Emulsions nanoemulsions

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. 

With emulsions, nanoemulsions and microemulsions, the surfactant adsorbs at the oil/water (O/W) interface, with the hydrophilic head group immersed in the aqueous phase and leaving the hydrocarbon chain in the oil phase. Again, the mechanism of stabilisation of emulsions, nanoemulsions and microemulsions depends on the adsorption and orientation of the surfactant molecules at the Uquid/liquid (L/L) interface. Surfactants consist of a small number of units and are mostly reversibly adsorbed, which in turn allows some thermodynamic treatments to be applied. In this case, it is possible to describe adsorption in terms of various interaction parameters such as chain/surface, chain solvent and surface solvent. Moreover, the configuration of the surfactant molecule can be simply described in terms of these possible interactions. 

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. 

R. Aboofazeh, Nanometric scaled emulsions (nanoemulsions), Iranian Journal of Pharmaceutical Research, 9 325-326,2010. 

Emulsions, Nanoemulsions and Solid Lipid Nanoparticles as Delivery Systems in Foods... 

Emulsions, Nanoemulsion and Solid Lipid Nanoparticles a Delivery Systems in Foods 171... 

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. 

Typically, emulsions for parenteral use should have droplet size less tlpan ((generally 100-1000 nm), and hence are often called submicron emulsions, or (less properly) nanoemulsions. Use of the latter term is unfortunate and can lead to confusion, since their droplet size is actually larger than the microemulsion systems described earlier. The term nanoemulsion has been proposed to include metastable emuisfotSO nm as well as thermodynamically stable microemulsions (Sarker, 2005). Manufacture of submicron emulsions require special homogenization equipment, as will be described later. 

Emulsions are two-phase systems formed from oil and water by the dispersion of one liquid (the internal phase) into the other (the external phase) and stabilized by at least one surfactant. Microemulsion, contrary to submicron emulsion (SME) or nanoemulsion, is a term used for a thermodynamically stable system characterized by a droplet size in the low nanorange (generally less than 30 nm). Microemulsions are also two-phase systems prepared from water, oil, and surfactant, but a cosurfactant is usually needed. These systems are prepared by a spontaneous process of self-emulsification with no input of external energy. Microemulsions are better described by the bicontinuous model consisting of a system in which water and oil are separated by an interfacial layer with significantly increased interface area. Consequently, more surfactant is needed for the preparation of microemulsion (around 10% compared with 0.1% for emulsions). Therefore, the nonionic-surfactants are preferred over the more toxic ionic surfactants. Cosurfactants in microemulsions are required to achieve very low interfacial tensions that allow self-emulsification and thermodynamic stability. Moreover, cosurfactants are essential for lowering the rigidity and the viscosity of the interfacial film and are responsible for the optical transparency of microemulsions [136]. 

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. 

In this technique, a hydrophobic polymer is dissolved in an organic solvent, such as chloroform, ethyl acetate, or methylene chloride and is emulsified in an aqueous phase containing a stabilizer (e.g., PVA). Just after formation of the nanoemulsion, the solvent diffuses to the external phase until saturation. The solvent molecules that reach the water-air interphase evaporate, which leads to continuous diffusion of the solvent molecules from the inner droplets of the emulsion to the external phase simultaneously, the precipitation of the polymer leads to the formation of nanospheres. The extraction of solvent from the nanodroplets to the external aqueous medium can be induced by adding an alcohol (e.g. isopropanol), thereby increasing the solubility of the organic solvent in the external phase. A purification step is required to assure the elimination of the surfactant in the preparation. This technique is most suitable for the encapsulation of lipophilic drugs, which can be dissolved in the polymer solution. 

Nanoemulsions Nanoscale emulsions Loading drugs, as a method to prepare nanoparticles 33,34... 

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. ... 

Hatanaka et al. (2008) examined a number of different types of encapsulation systems for coenzyme Qio- Systems examined included a novel liquid nanoemulsion and water-soluble powder formulations, acyclodextrin inclusion complex, and a dry emulsion. Of the delivery systems examined the novel nanoemulsion delivery system, which had the smallest particle size (60 nm) compared to the other delivery systems examined (770-2400 nm), had the highest bioavailability when tested in rat models (Hatanaka et al., 2008). 

These are transparent or translucent systems covering the size range from 5 to 50nm. Unlike emulsions and nanoemulsions (which are only kinetically stable), microemulsions are thermodynamically stable as the free energy of their formation is either zero or negative. Microemulsions are better considered as swollen micelles normal micelles can be swollen by some oil in the core of the micelle to form O/W microemulsions. Reverse micelles can be swollen by water in the core to form W/O microemulsions. 

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