RAPID METHODS FOR DETECTION OF AFLATOXIN M-1 BASED ON ELECTROCHEMICALTRANSDUCTION BY SELF-ASSEMBLED METAL-SUPPORTED BILAYER-LIPID MEMBRANES (S-BLMS) AND ON INTERFERENCES WITH TRANSDUCTION OF DNA HYBRIDIZATION

This work explores the interactions of Aflatoxin M-1 with self-assembl ed metal-supported bilayer lipid membranes (s-BLMs) and its effects on DNA hybridization. Alterations of electrochemical signals due to DNA hybridization can be used for rapid detection of this toxin. The inter actions of Aflatoxin M-1 with s-BLMs composed of egg phosphatidylcholi ne produced ion current increases which reproducibly appeared within c a. 8-10 s after exposure of the lipid membranes to the toxin when usin g a stirred solution. The magnitudes of the current signals were relat ed to the toxin concentration, which could be determined within the ra nge of 1.9-20.9 nM. In another series of experiments, Aflatoxin M-1 wa s found to affect the kinetics and time of signal generation due to DN A hybridization, which was electrochemically monitored by using s-BLMs , The ''receptor'' oligomer was single stranded deoxyribonucleic acid (ssDNA) thymidylic acid icosanucleotide terminated with a C-16 alkyl c hain to assist incorporation into s-BLMs (dT(20)-C-16). The target oli gomer was deoxyadenylic acid icosanucleotide (dA(20)) dT(20)-C-16 was incorporated into s-BLMs and complementary dA(20) (cDNA) was injected into the stirred bulk electrolyte solution. The electrochemical ion cu rrent across s-BLMs was found to increase due to the presence of ssDNA and decrease due to the formation of double stranded DNA (dsDNA), The toxin reduced the initial rate of signal change and increased the tim e to reach equilibrium. This provided a means for the rapid (less than 1 min) and sensitive (detection limit 0.5 nM) detection of Aflatoxin M-1 based on measurements of the initial rate of hybridization, (C) 19 98 Elsevier Science Ltd. All rights reserved.