How Cationic Lipid Mediated Transfection Works

Specially designed cationic lipids, such as the Lipofectamine® Transfection Reagents, facilitate DNA and siRNA delivery into cells (Chesnoy and Huang, 2000; Hirko et al., 2003; Liu et al., 2003). The basic structure of cationic lipids consists of a positively charged head group and one or two hydrocarbon chains. The charged head group governs the interaction between the lipid and the phosphate backbone of the nucleic acid, and facilitates DNA condensation. Often, cationic lipids are formulated with a neutral co-lipid or helper lipid, followed by extrusion or microfluidization, which results in a unilamellar liposomal structure with a positive surface charge when in water.

The positive surface charge of the liposomes mediates the interaction of the nucleic acid and the cell membrane, allowing for fusion of the liposome/nucleic acid transfection complex with the negatively charged cell membrane. The transfection complex is thought to enter the cell through endocytosis.

Once inside the cell, the complex must escape the endosomal pathway, diffuse through the cytoplasm, and enter the nucleus for gene expression. Cationic lipids are thought to facilitate transfection during the early steps of the process by mediating DNA condensation and DNA/cellular interactions.

Figure 1: Mechanism of cationic lipid-mediated delivery

The principle of delivery using cationic lipid reagents thus differs from prior attempts to use neutral liposomes for transfections. With cationic lipid reagents, the DNA solution is not deliberately encapsulated within the liposomes; rather, the negatively charged DNA binds spontaneously to the positively charged liposomes, forming DNA cationic lipid reagent complexes.

Cationic lipid-mediated delivery is a fast, simple, and reproducible means for easily introducing DNA, RNA, siRNA, or oligonucleotides into eukaryotic cells. It allows the highly efficient transfection of a broad range of cell types, including adherent, suspension, and insect cells, as well as primary cultures. When selecting a transfection reagent, you must consider the payload you wish to deliver (DNA, RNA, or protein) and the type of cellsyou want to transfect, because the choice of the transfection reagent strongly influences transfections results.

The tables below lists the key features and applications of various cationic-lipid transfection reagents available from our catalog. Click here for more information on each transfection reagent and for optimized transfection protocols for a wide range of cell lines.