Laser tells tale of DNA injury
doi:10.1038/nindia.2011.50 Published online 18 April 2011
New research has provided insight into how ultrashort laser pulses can induce damage to DNA molecules. This may open up avenues for intracellular nanosurgery and help design pathways for delivering genes aimed at single cells.
Studies of how radiation interacts with biological matter have long dealt with the quantification of energy transfer between the radiation field and the irradiated matter. However, it is not well understood how a given dose of radiation induces biological effects on vital biological molecules such as DNA.
To investigate the sequence of events that unfolds soon after biological matter is exposed to radiation, the researchers dissolved plasmid DNA — a type of bacterial DNA — in water. They then exposed this aqueous solution to near-infrared laser pulses of 45 fs duration.
The researchers claim that the energetic photons created hot plasma when passing through water. The hot plasma ionized the water molecules to generate hydrogen atoms and hydroxyl radicals. The electrons and hydroxyl radicals interacted with the plasmid DNA, inducing breaks in the DNA strands.
The hydroxyl radicals were four times more likely than low-energy electrons to induce strand breaks in the DNA. To investigate the individual roles of electrons and radicals in the process of DNA damage, the researchers carried out experiments that involved lacing the solution with 5 bromouracil and melatonin (electron scavengers), or sodium acetate and mannitol (hydroxyl radical scavengers). The study found that adding scavengers reduced DNA damage, thus proving the DNA-damaging roles of low-energy electrons and hydroxyl radicals.
"The insights gained from this study will yield ways to deliver foreign genetic material into cells by transiently altering the cells' permeability through exposure to tightly focused femtosecond laser light," says lead researcher Deepak Mathur.
The authors of this work are from: UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai, and Tata Institute of Fundamental Research, Mumbai, India.