DNA taxi

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DNA taxi

http://www.news-medical.net/?id=17640

Despite few successes to date, gene therapy is a highly promising

approach for medical therapy in the future.

One of the biggest difficulties with this process is finding a

suitable transport agent that can carry the nucleic acid being used

as a " drug " into the diseased target cell. Killed viruses have been

used as " taxis " for these genes, but these often have unexpected

health consequences.

Recently, nanoparticles have been developed for gene therapy. A

successful example of this has been described by V. M. Rotello, N. S.

Forbes, and their co-workers in Massachusetts, USA. They used tiny

spheres of gold with tightly packed, positively charged hydrocarbon

chains bound to their surface. These chains contain a photolabile

bond that is stable to visible light but breaks when irradiated with

UV light at a wavelength of 350 nm. This causes the positively

charged fragment to fall off, leaving the gold sphere with a negative

charge on its surface.

DNA contains negatively charged phosphate groups that allow it to

bind to the positively charged gold spheres through electrostatic

interactions. Cells that were brought into contact with gold spheres

loaded with DNA allowed these " DNA taxis " to pass into their

interior. The signal to " unload " was given by subsequent irradiation

with UV light: it destroyed the photolabile bond, reversing the

surface charge of the gold particles and releasing the DNA.

Fortunately, the DNA was not only brought into the cytoplasm; it made

its way to where it was needed: the cell nucleus. This is the

location in the cell where DNA molecules are copied for translation

into proteins or are multiplied for cell division.

This process offers a relatively simple possibility for the transport

and controlled release of DNA into living cells. In addition, the

authors believe that this method should make it possible to steer

interactions with other biomolecules, such as proteins or

pharmaceutical agents, making it possible to target specific cells.