Micelles, Membranes, Microemulsions, and Monolayers (original) (raw)
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Biomimetic Amphiphiles: Properties and Potential Use
Biosurfactants, 2010
S urfactants are the amphiphilic molecules that tend to alter the interfacial and surface tension. The fundamental property related to the structure of surfactant molecules is their self-aggregation resulting in the formation of association colloids. Apart from the packing of these molecules into closed structures, the structural network also results in formation of extended bilayers, which are thermodynamically stable and lead to existence of biological membranes and vesicles. From biological point of view the development of new knowledge and techniques in the area of vesicles, bilayers and multiplayer membranes and their polymerizable analogue provide new opportunities for research in the respective area. 'Green Surfactants' or the biologically compatible surfactants are in demand to replace some of the existing surfactants and thereby reduce the environmental impact, in general caused by classic surfactants. In this context, the term 'natural surfactants or biosurfactants' is often used to indicate the natural origin of the surfactant molecules. Most important aspect of biosurfactants is their environmental acceptability, because they are readily biodegradable and have low toxicity than synthetic surfactants. Some of the major applications of biosurfactants in pollution and environmental control are microbial enhanced oil recovery, hydrocarbon degradation, hexa-chloro cyclohexane (HCH) degradation and heavy-metal removal from contaminated soil. In this chapter, we tried to make a hierarchy from vital surfactant molecules toward understanding their behavioral aspects and application potential thereby ending into the higher class of broad spectrum 'biosurfactants'. Pertaining to the budding promise offered by these molecules, the selection of the type and size of each structural moiety enables a delicate balance between surface activity and biological function and this represents the most effective approach of harnessing the power of molecular self-assembly.
Structures Built by Amphiphiles and Frustrated Fluid Films
Le Journal de Physique Colloques, 1990
Resume-Les interfaces entre deux liquides non miscibles, tels que l'eau et l'huile, peuvent Btre stabiliskspar des molecules amphiphiles, telles que celles des savons, detergents et lipides. Les films interfaciaux construits par ces molecules prksentent un polymorphisme remarquable : cristaux liquides ordonnes, structures "gonfl6es", solutions micellaires et microemulsions d&sordonnees, liposomes et v6sicules. Nous decrivons ces structures, en insistant sur celles des cristaux liquides, et nous en proposons une approche georn&trique, qui conduit B les voir comme des structures de defauts et permet de developper la cristallographie des objets bi-dimensionnels necessaire pour leur analyse.
Amphiphilic Molecules in Drug Delivery Systems
Numerous drug delivery colloidal systems are formulated using polymers or surfactants or a mixture of both, typically due to their self-assembly properties. Molecular self-assembly creates the possibility to dissolve and protect drugs from adverse external environments. Therefore, it is important to understand the interactions behind the self-assembly phenomena of surfactant and polymer molecules, polymer-polymer and polymer-surfactant mixtures. A number of col-loidal structures used in drug delivery formulations such as micelles, vesicles, liquid crystalline phases, microemulsions, polymer gels, aerosols, polymer-polymer and polymer-surfactant complexes will be illustrated in this chapter and their main physicochemical properties will be highlighted, keeping in mind their relevance to the drug delivery research field.
Journal of Colloid and Interface Science, 2009
The solution behavior of the mixture of cetyltrimethylammonium bromide (CTAB) and polyoxyethylene (30) octylphenol (OP-30) has been investigated by measuring the conductance, fluorescence intensity, surface tension and absorbance of the surfactant mixtures. A strong interaction between the two surfactants is indicated from each of the measurements. The critical micelle concentration of CTAB is found to increase with increase in the amount of OP-30 in the mixture. This delaying in micellization of CTAB has been attributed to the diminution of its effective hydrophobicity due to interaction with monomers or micelles of OP-30. Below CMC of OP-30, the monomeric concentration of CTAB decreases due to the formation of a hydrophobic complex between OP-30 and CTAB. Above CMC of OP-30, CTAB monomers get solubilized into micellar core of OP-30 in 1:1 stoichiometric ratio. Micropolarity and the aggregation numbers of the mixed systems have been determined from fluorescence studies. The thermodynamics of micelle formation of CTAB coupled with fluorescence studies of the mixtures indicates that the complex grows in size with increase of OP-30 concentration till the micelle of latter is formed at higher concentrations. The treatment of theoretical model to the interaction of OP-30 and CTAB yields a positive interaction parameter showing antagonism behavior. A schematic model of interaction of OP-30 with CTAB below and above its CMC has been suggested.
Amphiphile nanoarchitectonics: from basic physical chemistry to advanced applications
Physical Chemistry Chemical Physics, 2013
This perspective article summarizes research on the self-assembly of amphiphilic molecules such as lipids, surfactants or block copolymers that are a focus of interest for many colloid, polymer, and materials scientists and which have become increasingly important in emerging nanotechnology and practical applications. Solution systems are introduced before progression to interfacial systems, which are roughly categorized as (i) basic properties of amphiphiles, (ii) self-assembly of amphiphiles in bulk phases, (iii) assembly on static surfaces, (iv) assembly at dynamic interfaces, and (v) advanced topics from simulation to application.
Molecular crowding effects on the distribution of amphiphiles in biological media
Colloids and Surfaces B: Biointerfaces, 2019
Biological systems are the result of the interactions established among their many distinct molecules and molecular assemblies. The high concentration of small molecules dissolved in the aqueous media alter the water properties with important consequences in the interactions established. In this work, the effects of high concentrations of the disaccharide trehalose on the solubility of a homologous series of fluorescent amphiphiles (NBD-Cn, n=4-16) and on their interaction with a lipid bilayer and a serum protein is quantitatively characterized. Both kinetic and equilibrium aspects are reported for a better understanding of the effects observed. The aqueous solubility of the most hydrophobic amphiphiles (n ³ 8) is strongly increased by 1 M trehalose, while no significant effect is observed for the most polar amphiphile (n=4). This results from a decrease in the magnitude of the hydrophobic effect at conditions of molecular crowding. A small decrease is observed on the equilibrium association with serum albumin. This is most significant for amphiphiles with longer alkyl chains, in agreement with their increased solubility in the aqueous media containing trehalose. The effects on the association of the amphiphiles with lipid bilayers are influenced by both equilibrium and kinetic aspects. On one hand, the decreased magnitude of the hydrophobic effect leads to a decrease in the affinity of the amphiphiles towards the membrane. However, this tendency may be overbalanced by the effects on the kinetics of the interaction (insertion/desorption) due to the increase in the viscosity of the aqueous media. It is shown that the distribution of amphiphilic drugs in the crowded biological media is significantly different from that predicted from studies in dilute solutions and that the effects are dependent on solute's hydrophobicity.
Description of the geometrical and topological structure in amphiphilic systems
Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 1995
A unified description of internal interfaces in oil-water-surfactant mixtures is proposed. Surfactant degrees of freedom are explicitly taken into account in the form of a vector field. A general definition of average curvatures in terms of the vector field is given. They are averages of the mean and Gaussian curvatures and characterize globally the geometrical and topological structure of the internal interface. It is argued that this definition can be applied to both sharp and di6'use oil-water interfaces, in ordered phases and in disordered microemulsions.