“…Lipid bilayers are ubiquitously entangled in biological processes, usually comprising the impact of changes in external conditions and the exposure to various substances. The static response of membranes to such conditions was extensively studied from a mechanical (π ) thermal (T) and -although to a lesser extend -electrical (ψ ) perspective [1][2][3][4][5][6][7][8][9][10][11][12][13]. Nonequilibrium studies on the macroscopic dynamics of lipid membranes, on the other hand, are only sparsely found, to date [14][15][16][17][18][19].…”
Hydrated interfaces are ubiquitous in biology and appear on all length scales from ions and individual molecules to membranes and cellular networks. In vivo, they comprise a high degree of self-organization and complex entanglement, which limits their experimental accessibility by smearing out the individual phenomenology. The Langmuir technique, however, allows the examination of defined interfaces, the controllable thermodynamic state of which enables one to explore the proper state diagrams. Here we demonstrate that voltage and pressure pulses simultaneously propagate along monolayers comprised of either native pork brain or synthetic lipids. The excitation of pulses is conducted by the application of small droplets of acetic acid and monitored subsequently employing time-resolved Wilhelmy plate and Kelvin probe measurements. The isothermal state diagrams of the monolayers for both lateral pressure and surface potential are experimentally recorded, enabling us to predict dynamic voltage pulse amplitudes of 0.1-3 mV based on the assumption of static mechanoelectrical coupling. We show that the underlying physics for such propagating pulses is the same for synthetic and natural extracted (pork brain) lipids and that the measured propagation velocities and pulse amplitudes depend on the compressibility of the interface. Given the ubiquitous presence of hydrated interfaces in biology, our experimental findings seem to support a fundamentally new mechanism for the propagation of signals and communication pathways in biology (signaling), which is based neither on protein-protein or receptor-ligand interaction nor diffusion.
“…Lipid bilayers are ubiquitously entangled in biological processes, usually comprising the impact of changes in external conditions and the exposure to various substances. The static response of membranes to such conditions was extensively studied from a mechanical (π ) thermal (T) and -although to a lesser extend -electrical (ψ ) perspective [1][2][3][4][5][6][7][8][9][10][11][12][13]. Nonequilibrium studies on the macroscopic dynamics of lipid membranes, on the other hand, are only sparsely found, to date [14][15][16][17][18][19].…”
Hydrated interfaces are ubiquitous in biology and appear on all length scales from ions and individual molecules to membranes and cellular networks. In vivo, they comprise a high degree of self-organization and complex entanglement, which limits their experimental accessibility by smearing out the individual phenomenology. The Langmuir technique, however, allows the examination of defined interfaces, the controllable thermodynamic state of which enables one to explore the proper state diagrams. Here we demonstrate that voltage and pressure pulses simultaneously propagate along monolayers comprised of either native pork brain or synthetic lipids. The excitation of pulses is conducted by the application of small droplets of acetic acid and monitored subsequently employing time-resolved Wilhelmy plate and Kelvin probe measurements. The isothermal state diagrams of the monolayers for both lateral pressure and surface potential are experimentally recorded, enabling us to predict dynamic voltage pulse amplitudes of 0.1-3 mV based on the assumption of static mechanoelectrical coupling. We show that the underlying physics for such propagating pulses is the same for synthetic and natural extracted (pork brain) lipids and that the measured propagation velocities and pulse amplitudes depend on the compressibility of the interface. Given the ubiquitous presence of hydrated interfaces in biology, our experimental findings seem to support a fundamentally new mechanism for the propagation of signals and communication pathways in biology (signaling), which is based neither on protein-protein or receptor-ligand interaction nor diffusion.
“…Touitou and co-workers, − however, have discovered and have been investigating lipid vesicular systems embodying ethanol in relatively high concentrations (20−50 wt %), which they named “ethosomes” and that are efficient at enhancing the skin permeation of a number of drugs. Furthermore, a few studies have been performed to demonstrate that surfactants can form bilayer or possibly vesicle structures in the presence of ethanol with high concentrations or even in pure ethanol. − Apparently, some work still need to be done in this area for more clear answers. 7 Cosolvent effects on the size and count rate of catanionic vesicles formed from SDS/DeTMAB = 1:1, total concentration = 10 mM.…”
This paper aims to provide a practical catanionic vesicle-boosting method by means of cosolvent addition in water and to propose a theoretical explanation which can delineate the general trend of cosolvent effects and elucidate the possible role of cosolvent in the formation of catanionic vesicles. Effects of four homologous cosolvents (methanol, ethanol, 1-propanol, and 1-butanol) on the spontaneous formation of vesicles from eight 1:1 anionic-cationic mixed surfactant systems, sodium alkyl sulfates-alkyltrimethylammonium bromides (C(n)SO4Na-C(m)N(CH3)3Br; n = 12, 14; m = 8, 10, 12, 14), at a total surfactant concentration of 10 mM were systematically studied. The experimental results revealed that varied changes in vesicle formability of different mixed surfactant systems may result from various kinds and amounts of cosolvent. Four types of cosolvent effects, however, can be classified. Among them, cosolvent effects type 2 and type 3 would serve the purpose and were exemplified by C12SO4Na-C10N(CH3)3Br, C14SO4Na-C10N(CH3)3Br, and C12SO4Na-C12N(CH3)3Br mixed surfactants. Furthermore, the effectiveness of vesicle boosting increases in the order 1-butanol > 1-propanol > ethanol > methanol. An explanation of cosolvent effects based on the medium dielectric constant was then proposed.
“…In nature, they are mainly present in archaebacteria and ensure the integrity of the bacterial membrane at high temperature (90 °C) and low pH (1−1.5) , . Membranes made from synthetic bolas, forming either nanotubes or vesicles, can also show an exceptional stability, some of them being stable even in the dry phase , or in some organic solvents . Unsymmetrical bolas, bearing two different polar head groups, assembled in a parallel fashion can form asymmetric membranes, so that the two opposite sides of the monolayer membrane present different functional groups (Figure ) , .…”
The success in gene therapy relies strongly on new efficient gene delivery vectors. Nonviral vectors based on lipids and polymers constitute an important alternative to the viral vectors. However, the key problem with these vectors is the poor structural control of their DNA complexes. In the present work, following new design we synthesized unsymmetrical bolaamphiphiles, molecules bearing neutral sugar (gluconic acid) and dicationic ornithine head groups connected by different long hydrophobic spacers. Within this design, a positively charged headgroup is expected to bind DNA, the hydrophobic spacer is to drive the formation of a monolayer membrane shell around DNA, while the neutral group is to be exposed outside of the complex. Our fluorescence and gel electrophoresis data showed that self-assembly of bolas and their interaction with DNA depend strongly on the bola structure. The size of bola/DNA complexes (bolaplexes) estimated from dynamic light scattering data was ∼100 nm at low N/P (cationic nitrogen/DNA phosphate molar ratio), while at higher N/Ps it was significantly larger due to neutralization of their surface charge. Atomic force microscopy studies revealed nanostructural rod-shaped or spherical morphology of the bolaplexes. Transfection efficiency of the bolaplexes in vitro was significant when either DOPE or chloroquine were used as helping agents, suggesting that the key barrier for their internalization is the endosomal escape. Finally, all bolas showed low cytotoxicity (cell viability >80%). The present results show that bolas are prospective candidates for construction of nonviral gene delivery vectors. We believe that further optimization of polar head groups and a hydrophobic spacer in the bolas will lead to vectors with controlled small size and high transfection efficiency.
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