Bifunctional clove oil nanoparticles for anesthesia and anti-bacterial activity in Nile tilapia (Oreochromis niloticus)

Clove oil (an essential oil extracted from the flower buds of clove plant, Syzygium aromaticum) is used as an anesthetic agent in order to reduce stress and mortality rate as well as other potential negative effects on fish homeostasis. However, utilization of essential oils in aquaculture has limited practicality due to their high volatility and water insolubility. In this study, we developed and evaluated an effective, cheap, safe, and easy-to-administer form of clove oil by encapsulating the poorly water-soluble clove oil into lipid-based nanoscale carriers used for safe anesthesia and antibiotic alternatives against infectious pathogens in farmed tilapia. Clove oil nanoparticle was prepared via the phase inversion composition technique (low energy method), physicochemically and biologically characterized. Our results showed that the well-dispersed water-soluble clove oil nanoparticles had negative charge with a narrow particle size distribution, and showed sustained release of active ingredients (eugenol) over an extended period of time up to 48 h. As compared to the standard clove oil, our results clearly indicated that shorter induction time and longer recovery time in tilapia were achieved with clove oil nanoparticles, confirming its stronger anesthetic effect. Additionally, this improved version of clove oil nanoparticle exhibited good anti-bacterial activity against two important tilapia pathogens namely Streptococcus agalactiae and Flavobacterium columnare. In conclusion, the so-called bifunctional clove oil nanoparticles has been successfully developed with enhanced solubility, and improved sedation and anesthesia with a sustained release, as well as the enhanced antimicrobial activity against fish pathogens.