DOTAP Liposomes for DNA/RNA Delivery

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BOC Sciences has developed DOTAP Liposomes with DOTAP content ranging from 0.5% to 50%. DOTAP stands for 1,2-di-O-octadecenyl-3-trimethylammonium propane, which is a cationic lipid. Cationic lipids are commonly used for gene delivery because they can bind to negatively charged nucleic acids and form stable complexes, which protects the nucleic acids from degradation and facilitates their uptake into the cell.

What are DOTAP Liposomes?

DOTAP liposomes are lipid nanoparticles composed of DOTAP, which can be used to deliver DNA and RNA molecules into cells. DOTAP is an amphiphilic molecule consisting of three main parts: a polar head (hydrophilic group), a linkage bond, and a hydrophobic tail. It is the polar head of DOTAP that binds to the negatively charged DNA molecule through electrostatic interaction, which usually consists of tertiary amines or quaternary ammonium salts, and later on imidazole head, amino acid head, and so on have been studied. Its polar head has an important effect on the encapsulation efficiency of nucleic acid molecules as well as cytotoxicity.

Characteristics of DOTAP Liposomes

Protect therapeutic genes from degradation during in vivo circulation. Through special modification of the surface groups of the liposomes, DOTAP liposomes can wrap DNA fragments well, promote the fusion of the complex with the cell membrane, and increase the uptake and expression of DNA.
Efficiently crosses cell and nuclear membranes and transfects cells to express/silence genes.
If the indication is cancer, it is able to selectively adsorb on negatively charged neoplastic tumor vascular endothelial cells for better anti-cancer effect.

Mechanism of Action of DOTAP Liposomes

Tight Binding to Nucleic Acids

Since DOTAP liposomes are positively charged liposomes, they can interact with negatively charged nucleic acid molecules such as DNA or RNA. This interaction is usually achieved by electrostatic attraction. DOTAP liposomes can form stable complexes called lipoplexes (liposome-nucleic acid complexes) when bound to nucleic acids.

Cellular Uptake

DOTAP liposomes are able to interact with cell membranes and facilitate the cellular uptake of the complexes. This interaction occurs primarily through charge mutual attraction and physical interaction with the cell membrane. After binding to the cell membrane, liposomes can enter the cell interior through different uptake pathways (e.g. endocytosis).

Crossing the Cell Membrane

Once DOTAP liposomes enter the cell, they can release nucleic acid molecules from the complex through mechanisms such as fusion or endocytosis. The fusion and endocytosis capabilities of liposomes can help release nucleic acids efficiently into the cytoplasm.

Nucleic Acid Release and Transfection

After nucleic acids enter the cytoplasm, they can play roles within the cell, such as synthesizing specific proteins or regulating gene expression. The efficiency of nucleic acid release and transfection depends on the nature of the liposomes and the stability of the complex.

Applications of DOTAP Liposomes

The higher the amount of DOTAP in DOTAP liposomes, the higher the drug loading capacity, but the higher the Zeta potential the higher the cytotoxicity and the safety of the formulation is affected, the two need to be balanced. For encapsulated chemotherapeutic drugs, drug loading is not dependent on DOTAP, and other neutral phospholipids such as DSPC, DPPC, can be added to the liposome formulation, which is less restricted in terms of dosage.

DOTAP was first used commercially as a transfection reagent, where the polar head of DOTAP binds stably to negatively charged DNA molecules through electrostatic interaction, and the two spontaneously form a stable complex when mixed. This method of transfection is very gentle and avoids the cytotoxic effects of lipid transfection or other methods of transfection, and the transfection efficiency is higher than that of other lipid reagents. Currently, the more successful application cases of DOTAP include EndoTAG-1, a cationic liposome of paclitaxel, and EndoTAG-2, a cationic liposome of camptothecin, which are also widely used as excellent transfection reagents.