However, sickle cell blood cells, that are rigid, do have problems in the circulation. Therefore, we believe

that flexibility is a more important issue than small size. In fact, BIV DNA-liposome complexes in the size range of 200 to 450nm produced the highest levels of gene expression in all tissues after iv injection [1]. Delivery vehicles, including nonviral vectors and viruses, that are not PEGylated and are smaller #CAL 101 keyword# than 200nm are cleared quickly by the Kupffer cells in the liver. Therefore, increased size of liposomal complexes could extend their circulation time particularly when combined with injection of high colloidal suspensions. BIVs are able to encapsulate nucleic acids and viruses apparently due to the presence of cholesterol in the bilayer (Figure 4). Formulations including DOPE instead of cholesterol could not assemble nucleic acids by a “wrapping type” of mechanism (Figure 5) and produced little gene expression in the lungs and no expression in Inhibitors,research,lifescience,medical other tissues after intravenous injections. Because the extruded DOTAP:Chol BIV complexes are flexible and not rigid, are stable in high concentrations of serum, and have extended half-life, they do not have difficulty circulating efficiently

in the bloodstream. Figure 4 Cryo-electron micrograph of BIV DOTAP:Chol-DNA liposome complexes. Inhibitors,research,lifescience,medical The plasmid DNA is encapsulated between two BIVs. Figure 5 Cryo-electron micrograph of extruded DOTAP: DOPE liposomes complexed to plasmid DNA. Although these liposomes were prepared by the same protocol that Inhibitors,research,lifescience,medical produces BIV DOTAP:Chol, these vesicles cannot wrap and encapsulate nucleic acids. … We believe that colloidal properties of nucleic acid-liposome complexes also determine the levels of gene expression produced after in vivo delivery [1, 34]. These Inhibitors,research,lifescience,medical properties include the DNA:lipid ratio that determines the overall charge density of the complexes and the colloidal suspension that is monitored by its turbidity. Complex Calpain size and shape, lipid composition and

formulation, and encapsulation efficiency of nucleic acids by the liposomes also contribute to the colloidal properties of the complexes. The colloidal properties affect serum stability, protection from nuclease degradation, blood circulation time, and biodistribution of the complexes. Our in vivo transfection data showed that an adequate amount of colloids in suspension was required to produce efficient gene expression in all tissues examined [1]. The colloidal suspension is assessed by measurement of adsorbance at 400nm using a spectrophotometer optimized to measure turbidity. Our data showed that transfection efficiency in all tissues correlated with OD400 of the complexes measured prior to intravenous injection. 6.