Some Electrochemical Features of Supported Bilayer Lipid Membranes

Influence of Nanotopography on Phospholipid Bilayer Formation on Silicon Dioxide

“…The formation of supported phospholipid bilayers (SPBs) on various surfaces has been thoroughly investigated for a variety of lipid chemistries, not only because SPBs resemble the cell membrane, but also owing to their potential in biotechnological applications such as biosensors, − bioMEMS, − and immunoassay development. , The two most common ways to form SPBs on hydrophilic surfaces are either to utilize the Langmuir−Blodgett transfer technique , or via the adsorption and spontaneous rupture of small unilamellar lipid vesicles (SUVs). − The latter technique is favorable due to its simplicity and the potential to incorporate different biomolecules during the vesicle preparation step, thereby enabling the immobilization of these biomolecules into subsequently formed SPBs . The adsorption of SUVs and their (eventual) transformation to SPBs are governed by a number of key parameters, such as vesicles size, lipid chemistry and charge, surface chemistry and charge, temperature, as well as the nature and concentration of ions in the buffer solution, as characterized using different surface-sensitive analytical techniques. ,− One of these powerful characterization tools is the quartz crystal microbalance with dissipation monitoring (QCM-D), which enables real-time monitoring of vesicle adsorption and bilayer formation. In particular, the method allows one to distinguish the spontaneous rupture of adsorbing vesicles from adsorption of intact vesicles …”

Fluorescence Study of the Fluidity and Cooperativity of the Phase Transitions of Zwitterionic and Anionic Liposomes Confined in Sol−Gel Glasses

“…For practical applications (biosensors, microarrays, screening platforms, etc. ), liposomes have been immobilized on different solid surfaces given the tremendous potential of the resulting materials to develop novel devices. − However, fixation of liposomes to solid surfaces easily disrupts the hydrophobic interactions that create lipid bilayers and modify the natural dynamic motions of the membrane and its gel−fluid phase transition temperature ( T m ), producing unstable immobilized structures and, in some cases, lysis of the bilayer. − Different strategies have been developed to overcome these difficulties. − Among them, use of sol−gel routes, involving the hydrolysis and condensation of alkoxysilane precursors, seems to be an interesting alternative to immobilize liposomes and proteoliposomes in silica and hybrid matrixes without the need for tethering the lipids to a solid surface. − The preservation of the bilayer structure upon sol−gel encapsulation requires the use of alcohol-free routes. ,,,, Otherwise, the alcohol resulting as a byproduct of the chemical reactions involved in the formation process of the silica matrix causes the disruption of the lipid bilayer structure. Nevertheless, it has been recently reported that for pure zwitterionic liposomes, (i.e., 1,2-dimyristoyl- sn -glycero-3-phosphocholine (DMPC), dipalmitoyl phosphatidylcholine (DPPC)) even the use of these alcohol-free routes produces a broadening of the lipid phase transition during aging, − suggesting irreversible alterations of the bilayer fluidity which prevent the use of these systems for practical applications such as controlled release.…”

Characterization of Fluorescent Phospholipid Liposomes Entrapped in Sol−Gel Derived Silica

“…A number of strategies have been reported for the immobilization of bilayer lipid membranes, including supporting of BLMs on the pores of filter paper, covalent attachment of monolayer or bilayer lipid membranes to surfaces, ,,, tethering of phospholipid liposomes to a surface by deposition, covalent attachment or attachment via avidin−biotin linkages, and entrapment of BLMs into polymer multilayers to provide a semihydrated internal surface to allow incorporation or bulkier membrane receptors and proteins . The dynamic and physical properties of such BLMs have been examined using a variety of techniques such as voltammetry, − electrostriction, electrical impedance spectroscopy, , and fluorescence spectroscopy . Such studies have shown that there are several limitations related to the use of supported BLMs as practical devices due to the intrinsic fragility of the membrane and the generally harsh nature of the immobilization methods employed.…”