Fabrication of Lipophilic Nanoparticles by Spontaneous Emulsification: Stabilization by Cosurfactants

Lipid nanoparticles are increasingly being used to encapsulate and deliver lipophilic bioactive components in food, pharmaceutical, and personal care products. These nanoparticles can be produced by high-energy or low-energy methods, with the latter approach having advantages in terms of simplicity, lower energy demands, and reduced production costs. In this study, a model system consisting of non-ionic surfactant (Brij 30), hydrocarbon oil (n-octadecane) and aqueous phase (citric acid buffer, pH 3.0) was used to examine the impact of cosurfactants on the stability of nanoemulsions produced by spontaneous emulsification. Initially, the optimum surfactant-to-oil ratio (SOR) for preparing nanoemulsions with small droplets was established: SOR = 0.5. In the absence of cosurfactants, the surfactant-oil-water (SOW) system formed by spontaneous emulsification contained large irregular structures (> 10 mu m) that remained after dilution. However, addition of cosurfactants (SDS or Tween 80) to the SOW system promoted the formation of nanoemulsions (d < 100 nm) that were stable to droplet growth. The nanoemulsions also had good thermal stability when SDS was used as a cosurfactant (25-90 A degrees C), but underwent rapid coalescence above 50 A degrees C when Tween 80 was used. This study suggests that cosurfactants improve the stability of nanoemulsions by disrupting the formation of liquid crystal like structures and altering the phase inversion temperature.