Citronella oil-loaded electro-spun single and core-shell nano fibers as sustained repellent systems against Aedes aegypti

Abstract

Devising a natural and an effective repellent system is the challenge that needs to be addressed to meet the current demand among the people, despite the progress made in the mosquito control. The effort towards this goal should constitute; natural repellent, biodegradability, higher repellent loading, sustained release of the repellent. In this work, natural, biodegradable, eco-friendly and long-lasting mosquito repellent has been prepared with higher loading of citronella oil (1 %) in Polyvinyl alcohol (PVA) nanofibers. Uniaxial (CP-U) and coaxial (CP-C) nanofiber-composites were electrospun using non-toxic, biodegradable PVA at 10 % w/w and citronella oil. It was found that maintaining the outer:inner flow rate ratio at 5:2 in coaxial process is imperative to produce good fibers. Average fiber diameter of CP-U fibers was 138.5 ± 62.5 nm and for CP-C fibers it was 367.3 ± 160.1 nm. TEM analysis confirmed the core-shell structure formed in CP-C fibers by coaxial electrospinning. FTIR analysis indicated CEO incorporation in both composites and thermal analyses showed mass losses corresponding to CEO decomposition, with CP-U fibers exhibiting better thermal stability due to stronger interactions between the oil and polymer. Encapsulation efficiency and loading capacity were 20.19 % ± 0.34 and 1.83 % ± 0.03 for CP-U, and 50.25 % ± 0.32 and 14.85 % ± 0.09 for CP-C, respectively. Further, release patterns and release kinetics were studied. CP-C fibers can effectively release 94.14 % of the encapsulated oil providing an extended protection window compared to matrix encapsulation (68.75 %) after 168 hours. Release kinetics followed the Korsmeyer-Peppas model, with CP-U exhibiting Fickian diffusion (n < 0.5) and CP-C showing non-Fickian diffusion (0.5 <n < 1). Mosquito repellent tests showed CP-C fibers were effective (85.4 ± 1.40 %) than CP-U (56.1 ± 2.79 %) and comparable to DEET (28.7 ± 4.94 %) even after 1 week. To the best of our knowledge, this is the first time neat-citronella oil has been encapsulated at the core of multi-layered nanofibers. Multi-layered encapsulation of essential oils turned out to be very effective in sustaining their repelling activity for longer periods. The outcome of this work has a high potential to be developed into an attractive-convenient product for the consumers and it can be more beneficial for infants and babies, adults with sensitive skin and school children.