Self-assembled Cellulose Nano Crystals as a novel approach to mosquito barrier and repellent

Mosquitoes are the deadliest of all combined insects and animals. They are vectors of disease such as malaria, zika, chikungunya, yellow fever, and more affecting millions and killing hundreds of thousands each year. Existing protection methods however are limited and include volatile compounds that actively repel mosquitoes such as DEET or different essential oils. Most are odorous compounds and require organic solvents for dispersion. A recent publication suggested an out-of-the-box solution using graphene sheets as a physical barrier based on the material`s unique strength, building a shield on the skin which prevents the mosquito’s proboscis to reach through the skin. Their work yielded a curious but effective barrier method where the graphene acted as a chemical shield disabling most cues mosquitoes seek to bite. This present work investigates the barrier properties of crystalline nanocellulose (CNC) as an analogy to the graphene barrier tested by Castilho et al. CNCs are known to self-assemble in strong, colourless transparent, chemical barrier films. Their surface chemistry is ideal for aqueous dispersion of many compounds. Simple washing is enough to remove the CNC layer from the skin. 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 A. Aegypti wherein CNC appears to act as a chemical camouflage to the many cues sought by the insects. The combined effect of CNC with a repllent reduced egg laying by 99.4% as compared to control.