Electroimmunoassay. A new competitive protein-binding assay using antibody-sensitive electrodes

A novel technique is reported in which an antibody-sensitive electrode for anti-prostaglandin E2 antisera was used to measure solution-phase PGE2 in nanomolar quantities. The electrode was constructed by incorporating a cation-selective ionophore-hapten (PGE2) conjugate into a polyvinyl chloride membrane. Transmembrane potential in a fixed potassium gradient was measured. The addition of anti-PGE2 antisera changed membrane potential in a concentration-dependent manner. The effect of anti-PGE2 antibodies on membrane potential was decreased by adding free PGE2 to the buffer-containing antisera. With this technique a competitive protein-binding assay was developed, and standard curves for solution-phase PGE2 were generated over a concentration range of 1 to 1,000 nM. The assay was relatively specific for PGE2; PGD2 and PGF2a had only minor effects on transmembrane potential over the effective concentration range for PGE2