Sensitized Latex Particles for the Detection of Chagas Disease

GONZALEZ, VERÓNICA D.G.; GUGLIOTTA, LUIS M.; GIACOMELLI, CARGA E.; MEIRA, GREGORIO R.

Foz de Iguazu, Paraná

Conferencia; 11th International Conference on Surface and Colloids Science; 2003

International Association of Colloid and Interface Scientists

The aim of this study is to prepare polymer latex particles sensitized with an antigen (Ag 36) that specifically recognizes antibodies in chagasic serum. These particles are designed to be used in agglutination immunoassays to detect Chagas disease. Two sequential reactions were used for the synthesis of core-shell carboxylated latexes. First, an emulsifier-free batch emulsion polymerization was carried out to produce a monodisperse polystyrene latex (the PS core). Then, the PS latex was utilized in the seeded emulsion copolymerization of styrene and methacrylic acid, where the particle shell was produced under batch or semibatch conditions, thus producing particles with two different surface charge density. A mathematical model was used to predict main reaction variables and design semibatch operation policies. The produced latexes were characterized determining: a) the particle diameters, by electron microscopy and dynamic light scattering (DLS) at single and multiple angles; b) the surface charge and carboxylic group density, by conductometric titration; c) the shell thickness and the hairy layer thickness by DLS; and d) the critical coagulation concentration, by a visual method and by DLS. In order to optimize the covalent coupling, both physical and chemical adsorption were first investigated with a model protein by varying the latex concentration, the carboxylic groups density, the initial protein concentration, and the pH. Afterwards, the latex particles were sensitized with the Ag 36 at the established conditions. Covalent attachment was performed using the carbodiimide method to activate the functional groups. Physical adsorption which is mainly driven by hydrophobic interactions, is also present when the activated particles are used. This non-specific adsorption was removed by using sodium dodecyl-sulfate (SDS).