Synthetic Bilayer Wetting on SiO₂ Surfaces

Abstract

Wetting on SiO2/Si wafers in the presence of dioctadecyldimethylammonium bromide (DODAB) bilayer vesicles is determined as a function of DODAB concentration and time of interaction between surface and vesicles. In 10 mM TRIS buffer at pH 7.4, the dynamic contact angle (θ) displays a maximum at an intermediate DODAB concentration (C) that corresponds to a minimum of contact angle hysteresis and is consistent with optimization of bilayer deposition. In pure water, θ is smaller than the contact angle for the bare surface consistently with adhesion of collapsed vesicles that carry water. In buffer, angles are larger than those for the bare surface, suggesting bilayer deposition under water and its conversion to a monolayer as the bilayer-bearing surface recedes into air. At a given C, θ against the interaction time (t) has an inverted-bell shape, indicating first vesicle adhesion, then bilayer deposition (at intermediate times), and finally further vesicle adhesion onto the deposited bilayer. Two major wettability parameters characterize bilayer deposition on the solid surface: minimization of contact angle hysteresis and maximization of the measured contact angle. Determination of dynamic contact angles is proposed as a quick and efficient technique to distinguish between vesicle adhesion and bilayer deposition on solid surfaces in general.

Supported Lipid Bilayer NanoSystems: Stabilization by Undulatory-Protrusion Forces and Destabilization by Lipid Bridging

“…The system then consists of (i) neutral SUVs that exhibit undulatory/protrusion repulsions and (ii) charged SLBs (ζ of about −25 mV), as seen in the TEM images (Figure ). Although SUVs have been observed adsorbed to SLBs on planar SiO 2 surfaces, we did not see charged SLB nanoparticles with adsorbed SUVs in the TEM images here. In the current case, in order to decrease the free energy of the system, the charged SLBs minimize their nearest-neighbor interactions and are thus separated by the neutral SUVs.…”

Supported Bilayers On Silica

“…From contact angle measurements for SiO 2 slides in the presence of phospholipid or DODAB vesicles, a substantial increase in surface hydrophobicity was obtained upon its interaction with the vesicles (27)(28)(29). Table 2 shows the wettability changes on a SiO 2 slide for experimental conditions analogous to those corresponding to bilayer adsorption in the adsorption isotherms (Figs.…”

Counterion Effects on Properties of Cationic Vesicles

“…Since their introduction as bilayer-forming synthetic compounds, , some synthetic lipoid amphiphiles as dihexadecyl phosphate or dioctadecyldimethylammonium salts have found many different uses in strategic applied areas . In particular, synthetic cationic liposomes have been sucessfully employed to interact with negatively charged surfaces or biomolecules such as prokaryotic 4-6 or eukaryotic cells, antigenic proteins, nucleic acids, , synthetic polymers and latex, − mineral surfaces, , viruses, , etc. Despite their practical utility as immunoadjuvants, gene, protein, or drug carriers, bactericides, flocculants, dispersing agents, membrane models, matrix for supporting biocomponents in biosensors, etc., they still are poorly characterized from the point of view of important physicochemical properties that determine their utility.…”