CONICET | Buscador de Institutos y Recursos Humanos

The useof natural oils as insect repellents has several advantages over syntheticrepellents. However, the protection time is short due to its high volatility. Therefore, itsapplication must be optimized to achieve a more lasting and effective effect. In this sense,encapsulation of essential oils in low-cost and biodegradable polymers emergesas an alternative strategy. Electrospray (EP), as an encapsulation method, isa versatile, effective, simple technique and is therefore suitable forincorporating natural oils into polymeric matrices. This work then proposesthe preparation of microcapsules (MC) of Poly-e-Caprolactone (PCL)with citronella oil (C) using the EP method, to evaluate the percentage ofrepellency against mosquitoes over time.By applying a certain voltage (10 kV), homogeneouspolymer/oil solutions were electrosprayed to obtain polymer/oil microcapsules.The flow of the polymer solution (0.5 mL/h) was regulated with an injectionpump and the particles were collected on a metal collector. The process wasevaluated by means of microscopy (optical, SEM) and infrared spectroscopy. Theencapsulation efficiency (EE) was calculated by HPLC for each proportion testedusing equation 1.EE =(Mt-Me)/Mt x100Eq. 1Where Mt and Me are the theoretical and experimentaloil masses respectively.The repellency tests were carried out in the CEPAVEinsectary with Aedes aegypti mosquitoes. An ethanol/water lotion with the CMwas applied to one arm, on a delimited surface of 75 cm2 (5 x 15). Therepellency percentage (R%) was calculated using equation 2:R (%) = [(C T)/C]x100 Eq. 2where C and T are the number of mosquitoes that reston or bite the control arm and the treated arm respectively.Throughmicroscopy, the formation of PCL capsules with citronella (PCL/C) was observedin the three proportions tested (1/1, 2/1 and 3/1). The presence of the oilwas confirmed with FTIR tests of the capsules where the appearance of bandsbelonging to the oil was observed. EE calculations showed that the highestefficiency was obtained in PCL-C 3/1 capsules with a value greater than 80%. The repellency testsshowed an increase in the protection time of the solution with themicrocapsules compared to the control, with satisfactory repellency values.Citronellaoil was successfully encapsulated in PCL capsules by electrospray. By using a lotioncontaining the capsules with citronella, the protection time against mosquitoeswas increased. Microencapsulation of citronella oil by EP is a potentially viablealternative as a long-lasting natural repellent.

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