Can’t Burn This: DNA Shows Surprising Flame-Retardant Properties

In addition to building organisms and storing Shakespeares sonnets, DNA could also keep your favorite nerd-shirt from going up in flames.

Normally, cotton fabrics are highly flammable.But when scientists tried to set fire to cottoncoated with herring sperm DNA, the fabric refused to burn, the team reported in Journal of Materials Chemistry A.

DNA can be considered as a natural flame retardant and suppressant, said materials scientistGiulio Malucelli, whose lab at Italys Politecnico di Torino, Alessandria branch,tested the fire-retardant properties of DNA. It could work also on other synthetic fabrics, or thin or thick plastic films.

Malucellis lab tested whether the macromolecule could stop fires by using DNA extracted from herring sperm. The team dissolved the DNA in water, coated cotton fabrics with it, let them dry, and tried to light them up. The coating behaved similarly to ammonium polyphosphate, a flame retardant commonly used on polymeric materials such as polyurethanes (found in foams and Spandex) and polyolefins (found in flexible foams and electrical insulation).

DNAs chemical structure makes it ideal for the flame-stopping job. When heated, its phosphate-containing backbone produces phosphoric acid, which chemically removes water from cotton fibers while leaving behind a flame-resistant, carbon-rich residue. The nitrogen-containing bases release ammonia which dilutes flammable gases and inhibits combustion reactions and can act as blowing agents, which help turn the carbon-rich deposits into a slow-burning protective layer. Ultimately, these ingredients stop combustion by forming either a carbon-rich foam, or a protective, glassy carbon coating called char.

I was surprised, and then as I looked at the chemical structure of DNA, it started to become obvious why DNA works as a fire retardant,said Alexander Morgan, a flame retardant materials scientist at the University of Dayton Research Institute.You probably get a mix of the glassy carbon and carbon foam forming during burning of DNA on the fabric.

As a naturally occurring compound, DNA could conceivably be a good green alternative to conventional flame retardants, with a few modifications. First, the cost needs to come down, Morgan says, since its between three and five times more expensive than current chemicals. And the toxicological profile needs to be determined. Though its a natural substance, Morgan notes the possibility that other organisms including the wearer of DNA-coated attire could pick up foreign fragments as the DNA breaks down.

Malucelli thinks thats unlikely. To the best of our knowledge, DNA is not toxic at all, Malucelli said. Its application as flame retardant should not be harmful.

Perhaps most problematically, for the time being, you cant wash a DNA-coated nerd-shirt. The coating is not yet water resistant and will rinse off in the wash. So far, scientists havent yet worked out how to make the treatment more permanent. But Malucelli and his colleagues are investigating a chemical cross-linking strategy, which would bind individual DNA strands to the fabric and to each other, creating a giant, insoluble matrix.

This is a key open issue that has to be solved, he said.

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Can't Burn This: DNA Shows Surprising Flame-Retardant Properties