Article

Cationic liposomes in mixed didodecyldimethylammonium bromide and dioctadecyldimethylammonium bromide aqueous dispersions studied by differential scanning calorimetry, Nile Red fluorescence, and turbidity.

Physics Department, São Paulo State University, São José do Rio Preto, SP, Brazil.
Langmuir (Impact Factor: 4.38). 05/2006; 22(8):3579-85. DOI: 10.1021/la053238f
Source: PubMed

ABSTRACT The thermotropic phase behavior of cationic liposomes in mixtures of two of the most investigated liposome-forming double-chain lipids, dioctadecyldimethylammonium bromide (DODAB) and didodecyldimethylammonium bromide (DDAB), was investigated by differential scanning calorimetry (DSC), turbidity, and Nile Red fluorescence. The dispersions were investigated at 1.0 mM total surfactant concentration and varying DODAB and DDAB concentrations. The gel to liquid-crystalline phase transition temperatures (Tm) of neat DDAB and DODAB in aqueous dispersions are around 16 and 43 degrees C, respectively, and we aim to investigate the Tm behavior for mixtures of these cationic lipids. Overall, DDAB reduces the Tm of DODAB, the transition temperature depending on the DDAB content, but the Tm of DDAB is roughly independent of the DODAB concentration. Both DSC and fluorescence measurements show that, within the mixture, at room temperature (ca. 22 degrees C), the DDAB-rich liposomes are in the liquid-crystalline state, whereas the DODAB-rich liposomes are in the gel state. DSC results point to a higher affinity of DDAB for DODAB liposomes than the reverse, resulting in two populations of mixed DDAB/DODAB liposomes with distinctive phase behavior. Fluorescence measurements also show that the presence of a small amount of DODAB in DDAB-rich liposomes causes a pronounced effect in Nile Red emission, due to the increase in liposome size, as inferred from turbidity results.

1 Bookmark
 · 
89 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Compressed CO2 triggers the formation of amphiphilic proline supramolecular assemblies in water, which catalyze the asymmetric aldol reaction without any additives. Compressed CO2 can dynamically regulate the size of the assemblies and subsequently the catalyst activity and selectivity. Furthermore, CO2 provides the merit of easy separation and purification, making the process sustainable and recyclable.
    Angewandte Chemie International Edition 06/2013; · 11.34 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A large, free-standing hybrid nanofilm (thickness 35 nm) of zirconia and cross-linked acrylate is stably dispersed in aqueous media via assembly with surfactants and lipid derivatives. These amphiphiles showed three different behaviours. Category 1 is represented by single-chain ionic surfactants of SDS and CTAB and by non-ionic surfactant of Triton X100. In this case, the amphiphile is adsorbed onto the surface of the nanofilm to stably disperse the supramolecular assembly in water but it is desorbed upon further transfer to pure water. Similar behavior is found for double-chain ionic amphiphiles of 2C12N+Br− and 2C10sucSO3−Na+. In Category 2 of non-ionic surfactants of poly(oxyethylene)-based C18En and TWEEN 20, the amphiphile–nanofilm assembly, once formed in aqueous amphiphile solution, remains intact even after transfer to pure water. A similar result is obtained, when 2C12sucSO3−Na+ is used. In the third category, the nanofilm cannot be dispersed in aqueous amphiphiles, as the supramolecular assembly is apparently not formed. Double-chain amphiphiles of 2C18N+Br−, 2C14sucSO3−Na+ and eggyolk lecithin show this behaviour. Although amphiphile–nanofilm assemblies are formed invariably under amphiphile concentrations above their CMCs (Category 1 and 2), some of them show quite slow desorption rate in water (Category 2). This situation is desirable in the design of useful amphiphile–nanofilm assemblies equipped with certain properties of biomembranes, such as fluid molecular ordering on surface and robust nanofilm structure.
    Soft Matter 01/2008; 4(4). · 4.15 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The behaviors of cat-anionic vesicles composed of dioctadecyldimethylammonium bromide (DODAB) and dihexadecyl phosphate (DHP) with varying lipid composition were investigated through the measurements of size, zeta potential and fluorescence polarization, morphological observations, determination of thermotropic phase behavior, cell viability assay, and examination of entrapment efficiency and colloid stability. DODAB is miscible with DHP in the bilayer domain, which expresses a non-ideal mixing characteristic. The DODAB-rich vesicles show a smaller particle size, higher positive zeta potential, lower main transition temperature, less angular structure, better storage stability, and higher encapsulation efficiency than the DHP-rich ones. Introduction of DODAB into DHP vesicles enhances the membrane fluidity in the ripple and liquid crystalline phases. The membrane fluidity of mixed DODAB-DHP vesicles with the near charge might have a significant effect on the survival of nontransformed human skin fibroblast Hs68 cells. The degree of the cytotoxicity of Hs68 cells is dominated mainly by the charge nature of DODAB-DHP vesicles with varying lipid composition. The results gathered provide necessary information for future drug/gene delivery applications.
    Physical Chemistry Chemical Physics 12/2013; · 4.20 Impact Factor

Full-text

Download
3 Downloads
Available from
Jul 25, 2014