Laurie Locascio-Brown

Liposome Behavior in Capillary Electrophoresis

The behavior of liposomes in capillary electrophoresis is studied for the purpose of developing a potential method for characterizing liposomes prepared for use in industrial and analytical applications. This study characterizes the electrophoretic behavior of liposomes under various conditions to provide information about electrophoretic mobility and liposome-capillary surface interactions. The results of this method are compared with the results obtained using traditional laser light-scattering methods to obtain size information about liposome preparations. Additionally, reactions of liposomes and the surfactant n-octyl-β-d-glucopyranoside are performed off-line in bulk solution experiments and on-line in the capillary. Automated delivery of lysis agents by multiple electrokinetic injections is demonstrated as a general method for inducing on-capillary reactions between liposomes and other reagents. Furthermore, some preliminary evidence on the use of liposomes as a hydrophobic partitioning medium for analytical separations is presented.

Measuring estrogens using flow injection immunoanalysis with liposome amplification

A solid-phase competitive immunoassay is performed in flow injection analysis for the measurement of the hormone 17-beta-estradiol. The flow injection analysis system incorporates a column-type reactor packed with solid silica particles onto which we have covalently immobilized the antigen 17-beta-estradiol. Anti-estradiol is noncovalently conjugated to the liposome through a streptavidin-biotin linkage. When mixed with a sample containing the antigen, the antibody binding sites on the liposomes are complexed which reduces the binding of liposomes to the solid support in a concentration-dependent manner. Sequential immunoassays are performed on-column following a simple regeneration step.

Radiometric and fluorimetric determination of aminosilanes and protein covalently bound to thermally pretreated glass substrates

Abstract Derivatization of solid soda-lime glass spheres with aminosilanes and the stability of these groups near physiological pH in flow streams of aqueous buffered solutions are described. The presence of immobilized and adsorbed amines in the nanomolar range is confirmed by using two independent methods, one based on a radiotracer and the other on the fluorescent marker, fluorescamine. A method for covalently attaching bovine serum albumin to the beads is described.

Flow Immunoassay Using Solid-Phase Entrapment

A flow injection immunoassay was performed using a column packed with reversed-phase sorbents to effect separation of the immunoreacted species by entrapping free analyte and allowing antibody-conjugated analyte to pass unretained. Fluorescein-labeled analyte was measured in a competitive assay for the anticonvulsant drug phenytoin. The simplicity of the assay was the greatest advantage of the technique, which allowed for measurement of phenytoin in a 2-min assay time. The reliable detection limit for the assay was 5 nmol L(-)(1) of phenytoin in serum. The columns were regenerated with periodic injections of ethanol solutions to remove the entrapped analyte and prepare the column for subsequent analyses.

Thermal detection of enzyme-labelled antigen-antibody complexes using fiber-optic interferometry

Abstract A fiber-optic interferometer is described for measuring the heat produced in an enzymatic reaction that is localized on the surface of the sensing fiber in a two-arm interferometer. Reactants are introduced to the sensing arm of the interferometer using a flow injection analysis system, while the reference arm is isolated in a separate compartment. Solution concentrations of hydrogen peroxide are quantified using the enzyme catalase immobilized to the sensing fiber. Catalase is also used as a detectable label in a solid-phase thermal immunosensing scheme. These initial results are presented, as well as a discussion of the potential advantages of using a sensor for thermal immunoassays.