Fight fire with DNA

A recent study shows that DNA can be an effective fire retardant. Basically, DNA is a chain of entities called nucleotides, which in turn contain a sugar, a molecule of phosphate and a molecule of nitrogen containing substance. The three constituents together give it its fire fighting quality, writes Kollegala Sharma.

Who hasn’t heard of DNA? The molecule ubiquitous in living things, however, remains a mystic chemical for the common man, heard mostly in association with high-profile research or crimes. That perception is going to change forever, if the efforts of a team of Italian chemists bears fruit. Prof. Giulio Malucelli of the Department of Applied Science and Technology, Torino Polytechnic, Alessandria, Italy along with his colleagues of the same Department in Torino, Italy plans to use DNA as a fire retardant. A preliminary result of the team’s efforts were published recently in the Journal of Material Chemistry-A.

Intumescents or fire retardants are big business. That is not a wonder because fabrics, synthetic or natural, are fire-friendly. Although there are umpteen number of fire retardants, some synthetic substances have gained popularity recently. If the Malucelli team’s plans fructify, DNA could be another addition to the growing list of intumescents.

It’s in the DNA

Among fire-retardant coatings, the most popular and efficient ones are hydroxylmethylphosphonium salts or N-methylol phosphono-propionamide compounds. The constitution of the DNA is similar to these popular fire retardants in that, like them, it also has an acid source, a carbon source (sugar) and a blowing agent (nitrogen containing compound) — three components vital to fire retardants. While the acid source reduces the temperature at which the carbon source catches fire, the blowing agent spews out water or carbon dioxide, putting off the fire instantly. Thus, in case of a fire, the retardant sacrifices itself to burn out into a protective char leaving the fabric underneath unscathed by the fire. The charred layer is crucial to resist any further fiery damage.

“Because DNA contains the three main ingredients of an intumescent system, we tried to use it as a fire retardant”, says Malucelli elaborating on the novel idea. For those who are new to the molecules, DNA is a chain of entities called nucleotides. Nucleotides in turn contain a sugar, a molecule of phosphate and a molecule of nitrogen containing substance. The three together give DNA its intumescent character, asserts the team.
Malucelli’s team has conducted intricate tests to find out whether their surmise that DNA can protect clothes from catching fire is real.

The team used herring’s DNA on cotton fabrics. Pieces of cotton fabric were soaked in a DNA solution, the excess solution was squeezed off and the cloth pieces were dried. The cotton cloth absorbed about one-fifth of its weight of DNA solution. Later, the DNA soaked cotton fabrics are put to a fiery test to see if they withstood high temperatures without catching fire. Not only that, the tested cloth was examined closely with sophisticated instruments to see if there were really any molecules of DNA on the cloth, before and after the fire test.

Test results

The tests, the team says, show that DNA can be an effective fire retardant. Cotton fabrics without coatings burned out within about 80 seconds whereas those coated with DNA burnt for just two seconds after which it was near impossible to light the fabric again. It could be clearly seen under the microscope that the cotton fibres in the DNA-coated piece remained more or less intact while in the uncoated piece, they were mostly broken down.

In another test where the fabric was held in a flame and burnt, the DNA-coated fabric contained more char (72 per cent) than the uncoated one, indicating that the flames had died down early in DNA coated fabric. A fabric fully consumed by the fire leaves little char.
The team says, “DNA is proved to be a potential flame retardant or suppressant thanks to its high char-forming character”. This gives a whole new twist to the uses of DNA. So far, commercially produced DNA finds use in laboratories for furthering biomedical research. Another idea, of molecular computing, is yet to get out of the laboratories. Molecular computing is all about using arrangement of nucleotides in the DNA for computing information aka microprocessors.

The Italian team’s new found use for DNA surely gives it an image makeover from an esoteric molecule to a down-to-earth chemical.

The only hitch that could retard the use of DNA as a fire-proofing coating could be its availability. As of now, commercially, DNA is produced from sperms of herring or salmon fish and is almost exclusively used for the purpose of research. But for this, as Malucelli points out, “DNA could be a green, natural flame retardant”, which leaves no scar on the environment in terms of persistent residues. That is one up on other commercial retardants.