Mosquito bite prevention through self-assembled cellulose nanocrystals

Mosquitoes are the deadliest of all combined insects and animals affecting millions and killing hundreds or thousands of people each year. Existing protection methods however are limited and include volatile compounds that actively repel mosquitoes such as N,N-Diethyl-meta-toluamide (DEET) or different essential oils such as geraniol and citronella. Most are odorous compounds and require organic solvents for dispersion. This work investigates the barrier properties of cellulose nanocrystals (CNCs). CNCs are known to self-assemble in strong, transparent, chemical barrier films. They are fully bio-based, and their surface chemistry is ideal for aqueous dispersion of many compounds. This work saw a significant 80% decrease in feeding on human skin when a thin CNC coat was applied. The effect was further confirmed by artificial feeding on Aedes aegypti wherein CNC appears to act as a chemical camouflage to the many cues sought by the insects. The combined effect of CNC with indole reduced egg laying post exposure to mammalian blood close to null with 99.4% less eggs as compared to control. The chemical barrier effect was assessed through a simple headspace experiment showing that the same CNC coat blocked the passage of ammonium hydroxide vapor, a commonly used mosquito attractant, when applied on a filter paper membrane.