Nanoemulsions production

Jafari SM, He YH, Bhandari B (2006) Nanoemulsion production by sonication and micro-fluidization - a comparison. Int J Food Prop 9 475-485... 

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. 

Ganta, S. and Amiji, M. (2009) Coadministration of paclitaxel and curcumin in nanoemulsion formulations to overcome multidrug resistance in tumor cells. Molecular Pharmacology, 6 (3), 928-939. Sonneville-Aubrun, O., Simonnet, J.-T. and L Alloret, F. (2004) Nanoemulsions a new vehicle for skincare products. Advances in Colloid and Interface Science, 108-109, 145-149. 

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. 

Patents have been granted for innovations involving the preparation and activities of broad-spectrum antimicrobial emulsions from 1977 (Sippos) to 2000 (Baker). All of these patents claim antibacterial activity, but all involve additives in the non-aqueous phase of the emulsion that are known to be antibacterial alone and before emulsification. Wide spectrum applications for these nanoemulsions have been claimed with positive results for bacteria, fungi, and viruses. The term nanoemulsion is used in US patents discussed below, but the generic term for the product of an emulsification (Gooch 2002, 1980) of a liquid within a liquid is an emulsion. United States patents 6,015,832 and 5,547,677 were examined and formulations in key claim statements were reproduced, and tested using standard methods for effectiveness. Additional patents listed in the reference section were reviewed as part of this study. 

One example that can demonstrate the effectiveness and great promise of nanoencapsulation is the curcumin nanoemulsions. Curcumin is the major yellow pigment in turmeric Curcuma longa Linn). In South and Southeast Asia, curcumin preparation or turmeric has been used extensively to treat inflammatory conditions and chronic diseases (Reddy and Rao 2003). Orally administered curcumin usually has low systemic bioavailability. Only trace amounts of curcumin (or its metabolites) appear in the blood, and most of ingested curcumin is excreted in the feces. One reason is that curcumin has low solubility and does not disperse for absorption. The absorbed curcumin is rapidly metabolized in the intestine and liver to several reduction products (di-, tetra-, and hexa-hydrocurcumin and hexahydrocurcuminol) and... 

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

Nanoemulsions can be applied for the dehvery of fragrants, which are often incorporated in many personal care products. The same could apply to perfumes, which preferably are formulated alcohol-free. 

There is a perception in the personal care products and cosmetic industries that nanoemulsions are expensive to produce indeed, expensive equipment is required and high concentrations of emulsifiers are used when compared to macroemulsion production. 

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. 

The droplet deformation increases with increases in the Weber number which means that, in order to produce small droplets, high stresses (i.e., high shear rates) are require. In other words, the production of nanoemulsions costs more energy than does the production of macroemulsions [4]. The role of surfactants in emulsion formation has been described in detail in Chapter 10, and the same principles apply to the formation of nanoemulsions. Thus, it is important to consider the effects of surfactants on the interfacial tension, interfacial elasticity, and interfacial tension gradients. 

HPH has emerged as a reliable and powerful technique for the preparation of SLN. HPH has been used for years for the production of nanoemulsions for parenteral nutrition. In contrast to other techniques, scaling up represents no or minor problems in most cases. High-pressure homogenizers push a liquid with high pressure (10 to... 

The primary product of the hot homogenization is a nanoemulsion resulting from the liquid state of the lipid. Solid particles are expected to be formed by the cooling of the sample to room temperature or below. Because of the small particle size and the presence of the emulsifiers, lipid crystallization may be highly retarded, and the sample may remain as a supercooled melt (nanoemulsion) for several months [28], Westesen and Bunjes found that purported SLN data published by another group were, in fact, measurements from supercooled melts [29],... 

The apparatus used is known as a microfluidizer with a high-pressure positive displacement pump (500-200 PSI). A microfluidizer consists of small channels called microchannels through which product flows on to an impingement area, resulting in very fine particles of submicron range when pressure is applied by the attached pump Similar to the sonication method, this is also useful for small-batch production of nanoemulsions. Shear forces generated by ultrasonic cavitation result in production of vacuum bubbles which disintegrate the particles to nanometer scale... 

Nanoemulsions do not form spontaneously and so the droplet structure is predominantly a product of the sequence and magnitude of shear stresses used in their formation. These shear stresses have to work against the interfacial... 

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... 

Parenteral nanoemulsions, like all parenteral products, are required to meet pharmacopeial specifications. The emulsions must be sterile, isotonic, nonpyrogenic, nonirritant, biodegradable, non hemolytic and stable, both physically and chemically. Furthermore, the particle size of the droplets must be smaller than 1 pim and generally ranges from 100-500 nm. More or less, the same requirements are valid for ocular nanoemulsions. 

Nanoparticles in skincare products include various types of dehvery systems and can be subdivided on the basis of the encapsulating membrane structure into hposomes, nanoemulsions, nanosomes, and nanotopes. They can carry many actives to penetrate into skin quickly and into intracellular structures while conventional skincare products usually do not penetrate the skin and release the active by diffusion or by capsule destruction. Nanoparticles also bring up many other new applications. For example, skin whitening or Kghtening is a more recent apphcation in which actives carried by nanoparticles penetrate beyond the skin barrier, and more active reaches the necessary site of action in the skin, resulting in improved performance. 

These surfactants have many uses, in particular as colloid and nanoemulsion dispersants, wetting agents, detergents and even additive to dehydrate crude oils. However, most polymeric surfactants are graft-type, particularly synthetic products such as polyelectrolytes, which are not strictly surfactants or are not used for their surfactant properties. It is the case of hydrosoluble or hydrodispersible polyelectrolytes which are utilized for the antiredeposition, dispersant and viscosity-enhancing properties such as carboxymethyl cellulose, polyacrylic acid and derivatives. 

In this chapter we will start with a section on the raw materials used to produce HMI, the possible production methods of this product and its safety. The second section will give a short description of the solution properties of long-chain inulin and HMI. This is followed by a section on the interfacial properties of HMI at the air/liquid, liquid/liquid and solid/liquid interfaces. Particular attention will be given in describing the effectiveness of HMI as a stabilizer for various disperse systems, e.g. emulsions, nanoemulsions and latexes. The application of HMI in the formulation of emulsions, latex dispersions and nano-emulsions will be described in subsequent sections. 

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