Microemulsion Microstructure(s): A Tutorial Review

Abstract

Microemulsions are thermodynamically stable, transparent, isotropic single-phase mixtures of two immiscible liquids stabilized by surfactants (and possibly other compounds). The assortment of very different microstructures behind such a univocal macroscopic definition is presented together with the experimental approaches to their determination. This tutorial review includes a necessary overview of the microemulsion phase behavior including the effect of temperature and salinity and of the features of living polymerlike micelles and living networks. Once these key learning points have been acquired, the different theoretical models proposed to rationalize the microemulsion microstructures are reviewed. The focus is on the use of these models as a rationale for the formulation of microemulsions with suitable features. Finally, current achievements and challenges of the use of microemulsions are reviewed.

Microemulsions as Solubilizers and Penetration Enhancers for Minoxidil Release from Gels

“…There is also other experimental evidence that similar to the emulsions the ME type can be predicted based on the HLB value of surfactant/co-surfactant/oil mixture. If the HLB is from 3 to 6, the most probably it is the ME type w / o , while the HLB value from 8 to 18 predicts the ME type o / w [ 13 , 30 ]. Finally, the same is confirmed by the HLB calculation [ 29 ] of surfactant(s)/co-surfactant/oil mixture (ME R ~7.79, ME L ~7.76, ME G ~7.85).…”

“…They contain an aqueous phase, an oil phase, a surfactant, and when needed a co-surfactant. MEs are thermodynamically stable and optically isotropic [ 12 , 13 ]. Due to a continuously fluctuating interface, they are characterized as perfect drug solubilizers [ 14 ].…”

Recent strategies in nanodelivery systems for natural products: a review

“…2018). By contrast, microemulsions can generate spontaneously when all the components are mixed together and they are optical isotropic, homogeneous and thermodynamically stable transparent systems (Tartaro et al 2020). They can be described as oil in water emulsions, water in oil emulsion or biphasic bicontinuos systems (Fig.…”

“…In addition, formulation challenges such as ease of synthesis at large scale, storage and stability must be addressed in view of the therapeutic application (Tayeb at al. 2018;Tartaro et al 2020).…”

The Interfacial Interactions of Glycine and Short Glycine Peptides in Model Membrane Systems

“…The surfactant, in this case, is Aerosol-OT (AOT), also known as sodium 2-diethylhexylsulfosuccinate, which arranges itself such that the water pool is contained by the negatively charged head groups of the AOT, and surfactant tails extend outward into the organic solvent—in this case, isooctane (2,2,4-trimethylpentane) [ 33 , 34 ]—and commonly, water droplets contained in this system range from a size of 1 to 10 nm [ 35 , 36 ]. The RM system provides both a hydrophilic and hydrophobic environment at a negatively charged interface, making it a good model system to investigate the interactions of molecules with membrane interfaces [ 37 , 38 ].…”