Characterization and aging of aqueous vesicular dispersions of sodium 4-(1′-heptylnonyl)benzenesulfonate

Spontaneous formation of vesicles

his review highlights the relevant issues of spontaneous formation of vesicles. Both the common characteristics and the differences between liposomes and vesicles are given. The basic concept of the molecular packing parameter as a precondition of vesicles formation is discussed in terms of geometrical factors, including the volume and critical length of the amphiphile hydrocarbon chain. According to theoretical considerations, the formation of vesicles occurs in the systems with packing parameters between 1/2 and 1. Using common as well as new methods of vesicle preparation, a variety of structures is described, and their nomenclature is given. With respect to sizes, shapes and inner structures, vesicles structures can be formed as a result of self-organisation of curved bilayers into unilamellar and multilamellar closed soft particles. Small, large and giant uni-, oligo-, or multilamellar vesicles can be distinguished. Techniques for determination of the structure and properties of vesicles are described as visual observations by optical and electron microscopy as well as the scattering techniques, notably dynamic light scattering, small angle X-ray and neutron scattering. Some theoretical aspects are described in short, viz., the scattering and the inverse scattering problem, angular and time dependence of the scattering intensity, the principles of indirect Fourier transformation, and the determination of electron density of the system by deconvolution of p(r) function. Spontaneous formation of vesicles was mainly investigated in catanionic mixtures. A number of references are given in the review.

Lung lamellar body amphiphilic topography: a morphological evaluation using the continuum theory of liquid crystals: I. Closed surfaces: closed spheres, concentric tori, and Dupin cyclides

The structure and symmetry of the bilayers of in vivo phospholipid lung lamellar bodies is shown to be analogous to thermotropic smectic-A liquid crystals and in vitro lyotropic multilamellar liquid crystalline liposomes. This structural similarity has led us to extend biophysical and geometrical principles that have long been used to predict the layer conformation in these in vitro systems to in vivo lung lamellar bodies. These configurations were demonstrated by electron micrographs of thin sections of rodent, monkey, and human lung lamellar bodies prepared by lipid-retaining embedment procedures. The bilayer configurations in all species were consistent with the two geometries predicted by minimal energy solutions of a continuum theory of liquid crystals subject to the boundary conditions imposed by the amphiphilic nature of lung surfactant lipid: concentric (either closed or partially closed) spheres and Dupin cyclides. These bilayer arrangements in lung lamellar bodies were virtually identical to the bilayer configuration of in vitro multilamellar liposomes. The agreement between the two predicted configurations and our observations shows that multilamellar liquid crystalline bilayer aggregate organization is universal in any aqueous environment.