A team led by inStem researchers has developed a gel for topical application to prevent organophosphate-based pesticides from causing any adverse effects including death. The gel hydrolyses ester found in pesticides into acid thereby making the pesticides inactive and harmless. When applied on rat skin, protection lasted for four days at a stretch. Trials on humans will be taken up soon.

Indian researchers have developed a gel which when applied on the skin can inhibit the most commonly used organophosphate-based pesticides from getting absorbed thus averting serious adverse effects and even deaths. Organophosphate-based pesticides, which are commonly used by farmers in India, are toxic to the nervous system and heart, and can cause cognitive dysfunction.

When esters present in the organophosphate-based pesticides enter the body they bind and inhibit an enzyme (acetylcholinesterase or AChE) critical for neuromuscular function. This causes neurological disorders, suffocation, paralysis, and even death. So a team led by Dr. Praveen Kumar Vemula from the Institute for Stem Cell Biology and Regenerative Medicine (inStem), Bengaluru used the well-known chemical reaction (hydrolyse) to convert the ester into acid by using a catalyst to make the pesticide inactive.

Since majority of the organophosphate-based pesticides are absorbed through the skin (the nasal/inhalation route constitutes about 10-15%) the researchers made a gel for topical application. The active ingredients of the gel are attached to chitosan (a substance found in the hard outer shells of crab and shrimp) so the gel does not penetrate the skin.

Studies on rats found that the gel was effective in a range of temperatures (20-40 degree C) and a single application could protect the animals for four continuous days of pesticide exposure. “As long as there is a thin layer of the gel present on the skin it can offer protection from pesticides,” says Dr. Vemula. “The gel does not act like a physical barrier but chemically deactivates the pesticides thereby limiting the inhibition of the enzyme.” The gel can be washed off using soap.

While the rats that did not receive the gel application and exposed to the pesticide died within seven days, all the animals that received the gel survived. Even 30 days after exposure to pesticides none of the rats that received the gel application showed any visible signs of toxicity. Brain tissue harvested from these rats showed that the gel was effective in preventing the inhibition of the enzyme in the brain. Other studies on rats showed the gel prevented the loss of motor coordination, loss of endurance and altered neuromuscular signalling. The results of the study were published in the journal Science Advances.

“Besides being effective against organophosphate-based pesticides, which constitute 70% of all pesticides used, the gel is effective against carbamate and pyrethrins too,” Dr. Vemula says.

The researchers are also working on developing a face mask to prevent ingestion through the nasal route. “We are carrying out more studies on animals, which will be completed in about four months. We are in the process of setting up a start-up company and plan to carry out trials on humans once we finish preclinical studies,” he says.

Published in The Hindu on October 19, 2018