Pesticide analysis for foods and biological samples are often performed via liquid chromatography-mass spectrometry (LC-MS), an accurate and sensitive, but also complex and expensive, analytical method. In low-income regions of the world, where expensive analytical equipment is not readily available, methods for detecting pesticides are more limited, and acute, even fatal, poisoning cases in agriculture are more common. In an effort to design a simpler, less expensive and more accessible testing method for toxic organophosphate pesticides, researchers from the Vidyasirimedhi Institute of Science and Technology (VISTEC), Mahidol University, Burapha University and the Japan National Institute of Advanced Industrial Science and Technology (AIST) have developed a new, novel process modeled on the bioluminescence of fireflies.
Luciferin is the compound in fireflies that causes them to glow when it reacts with oxygen - the catalyst for this reaction is luciferase. In order to develop a method that leverages the luminescence of luciferin, the researchers designed a new enzymatic cascade reaction that synthesizes luciferin analogs from phenolic compounds, a process they call the HELP (HadA Enzyme for Luciferin Preparation) reaction. This reaction makes it incredibly easy to synthesize these luminescent materials without the need for special expertise or toxic chemicals. The luciferin analogs created in this process produce luminescence at different wavelengths, allowing for parallel detection of different target molecules. Additionally, the team produced two previously unknown luciferin analogs, one of which produces brighter light of a longer wavelength than the original luciferin.
The organophosphate detection method based on HELP, called LUMOS (Luminescence Measurement of Organophosphate and Derivatives), includes three reaction steps: first, an enzyme from soil bacteria breaks down the organophosphate pesticides and/or their metabolites into phenol derivatives. Second, these derivatives are converted into luciferin analogs via the HELP reaction. Finally, the luciferin derivatives produce bioluminescence signals with firefly luciferase, and the wavelengths can be used to differentiate between different organophosphate pesticides, including parathion, methyl parathion, EPN, profenofos and fenitrothion. The team was able to detect these pesticides in concentrations of parts per trillion in urine, blood serum and fruit, without sample preparation. This research was published in Angewandte Chemie International Edition.
Due to its simplicity and low cost, LUMOS could potentially be used to detect toxic organophosphate pesticides in regions without access to more complex analytical instruments, and offers better sensitivity and reliability than other test kits available, according to the researchers. LUMOS is also an environmentally friendly method as it does not require the use of toxic chemicals.