Nanoemulsions versus microemulsions: terminology, differences, and similarities

TLDR

Colloidal delivery systems based on microemulsions or nanoemulsions are increasingly used in food and pharmaceutical industries to encapsulate, protect, and deliver lipophilic bioactive components, yet confusion over the terms persists because microemulsions are thermodynamically stable while nanoemulsions are not, making it essential to distinguish them for fabrication, stabilization, and functional design. The article reviews the differences and similarities between nanoemulsions and microemulsions in composition, structure, fabrication, properties, and stability, and seeks to clarify terminology and explain the source of confusion. The review compares nanoemulsions and microemulsions across composition, structure, fabrication, properties, and stability. Nano‑ and microemulsion particles smaller than 100 nm offer enhanced long‑term stability, high optical clarity, and increased bioavailability.

Abstract

Colloidal delivery systems based on microemulsions or nanoemulsions are increasingly being utilized in the food and pharmaceutical industries to encapsulate, protect, and deliver lipophilic bioactive components. The small size of the particles in these kinds of delivery systems (r < 100 nm) means that they have a number of potential benefits for certain applications: enhanced long-term stability; high optical clarity; and, increased bioavailability. Currently, there is considerable confusion about the use of the terms "microemulsions" and "nanoemulsions" in the scientific literature. However, these are distinctly different types of colloidal dispersions: a microemulsion is thermodynamically stable, whereas a nanoemulsion is not. It is therefore important to distinguish between them since this impacts the methods used to fabricate them, the strategies used to stabilize them, and the approaches used to design their functional attributes. This article reviews the differences and similarities between nanoemulsions and microemulsions in terms of their compositions, structure, fabrication, properties, and stability. It also attempts to highlight why there has been so much confusion in this area, and to clarify the terminology used to refer to these two kinds of colloidal dispersion.