Biological systems, interactions with nonionic surfactants

In this section several recently published studies on the interaction of nonionic surfactants with a variety of biological systems, including enzymes, bacteria, erythrocytes, leukocytes, membrane proteins, low density lipoproteins and membranes controlling absorption from the gastrointestinal tract, nasal and rectal cavities, will be assessed. This is a selective account, work having been reviewed that throws light on structure-activity relationships and on mechanisms of surfactant action. 

Choice of surfactant(s) for the preparation of multiple emulsions can, in principle, be made from any of the four classes of surfactants discussed in Chapter 3, although nonionics tend to be materials of choice because they are more easily tailored to meet the needs of the system. The choice will be determined by the characteristics of the final emulsion type desired, such as the natures of the various phases, additives, and solubilities. In many applications (e.g., foods, drugs, cosmetics), the choice may be further influenced by such questions as toxicity, interaction with other addenda, and biological degradation. In a given system, several different surfactants may perform adequately in terms of stability, but produce different types of multiple emulsions (A, B, or C in Figure 11.15), so that the choice will depend on application as well as function. 

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