Electrochemical investigation of interactions of bilayer lipid membranes (BLMs) with incorporated resorcin[4]arene receptor with ephedrine for the development of a stabilized lipid film biosensor for ephedrine

Abstract

This work explores the electrochemical investigation of interactions of ephedrine with bilayer lipid membranes (BLMs) in which a resorcin[4]arene receptor or ssDNA were incorporated that can be used for the rapid electrochemical detection of ephedrine. BLMs were composed of egg phosphatidylcholine (PC) and 35% (w/w) dipalmitoyl phosphatidic acid in which the receptor was incorporated or by PC and ssDNA in BLMs without the receptor. The interactions of ephedrine with self-assembled lipid membranes were investigated. These interactions have provided current increases or ion channel events depending on the composition of the lipid film. A comparison of signals between those obtained with self-assembled lipid films with incorporated resorcin[4]arene receptor and DNA was made herein. The use resorcin[4]arene receptor has provided ion current increases which were more sensitive than those in its absence or using BLMs with incorporated DNA. The linear also concentration range was increased in the presence of the resorcin[4]arene receptor. The response times in the presence of the resorcin[4]arene receptor was found to be smaller than those of BLMs without receptor or in the presence of DNA. Freely suspended BLMs with incorporated receptor were used to develop a rapid detection biosensing technique for ephedrine. The interactions of this compound with freely suspended lipid membranes were found to be electrochemically transduced in the form of a transient current signal with duration of seconds, which reproducibly appeared within 20 s after exposure of the membranes to ephedrine. The magnitude of the transient current signal was related to the concentration of the stimulating agent in bulk solution in the micromolar range. No interferences from ascorbic acid were noticed, because of the use of the negatively charged lipids in membranes. A large number of other compounds were also investigated as interferences. Stabilized after storage in air lipid membranes (i.e. the lipid film is formed by polymerisation on supports of glass fiber microfilters) were investigated as practical chemical biosensors for the rapid detection of ephedrine, which will allow further commercialization of these devices. Methacrylic acid was the functional monomer, ethylene glycol dimethacrylate was the crosslinker and 2,2′-azobis-(2-methylpropionitrile) was the initiator, whereas the lipid and the receptor were enclosed within the polymer. The interactions of these polymerized lipid films with ephedrine were also found to provide transient current signals with duration of seconds, which reproducibly appeared after about 1.5 min after exposure of the films to ephedrine. The magnitude of the transient current signal was also related to the concentration of the stimulating agent in bulk solution in the micromolar range and these stabilized lipid films can used again after storage in air. The present technique can be used as a practical sensor for the rapid detection of ephedrine and keep prospects for its determination in biofluids of athletes.