A triazine herbicide minisensor based on surface-stabilized bilayer lipid membranes

This work describes an electrochemical technique that is suitable for rapid and sensitive screening of the triazine herbicides simazine, atrazine, and propazine. Egg phosphatidylcholine and dipalmitoylphosphatidic acid (DPPA) were used for the formation of self-assembled bilayer lipid membranes supported on silver wire (s-BLMs). Evidence that BLMs could form on silver wires was collected by means of ellipsometry which was done to investigate samples consisting of lipids deposited on planar reflective silver films. The interactions of triazines with s-BLMs produced electrochemical ion current increases which reproducibly appeared within ∼10 s after exposure of the lipid membranes to the herbicides. The sensitivity of the response was maximized by use of BLMs composed of 35% (w/w) DPPA and by alteration of the phase distribution within membranes by the introduction of 1.0 mM calcium ions in bulk solution. The mechanism of signal generation could be a result of rapid adsorption of the triazine on the surface of s-BLMs with a consequent rapid reorganization of the electrostatics of the membrane. The magnitude of the current signal was linearly related to the herbicide concentration, which could be determined at the nanomolar level. The present triazine minisensor exhibited good mechanical stability and longevity (routinely over 48 h), reproducible response characteristics (i.e., sensitivity and response to a given concentration of triazine in solution), fast response times, and low detection limits. The sensor can be simply and reliably fabricated at low cost. Studies have shown high selectivity for triazines in the presence of insecticides and pesticides.