Fabrication of Lipophilic Nanoparticles by Spontaneous Emulsification: Stabilization by Cosurfactants

Abstract

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 μm) 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 °C), but underwent rapid coalescence above 50 °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.