Liposome wrapping is a way of getting DNA into cells without using a virus. It is used mainly for animal cells, including in human gene therapy.Liposomes are small spheres surrounded by a phospholipid bilayer, like a tiny artificial vesicle. For gene delivery, positively charged (cationic) lipids are used because they bind to the negatively charged phosphate groups of DNA.How it works
1. The DNA, often in a plasmid, is mixed with the lipids, which form liposomes around it.
2. Because the liposome membrane is made of phospholipids like the cell surface membrane, the liposome fuses with the membrane or is taken in by endocytosis.
3. The DNA is released into the cytoplasm and some reaches the nucleus, where the gene is expressed.
Example: cystic fibrosis
In gene therapy trials for cystic fibrosis, liposomes carrying a working CFTR gene were inhaled as an aerosol spray. They reached the epithelial cells lining the airways, and some cells produced functional CFTR protein. The effect was modest and temporary because the epithelial cells lining the airways are regularly replaced, so the treatment would need to be repeated.Advantages
• Liposomes are less likely than viral vectors to trigger an immune response.
• They cannot cause infection and can carry large pieces of DNA.
• They are simple and cheap to make.Disadvantages
• Transfer is inefficient: much of the DNA is broken down before reaching the nucleus.
• The DNA usually does not insert into chromosomes, so expression is short-lived.
1. The DNA, often in a plasmid, is mixed with the lipids, which form liposomes around it.
2. Because the liposome membrane is made of phospholipids like the cell surface membrane, the liposome fuses with the membrane or is taken in by endocytosis.
3. The DNA is released into the cytoplasm and some reaches the nucleus, where the gene is expressed.
Example: cystic fibrosisIn gene therapy trials for cystic fibrosis, liposomes carrying a working CFTR gene were inhaled as an aerosol spray. They reached the epithelial cells lining the airways, and some cells produced functional CFTR protein. The effect was modest and temporary because the epithelial cells lining the airways are regularly replaced, so the treatment would need to be repeated.Advantages
• Liposomes are less likely than viral vectors to trigger an immune response.
• They cannot cause infection and can carry large pieces of DNA.
• They are simple and cheap to make.Disadvantages
• Transfer is inefficient: much of the DNA is broken down before reaching the nucleus.
• The DNA usually does not insert into chromosomes, so expression is short-lived.