Realization of the potential of nucleic acids as drugs is intricately linked to their in vivo delivery. Cationic lipids demonstrated tremendous potential as safe, efficient, and scalable in vitro carriers of nucleic acids. Cationic lipids employed in formulating liposomes designed for the delivery of nucleic acids are amphiphilic in nature and consist of a positively charged (cationic) amine head group linked to a hydrocarbon chain or cholesterol derivative via glycerol. An important property of these lipids is the ability of their positively charged head group to undergo electrostatic interaction with the negatively charged nucleic acids, permitting the encapsulation of the nucleic acid in the core of the lipid-based nanoparticles. The cationic lipid complex with nucleic acid has at least three functions. First, by electrostatic binding to nucleic acids, the cationic lipid coats and partially condenses the nucleic acids to form transfection-competent particles. Second, the presence of cationic lipids results in an overall positive charge, which enhances the binding of liposomes to negatively charged cell surfaces, leading to cellular uptake via endocytosis. Third, following uptake, the cationic lipids act to destabilize the endosomal membrane, thereby facilitating the delivery of nucleic acids in the cytoplasm.
Composition of the cationic lipids
Although the reported cationic lipids vary in structure, most of them contain three basic components, the cationic head group, the hydrophobic lipid anchor group, and the linker group.
Cationic head group
The head group, i.e., the cationic module of the lipid, is a quaternary ammonium group. Very successful cationic lipids were designed using this group. In addition, polyamines, guanidinium, heterocyclic, amino acid- and peptide-based head groups have been tested successfully. The main function of cationic head groups is to condense negatively charged nucleic acids by means of electrostatic interaction to slightly positively charged nanoparticles, leading to enhanced cellular uptake and endosomal escape.
Hydrophobic lipid anchor group
The hydrophobic fraction usually contains simple aliphatic hydrocarbon chains, such as fatty acid chains of different lengths and unsaturated states, or steroids, such as cholesterol, which contribute to the formation of liposomes and exchange of lipids on cell membranes. The type and length of the aliphatic chains affect the transfection efficiency. The most efficient cationic lipids are the two linear fatty acid chains such as 1,2-di-O-octadecenyl-3-trimethylammonium-propane (DOTMA) and 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP).
The linker group is a very important component of the cationic lipid molecule, which determines the chemical stability, biodegradability, and transfection efficiency of the cationic lipid. Ether bonds and C-N bonds are more chemically stable, but they are not easily biodegradable and are generally not suitable for in vivo experiments. Cationic liposomes containing ester bonds are more readily biodegradable and less cytotoxic, but they are usually less chemically stable. The commonly used linker groups are amide and carbamoyl bonds, which are chemically stable and biodegradable.
What we offer
The ability of cationic lipids to promote formation of non-bilayer structure and the correlation between this property and intracellular delivery of macromolecules such as nucleic acids offer the possibility of rational design of intracellular delivery systems. This nucleic acid delivery process is safe, rapid, and scalable. Alfa Chemistry supplies cationic lipids to companies researching nucleic acid delivery systems. If you cannot find the cationic lipid you need, please contact us. We also offer product customization according to customer's detailed requirements.
Our products and services are for research use only and cannot be used for any clinical purposes.