Implicating ABC Transporters in Insecticide Resistance: Research Strategies and a Decision Framework.

Pest insects damage crops, transmit diseases, and are household nuisances. Historically, they have been controlled with insecticides, but overuse often leads to resistance to one or more of these chemicals. Insects gain resistance to insecticides through behavioral, metabolic, genetic, and physical mechanisms. One frequently overlooked strategy is through the use of ATP-binding cassette (ABC) transporters. ABC transporters, present in all domains of life, perform natural excretory functions, thus the exploitation of these transporters to excrete insecticides and contribute to resistance is highly plausible. Previous work has implicated ABC transporters in some cases of insecticide resistance. Proposed herein is a framework meant as a formal guide for more easily incorporating the analysis of ABC transporters into existing resistance monitoring using suggested simple research methods. This framework functions as a simple decision tree and its utility is demonstrated using case examples. Determining a role for ABC transporters in insecticide resistance would help to shape future resistance management plans and guide the design of new insecticides.

Development of a biopolymer nanoparticle-based method of oral toxicity testing in aquatic invertebrates.

Aquatic toxicity testing generally focuses on the water absorption/dermal route of exposure to potential toxic chemicals, while much less work has been done on the oral route of exposure. This is due in part to the difficulties of applying traditional oral toxicity testing to aquatic environments, including the tendency for test chemicals to dissolve into water. The use of biopolymer nanoparticles to encapsulate test chemicals onto food to prevent dissolution is one solution presented herein. The biopolymers zein and chitosan were explored for their previously known nanoparticle-forming abilities. Nanoparticles containing the test chemical rhodamine B were formed, applied as films to coat food, and then fed to the test organism, the freshwater amphipod Hyalella azteca. In feeding trials both zein and chitosan nanoparticles showed a significantly lower release rate of rhodamine B into water than food dyed with rhodamine B without biopolymer nanoparticles. Zein nanoparticles also showed better retention ability than chitosan nanoparticles. Both kinds of nanoparticles showed no significant effect on the survival, growth, or feeding behavior of H. azteca. Thus these biopolymers may be an effective system to encapsulate and deliver chemicals to aquatic invertebrates without interfering with common toxicity assessment endpoints like survival and growth.