Development and characterization of clove oil nanoemulsions and self-microemulsifying drug delivery systems

Abstract This study was carried out to develop clove oil nanoformulations with reduced or no ethanol to increase the aqueous miscibility of clove oil for use in fish anesthesia. The droplets of clove oil nanoemulsion (C-NE) and self-microemulsifying drug delivery systems (C-SMEDDS) were characterized using photon correlation spectroscopy and transmission electron microscope. The droplet size of C-NE containing 10–20% clove oil and 5–15% polysorbate 20 was 23–133 nm, whereas that of C-SMEDDS composed of 10% clove oil and 90% polysorbate 20 or 10% clove oil and 60% polysorbate 20 and 30% ethanol or isopropanol was 11–44 nm. The droplets were roughly spherical. After stored for 90 days, at 4 °C, most C-NE and C-SMEDDS showed no change in appearance and droplet size. Low degradation rate of eugenol, a major compound of clove oil, was found at this temperature. Anesthesia induction times of C-NE composed of 10–20% clove oil and 5–10% polysorbate 20, and C-SMEDDS composed of 60% polysorbate 20 and 30% co-solvent in goldfish were 4.0 ± 0.6 min and 3.8 ± 0.9 min, respectively, significantly shorter than that of clove oil ethanolic solution (5.0 ± 0.9 min), but there was no significant difference in the recovery time.