Electrochemical impedance spectroscopy study of liposome adsorption and rupture on self-assembled monolayer: Effect of surface charge

Abstract We report here that the selection of the electrode surface charge is very crucial in evaluating the adsorption of liposomes and their ruptures by means of electrochemical impedance spectroscopy (EIS). We prepared three types of electrodes whose surface characteristics were controlled by self-assembled monolayers (SAMs). The chemicals for SAM contained the same straight-chain alkanes with thiol groups at one end to bind with the Au electrode surface. The head groups were CH3 for 1-dodecanethiol (DDT), CH2OH for 11-mercapto-1-undecanol (MUD), and CH2NH2 for 11-amino-1-undecanthiol (11-AUT). The surface charges were neutral for DDT, negative for MUD, and positive for 11-AUT. Resulting from liposome adsorption and rupture, the Nyquist plots changed differently, depending on the surface charges. We concluded that the easiest and most sensitive surface to handle was obtained by 11-AUT SAM. The EIS measurements, obtained from the electrode containing 11-AUT SAM, successfully estimated the critical micelle concentration (CMC) of the surfactant, Triton X-100 through the observation of the liposome rupture process.