Nanoemulsions as Optimized Vehicles for Essential Oils

During the last few years, a great interested has been given in for nanotechnology applications in pharmaceutical technology. At the same time, there is a growing research effort in the search for healthier and safer products. In this context, the use of naturally originate raw materials, essential oils for instance, rises as an interesting approach for replacing several synthetic active pharmaceutical ingredients. However, these materials often feature low bioavailability, uncontrolled volatility or low long-term stability, which require novel encapsulation techniques. Therefore, research efforts have been focusing on nanoemulsion technology that is particularly suited to produce novel products. Nanoemulsions constitute one interesting vehicle for enhancing solubility, stability and delivering natural oils, by encapsulating them into nanosized micelles with sizes ranging from 20–200 nm. They gather some unique characteristics as small size, increased surface area and stability which can increase efficiency and biological effects of pharmaceutical dosage forms. The wide application of nanoemulsions to the encapsulation of bioactive molecules still require much development in order to achieve the optimization of the obtention methods for large-scale production. This chapter includes an overview about nanoemulsion stability characteristics and the different approaches for obtaining nanoemulsions, including high energy methods like high-pressure homogenization, microfluidizers and ultrasonic homogenization, which are the most used approaches, and low energy methods such as phase inversion composition and phase inversion temperature, simple but still less reproduceable methods. In addition, we present the main aspects of nanoemulsion formulations, type of surfactants and oil phase, and the techniques for characterizing nanoemulsions, for example, dynamic light scattering, zeta potential, microscopy and X-ray diffraction. Moreover, applications of nanoemulsions to pharmaceutical technological approaches for essential oils encapsulation, such as the improvement of bioactive oils bioavailability and solubilization, masking unpleasant aspects of oils and enhancement of essential oils pharmacological activity are also discussed.