posted on 2018-10-23, 00:00authored byClaire Albert, Nicolas Huang, Nicolas Tsapis, Sandrine Geiger, Véronique Rosilio, Ghozlene Mekhloufi, David Chapron, Baptiste Robin, Mohamed Beladjine, Valérie Nicolas, Elias Fattal, Florence Agnely
Pickering emulsions
were formulated using biodegradable and biocompatible poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) prepared without
surfactants or any other polymer than PLGA. A pharmaceutical and cosmetic
oil (Miglyol) was chosen as the oil phase at a ratio of 10% w/w. These
emulsions were then compared with emulsions using the same oil but
formulated with well-described PLGA-poly(vinyl alcohol) (PVA) NPs,
i.e., with PVA as NP stabilizers. Strikingly, the emulsions demonstrated
very different structures at macroscopic, microscopic, and interfacial
scales, depending on the type of NPs used. Indeed, the emulsion layer
was significantly thicker when using PLGA NPs rather than PLGA-PVA
NPs. This was attributed to the formation and coexistence of multiple
water-in-oil-in-water (W/O/W) and simple oil-in-water (O/W) droplets,
using a single step of emulsification, whereas simple O/W emulsions
were obtained with PLGA-PVA NPs. The latter NPs were more hydrophilic
than bare PLGA NPs because of the presence of PVA at their surface.
Moreover, PLGA NPs only slightly lowered the oil/water interfacial
tension whereas the decrease was more pronounced with PLGA-PVA NPs.
The PVA chains at the PLGA-PVA NP surface could probably partially
desorb from the NPs and adsorb at the interface, inducing the interfacial
tension decrease. Finally, independent of their composition, NPs were
adsorbed at the oil/water interface without influencing its rheological
behavior, possibly due to their mobility at their interface. This
work has direct implications in the formulation of Pickering emulsions
and stresses the paramount influence of the physicochemical nature
of the NP surface into the stabilization of these systems.