Development of nonionic nanoemulsions to improve hydrophobic 9'-cis-bixin stability in acidic aqueous medium with in vitro cytosis and nanosafety evaluation.

ABSTRACT

Nonionic oil-in-water (O/W) nanoemulsion provides potential to stabilize hydrophobic bio-functional components in aqueous medium. Understanding safety of nanoemulsion droplets via investigating in vitro cell uptake and cellular substructural changes is important to achieve their practical applications. Herein, we developed a nonionic O/W nanoemulsion to stabilize representative bio-functional hydrophobic component of 9'-cis-bixin at pH 3-7 and ultraviolet (UV)-induced degradation at 365, 302, and 254 nm. In vitro cell uptake demonstrated that Caco-2 cells adequately enriched 9'-cis-bixin through fast uptake of nanoemulsion droplets within 15 min. However, excessive nanoemulsion droplets greatly decreased cell survival rate, which was due to the potential destruction of cellular substructures of mitochondria, nuclear membrane, and cell membrane. Lower nanoemulsion concentration provided no significant effects on Caco-2 cell survival. This work provided objective understanding on bio-functional component stability by nanoemulsion with in vitro safety evaluation.