ANOMALOUS COLLOIDAL STABILITY OF LATEX-PROTEIN SYSTEMS

An experimental study on the colloidal stability of latex-F(ab')(2) an d latex-IgG systems is described. The stability domains were obtained using a low-angle scattering technique to measure the rates of aggrega te formation and plotting the stability ratio as a function of electro lyte concentration. The protein-coated particles present an anomalous stability at high ionic strength when the classical theory predicts ag gregation. This observed deviation from DLVO behavior appears for elec trolyte concentrations above some critical bulk concentration called c ritical stabilization concentration (csc). As we have suggested in pre vious publications, the existence of an additional short-range repulsi ve ''hydration force'' can explain this anomalous stability. In order to resolve more fully if this anomalous stability at high ionic streng th is due to the hydration forces, the effects of pH, cation and anion type, temperature, and polyethylene glycol (a dehydrating polymer) on the experimental stability are investigated. Finally, the immunoreact ivity of an anti-CRP F(ab')(2)-latex conjugate is studied in reaction buffers with high ionic strength. (C) 1998 Academic Press.