Nanoemulsion-based delivery systems for testing nutraceutical efficacy using Caenorhabditis elegans: Demonstration of curcumin bioaccumulation and body-fat reduction

The genome of the nematode Caenorhabditis elegans shares many similarities with that of humans and so it is widely used as a model in pharmaceutical and nutritional studies. C. elegans has a small mouth and therefore very fine lipid particles are required to orally deliver hydrophobic nutraceuticals. In this study, a nanoemulsion-based delivery system was developed to deliver curcumin to C. elegans. Nanoemulsion were fabricated with different mean particle diameters (d32 = 150 nm and 300 nm), lipid types (Medium chain triglyceride, corn, and fish oil), and emulsifier types (Tween 80 and whey protein). The auto-fluorescence intensity of curcumin was used as an indicator of curcumin accumulation in C. elegans. The structure and composition of nanoemulsions had a significant influence on curcumin bioaccumulation in C. elegans. Curcumin bioaccumulation increased with increasing droplet size, was found to be higher in nanoemulsion containing corn oil compared with those containing fish oil or MCT, and was higher for droplets coated by whey protein than by Tween 80. The nematodes treated with curcumin-loaded nanoemulsions showed significantly reduced fat accumulation compared to the control group. This study could provide useful information to widen the application of C. elegans in research involving lipophilic compounds.