| abstract |
A lipid assembly, such as a liposome, for improving the fusibility of the lipid assembly, comprising a transfection enhancer element (TEE) that forms a complex with the lipid assembly by ionic interaction, or Lipids incorporating such TEEs are disclosed. TEE has the following formula: Hydrophobic moiety-pH sensitive hydrophilic moiety (II) The pH sensitive hydrophilic portion of each TEE is a zwitterionic structure of pKa 3-8 containing a weak acid of pka 2-6, or a combination of an acidic group and a weak base. A lipid incorporating one or more such TEEs has the following formula (I): Lipid moiety- [hydrophobic moiety-pH sensitive hydrophilic moiety] (I) |