Cryogenic transmission electron microscopy study: preparation of vesicular dispersions by quenching microemulsions

Abstract

We previously showed that long-lived nanoemulsions, seeming initially vesicular, might be prepared simply by diluting and cooling (quenching) warm microemulsions with n-hexadecane with precooled water. In this paper, we confirm that these systems are vesicular dispersions when fresh, and they can be made with similar structures and compositional dependence using alkanes with chain lengths ranging from octane to hexadecane. The nanostructures of fresh nanoemulsions are imaged with cryogenic transmission electron microscopy (cryo-TEM). We confirm that water-continuous microemulsions give simple dispersions of vesicles (sometimes unilamellar), typically less than 100 nm in diameter; these systems can avoid separation for over 2 months. Selected samples were also prepared using halogenated alkanes to create additional contrast in the cryo-TEM, allowing us to confirm that the oil is located in the observed vesicular structures.

Synthesis of Oil-Laden Poly(ethylene glycol) Diacrylate Hydrogel Nanocapsules from Double Nanoemulsions

“…There have been only a few reports of double and complex nanoscale emulsions with well-specified morphology to date; of these, most examples consist of water–oil–water (W/O/W) double nanoemulsions, in which the inner aqueous droplets are stabilized in oil globules, which are further suspended in an external aqueous phase. − Zhao et al induced the formation of W/O/W double nanoemulsions in a cetyltrimethylammonium bromide (CTAB)/water/heptane mixture by introducing compressed CO 2 into the system and demonstrated their use as templates for hollow silica nanoparticles . Shakeel et al created a double W/O/W nanoemulsion via spontaneous emulsification to deliver 5-fluorouracil for cancer therapy .…”

“…Lee at al. were able to produce complex structured nanoemulsions using a mixture of surfactants and cosurfactants. , …”

“…were able to produce complex structured nanoemulsions using a mixture of surfactants and cosurfactants. 42,45 Alternatively, the templating of hydrogel nanoparticles within emulsions requires the opposite emulsion structure, i.e., O/W/O nanoemulsions. However, compared to W/O/W double nanoemulsions, literature on the formation of O/W/O double nanoemulsions is even more limited.…”

Self-assembly and structures of nanoscale double emulsion droplets through coarse-grained molecular dynamics simulations

“…However, experimental examples of multiple emulsion droplets with sizes o100 nm are still very rare. [30][31][32][33][34][35][36] The existence of multiple emulsion droplets in the size range of 1-10 nm has not yet been reported.…”

Controlling Complex Nanoemulsion Morphology Using Asymmetric Cosurfactants for the Preparation of Polymer Nanocapsules

“…There have been several singular cases of the successful production of water-in-oil-in-water (W/O/W) double nanoemulsions via either spontaneous emulsification or phase inversion methods. − Compared to W/O/W double nanoemulsions, the development of oil-in-water-in-oil (O/W/O) double nanoemulsions is even more lacking. Several groups have employed surfactants and high-energy methods to form reverse vesicle-type structures with an aqueous shell encapsulating an oil core. , Recently, Zhang et al demonstrated the production of oil-in-water-in-oil (O/W/O) double nanoemulsions using sequential high-energy emulsification and used them to produce oil-laden nanogels for drug delivery .…”