Droplet Core Intermolecular Interactions and Block Copolymer Composition Heavily Influence Oil-In-Water Nanoemulsion Stability.

Colloidal oil-in-water nanoemulsions are gaining increasing interest as a nanoparticle delivery system because of their large oil droplet core that can carry a large payload. In order to formulate these particles with long-term stability, an appropriate oil media and block copolymer pair must be selected. The interaction between the nanoemulsion core and the polymer shell is critical to forming stable nanoparticles. Herein, we probed how interactions between various polymers with hydrocarbon and perfluorocarbon oil media influenced nanoemulsion formation, stability, and size. Through a series of nanoemulsions with unique polymer/oil media combinations, we examined the effects of oil core hydrophobicity, fluorophilicity, surface charge, and volume as well as the effects of polymer tail composition. Surprisingly, we found that nanoemulsions formulated with pure perfluorocarbon oil cores versus perfluoro poly(ether) oil cores exhibited very different characteristics. We also found that both hydrocarbon and fluorocarbon polymer tails interacted favorably with perfluoro poly(ethers) as well as hydrocarbon oil cores forming stable nanoemulsions. We believe these results are focused on the unique properties of perfluorocarbons especially their rigidity, low polarizability, and near-zero surface charge. Interestingly, we saw that perfluoro poly(ethers) deviated from these expected properties resulting in an increased versatility when formulating nanoemulsions with perfluoro poly(ether) oil cores compared to pure perfluorocarbon oil cores. Nanoemulsion size, stability, growth rate, and life time were explored to probe these factors. Experimental and computational data are presented as a rationale.

Multicompartment Theranostic Nanoemulsions Stabilized by a Triphilic Semifluorinated Block Copolymer.

The presence of a perfluorocarbon block in a multiblock polymer has been shown to be an additional driving force toward nanoparticle assembly. In the preparation of nanoemulsions, this perfluorocarbon block also provides enhanced particle stability. Herein, the synthesis of a new triphilic, semifluorinated copolymer, M2F8H18, is introduced. This ABC type block copolymer can be used to formulate extremely stable nanoemulsions, assembled around a lipophilic droplet, with lifetimes of one year or more. The central oil droplet can stably solubilize high concentrations of hydrophobic drugs, making this system an ideal drug delivery vehicle. The incorporation of the perfluorocarbon block modulates drug release from the lipophilic core via the surrounding fluorous shell. Fluorous imaging agents incorporated into the fluorous shell prolong drug release even further as well as provide potent 19F-MRI contrast ability. In vitro studies show that these nanoemulsions efficiently inhibit cancer cell growth, thus providing a theranostic drug delivery system.