Reduction in aggregation and energy transfer of quantum dots incorporated in polystyrene beads by kinetic entrapment due to cross-linking during polymerization.

We report the development of barcoded polystyrene microbeads, approximately 50 μm in diameter, which are encoded by incorporating multicolored semiconductor fluorescent nanocrystals (quantum dots or QDs) within the microbeads and using the emission spectrum of the embedded QDs as a spectral label. The polymer/nanocrystal bead composites are formed by polymerizing emulsified liquid droplets of styrene monomer and QDs suspended in an immiscible continuous phase (suspension polymerization). We focus specifically on the effect of divinylbenzene (DVB) added to cross-link the linearly growing styrene polymer chains and the effect of this cross-linking on the state of aggregation of the nanocrystals in the composite.

Understanding interactions between immunoassay excipient proteins and surfactants at air-aqueous interface.

Air-aqueous interfacial properties of four excipient proteins commonly used in immunoassay reagent formulations were studied with shear rheology and surface characterization methods. A Du Noüy ring geometry was utilized to quantify the elastic (G') and viscous (G″) shear moduli of protein interfacial networks and to probe the effect of several nonionic surfactants at various concentrations. Time sweep protocols of buffered protein solutions yielded G' in the range of 16 mN/m for bovine serum albumin (BSA), 6 mN/m for bovine gamma globulin (BGG), 7 mN/m for Mouse IgG, and 0.

Improvement and multicenter evaluation of the analytical performance of an automated chemiluminescent immunoassay for alpha fetoprotein.

Background: A new ARCHITECT® alpha fetoprotein (AFP) assay was developed to improve the linearity at the upper end of the calibration curve and to enhance other performance characteristics. In addition, this reformulation eliminated the possibility of falsely depressed samples at high AFP concentrations. The purpose of this study was to evaluate its analytical performance at multiple sites.

Spectral bar coding of polystyrene microbeads using multicolored quantum dots.

This paper focuses on encoding polystyrene microbeads, 10-100 microm in diameter, with a luminescent spectral bar code composed of mixtures of quantum dots (QDs) emitting at different wavelengths (colors). The QDs are encapsulated in the bead interior during the bead synthesis using a suspension polymerization, and the bar code is constructed by varying both the number of colors included in the bead and, for each color, the number of QDs of that color. Confocal laser scanning microscopy images of the beads demonstrate that the multicolored QDs are pushed together into inclusions within the bead interior.

Arraying of intact liposomes into chemically functionalized microwells.

Here, we describe a protocol to bind individual, intact phospholipid bilayer liposomes, which are on the order of 1 microm in diameter, in microwells etched in a regular array on a silicon oxide substrate. The diameter of the wells is on the order of the liposome diameter, so only one liposome is located in each well. The background of the silicon oxide surface is functionalized with a PEG oligomer using the contact printing of a PEG silane to present a surface that resists the adsorption of proteins, lipid material, and liposomes.