IMMUNOLOGICAL AGGLUTINATION KINETICS OF LATEX-PARTICLES WITH COVALENTLY IMMOBILIZED ANTIGENS

Hen egg-white lysozyme (HEL), ovalbumin and bovine serum albumin (BSA) were covalently immobilized onto styrene/methacrylic acid [P(St/MAA)] copolymer latex particles by the carbodiimide method. The initial rates of the immunological agglutination of these particles initiated by the addition of antibodies were quantified by the absorbance changes at a wavelength of 680 nm. The sensitivity of the immunological agglutination of the particles with covalently immobilized antigens was higher than that with physically adsorbed ones. The immunological agglutination kinetics showed a similar tendency irrespective of antigen-antibody systems. That is, the initial agglutination rates (i) increased with increasing immobilized amount of antigens, (ii) were largest in the ionic strength range of 0.02 to 0.05 at pH 7 and (iii) decreased with increasing pH. These results indicate that the electrostatic interactions of particle-particle and particle-antibody are main factors which control the immunological agglutination. On the other hand, the sensitivity of the immunological agglutination increased with increasing molecular size of antigens.