Immunoassay Using Ion Selective Electrode and Protein Pendant Liposomes

Abstract

Immunoassay for an anti-human IgG antibody and a human IgG is presented. Thin-layer potentiometry, i.e., a combination of fluoride ion selective electrode and silver chloride coated silver-plate reference electrode was used to monitor fluoride release from the multilamellar liposome. Human IgG was attached to the surface of liposome membrane by the use of cross-linking reagent N-hydroxysuccinimidyl3-(2-pyridyldithio)propionate (SPDP). The antigen/antibody/complement reaction triggered the formation of "channel-like" holes across the liposome membrane which enabled entrapped fluoride anion flow through the hole. The fluoride ion release was specific for anti-human IgG and depended on the presence of complement. By the use of human IgG pendant liposomes, determination of about 10^-14mol of anti-human IgG (rabbit) and 10^-14mol human IgG was feasible.