Studies on microcapsules to replace erythrocytes in the passive agglutination reaction

Two kinds of microcapsules were made from polyurethane and polyurea. Each capsule had a mean diameter of 6 microns, a specific gravity of 1.10, and was red in color. The capsules were coated with ovalbumin condensed with glutaraldehyde. The coated capsules were agglutinated with anti-ovalbumin antibody. The polyurethane capsule (positive charge) bound more ovalbumin and showed a higher sensitivity than did the polyurea capsule (negative charge) or erythrocytes.