The Interactions between Surfactants and Vesicles
Date Issued
2008
Date
2008
Author(s)
Huang, Kuei-Chun
Abstract
The goal of all sophisticated drug delivery systems (DDS) is to deploy medicines completed to specifically targeted parts of bodies through a medium which can control the administration of the therapy by means of either a chemical or physiological trigger. To achieve the goal, researchers are turning to advances in the world of nanotechnology. During the past decades, lipsomes have been shown to be effective in enhancing drug targeting specificity, improving treatment absorption rates, lowering systemic drug toxicity, and providing protections for pharmaceuticals against biochemical degradation, therefore lipsomes are widely used as drug carriers. Nevertheless, the in vivo stability of liposomes poses limitations on their applications. For example, an enough amount of biosurfactant can solubilize liposomes. Thus, the understanding of the solubilization of liposomes is of great importance.n this work, the dissipative particle dynamics (DPD) is employed to investigate the interactions between surfactants and vesicles (liposomes). In general, liposome solubilization can be described by the three-stage hypothesis, including vesicular region, vesicle-micelle coexistence, and mixed micellar region. First, we focus on the first stage and study the partition of surfactants between the bilayer phase and the aqueous phase. The partition coefficient K can be related to the surfactant concentration in the bilayer, Db, and that in the solution, Dw, for a given concentration of lipid, L, by Db/Dw(L+Db). A higher value of K indicates that more surfactant molecules are incorporated in the bilayers. As the “hydrophobicity” of surfactants increase, K increases and vice versa. The hydrophobicity of surfactants can be achieved by increasing tail length or the repulsive interaction between tail and water. When the amounts of surfactants reach a critical point, the solubilization begins and the coexistence of vesicles and mixed micelles is found. At this time, the surfactant in lipid phase/lipid molar ratio Re is defined as Reb, which is found to rise as the hydrophobicity of surfactants increases. The results indicate that surfactant with less hydrophobicity has stronger ability to damage the vesicle construction. Further increase of the surfactant concentration results in total collapse of the vesicle. Our simulations clearly observed the process of the liposome solubilization and confirm the validity of the three-stage hypothesis.
Subjects
dissipative particle dynamics
Surfactant
Vesicle
lipsome
solubilization
Drug Delivery System
Type
thesis
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