UK researchers have developed a liposome with a lower overall positive charge that is therefore less prone to aggregation but retains its ability to deliver DNA. This non-viral vector system for nucleic acid delivery has the potential to be used for gene therapy.

Cationic liposomes are spherical lipid bilayers usually made from a 1 : 1 mixture of a neutral lipid and a synthetic cationic lipid. They work by forming a complex with anionic DNA, and carrying it into cells. However, they have a fundamental flaw - the charge of the liposomes encourages aggregation in biological fluids, which renders them useless. 

Andrew Miller and colleagues, from Imperial College London, developed a neutral lipid that enables the proportion of cationic lipid in the liposome to be reduced significantly. This lowers the overall charge of the liposome complex without causing any loss in activity.

Virus-based equivalents of liposomes currently do a better job of DNA delivery but they can be toxic. Therefore, the development of these 'artificial viruses' is important for the development of treatments such as gene therapy. Miller says that these rational approaches will ensure that 'we will be able to make tailor-made artificial virus particles for clinical use before very long.'

David J Barden