Hamilton, ON – In the past, officials wanting to test soil and groundwater for malathion—a widely used organophosphate pesticide that can lead to Alzheimer’s, ADHD, reduced IQ and death—had to carry the unstable agents needed to carry out the test in dry ice and bulky packaging out into the field. Any change in temperature could affect the chemical nature of the agents and render them useless.
Now, those officials have an alternative. Sentinel Bioactive Paper Network researchers working in the Biointerfaces Institute and Department of Chemical Engineering at McMaster University, Sana Jahanshahi-Anbuhi (lead author), Kevin Pennings, Vincent Leung, Meng Liu, Carmen Carrasquilla, Balamurali Kannan, Yingfu Li, Robert Pelton, John Brennan and Carlos Filipe have found a way to ship and store chemically unstable agents and the preservatives to improve their shelf-life in pre-measured tablets.
The researchers used tablets made of pullulan, a natural polysaccharide that dissolves in water but resolidifies into a film when it dries. Pullulan is the only material that meets all the criteria for shipping agents: ships easily, protects against thermal and chemical damage, dissolves in water, releases the agent and does not interfere with the test.
“The ability to keep highly unstable agents such as acetylcholinesterase (AChE) stable for months at room temperature has never been demonstrated before,” says Filipe. “It now becomes possible to take reagents into the field, store them in remote locations under ambient conditions, and then use them when needed,” adds Brennan.
Instead of preparing a fresh batch of solution for each test, officials now simply drop a tablet of AchE into the sample, followed by a tablet of indoxyl acetate, and wait for the sample to turn faint blue or remain colourless if malathion is present.
The research was published (April 25, 2014) by the German Chemical Society in its journal, Angewandte Chemie.
Paper-based biosensors (bioactive paper) offer one of the best approaches for monitoring pesticides because of their low-cost, simplicity and rapid response time. The film-forming property of pullulan has been used in some unique applications in the pharmaceutical and food industries, such as breath fresheners and food additives. Pullulan coatings applied to food packaging can act as oxygen barriers to prolong the shelf-life of various foods. Pullulan has been shown to preserve the viability of bacteria under certain storage conditions.