Ultrashort pulses help gene therapy

19 Jul 2002

Scientists in Germany have used a Ti:sapphire laser to transfer DNA into a cell.

Femtosecond lasers improve the transfer of DNA into cells and could advance the fields of gene therapy and DNA vaccination, claim two scientists in Germany.

In this week's Nature, Karsten König and Uday Tirlapur describe how they pierced a cell membrane with a Ti:sapphire laser, allowing DNA delivery through the resulting hole (a process known as transfection). This hole soon closes up, with the implanted cell and the new DNA appearing undamaged by the whole process (Nature 418 290).

The team, from Friedrich Schiller University in Jena, says that this is a better method than conventional cell-perforation techniques. For instance, electroperforation cannot target individual cells, while mechanical or chemical techniques can damage either the cell or the foreign DNA.

Nanosecond laser pulses from a frequency-tripled Nd:YAG source have also been tried, but according to the researchers, this technique damages the cells beyond repair.

The femtosecond pulses were focused at the cell membrane using a high-numerical-aperture objective lens. The target cells were exposed to the 50-100 mW average power beam for 16 ms during transfection.

Having implanted the foreign DNA into the target cells, König and Tirlapur used the same setup to study the success of the transfer. To do this, they tagged the foreign genes with green fluorescent protein (GFP). The Ti:sapphire source then generated two-photon fluorescence images of the cell expressing the GFP.

The researchers say that irrespective of the type of cell implanted with foreign DNA, the femtosecond laser method worked each time. They add that the high level of selectivity prevented transfection into any neighboring cells, and claim "no detrimental effects on growth and division, and virtually no cell death".

In gene therapy, a cell which lacks a certain gene is fixed by implanting foreign DNA that can express the missing gene. Though potentially revolutionary, the technique is also highly controversial.

Author
Michael Hatcher is technology editor of Opto and Laser Europe magazine.