Lasers ease DNA into living cells

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A team of scientists in South Korea has developed a new and highly precise way of inserting DNA into cells. They used a femtosecond laser to make a precisely positioned hole into the surface of a single cell and then gently tugged a piece of DNA through it using optical tweezers, drawing on the electromagnetic field of another laser. The team’s approach has been published in the Optical Society’s (OSA) open-access journal Biomedical Optics Express

The significance of the new method is that it is precise enough to work on a single cell at a time. Previous techniques to graft DNA into cells often used so-called 'gene guns' to fire particles coated with strands of DNA, known as plasmids, at large populations of cells.

Other methods involved scientists puncturing the membranes of individual cells with lasers, placing the cells in a plasmid soup, and then letting the genes diffuse into the perforated cells on their own.

While both of the older methods transfect some of the cells in a population, researchers were not able to control whether any individual cell incorporated the desired genes.

'What is magical is that all this happens for one cell,' said 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 team who carried out the study. 'Until today, the outcome has been observed as a statistical average and no observations have been made on individual cells.'

To manipulate the foreign DNA, the Korean scientists used optical tweezers to grab hold of and transport a plasmid-coated particle to the surface of the cell membrane and then, guided by its position, they 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.

Lee hopes the work will allow other researchers to investigate the effects of transfection on individual cells, not just large populations.