Repellency effects of nanoliposomal gels bearing Clove (Syzygium aromaticum) or Tea tree (Melaleuca alternifolia) essential oils against the main malaria vector, Anopheles stephensi

Abstract

BackgroundThe development of safe and effective plant-based repellents is crucial to control malaria transmission, particularly given the spread of insecticide resistance in major vectors like Anopheles stephensi. Essential oils (EOs) are promising candidates, yet their high volatility and hydrophobicity limit their efficacy. This study aimed to design and evaluate nanoliposomal gels containing Syzygium aromaticum (clove) or Melaleuca alternifolia (tea tree) EOs to enhance their repellent durability against An. stephensi. MethodsThe chemical profiles of the EOs were determined via Gas Chromatography-Mass Spectrometry (GC-MS). Nanoliposomes bearing 3% of each EO were made ready with the ethanol injection method, and incorporated into a carboxymethyl cellulose (CMC) gel. Formulations were characterized for particle size, zeta potential, viscosity, and chemical interactions (FTIR). Repellent efficacy was evaluated using the arm-in-cage method, recording the complete protection time (CPT) for nanoliposomal gels (LipoGel 3%), in comparison with nonformulated EOs and the gold-standard repellent, DEET (40%). ResultsGC-MS analysis identified eugenol (79.51%) and terpinen-4-ol (73.53%) as the major constituents of clove and tea tree EOs, respectively. Nanoliposomes exhibited sizes of 82.3 {+/-} 3 nm (clove) and 102 {+/-} 4 nm (tea tree), with narrow size distributions. The clove LipoGel demonstrated a significantly enhanced CPT (341 {+/-} 17 min), which was statistically comparable to 40% DEET (351 {+/-} 16 min, P>0.05). In contrast, the nonformulated EOs resulted in only 45 min of protection, highlighting the critical role of the nanocarrier system. ConclusionThe nanoliposomal gel formulation, particularly containing clove EO, represents a potent and safe botanical alternative to conventional synthetic repellents. This approach offers a promising strategy for integrated vector management, warranting further field-based investigations.