Larvicidal Activity of Calcium Alginate Microcapsules Containing Clove Essential Oil Obtained by Microfluidics

Essential oils (EO) have diverse applications, such as antibacterial and antifungal activity. However, they are susceptible to oxidation in the presence of air, light, and moisture. In addition, they are thermally unstable. In this sense, it is necessary to develop techniques to increase the lifespan of EO. In this work, EO was obtained from cloves and characterized by different techniques. The major compounds found were eugenol (83%), eugenol acetate (9%), and β-caryophyllene (8%). The EO was encapsulated by extrusion using a microfluidic device. The sodium alginate was used as wall material, and the CaCl₂ solution was used as a crosslinking agent. The microcapsule presented sizes of 164.7 ± 0.3 μm, with an encapsulation yield of 64 ± 14%. Functional characteristic groups of EO were observed in the microcapsule by infrared and Raman spectroscopies. The microcapsule increased the thermal decomposition of the EO from 162 to 230 °C. Release kinetics of the capsule was performed, with an equilibrium time of 72 h and release of 54% of the EO. Finally, the pure EO and encapsulated EO-microcapsules were applied in the Aedes aegypti larvae control, showing mean lethal concentration necessary to eliminate 50% (LC₅₀) values of 74.4 and 96.9 μg mL^-1 and lethal concentration necessary to eliminate 90% (LC₉₀) of 106.2 and 133.3 μg mL^-1 for pure EO and encapsulated EO, respectively. Therefore, it was concluded that these microcapsules have the potential for application in the Aedes aegypti larvae control.

Keywords:
Aedes aegypti ; natural products; dengue control; microencapsulation