Colloidal stability of IgG- and IgY-coated latex microspheres.

The stabilization of antibody-latex complexes at high salt concentration is an event that cannot be explained by the widespread DLVO theory. Adsorption of antibodies on polystyrene latex usually leads to a loss in colloidal stability. However, after the expected particle aggregation induced by an increase in ionic strength, an 'anomalous' restabilization occurs when the electrolyte concentration increases even more. This non-DLVO behaviour can be explained taking into account the hydration forces, which become significant in hydrophilic surfaces. This restabilization has already been observed in different protein latex complexes. In the present work, a study on the stability patterns of polystyrene particles covered independently by mammalian and chicken antibodies has been performed. This study reveals that avian antibodies present a more hydrophobic surface than that of mammalian antibodies. In addition, it has been possible to obtain some information about the molecular orientation of the adsorbed antibodies from the stability experiments. This information has been corroborated by an immunoreactivity study.