**6. Neutral lipids**

The commonly used neutral lipids are dioleoylphosphatidylethanolamine (DOPE), as given in **Figure 15**, and dioleoylphosphatidylcholine (DOPC), as given in **Figure 16**. These neutral lipids are used in combination with the other cationic polymers. The gene transfection efficiencies of the cationic polymer are increased when it is used in combination with the helper neutral liquids. The increase in gene transfection efficiency is due to conformational shift to an inverted hexagonal packing structure like a honeycomb by DOPE at lower or acidic pH. The formation

**Figure 15.** Structure of DOPE.

**Figure 16.** Structure of DOPC.

in DOGS are linked to the head group through a peptide bond. The packing ability of DNA by DOGS is due to its large head group molecule and the length of long unsaturated carbon chains. DOGS have efficient packing of DNA, due to its spermine head group. The presence

The commonly used neutral lipids are dioleoylphosphatidylethanolamine (DOPE), as given in **Figure 15**, and dioleoylphosphatidylcholine (DOPC), as given in **Figure 16**. These neutral lipids are used in combination with the other cationic polymers. The gene transfection efficiencies of the cationic polymer are increased when it is used in combination with the helper neutral liquids. The increase in gene transfection efficiency is due to conformational shift to an inverted hexagonal packing structure like a honeycomb by DOPE at lower or acidic pH. The formation

of spermine head group in DOGS leads to efficient packing of DNA [94, 105–107].

**6. Neutral lipids**

**Figure 15.** Structure of DOPE.

**Figure 14.** Structure of DOGS.

148 Advanced Technology for Delivering Therapeutics

of inverted hexagonal-packing structure condenses the DNA inside by electrostatic interactions. During gene transfection, fusion and destabilization of the lipoplex occur which lead to the release of DNA from endosomal vesicles. Cationic polymers DOTAP, DC-Chol and other cholesterol derivatives have been incorporated with DOPE for gene transfection efficiency [94, 103, 108–114].
