A new approach for the study of cationic lipid–DNA complexes by energy dispersive X-ray diffraction

New views and insights into intracellular trafficking of drug-delivery systems by fluorescence fluctuation spectroscopy

Biomaterials in the nanometer size range can be engineered for site-specific delivery of drugs after injection into the blood circulation. However, translation of such nanomedicines from the bench to the bedside is still hindered by many extracellular and intracellular barriers. To realize the concept of targeted drug delivery with nanomedicines, research groups are studying intensively the extra- and intra-cellular mechanisms involved as a response to the physicochemical properties of the nanomedicines. In this review, we highlight the contributions of fluorescence fluctuations spectroscopy techniques to better understand, and in turn to bypass, the major hurdles to therapeutic delivery, focusing mostly on the intracellular dynamics of drug-delivery systems.

Fine tuning of the morphology of copper oxide nanostructures and their application in ambient degradation of methylene blue

In this work, flower-like, boat-like, plate-like and ellipsoid-like copper oxide (CuO) nanostructures were fabricated by simple modulation of reaction conditions. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, nitrogen adsorption-desorption measurements and UV-visible diffuse reflectance spectra were employed to characterize the obtained CuO nanostructures. Reactants, hydrothermal temperature and time were found to largely affect the morphology and structure of CuO nanostructures. Flower-like and boat-like CuO nanostructures were successively fabricated by increasing hydrothermal time. Plate-like and ellipsoid-like CuO nanostructures were produced by modulating the use of polyethylene glycol (PEG) and NH(3)·H(2)O. The formation mechanisms were proposed based on the experimental results, which show that both PEG and NH(3)·H(2)O play an important role in the formation of the morphology and structure of CuO. The catalytic activity of the as-prepared CuO nanostructures was demonstrated by catalytic oxidation of methylene blue (MB) in presence of hydrogen peroxide (H(2)O(2)). The as-prepared CuO nanostructures all show good catalytic activity.

Two-dimensional lipid mixing entropy regulates the formation of multicomponent lipoplexes

The mechanism of formation of multicomponent lipoplexes was investigated by means of synchrotron Small-Angle X-ray Diffraction (SAXD). Mixed lipid dispersions were prepared by mixing different populations of binary cationic liposomes. When adding DNA to mixed lipid dispersions, multicomponent lipoplexes spontaneously formed exhibiting structural properties, i.e., membrane thickness, surface charge density, and one-dimensional DNA packing density, intermediate between those of binary lipoplexes. These results suggested that DNA lets liposomes come into contact and fuse and that a complete lipid mixing at the molecular level occurs. The equilibrium structure of multicomponent lipoplexes was found to be unique and did not depend on the number and kind of populations composing lipid dispersion but only on the lipid species involved and on their relative molar ratio. According to recent theoretical models we identified two-dimensional lipid mixing entropy as the key factor regulating the existence of only multicomponent lipoplexes with ideally mixed lipid species.

The analysis of serum effects on structure, size and toxicity of DDAB–DOPE and DC-Chol–DOPE lipoplexes contributes to explain their different transfection efficiency

The effect of serum on structural properties of dimethyl-dioctadecyl-ammonium bromide (DDAB)-1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) liposomes and DDAB-DOPE/DNA lipoplexes has been investigated by energy dispersive X-ray diffraction (EDXD) technique, at different cationic lipid/DNA weight ratios (rho). The role of serum on the size of lipoplexes has also been studied by dynamic light scattering. Lipoplex transfection efficiency (TE) as a function of rho, and lipoplex toxicity to C6 rat glioma cells have been evaluated in Dulbecco's Modified Eagle Medium (DMEM) with and without serum. A multi-parametric analysis concerning the role of size, structure and cytotoxicity on transfection efficiency contributes to explain the experimental observation that 3beta-[N-(N',N'-dimethylaminoethane)carbamoyl]-cholesterol (DC-Chol)-DOPE/DNA transfect C6 cells better than DDAB-DOPE/DNA lipoplexes.

Dynamic properties of an oriented lipid/DNA complex studied by neutron scattering

The formation of lipid-DNA (CL-DNA) complexes called lipoplexes, proposed as DNA vectors in gene therapy, is obtained by adding DNA to a solution containing liposomes composed of cationic and neutral lipids. The structural and dynamic properties of such lipoplexes are determined by a coupling between the electrostatic interactions and the elastic parameters of the lipid mixture. An attempt to achieve a better understanding of the structure-dynamics relationship is reported herein. In particular, an elastic neutron scattering investigation of DOTAP-DOPC (dioleoyl trimethylammonium propane-dioleoyl phosphatidylcoline) complexed with DNA is described. Proton dynamics in this oriented CL-DNA lipoplex is found to be strongly dependent upon DNA concentration. Our results show that a substantial modification of the membrane dynamics is accompanied by the balancing of the total net charge inside the complex, together with the consequent displacement of interlayer water molecules.

Correlation between structure and transfection efficiency: a study of DC-Chol−DOPE/DNA complexes

The supramolecular structural nature of some cationic liposomes-DNA complexes, currently used as vehicles in non-viral gene delivery, has been elucidated by recent X-ray diffraction experiments. The relationship between the chemico-physical properties of these self-assembled structures and their transfection efficiency is extensively studied. Here we report a first comprehensive structural study by using energy dispersive X-ray diffraction, of the complex DC-Chol--DOPE/DNA (3beta[N-(N',N'-dimethylaminoethane)-carbamoyl]cholesterol dioleoylphosphatidylethanolamine/DNA), which has been classified as one of the most effective in in-vivo experiments. Our results show that DC-Chol--DOPE/DNA lipoplexes have a columnar inverted hexagonal structure, which is not influenced by the cationic liposome/DNA charge ratio. The transfection efficiency of C6 rat glioma cells by DC-Chol--DOPE/DNA lipoplexes and the toxicity of lipoplexes to cells are dramatically affected by cationic liposome/DNA weight ratio. It seems therefore that the lipoplex structures have not any influence on transfection efficiency and toxicity in our experimental system.