DIRECT ELECTROCHEMICAL TRANSDUCTION OF AN IMMUNOLOGICAL REACTION BY BILAYER-LIPID MEMBRANES

This work reports the electrochemical transduction of an immunological interaction by use of bilayer lipid membranes (BLMs) which were prepared from mixtures of egg phosphatidylcholine (PC) and dipalmitoyl phosphatidic acid (DPPA). Thyroxin (T4)/anti-rabbit T4 was used as a representative immunological reaction for these studies. Antibody-antigen complexation caused transient ion current signals due to dynamic changes of the electrostatic fields at the surface of such membranes. The mechanism of signal generation is based on the perturbation of the electrical double layer and surface structure of the BLMs. The transient charging signals occurred as singular or multiple events which lasted for a period on the order of seconds. The magnitude of these transient ion current signals was directly related to the concentration of the antigen in bulk solution, which could be determined over a range of nM to mM levels in a period of seconds to minutes. Investigation of the effects of lipid composition of BLMs, pH and the presence of Ca2+ in bulk electrolyte solution indicated that the response could be optimized for sensitivity and speed.