The environmental damage wrought by crop pesticides, herbicides and fungicides are legion. They can contaminate soil, water and air, and cause a host of health problems in humans and wildlife alike.
That’s why chemists are working to mitigate the effects of protecting our food from destructive infestations and infections. McMaster University chemical engineer Todd Hoare is among them. He is working with Canadian energy company Suncor to create a new type of chemical spray that helps plants fight their own battles and is less harmful to the environment.
His job is to develop a particle that can deliver to the plant a pair of chlorophyl-based chemicals designed by Suncor researchers. The first chemical – sodium magnesium chlorophyllin – is a photosensitizer that produces reactive oxygen when exposed to sunlight. This is important because reactive oxygen kills pests.
“Plus, it would be very difficult for pests to form a resistance,” says Suncor’s project lead, chemist Michael Fefer. “That’s because reactive oxygen doesn’t attack just one biochemical pathway, but many at once.”
The second chemical – sodium copper chlorophyllin – strengthens the plant’s immune system so it can better withstand drought, heat and salty soils. Ideally, the two chlorophyll-based chemicals could be applied sequentially, says Fefer.
Hoare and his team have had good results in trials of a delivery system based on a hybrid nanoparticle composed of sodium dodecylbenzenesulfonate and cetyltrimethylammonium bromide. The nanoparticle successfully delivered sodium copper chlorophyllin into the plant’s leaves and roots while protecting the chemical from washing off in the rain, or degrading in sunlight.
The hybrid nanoparticle has a hydrophobic tail and a hydrophilic head that temporarily weakens the junction between the plant’s cells so that it can penetrate the plant, rather than simply coat its surface. This penetration does two things – it gets the chlorophyl-based chemicals to where they need to be, and requires less spraying because rain and morning dew won’t wash it off. Some research suggests plants retain less than 0.1 per cent of conventional sprayed pesticides and insecticides because much of it washes away.
Hoare’s team is now experimenting with various amphipathic particles – including non nanoparticles – to find the most effective one. “We’re hopeful one of the strategies will become a commercial product,” says Hoare, Canada Research Chair in Engineered Smart Materials. “Instead of using chemicals that kill a bunch of stuff, we’re trying to enhance the plant’s ability to protect itself.”
McGill University’s Canada Research Chair in Sustainable Nanotechnology for Food and Agriculture Saji George says while there are significant benefits to Hoare’s approach, he has general concerns about the safety of nano-sized agrochemicals.
“The Cu-Chl encapsulated in nanovesicles showed no toxicity in tested duck weed (a model plant). However, concerns to aquatic organisms and human cannot be overruled as the nanovesicles are made of surfactants,” says George, who was not involved in the project. “Further concerns regarding the scalability and stakeholder acceptance are other factors to be addressed for successful translation of this technology.”
Fefer says Suncor is sensitive to such concerns and that any potential nanoparticle delivery system would need to satisfy all health and safety regulations.
“While nanoparticle chemistry is interesting, we do not foresee their commercialization, at least in the near term,” says Fefer. “Rather we will use what was learned with nanoparticles as a technical platform to formulate pest control products that do not fall into the definition of nanoparticles.”