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Anthraquinone compound aloe-emodin (AE) has shown antineoplastic, antibacterial, antiviral, and anti-inflammatory properties and scavenging activity on free radicals. Because of these therapeutic features, AE has been attracting increasing interest and could be applied in the curing of many diseases. However, until now the physicochemical features of this compound have not been fully investigated; furthermore, its wide application might be hindered by its scarce solubility in aqueous media (∼19 μM). The inclusion of AE in nanocarriers, such as cationic liposomes, could allow its delivery effectively and selectively to target sites, reducing side effects in the remaining tissues. In this work, the weak acid nature of AE, because of its two phenolic functions, was exploited to load it remotely in the internal aqueous phase of liposomes in response to a difference in pH between the inside and outside of the liposomes, pHin > pHout. The inclusion of AE in gemini-based cationic liposomes by the acetate gradient method was obtained at high AE/lipid ratios (up to 1:30).

Chiral recognition was observed in a biomembrane model. Micellar aggregates formed by enantiopure N-alkyl-N,N-dimethyl-N-(1-phenyl)ethylammonium bromide were in fact able to convert the racemic mixture of bilirubin-IXalpha into an enantiomerically enriched mixture. The stereochemical preference and the extent of enantiomeric enrichment depend on the length of the hydrophobic portion of the surfactant and on the concentration conditions, and changes in the stereochemical bias are reversible.

The preparation and characterization of three stereoisomeric cationic gemini surfactants, 2,3-dimethoxy-1,4-bis(N-hexadecyl-N,N-dimethylammonio)butane dibromide, are described. The aggregation properties have been studied by fluorescence, electrical conductivity, and quasi-elastic light scattering. A conformational study of the surfactant headgroups has been performed by molecular mechanics calculations to investigate the effect of the stereogenic centers on the surfactant molecular shape and therefore on the different organizations of the monomers in the aggregates. Results show that the stereochemistry of the spacer strongly influences the aggregation behavior of the diasteromeric gemini in water.

While much is known about the self-assembly of lipids on nanoscale, our understanding of their biologically relevant mesoscale organization remains incomplete. Here, we show for a cationic gemini lipid a sharp and reversible transition from small vesicles with an average diameter of approximately 40 nm to giant vesicles (GVs) with an average diameter of approximately 11 microm. This transition is dependent on proper [NaCl] and specific temperature. Below this transition and in the vicinity of the air/water interface, a series of mesoscale morphological transitions was observed, revealing complex structures resembling biological membranes. On the basis of microscopy experiments, a tentative [NaCl] versus temperature shape/size phase diagram was constructed. To explain this unprecedented transition, we propose a novel mechanism whereby a specific interaction of Cl(-) counterion with the cationic gemini surfactant initiates the formation of a commensurate solute counterion lattice with low spontaneous curvature. In keeping with the high bending rigidity of NaCl crystal, this tightly associated ionic lattice enslaves membrane curvature and the mesoscale 3-D organization of this lipid.

Cationic liposomes formulated with neutral 1,2-dimyristoyl-sn-glycero-3-phosphocholine and cationic gemini surfactants were used for transfecting different cell lines with a reporter gene. The efficiency in the transfection has been correlated to the high extent of DNA condensation observed by circular dichroism, condensation shown to depend heavily on the gemini spacer structure. Transfection efficiency was better than that obtained with a commercial lipofection kit.

Mixed cationic liposomes composed by different ratios of dimyristoyl-sn-glycero-phosphatidylcoline (DMPC) and a cationic gemini surfactant have been studied by various physicochemical tools as vehicles for m-tetrahydroxyphenylchlorin (m-THPC), a photosensitizer used in photodynamic therapy. Entrapment and location of m-THPC within the lipid double layer have been evaluated by different techniques and the new formulations have been tested on a stabilized cell line from a human colon tumor, COLO206. A correlation between the physicochemical features of formulations and their efficiency as photosensitizers vector was found.

The efficiencies of the binary liposomes composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine and cationic gemini surfactant, (2S,3R)-2,3-dimethoxy-1,4-bis(N-hexadecyl-N,N-dimethylammonium)butane dibromide as transfection vectors, were measured using the enhanced green fluorescent protein coding plasmid and COS-1 cells. Strong correlation between the transfection efficiency and lipid stoichiometry was observed. Accordingly, liposomes with X(SR-1) > or = 0.50 conveyed the enhanced green fluorescent protein coding plasmid effectively into cells. The condensation of DNA by liposomes with X(SR-1) > 0.50 was indicated by static light scattering and ethidium bromide intercalation assay, whereas differential scanning calorimetry and fluorescence anisotropy of diphenylhexatriene revealed stoichiometry dependent reorganization in the headgroup region of the liposome bilayer, in alignment with our previous Langmuir-balance study. Surface charge density and the organization of positive charges appear to determine the mode of interaction of DNA with (2S,3R)-2,3-dimethoxy-1,4-bis(N-hexadecyl-N,N-dimethylammonium)butane dibromide/1,2-dimyristoyl-sn-glycero-3-phosphocholine liposomes, only resulting in DNA condensation when X(SR-1) > 0.50. Condensation of DNA in turn seems to be required for efficient transfection.

Fluorescently-tagged lipids are a powerful tool for investigating the dynamics of lipids in cell biological studies and in biophysical applications. Herein we report the synthesis and the characterization of a new bola amphiphile, PC12, based on a bisimidic perylene moiety: a central perylene unit is symmetrically linked to two aliphatic chains both ending with a quaternary ammonium group. Absorption and fluorescent properties of the newly synthesized compound were investigated in DMSO and in water as a function of concentration and temperature. Further, the entrapment efficiency, the fluorescence behavior in dimyristoyl-sn-glycero-phosphocholine (DMPC) liposomes, and cell uptake on human and murine glioblastoma cell lines were evaluated. When loaded in liposomes, PC12 follows the same destiny of liposomes themselves in the cell cultures: this is an interesting result because PC12 could be used both as an aspecific dye (free form) and as an organelle-specific lipid probe. [ABSTRACT FROM AUTHOR]