Latex fluorescent

Protein adsorption has been studied with a variety of techniques such as ellipsome-try [107,108], ESCA [109], surface forces measurements [102], total internal reflection fluorescence (TIRE) [103,110], electron microscopy [111], and electrokinetic measurement of latex particles [112,113] and capillaries [114], The TIRE technique has recently been adapted to observe surface diffusion [106] and orientation [IIS] in adsorbed layers. These experiments point toward the significant influence of the protein-surface interaction on the adsorption characteristics [105,108,110]. A very important interaction is due to the hydrophobic interaction between parts of the protein and polymeric surfaces [18], although often electrostatic interactions are also influential [ 116]. Protein desorption can be affected by altering the pH [117] or by the introduction of a complexing agent [118]. 

The original polymeric latex particles still are widely used for separation and detection. Polymers provide a matrix that can be swollen for embedding other molecules in their core, such as organic dyes or fluorescent molecules. Even nanoparticle quantum dots can be incorporated into larger latex particles to form highly fluorescent composite microparticles. 

Our experiments are typically carried out at DNA concentrations of 20-50 /ig/ml with 1 ethidium per 300 bp, so that depolarization by excitation transfer is negligible.(18) The sample is excited with 575-nm light, and the fluorescence is detected at 630, 640, or 645 nm. Less than one fluorescent photon is detected for every 100 laser shots. The instrument response function e(t) is determined using 575-nm incident light scattered from a suspension of polystyrene latex spheres. 

A variety of particles have been utilized in flow cytometric phagocytosis assays, including latex microspheres (7,8,12), bacteria (10,13,16), zymosan (9,13), and baker s yeast (11). Most of these particles are commercially available as fluorescent reagents. However, microorganisms may also be directly fluoro-chrome-conjugated (see Notes 1 and 2). 

When selecting a particle for analysis, it is important to consider the effects of particle size on fluorescence histogram coefficient of variation (CV). Small particles of uniform size, such as 1 pm diameter latex spheres, exhibit a sharp, narrow histogram with a relatively small CV (Fig. lA). Spherical bacteria. 

Fig. 1. Fluorescence histogram profiles of singlet and doublet 0.92-pm latex particles (A), S. aureus Bioparticles (B), and Zymosan Bioparticles (C).

Fig. 3. Effects of photodetector settings on fluorescence histogram profiles of granulocytes exposed to opsonized 0.92- j,m latex particles. Photodetector settings that are too low (A) or too high (B) are compared with correctly adjusted photodetection (C).

Dunn, P. A. and Tyrer, H. W. (1981) Quantitation of neutrophil phagocytosis, using fluorescent latex beads. Correlation of microscopy and flow cytometry. J. Lab. Clin. Med. 98, 374-381. 

Illumina produces fiberoptic random bead arrays. Latex beads are encoded using different fluorescent dye mixtures that are either adsorbed into the particles or attached to the surfaces. Presynthesized oligonucleotides are attached to selected bead populations so that a single dye or dyerdye ratio identifies the attached oligonucleotide. Populations are mixed in bulk and then loaded onto the tips of a fiberoptic, one end of which has been acid etched to form microscopic nanowells. The nanowells are filled at random with the mixed bead population to create a BeadArray . Such bxmdles can... 

Another example of a delivery system based on microbubbles and ultrasound is the delivery of circulating microparticles (polymer latex beads) or fluorescent red blood cells outside of the capillaries into the surrounding tissues by the action of ultrasound on the co-injected Optison microbubbles [79]. Interestingly, polymer beads and red blood cells could be detected tens of micrometers away from the capillaries where the bubble destruction took place. This may imply that during rapid destruction of a microbubble in a very strong ultrasound field, adjacent microsphere beads in the bloodstream can be propelled deep into the surrounding tissues. 

The latexes were ion-exchanged with Dowex 50W(H+) resin and the Dowex 50W(H+)-Dowex 1 (0H ) mixed resin in combination with the Dowex 50W(Na" ")-Dowex 1 (0H ) resin, and the ion-exchanged samples were titrated conductometrically. The samples treated were the latex, the aqueous serum, the latex particles separated from the serum, and the latex particles swollen or dissolved in 80 20 dioxane-water mixture. The total oxygen content was determined by neutron activation and the total sulfur content by X-ray fluorescence. Material balances of acrylic or methacrylic acid found in the serum, on the particle surface, and inside the particle agreed with the amount added to within 5-10%. 

Medina, M.B. 2004. Development of a fluorescent latex immunoassay for detection of a spectinomycin antibiotic. J. Agric. Food Chem. 52 3231-3236. 

Several configurations for the sensor are possible. An especially viable alternative would seem to be the competitive displacement of fluorescent label. Since this is an equilibrium, fouling or contamination of the surface should not alter the absolute result. Krull et al (75) have reported the reproducible immobilisation of a stable phospholipid membrane containing fluorophore in this context. Concurrent fluorescence polarisation measurements can offer the possibility of multidimensional analysis (76) and are in any case experiencing a rejuvenation of interest as a highly selective technique, when the effective molecular weight of the antibody is increased relative to the antigen, by immobilisation on a latex or metal particle (77)... 

Newer immunodetection applications, and particularly the so-called microarrays, employ new fluorescent probes such as europium chelates (Scorilas et al., 2000), lanthanide oxide nanoparticles (Dosev et al., 2005 Nichkova et al., 2006), fluoro-phore loaded latex beads (Orth et al., 2003), dye-doped silica nanoparticles (Zhou and Zhou, 2004 Yao et al., 2006), and inorganic nanocrystals (Gerion et al., 2003 Geho et al., 2005). 

Fig. 13. NSOM fluorescence (left) and force (right) images of 50 nm fluorescent latex spheres in a thin film. The fluorescence image exhibits high resolution while the small spring constant of the probe allowed the force image to be taken in contact mode without damaging the NSOM aperture.

The introduction of a fluorescence dye into the latex particles enabled us to confirm that the association took place specifically between different kinds of latex particles. 

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