Synthetic cationic lipids, which form complexes (lipoplexes) with polyanionic DNA, are presently the most widely used constituents of nonviral gene carriers. Cationic lipid has three important domains in its structure, i.e. a polar headgroup, a hydrophobic moiety, and a linker. While hydrophobic regions, including the length and the degrees of nonsaturation of the alkyl chains, are relatively similar, the structure and component of polar headgroup and linkers are substantially different. The headgroups of cationic lipids exhibiting one or more positive charges can condense negatively charged nucleic acids through electrostatic attraction.