are electrostatically bound to the surface of nonporous surface-sulfonated or sur-face-carboxylated PS/DVB and EVB/DVB copolymer beads. This approach to stationary-phase design provides a number of advantages including the following ... 

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