Selective electrochemical biosensors from state-switching of bilayer and monolayer lipid membranes by lectin-polysaccharide complexes

Abstract

Interaction of the lectin concanavalin A with the polysaccharide glycogen can provide rapid spontaneous transients of the surface potential at bilayer and monolayer lipid membranes. The selective binding process can cause large, rapid potassium ion current fluctuations across bilayer membranes in a manner that is periodic and reproducible. The frequency of these transient ion current signals was shown to be related to sub-nanomolar concentrations of the reactive agents in aqueous solution. The physical mechanism responsible for ion current modulation was investigated by fluorescence methods using lipid vesicles, by the thermal dependence of the potassium ion current across planar bilayers and by pressure-area and dipolar potential measurements of lipid monolayers at an air-water interface. The mechanism is primarily associated with physical perturbations of lipid membranes by lectin-polysaccharide aggregates, resulting in the formation of localised domains of variable electrostatic potential and conductivity.