Cationic liposomes
The structure of cationic liposomes generally consists of three parts:
one or more cationic heads, a linker bond, and a hydrophobic tail. The
cationic head mostly contains amino groups, such as amino, methyl or
hydroxyethyl substituted quaternary ammonium compound (Table 1). The
multivalent polar head group or the polar head with multiple positive
charges has higher transfection efficiency and allows the endosome to
escape, and the tertiary amine group head has higher transfection
activity and lower toxicity than the quaternary ammonium group head.
Linkage bonds mainly include ester bond, amide bond and carbamate bond,
which determine the chemical stability and biodegradability of cationic
lipid molecules. Long-chain aliphatic hydrocarbons in cationic liposomes
can significantly enhance the interaction with cell membrane and have
high transfection efficiency. And the hydrophobic tails of common
cationic liposomes are mainly composed of aliphatic hydrocarbon chains
and cholesterol [36].