Cationic liposomes in mixed didodecyldimethylammonium bromide and dioctadecyldimethylammonium bromide aqueous dispersions studied by differential scanning calorimetry, Nile Red fluorescence, and turbidity.
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.
SourceAvailable from: Ana Lilia Barrán Berdón[Show abstract] [Hide abstract]
ABSTRACT: Lipoplex-type nano-aggregates prepared from pEGFP-C3 plasmid DNA (pDNA) and mixed liposomes, with a gemini cationic lipid (CL) [1, 2-bis(hexadecyl imidazolium) alkanes], referred as (C16Im)2Cn (where Cn is the alkane spacer length, n = 2, 3, 5 or 12 between the imidazolium heads) and DOPE zwitterionic lipid, have been analyzed by zeta potential, gel electrophoresis, SAXS, cryo-TEM, fluorescence anisotropy, transfection efficiency, fluorescence confocal microscopy and cell viability/cytotoxicity experiments to establish a structure-biological activity relationship. The study, carried out at several mixed liposome compositions, α, and effective charge ratios, ρeff, of the lipoplex, demonstrates that the transfection of pDNA using CLs initially requires the determination of the effective charge of both. The electrochemical study confirms that CLs with a delocalizable positive charge in their headgroups yield an effective positive charge which is 90% of their expected nominal one, while pDNA is compacted yielding an effective negative charge which is only 10-25% than that of the linear DNA. SAXS diffractograms show that lipoplexes formed by CLs with shorter spacer (n = 2, 3, or 5) present three lamellar structures, two of them in coexistence, while those formed by CL with longest spacer (n = 12) present two additional inverted hexagonal structures. Cryo-TEM micrographs show nano-aggregates with two multilamellar structures, a cluster-type (at low α value) and a fingerprint-type that coexists with the cluster-type at moderate α composition. The optimized transfection efficiency (TE) of pDNA, in HEK293T, HeLa and H1299 cells was higher using lipoplexes containing gemini CLs with shorter spacers at low α value. Each lipid formulation did not show any significant levels of toxicity, the reported lipoplexes being adequate DNA vectors for gene therapy and considerably better than both Lipofectamine 2000, and CLs of the 1,2-bis(hexadecyl ammnoniun) alkane series, recently reported.Biomacromolecules 10/2013; 14(11). DOI:10.1021/bm401079h · 5.79 Impact Factor
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ABSTRACT: Liposomes have been extensively used as effective nanocarriers, providing better solubility, higher stability and slower release of drugs compared to free drug administration. They are also preferred due to their nontoxic nature as well as their biodegradability and cell membrane mimicking abilities. In this study, we examined noncovalent integration of a cell penetrating arginine-rich peptide amphiphile into a liposomal formulation of negatively charged 1,2-dioleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DOPG) phospholipids in the presence of cholesterol due to its amphipathic character. We studied changes in the physical characteristics (size, surface potential and membrane polarity) of the liposomal membrane, as well as in the encapsulation of hydrophilic and hydrophobic agents due to peptide amphiphile incorporation. The activities of peptide integrated liposomal systems as drug delivery agents were investigated by using anticancer drugs, doxorubicin-HCI and paclitaxel. Enhancement in liposomal uptake due to arginine-rich peptide integration, and enhanced efficacy of the drugs were observed with peptide functionalized liposomes compared to free drugs.Faraday Discussions 01/2013; 166:269-83. DOI:10.1039/c3fd00058c · 4.19 Impact Factor
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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; 16(4). DOI:10.1039/c3cp54176b · 4.20 Impact Factor