PHOSPHOTRIESTERASE LOADED MICROPARTICLES TO CONTROL ORGANOPHOSPHATE TOXICITY IN POLLINATORS

Abstract

Bee pollination supports the production of 87 of the leading food crops worldwide and contributes $19.2 billion to U.S. farm income. Organophosphates are a heavily used group of insecticides that are considered detrimentally impactful to pollinator health. Exposure at lethal and sub-lethal doses can impair individual and colony fitness, risking pollination quality and food security. In vivo detoxification of major insecticides within managed honeybee populations presents a strategy to mitigate colony collapse disorder. In synthesizing a pollen mimicking microparticle treatment (OPT-GCMP), we have improved the stability, efficacy and retention of the phosphotriesterase (OPT), whilst fabricating uniform and degradable microparticles capable of loading OPT at 90% efficiency. Microcolonies of bumblebees fed malathion-contaminated pollen patties have demonstrated 100% survival when fed OPT-GCMP, 0% survival with OPT and 0% survival with plain sucrose. Bumblebee survival was also improved via OPT-GCMP treatment under paraoxon exposure. Improved enzyme activity can be attributed to reduced OPT degradation in the case of OPT-GCMP due to the acid scavenging capability of the microparticles. Imaging of fluorescently tagged OPT-GCMP and OPT, demonstrated higher digestive retention of microparticles. OPT-GCMP could be visualized throughout digestion (4 hrs) as their pollen-mimicking geometry allowed good extraction of the treatment into the midgut. Free-OPT solely remained bioactive up to 1 hour after consumed and could not be detected in the posterior section of the GI tract. This design presents a versatile and scalable treatment for bees which can be integrated into dietary syrup to safeguard pollinators from intensive organophosphate application.