Surface-active solid lipid nanoparticles as Pickering stabilizers for oil-in-water emulsions

Oil-in-water (O/W) emulsions solely stabilized by surface-active solid lipid nanoparticles (SLNs) were developed. The SLNs were generated by quench-cooling hot O/W nanoemulsions consisting of 7.5% glyceryl stearyl citrate (GSC) dispersed in water. Their initial volume-weighted mean particle diameter (∼152 nm) and zeta potential (ca.-49 mV) remained unchanged for 24 weeks. O/W emulsions (oil phase volume fraction: 0.2) containing 7.5% (w/w) GSC SLNs in the aqueous phase were kinetically-stable for 12 weeks and did not visually phase-separate over 24 weeks. The O/W emulsions generated with solid-state GSC SLNs had a volume-weighted mean oil droplet diameter of ∼459 nm and a zeta potential of ca.-43 mV. Emulsion microstructure evaluated with TEM revealed dispersed oil droplets sparsely covered with adsorbed Pickering-type SLNs as well aggregated SLNs present in the continuous phase. Gradual emulsion destabilization resulted from GSC SLN dissolution during the experimental timeframe. Overall, surface-active SLNs developed via nanoemulsions effectively kinetically stabilized O/W emulsions.