In Vitro Characterization and Mosquito (Aedes aegypti) Repellent Activity of Essential-Oils-Loaded Nanoemulsions

Abstract

Abstract. The nanoemulsions composed of citronella oil, hairy basil oil, and vetiver oil with mean droplet sizes ranging from 150 to 220 nm were prepared and investigated both in vitro and in vivo. Larger emulsion droplets (195-220 nm) shifted toward a smaller size (150-160 nm) after high-pressure homogenization and resulted in higher release rate. We proposed that thin films obtained from the nanoemulsions with smaller droplet size would have higher integrity, thus increasing the vaporization of essential oils and subsequently prolonging the mosquito repellant activity. The release rates were fitted with Avrami's equations and n values were in the same range of 0.6 to 1.0, implying that the release of encapsulated limonene was controlled by the diffusion mechanism from the emulsion droplet. By using high-pressure homogenization together with optimum concentrations of 5% (w/w) hairy basil oil, 5% (w/w) vetiver oil (5%), and 10% (w/w) citronella oil could improve physical stability and prolong mosquito protection time to 4.7 h due to the combination of these three essential oils as well as small droplet size of nanoemulsion.

The use of Brazilian vegetable oils in nanoemulsions: an update on preparation and biological applications

“…The high-energy methods use mechanical shear stress to break up the oil and water phases to form nanosized droplets. The methods used in this case are high pressure homogenizers, microfluidizers or ultrasound (Kourniatis et al, 2010;Puglia et al, 2010;Nuchuchua et al, 2009;Sakulkua et al, 2009).…”

“…The in vivo repellent activity against Aedes aegypti by citronella oil (Cymbopogon nardus) combined with VO of hairy basil (Ocimum americanum) and vetiver (Vetiveria zizanioides) was also investigated by Nuchuchua et al (2009). The NE were prepared with and without HPH.…”

“…The high-energy methods use mechanical shear stress to break up the oil and water phases to form nanosized droplets. The methods used in this case are high pressure homogenizers, microfluidizers or ultrasound (Kourniatis et al, 2010;Puglia et al, 2010;Nuchuchua et al, 2009;Sakulkua et al, 2009).Despite the wide use of the high-energy methods in the cosmetic and pharmaceutical industry, the high cost of manufacturing devices may limit its applicability (Fortunato, 2005). Thus, simple and cheaper strategies to obtain NE are the use of low energy approaches based on the spontaneous emulsification (SE, also called solvent displacement or self-emulsification) of oil droplets in oil-water surfactant by modifying the composition or environment (Sajjadi, 2006;McClements, 2012;Yukuyama et al, 2016).…”

“…An increase in surfactant concentration led to decreasing droplet size, increasing homogeneity and protection time. Moreover, the release of citronella oil from a high amount of glycerol was much slower than that from the low amount, resulting in sustained mosquito protection time (Sakulkua et al, 2009).The in vivo repellent activity against Aedes aegypti by citronella oil (Cymbopogon nardus) combined with VO of hairy basil (Ocimum americanum) and vetiver (Vetiveria zizanioides) was also investigated by Nuchuchua et al (2009). The NE were prepared with and without HPH.…”

Evolution, Current Status and Prospects of Phyto-Repellents against Mosquitoes

“…Nanoemulsions [118,119], novel and improved formulations [57,120,121], formulations for spatial applications [122][123][124][125][126] and excitorepellents are few to name. Nerio et al [127] have endorsed the potency of plant essential oils as an effective resource for developing environment-friendly mosquito repellent formulations and discussed the synergistic activity of other natural compounds like vanillin for enhancing the mean time of effectiveness of the formulations.…”