Formulation and evaluation of cashew nut shell oil and pungam oil-loaded nanocapsules for larvicidal activity against Aedes aegypti

Abstract

Objectives: Mosquitoes are the potential vectors of many diseases such as dengue malaria and brain fever. Effective
control of vector borne diseases is possible by early diagnosis and prompt treatment of vector control. Nanotechnology,
a promising field of research in the present decade, is expected to give major impulses to technical innovation.
Larviciding is a key strategy used in many vector control programs around the world. In recent years, essential oilbased
larvicides have been introduced as alternatives to industrial ones. Methods: The present work was carried out
to formulate nanocapsules containing natural oils (Cashew nut shell oil [CNSL] and pungam oil) using gum Arabic
and maltodextrin as polymer which does not require complex apparatus and special precautions by emulsion diffusion/
solvent evaporation method and to determine the mortality rate of the dengue larva using various concentrations of
prepared nanocapsules. Physicochemical properties and duration of larvicidal action of the formulated nanocapsules
were investigated. Results: The formulation F4 has better encapsulation efficiency (78.08 ± 0.91) when compared
to other formulated nanocapsules and the particle size was found to be 714.1 nm with polydisperse index of 0.105.
Zeta potential of the nanocapsule formulation was found to be around −42.0 mV which is essential for long stable
formulation. The comparison of FTIR spectra of pure oil samples (CNSL: Pungam oil) and formulated nanocapsule
F4 confirms the entrapment of drug in the formulation, without any chemical interaction. The scanning electron
microscopy photographs reveal that the particle size of the nanocapsules were within 1000 nm. The mean particle size
of the nanocapsule observed by transmission electron microscopy is comparable with the mean size obtained using
the Malvern Zetasizer. In 2000 μg/mL concentration of nanocapsules, metabolite showed strong activity against Aedes
aegypti larvae and the mortality rate was higher. The LC50 value of the given test samples (Pungam Oil, CNSL, and
Nanocapsule Formulation F4) was found to be 1402.81 μg/mL, 270.39 μg/mL, and 1545.25 μg/mL, respectively. The
stereomicroscopical study of CNSL and pungam oil nanocapsules of 2000 μg/mL concentration treated with A. aegypti
induced toxic effects on many effects on many regions of the body. Conclusion: In summary, our study shows that the
prepared nanocapsules present a clear larvicidal effect against third instar larvae of A. aegypti larvae. Therefore, the
results suggest that CNSL and pungam oil has the potential to be used for the development of novel larvicides against
dengue larva. The polymeric nanocapsules showed a longer duration of action and also higher efficacy.