Development of a high sensitivity IgG-latex immunodetection system stabilized by hydration forces

We present the application of hydration forces to obtain high sensitivity I gG-latex immunosystems. To compare these with another standard system, a st udy is presented of IgG- and F(ab')(2)-latex conjugates in terms of colloid al stability and immunoreactivity. The stability domains have been examined using a low-angle light scattering technique (nephelometer). The protein-c oated particles present an anomalous stability at high ionic strength when the classical theory predicts aggregation, and this stabilization is attrib uted to hydration forces. Different electrolyte concentrations and counteri on valences have been tested to determine the most influential factors on t his stabilization mechanism. Long-term aggregation of the conjugates has al so been studied by measuring the aggregate size by photon correlation spect roscopy. To quantify the immunoresponse of the agglutination tests, aggrega tion in the presence of antigen is followed as a function of time with the nephelometer. The considerable increase in immunoresponse, together with th e decrease in possible perturbing side-reactions enhances the technical int erest of this method of stabilizing immunolatexes, (C) 1999 Society of Chem ical Industry.