1,721,113 research outputs found
Formation of overcharged cationic lipid/DNA complexes
No full textThe widely accepted 'counterions release' mechanism predicts the existence of charge-neutral cationic lipid/DNA complexes (lipoplexes). Formation of overcharged complexes, both positively and negatively charged, is supposed to be driven by thermodynamics. Here we report a synchrotron small angle X-ray diffraction and dynamic light scattering study aimed to shed light on the mechanism of formation of lipoplexes. By using a two-step process, consisting in adding excess material to preformed isoelectric lipoplexes, we showed that excess DNA does enter preformed complexes while excess lipid does not. Our findings imply that DNA may play a special role in the formation of overcharged lipoplexes. (c) 2006 Elsevier B.V. All rights reserved
Size and charge of nanoparticles following incubation with human plasma of healthy and pancreatic cancer patients
No full textWhen nanoparticles (NPs) enter a biological environment, proteins bind to their surface forming a protein coating, which alters NP features giving it a biological identity, which controls its physiological response. The NP biological identity (size, charge and aggregation state) does strictly correlate with its physicochemical properties and the nature of the biological environment. While the former relationship has been extensively investigated, whether and how alterations in the physiological environment affect the biological identity of the NPs remains unclear. In this work we enrolled healthy and histologically proven pancreatic cancer patients. A statistically significant reduction in the level of clinically relevant proteins in cancer patients occurred. Positively and negatively charged lipid nanoparticles with two different surface chemistries (plain and PEGylated) were incubated with human plasma from both groups and characterized thoroughly by dynamic light scattering and zeta potential measurements. Only when plain positively charged NPs were tested, significant difference in zeta-potential between healthy and pancreatic cancer groups was found. This result implies that pooling human plasma from healthy volunteers might lead to a bias and thus unpredictable consequences in regard to previously optimized targeting profile.When nanoparticles (NPs) enter a biological environment, proteins bind to their surface forming a protein coating, which alters NP features giving it a biological identity, which controls its physiological response. The NP biological identity (size, charge and aggregation state) does strictly correlate with its physicochemical properties and the nature of the biological environment. While the former relationship has been extensively investigated, whether and how alterations in the physiological environment affect the biological identity of the NPs remains unclear. In this work we enrolled healthy and histologically proven pancreatic cancer patients. A statistically significant reduction in the level of clinically relevant proteins in cancer patients occurred. Positively and negatively charged lipid nanoparticles with two different surface chemistries (plain and PEGylated) were incubated with human plasma from both groups and characterized thoroughly by dynamic light scattering and zet
Dynamical properties of oriented lipid membranes studied by elastic incoherent neutron scattering
No full textWe have studied the H-bonded dynamics in highly oriented lamellar DOTAP-DOPC model membranes as a function of the DOPC/(DOPC + DOTAP) ratio Φ, by elastic incoherent neutron scattering in the 100 ps time domain on the spectrometer IN13 at ILL. Motions in the in-plane and out-of plane directions have been explored by orienting the momentum transfer predominantly parallel and normal to the surface of highly oriented multilayers, respectively. Increasing the neutral lipid (DOPC) concentration from Φ = 0.5-0.8 we reveal a reduction of the dynamics along the direction normal to the membrane and an unchanged dynamics on the membrane plane
Correlation between Structure and Transfection Efficiency: a Study of DC-Chol-DOPE/DNA Complexes
No full textThe 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 (3β[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
Multicomponent cationic lipid-DNA complex formation: Role of lipid mixing
No full textMulticomponent cationic lipid-DNA complexes (lipoplexes) were prepared by adding linear DNA to mixed lipid dispersions containing two populations of binary cationic liposomes and characterized by means of small angle X-ray scattering (SAXS). Four kinds of cationic liposomes were used. The first binary lipid mixture was made of the cationic lipid (3?[N-(N?,N?-dimethylaminoethane)-carbamoyl]cholesterol (DC-Chol) and the neutral helper lipid dioleoylphosphocholine (DOPC) (DC-Chol/DOPC liposomes), the second one of the cationic 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and the neutral dio- leoylphosphatidylethanolamine (DOPE) (DOTAP/DOPE liposomes), the third one of DC-Chol and DOPE (DC-Chol/DOPE liposomes), and the fourth one of DOTAP and DOPC (DOTAP/DOPC liposomes). Upon DNA-induced fusion of liposomes, large lipid mixing at the molecular level occurs. As a result, highly organized mixed lipoplexes spontaneously form with membrane properties intermediate between those of starting liposomes. By varying the composition of lipid dispersions, different DNA packing density regimes can also be achieved. Furthermore, occurring lipid mixing was found to induce hexagonal to lamellar phase transition in DOTAP/DOPE membranes. Molecular mechanisms underlying experimental findings are discussed
How lipid hydration and temperature affect the structure of DC-Chol-DOPE/DNA lipoplexes
No full textEffect of lipid hydration on the structure of lamellar lipoplexes made of the cationic lipid 3-[N-(N,N-dimethylaminoethane)-carbam- oyl]cholesterol (DC-Chol), the neutral ‘helper’ lipid dioleoylphosphatidylethanolamine (DOPE) and calf-thymus DNA was investigated by synchrotron small angle X-ray diffraction (SAXD). Here, we show that lipid hydration is the key factor regulating the equilibrium structure of lipoplexes. Thermotropic behavior was also investigated between 5 and 65 °C. Both the membrane thickness and the water layer thickness were found to decrease linearly as a function of temperature while the one dimensional DNA rod lattice between lipid bilayers was found to enlarge. Structural results were interpreted in terms of recently proposed theoretical models
One-dimensional thermotropic dilatation area of lipid headgroups within lamellar lipid/DNA complexes
No full textUsing simultaneous synchrotron small- and wide-angle X-ray diffraction (SWAXD), we investigated the thermotropic behavior of a cationic lipid mixture of DOTAP-DOPC (1,2-dioleoyl-3-trimethylammonium-propane-dioleoylphosphatidylcholine) liposomes complexed with calf thymus DNA. The DOTAP-DOPC/DNA complex reacts to temperature change by a bilayer compression normal to its surface and an expansion of the DNA in the plane of the rod lattice. By applying two independent recently developed models, we show here for the first time that the thermotropic dilatation area of lipid headgroups within the complexes is not isotropic but occurs parallel to the I D DNA lattice (i.e., along the direction perpendicular to the DNA axis). Our results shed light on the role of spatial dimensionality in the DNA packing density within lamellar lipoplexes and provide experimental evidence that the interaction between DNA molecules confined between lipid bilayers can be regarded as a ID problem
MULTI-COMPONENT CATIONIC LIPOSOME/DNA COMPLEXES: NEW EFFICIENT VECTORS FOR GENE DELIVERY
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