Formulation of Nanoemulsions

The attraction of nanoemulsions for application in personal care products and cosmetics, as well as in healthcare, is due to the following advantages  

Formulation of Disperse Systems Science and Technology, First Edition. Tharwat F. Tadros. 

In spite of the above advantages, nanoemulsions have attracted interest only 

In spite of the above difficulties, several companies have introduced nanoemulsions onto the market, and their benefits will be evaluated within the next few years. Nanoemulsions have been used in the pharmaceutical industry as drug-delivery systems [5], although the acceptance by customers of nanoemulsions as a new type of formulation depends on how they are perceived and their efficacy. With the advent of new instruments for high-pressure homogenisation, and the competition between various manufacturers, the cost of nanoemulsion production wiU surely and may even approach that of classic macroemulsions. Fundamental investigations into the role of surfactants in the process [6,7] will lead to optimised emulsifier systems such that a more economic use of surfactants will doubtless emerge. 

As mentioned in Chapter 10, the preparation of an emulsion requires oil, water, a surfactant, and energy. This can be considered on the basis of the energy required to expand the interface, AAy (where AA is the increase in interfacial area when the bulk oil with area Aj produces a large number of droplets with area Aj Aj Aj, where y is the interfacial tension). Since y is positive, the energy to expand the interface is large and positive. This energy term cannot be compensated by the small entropy of dispersion TAS (which is also positive), and the total free energy of formation of an emulsion, AG is positive. 

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Since the gravity force is proportional to R, then if R is reduced by a factor of 10, the gravity force is reduced by 1000. Below a certain droplet size (which also depends on the density difference between oil and water), the Brownian diffusion may exceed gravity and creaming or sedimentation is prevented. This is the principle of formulation of nanoemulsions (with size range 20-200 nm) that may show very little or no creaming or sedimentation. The same applies for microemulsions (size range 5-50 nm). 

Anton, N., Benoit, J.P. and Saulnier, P. (2008) Design and production of nanopartides formulated from nanoemulsion templates - a review. Journal of Controlled Release, 128, 185—199. 

In pharmaceutical preparations, soybean oil emulsions are primarily used as a fat source in total parenteral nutrition (TPN) regimens. Although other oils, such as peanut oil, have been used for this purpose, soybean oil is now preferred because it is associated with fewer adverse reactions. Emulsions containing soybean oil have also been used as vehicles for the oral and intravenous administration of drugs drug substances that have been incorporated into such emulsions include amphotericin, " diazepam, retinoids, vitamins, poorly water-soluble steroids, fluorocarbons, and insulin. In addition, soybean oil has been used in the formulation of many drug delivery systems such as liposomes, microspheres, dry emulsions, self-emulsifying systems, and nanoemulsions and nanocapsules. ... 

Several classes of formulations of disperse systems are encountered in the chemical industry, including suspensions, emulsions, suspoemulsions (mixtures of suspensions and emulsions), nanoemulsions, multiple emulsions, microemulsions, latexes, pigment formulations, and ceramics. For the rational preparation of these multiphase systems it is necessary to understand the interaction forces that occur between the particles or droplets. Control of the long-term physical stability of these formulations requires the application of various surfactants and dispersants. It is also necessary to assess and predict the stability of these systems, and this requires the application of various physical techniques. 

A lack of understanding of the interfacial chemistry involved in production of nanoemulsions. For example, few formulations chemists are aware of the concepts of phase inversion composition (PIC) and phase inversion temperature (PIT), and how these can be usefuUy apphed to produce small emulsion droplets. 

Vatsraj S, Chauhan K, Pathak H. Formulation of a novel nanoemulsion system for enhanced solubility of a sparingly water soluble antibiotic, clarithromycin. Journal of Nanoscience. 2014 2014 268293. 

In addition to solutions and suspensions, liposomal formulations of active substances are used and various nanoemulsion-based formulations and micellar solutions are explored for nebulisation [55]. Currently, no marketed inhaled liposomal products are available... 

There is no doubt that the approval of Restasis by the FDA is an important milestone in lipid emulsion research for ophthalmic application. This approval reflects the achievements of the last decade in terms of the availability of better ingredients, improved manufacturing processes, feasibility of sterilization, and better understanding of the optimization process as reflected by a recent publication where the authors showed that under appropriate experimental conditions and optimal formulation, it is possible to reduce markedly the ocular surface toxicity of quaternary ammonium following its incorporation in a cationic nanoemulsion. Indeed, a free drug cationic nanoemulsion (Cationorm , Novagali Pharma, France) has been recently launched in the French market for moderate dry eye syndrome treatment. Research efforts are underway to further explore and enhance the ocular clinical performance of nanoemulsions. 

It is preferable to formulate ophthalmic nanoemulsions devoid of preservative agents and fill them in sterile single dose packaging units to prevent potential contamination due to repeated use of multi-dose packaging. ... 

The main objective of this volume is to demonstrate the importance of the fundamental aspects of interfadal phenomena in various industrial applications. For this purpose 1 have chosen five different topics which are described in five parts. The first part deals with cosmetics and personal care formulations. Several cosmetic formulations can be identified lotions, hand creams (cosmetic emulsions), nanoemulsions, multiple emulsions, liposomes, shampoos and hair conditioners, sunscreens and color cosmetics. The formulation of these complex multiphase systems requires understanding the colloidal forces that eire responsible for their preparation, stabilization and application. The fundamental principles that are responsible for the formulation of the cosmetic formulations must be considered. 

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