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 prepa red from mixtures of egg phosphatidylcholine (PC) and dipalmitoyl phos phatidic acid (DPPA). Thyroxin (T4)/anti-rabbit T4 was used as a repre sentative immunological reaction for these studies. Antibody-antigen c omplexation caused transient ion current signals due to dynamic change s of the electrostatic fields at the surface of such membranes. The me chanism of signal generation is based on the perturbation of the elect rical double layer and surface structure of the BLMs. The transient ch arging signals occurred as singular or multiple events which lasted fo r a period on the order of seconds. The magnitude of these transient i on current signals was directly related to the concentration of the an tigen in bulk solution, which could be determined over a range of nM t o mM levels in a period of seconds to minutes. Investigation of the ef fects of lipid composition of BLMs, pH and the presence of Ca2+ in bul k electrolyte solution indicated that the response could be optimized for sensitivity and speed.