Nano-carbon: New India-made weapon against mosquitoes?

Bengaluru: Toxic smog has once again threatened to engulf the National Capital Region (NCR) as farmers in parts of Haryana and Punjab have begun to burn their crop residue. And the zika virus, spread by Aedes Aegypti mosquitoes, has mysteriously raised its head in Rajasthan, having already infected about 90 people and worrying health officials.

Now a team led by Sabyasachi Sarkar, visiting professor and nano-technologist at the Indian Institute of Engineering Science and Technology (IIEST) in Shibpur, West Bengal, has proposed a single solution to solve these twin problems.

The novel method (for simultaneous mosquito and smog control) has been reported in a recent issue of the Journal of Vector Borne Diseases.

The female Aedes mosquitoes that spread dengue, chikungunya, and zika viruses, lay eggs in water bodies along the roadside and in decorative flower pots and vases in homes or offices.

In laboratory studies, the researchers have now shown that water-soluble nano-carbon particles (wsNCP) dissolved in water prevent respiration of mosquito larvae, causing anoxia (lack of oxygen) and ultimately their death. In fact, the larvae exposed to these nano-particles fail to reach even the pupae stage -- one step before becoming an adult mosquito.

"And interestingly, these nano-carbon particles, that are a potent new weapon against the Aedes mosquitoes, can be obtained from 'controlled burning' of crop residue," Sarkar, formerly a chemistry professor at the Indian Institute of Technology-Kanpur, told this correspondent.

The odorless nano-carbon thus produced is environment friendly and is non-toxic to humans. It has also been shown to be harmless to fish and other living species in water, the report says.

For their study, the researchers collected a few Aedes aegypti mosquito larvae from a shallow pool near their institute and reared them in an aquarium containing "fluorescent" wsCNP at a concentration of three micro-grams per millilitre (3ig/ml).

According to the report, "fluorescent imaging" of the entire life cycle of mosquitoes revealed that larvae exposed to the carbon nano-particles died even before attaining the pupae stage. The nano-particles displayed a unique property by getting deposited over the air tube of the larvae choking their respiration causing anoxia and death.

"Based on these observations it can be concluded that the use of non-toxic, wsCNP is safe to prevent growth of mosquitoes in water pots and other hot-spots around house-hold premises," says the report.

"These nano-particles could be economically produced and preserved in the solid form for a long time and can be used as and when required by people without any need to spray chemical insecticides or fogging," Sarkar said. "Once added to water, being non-destructive, it may not require much replenishment."

Sarkar said their study has incidentally shown a solution to the air pollution over the nation's capital due to uncontrolled crop residue burning in neighboring states.

"Under controlled burning of the crop residue, one can get tonnes of such nano products with little chemical modification," Sarkar said. "This carbon based nano-powder so obtained can be distributed to the people for application on any suspected waterbody near homes, offices and schools."

However some experts are sceptical about nano-carbon emerging as a weapon against mosquitoes.

"This will work only in a petri-dish," Payyalore Rajagopalan, former director of the health ministry's Vector Control Research Centre in Puducherry told this correspondent in an email, adding: "But not in nature."