Series of lipids 1a–d and 2a, b, with carbamate linkages between hydrocarbon chains and ammonium or tertiary amine head, which were pH sensitive, were synthesized for liposome- mediated gene delivery. The variable length of carbon chains and quaternary ammonium or neutral tertiary amine heads allowed to find the structure–function relationship of how these factors affect cationic lipids on gene delivery performance.
