Therefore, the choice of lipids alone is not sufficient for optimal DNA delivery, and the morphology of the complexes is essential. Figure 2 Proposed model showing cross-sections of extruded DOTAP: Chol liposomes (BIVs) interacting with nucleic acids. Nucleic acids adsorb onto a BIV via electrostatic interactions. Attraction of a second BIV to this complex results in further charge neutralization. … Figure 3 Proposed model showing cross-sections of an extruded DOTAP:Chol
liposome (BIV) interacting with adenovirus. Adenovirus interacts with a BIV causing negative curvature and wrapping around the virus particle. 4. Optimal Lipids and Liposome Morphology: Effects on Gene Delivery Inhibitors,research,lifescience,medical and Expression Choosing Inhibitors,research,lifescience,medical the best cationic lipids and neutral lipids are also essential for producing the optimal in vivo formulation. For example, using our novel manual extrusion procedure does not produce BIVs using the cationic lipid dimethyldioctadecylammonium bromide (DDAB). Furthermore, DOTAP is biodegradable, whereas DDAB is not biodegradable. Use of biodegradable lipids is preferred for use in humans. Inhibitors,research,lifescience,medical Furthermore, only DOTAP and not DDAB containing liposomes produced highly efficient gene expression in vivo . DDAB did not produce
BIVs and was unable to encapsulate nucleic acids. Apparently, DDAB and DOTAP containing SUVs produce similar efficiency of gene delivery in vivo; however, these SUVs are not as efficient as BIV DOTAP:Chol . In addition, use of L-α dioleoyl phosphatidylethanolamine (DOPE) as a neutral lipid creates liposomes that cannot
wrap or encapsulate nucleic acids. Several investigators have reported efficient transfection of cells in culture using DOPE in liposomal formulations. Inhibitors,research,lifescience,medical However, our data showed that Inhibitors,research,lifescience,medical formulations consisting of DOPE were not efficient for producing gene expression in vivo . Investigators must also consider the source and lot variability of certain lipids purchased from companies. For example, different lots of natural check details cholesterol from the same vendor can vary dramatically and will affect the formulation of liposomes. We use synthetic cholesterol instead of natural cholesterol that is purified from the wool of sheep. Synthetic cholesterol is required by the Food and Drug Administration for use in producing therapeutics for injection into humans. Our BIV formulations are also stable for a few years as liquid suspensions. Freeze-dried Ketanserin formulations can also be made that are stable indefinitely even at room temperature. Stability of liposomes and liposomal complexes is also essential particularly for the commercial development of human therapeutics. 5. Liposome Encapsulation, Flexibility, and Optimal Colloidal Suspensions A common belief is that artificial vehicles must be 100nm or smaller to be effective for systemic delivery. However, this belief is most likely true only for large, inflexible delivery vehicles.