AFM Studies of Solid-Supported Lipid Bilayers Formed at a Au(111) Electrode Surface Using Vesicle Fusion and a Combination of Langmuir−Blodgett and Langmuir−Schaefer Techniques

Abstract

Atomic force microscopy (AFM) has been used to characterize the formation of a phospholipid bilayer composed of 1,2-dimyristyl-sn-glycero-3-phosphocholine (DMPC) at a Au(111) electrode surface. The bilayer was formed by one of two methods: fusion of lamellar vesicles or by the combination of Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) deposition. Results indicate that phospholipid vesicles rapidly adsorb and fuse to form a film at the electrode surface. The resulting film undergoes a very slow structural transformation until a characteristic corrugated phase is formed. Force-distance curve measurements reveal that the thickness of the corrugated phase is consistent with the thickness of a bilayer lipid membrane. The formation of the corrugated phase may be explained by considering the elastic properties of the film and taking into account spontaneous curvature induced by the asymmetric environment of the bilayer, in which one side faces the gold substrate and the other side faces the solution. The effect of temperature and electrode potential on the stability of the corrugated phase has also been described.

Ubiquinone-10 in gold-immobilized lipid membrane structures acts as a sensor for acetylcholine and other tetraalkylammonium cations

“…The layer was formed upon liposome attachment to the gold surface. As will be shown in the results, this layer can consist either of an ILL or of a SLB, depending on the gold surface roughness and experimental conditions, in agreement with previous reports [26][27][28][29]. For the sake of simplicity, this layer will be termed "sensing layer", regardless of its structure.…”

“…However, it is important to notice that the gold surface of the QCM-D sensors is not as smooth as that employed in section 3.1. Previous reports have shown that liposome rupture and spreading does not occur on QCM-D gold sensors [28], leading to the formation of an ILL, in contrast to what is observed in atomically smooth gold surfaces [26,27,35]. EQCM-D measurements enabled following the formation of the sensing layer both by monitoring the changes in frequency and dissipation of the sensor crystal, as well as by the appearance of the UQ redox signal in CV.…”

Atomic Force Microscopy and Electrochemical Studies of Melittin Action on Lipid Bilayers Supported on Gold Electrodes

“…DMPC is broadly used for preparation of biomimetic membranes. It was chosen as a model system since the structure of gold supported bilayers of this particular lipid are very well characterized using photon polarization modulation infrared reflection absorption spectroscopy (PMIRRAS) [25,26], atomic force microscopy (AFM) [27], and neutron reflectivity (NR) [28]. Cholesterol is a common component of the membranes of eukaryotic cells [29].…”

Application of Polarization Modulation Infrared Reflection Absorption Spectrosocpy Under Electrochemical Control for Structural Studies of Biomimetic Assemblies

“…Vesicles spreading and combined Langmuir-Blodgett and Langmuir-Schaefer (LB-LS) transfer are predominantly used to fabricate lipid bilayers on electrode surfaces [8, 9, 31-34, 88, 118, 124]. Numerous electrochemical, in situ PM IRRAS and AFM studies show clearly that pure phospholipid bilayers prepared on the Au electrode surface by vesicles spreading have poorly defined structure [8,9,32,120,125]. Defects are present in these bilayers and the hydrocarbon chains at phospholipid molecules adapt a large tilt with respect to the electrode surface [8,120].…”