Mechanism of Electrochemical Detection of DNA Hybridization by Bilayer Lipid Membranes

Abstract

Recent reports have suggested that bilayer lipid membranes (BLMs) and stabilized self-assembled bilayer lipid membranes (s-BLMs) can detect DNA hybridization, but have not explained the actual mechanism of signal generation. The electrochemical experiments have demonstrated that hybridization of complementary single-stranded DNA (ssDNA) 20mers, where one sequence is terminated by a C16 alkyl chain to assist incorporation into the lipid membrane, can cause reduction of ion current through membranes. The present work has explored egg-phosphatidylcholine monolayers at the air–water interface as a model of BLMs, and has investigated the effect of DNA on pressure–area relationships, electrostatic fields as measured using a noncontacting electrostatic voltmeter, and fluorescence microscopy of membranes that were loaded with fluorescein labelled DNA. Each of these experiments confirms that ssDNA partitions onto and changes the structural and electrostatic properties of lipid monolayers. On hybridization the DNA desorbs from the surface of the lipid membrane, causing a substantial alteration of surface properties.