Scientists Devise More Efficient, Precise Method of Inserting DNA into Living Cells

A team of scientists have devised a new method of inserting foreign DNA into cells that, they say, is far more gentle and precise than any that have come before it.

Described in the journal Biomedical Optics Express, the technique includes poking holes on the surface of a cell using a high-powered "femtosecond" laser and retrieving a piece of DNA with "optical tweezers" like a high-tech version of the game Operation.

The process, the researchers say, is an improvement on past methods for a number of reasons, including efficiency (many current techniques are clumsy and often require many tries) as well as its control at the single-cell level.

"What is magical is that all this happens for one cell," Yong-Gu Lee, an associate professor in the School of Mechatronics at the Gwangju Institute of Science and Technology in South Korea and one of the researchers who carried out the study, said in a press release. "Until today, gene transfection has been performed on a large quantity of agglomerate cells and the outcome has been observed as a statistical average and no observations have been made on individual cells."

As a result, Lee explains, former methods could not control whether any individual cell would incorporate a desired gene and that they often left masses of carcasses in its wake.

On the other hand, the study's press release decribes the new technique as working as follows:

"To manipulate the foreign DNA, the scientists used optical tweezers, which essentially tweaks a laser beam whose electromagnetic field can grab hold of and transport a plasmid-coated particle. The researchers first moved the particle to the surface of the cell membrane. Guided by the trapped particle, they then created a tiny pore in the cell membrane using an ultra-short laser pulse from a femtosecond laser. While another laser beam detected the exact location of the cell membrane, they pushed the particle through the pore with the tweezers. Using this technique, the scientists were able to ease a microparticle right up to the pore in the membrane and drop it into the cell, like a golfer sinking an easy putt."

In order to determine whether or not they had succeeded, the researchers inserted a gene that, in the case that all went according to plan, would turn the cell fluorescent green. As it turned out, one in six cells reacted the way the researchers had hoped. 

While this rate is lower when compared to some other methods, the study's authors argue that the new technique's value lies in its precision as well as specificity, which Lee says, allow researchers for the first time to "put one gene into one cell, another gene into another cell, and none into a third" and thus "study exactly how it works."