Manipulating Solid Forms of Contact Insecticides for Infectious Disease Prevention

Area of Science:

• Solid-state chemistry
• Insect toxicology
• Vector control

Background:

• Vector resistance to pyrethroids in insecticidal nets threatens malaria control.
• DDT, a crystalline insecticide, is being reconsidered despite its notoriety.
• DFDT, a difluoro congener of DDT, showed promise but was dismissed historically.

Purpose of the Study:

• To explore amorphous and crystalline forms of DFDT and MFDT, a fluorinated congener.
• To evaluate their efficacy against disease vectors like *Anopheles* and *Aedes* mosquitoes.
• To establish a link between solid-state properties and insecticidal activity.

Main Methods:

• Synthesis and characterization of amorphous and crystalline DFDT and MFDT.
• Evaluation of insecticidal activity against *Drosophila*, *Anopheles*, and *Aedes*.
• Measurement of knockdown time and correlation with thermodynamic stability.

Main Results:

• Amorphous and crystalline DFDT and MFDT demonstrated faster knockdown times than DDT.
• Amorphous forms exhibited even faster action.
• Knockdown speed was inversely related to thermodynamic stability.
• One enantiomer of MFDT showed faster knockdown, indicating chiral discrimination.

Conclusions:

• Solid-state chemistry manipulation of contact insecticides is a viable strategy for disease vector control.
• DFDT and MFDT offer potential alternatives with improved speed of action.
• Reduced thermodynamic stability correlates with faster knockdown, aiding resistance management.
• Chiral discrimination in MFDT suggests specific interactions at the molecular level.