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.

Critical micelle concentration (CMC) is the main chemical physical parameter to be determined on pure surfactants for their characterization in terms of surface activity and self-assembled aggregation. CMC values can be calculated using different techniques (e.g. tensiometry, conductivity, fluorescence spectroscopy), able to follow the variation of a physical property over surfactant concentrations. Different mathematical approaches have been applied for the determination of CMC values from the raw experimental data. Most of them are independent from the operator, despite not all the fitting procedures employed so far can be applied for all techniques. In this experimental work, the second derivative of the experimental data has been proposed as a unique approach to determine CMC values from different techniques (tensiometry, conductimetry, densimetry, spectrofluorimetry and high-resolution ultrasound spectroscopy). To this end, CMC values of five different surfactants, specifically, three anionic (sodium dodecyl sulfate, sodium deoxycolate and N-lauroyl sarcosinate) and two non-ionic as polyethylene glycol ester surfactants (Polyethylenglicol (8) monostearate and Polyethylenglicol (8) monolaurate) have been determined by this approach. The “second derivate” approach provides a reliable determination of the CMC values among all the techniques investigated, which were comparable to those calculated from the other operator-free routinely methods employed such as segmental linear regression or Boltzmann regression. This study also highlighted the strengths and shortcomings of each technique over the others providing an overview on the CMC values of commonly used anionic and non-ionic surfactants in the pharmaceutical field, determined by employing different experimental approaches.

The management of parasites, insect pests and vectors requests development of novel, effective and eco-friendly tools. The development of resistance towards many drugs and pesticides pushed scientists to look for novel bioactive compounds endowed with multiple modes of action, and with no risk to human health and environment. Several natural products are used as alternative/complementary approaches to manage parasites, insect pests and vectors due to their high efficacy and often limited non-target toxicity. Their encapsulation into nanosystems helps overcome some hurdles related to their physicochemical properties, for instance limited stability and handling, enhancing the overall efficacy. Among different nanosystems, micro- and nanoemulsions are easy-to-use systems in terms of preparation and industrial scale-up. Different reports support their efficacy against parasites of medical importance, including Leishmania, Plasmodium and Trypanosoma as well as agricultural and stored product insect pests and vectors of human diseases, such as Aedes and Culex mosquitoes. Overall, micro- and nanoemulsions are valid options for developing promising eco-friendly tools in pest and vector management, pending proper field validation. Future research on the improvement of technical aspects as well as chronic toxicity experiments on non-target species is needed.