Absorption-enhanced solid-phase immunoassay method via water-swellable poly(acrylamide) microparticles.
Water-swellable hydrogel microspheres based on cross-linked polyacrylamide were used as solid supports in immunoassay formats. Capture antibody was covalently bound at the surfaces and the pore size of particles was such that these antibodies were excluded from the interiors. Upon contact with a solution containing immunological reactants, water molecules quickly penetrated the microspheres, causing them to swell, thereby concentrating analyte at the surface. Using swellable particles, the antigen capture rate during the first 5 min of incubation with antigen was two times that of antibody-coated 0.79 cm polystyrene beads. In addition, antibodies attached to lightly cross-linked swellable microparticles proved resistant to inactivation by ultrasonic energy, which can be used to accelerate immunological interactions.