Papers by Keyword: Amphiphiles

Abstract: A dissipative particle dynamics simulation method is used to get insight into molecular-level details of vesicle fusion in this study. For simplicity, the simulation system contains water and amphiphiles. The fusion mechanism is investigated in detail. It is found that the whole fusion process is in well agreement with the “stalk-pore” hypothesis. The dynamics of vesicle fusion is analyzed by monitoring the time evolutions of morphologies.

Abstract: Self-assembled amphiphile systems are utilized in a wide variety of applications including drug delivery and energy storage. Nano-scale physical and chemical interactions govern the packing of self-assembled amphiphilic molecules, resulting in thermodynamically stable phases of defined geometries. Possible phases include micellar, hexagonal, cubic, lamellar and sponge phases. The internal nano-structure of the amphiphile self-assembly materials plays an important role in the properties of these systems and their application. To date small angle x-ray scattering (SAXS) has been the most common technique used to characterise their structure. We explore positron annihilation lifetime spectroscopy (PALS) as an alternative and/or complementary technique for this purpose, using the phytantriol/water system. While PALS is a well established technique for characterising many materials, the coexistence of aqueous and hydrophobic regions in a soft self-assembled amphiphile material poses a challenge to the analysis and interpretation of the results. In order to alleviate these difficulties we developed a computer program for general-purpose PALS data analysis called PAScual. Amongst the most salient features of this new code are the possibility to perform bounded fits and the option of using advanced algorithms to provide a more robust and unbiased fit: on the one hand, it incorporates a global nonlinear optimisation routine based on the Simulated Annealing algorithm and, on the other hand it gives information on the reliability of the results by means of a Markov Chain Monte-Carlo Bayesian Inference method. In this work we present the newly developed PALS data analysis techniques as well as the results for the phytantriol/water system, comparing them with additional data obtained from complementary techniques.

Abstract: A commercial available amphiphilic polymer, Cholesterol terminated PEO (Chol-PEO), was used as novel biomimetic drug delivery system. The association behavior of Chol-PEOs in aqueous solution was studied by fluorescence probe technique and transmission electron microscope (TEM). Fluorescence excitation spectra for pyrene probe solubilized in the aggregates of Chol-PEOs suggested the presence of a critical micelle concentration (cmc) in water. TEM images of the aggregates suggested that the PEO block formed the biocompatible micelle coronas and the cholesterol block formed the hydrophobic micelle cores. These new biomimetic diblock copolymers were evaluated as nanocapsules for the delivery of hydrophobic drugs and drug release behavior of a hydrophobic anti-cancer drug, adriamycin (ADR), was examined.