BILAYER-LIPID MEMBRANES AS ELECTROCHEMICAL DETECTORS FOR FLOW INJECTION IMMUNOANALYSIS

This work describes the use of filter-supported stabilized bilayer lip id membranes (BLMs) for the rapid electrochemical monitoring of an imm unological reaction in flowing solution streams. BLMs were prepared fr om egg phosphatidylcholine (egg PC) and dipalmitoyl phosphatidic acid (DPPA) and the ultrafiltration membranes used were composed of glass m icrofibers. Thyroxin (TL)/anti-rabbit T4 was used as a representative immunological reaction for these studies. Antibody was incorporated in to a floating lipid matrix at an air-electrolyte interface, and then a casting procedure was used to deliver the Lipid onto the filter suppo rts for BLM formation. Injections of antigen were made into flowing st reams of a carrier electrolyte solution. Experiments were done in a st opped-flow mode using lipid mixtures containing 15% (w/w) DPPA to prov ide only a single transient current signal with a magnitude related to the antigen concentration. Differential scanning calorimetric experim ents provided evidence that the antibody-lipid interactions at the BLM s occurred through electrostatic interactions. BLMs containing 35% DPP A were used to examine regeneration of the active sites of antibody af ter complex formation by washing with the carrier electrolyte solution . Repetitive cycles of injection of antigen followed by regeneration o f antibody binding activity have shown that the maximum number of cycl es is about 5, followed by a degradation of signal for a larger number of injections. However, the sensor can also be easily regenerated by recasting of the existing lipid/antibody film at the air-electrolyte i nterface to form fresh BLMs.