Electrochemical transduction of interactions of atrazine with bilayer lipid membranes

This work investigates the interactions of atrazine with bilayer lipid membranes (BLMs) that can be used for the direct electrochemical sensing of this herbicide. Egg phosphatidylcholine (PC) and dipalmitoylphosphatidic acid (DPPA) were used for the formation of solventless BLMs. The interactions of atrazine with these membranes were found to be electrochemically transduced by BLMs in the form of a transient current signal with a duration of seconds, which reproducibly appeared within 1 min after exposure of the membranes to atrazine. 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 calcium ions in bulk solution. The mechanism of signal generation was related to the adsorption of atrazine with a consequent rapid reorganization of the membrane electrostatics due to atrazine aggregation at the surface of BLMs. Hydro en bonding between atrazine and the carbonyl group of the lipid was explored by addition of platelet-activating factor (PAF; an ether analog of PC) in BLMs composed of PC. Differential scanning calorimetry of vesicles composed of 15% DPPA was used to study the aggregation of atrazine in membrane domains enriched in the charged lipid. The magnitude of the transient current signal was linearly related to the concentration of atrazine in bulk solution with sub-micromolar detection limits. This electrochemical transduction of atrazine interactions with BLMs holds prospects for flow injection monitoring of triazine herbicides.