Non-viral approaches to gene therapy.

There have been rapid advances in the development of non-viral techniques for gene transfer. Although viruses are highly evolved to infect mammalian cells, they have several limitations. The general theme is to mimic the advantageous components of viral systems whilst separating them from their limiting functions. The systems described here are broadly divided into true non-viral techniques and viral-assisted technologies. The merits and limitations of each method are presented, and examples of their application to current developments in gene therapy are discussed. At present no preferred technique has emerged as a clear favourite for non-viral delivery. Further refinement of the technology with particular emphasis on achieving long-term gene expression is required before initiating clinical trials of non-viral gene delivery.