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Review
. 2020 Jan 12;10(1):135.
doi: 10.3390/nano10010135.

An Overview of Micro- and Nanoemulsions as Vehicles for Essential Oils: Formulation, Preparation and Stability

Lucia Pavoni  1 , Diego Romano Perinelli  1 , Giulia Bonacucina  1 , Marco Cespi  1 , Giovanni Filippo Palmieri  1
Affiliations
Review

An Overview of Micro- and Nanoemulsions as Vehicles for Essential Oils: Formulation, Preparation and Stability

Lucia Pavoni et al. Nanomaterials (Basel). .

Abstract

The interest around essential oils is constantly increasing thanks to their biological properties exploitable in several fields, from pharmaceuticals to food and agriculture. However, their widespread use and marketing are still restricted due to their poor physico-chemical properties; i.e., high volatility, thermal decomposition, low water solubility, and stability issues. At the moment, the most suitable approach to overcome such limitations is based on the development of proper formulation strategies. One of the approaches suggested to achieve this goal is the so-called encapsulation process through the preparation of aqueous nano-dispersions. Among them, micro- and nanoemulsions are the most studied thanks to the ease of formulation, handling and to their manufacturing costs. In this direction, this review intends to offer an overview of the formulation, preparation and stability parameters of micro- and nanoemulsions. Specifically, recent literature has been examined in order to define the most common practices adopted (materials and fabrication methods), highlighting their suitability and effectiveness. Finally, relevant points related to formulations, such as optimization, characterization, stability and safety, not deeply studied or clarified yet, were discussed.

Keywords: co-surfactant; essential oil; microemulsion; nanoemulsion; surfactant.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Pie charts of the Scopus database subject area (period 2009–2019) related to scientific production of the essential oils based microemulsions (A) and nanoemulsions (B).
Figure 2
Figure 2
Surfactant-to-oil ratio (SOR) values of essential oils-based micro- and nanoemulsions, expressed as percent frequency, on the basis of the data obtained from the Scopus database (period 2009–2019). The publications that do not contain enough information to calculate it were classified as NR (Not Reported).
Figure 3
Figure 3
The most used surfactants for the formulation of essential oils-based micro- and nanoemulsions, expressed as percent frequency, on the basis of the data obtained from the Scopus database (period 2009–2019).
Figure 4
Figure 4
Stability studies (A) and accelerated stability studies (B) carried out on essential oils-based micro- and nanoemulsions, expressed as percent frequency, on the basis of the data obtained from the Scopus database (period 2009–2019). The publications that do not reported stability information were classified as NR (Not Reported).
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