Emulsion solubilization method

RME shows particular promise in the recovery of proteins/enzymes [12-14]. In the past two decades, the potential of RME in the separation of biological macromolecules has been demonstrated [15-20]. RMs have also been used as media for hosting enzymatic reactions [21-23]. Martinek et al. [24] were the first to demonstrate the catalytic activity of a-chymotrypsin in RMs of bis (2-ethyl-hexyl) sodium sulfosuccinate (Aerosol-OT or AOT) in octane. Since then, many enzymes have been solubilized and studied for their activity in RMs. Other important applications of RME include tertiary oil recovery [25], extraction of metals from raw ores [26], and in drug delivery [27]. Application of RMs/mi-croemulsions/surfactant emulsions were recognized as a simple and highly effective method for enzyme immobilization for carrying out several enzymatic transformations [28-31]. Recently, Scheper and coworkers have provided a detailed account on the emulsion immobiUzed enzymes in an exhaustive review [32]. 

Most monomers polymerizing by the radical mechanism are almost insoluble in water. Intensive stirring of a mixture of such a monomer with water produces an emulsion which remains stable, however, only in the presence of a surface active compound (tenside), e. g. soap. By the addition of a water-soluble initiator to this emulsion, the monomer polymerizes at a rate several times higher than would be observed by any other radical method with an initiator of equal efficiency. At the same time, a higher polymer with a narrower molecular mass distribution is formed. At the initial stages of the reaction, the monomer is present as three types of particle in tenside-stabilized monomer droplets of diameter 10-3 to 10 4cm (about 1012 such droplets are present in 1 cm3 of emulsion of average concentration) in solubilized micelles about 10 nm in size and concentration 1018 cm 3 and in the growing, emulsifier-stabilized monomer—polymer particles 50-100 nm in size. This situation is illustrated schematically in Fig. 14(a). 

Ultrasound-assisted electrolytic reduction of emulsions of activated unsaturated systems provides a method for hydrogenation of water-insoluble materials in an aqueous environment [284]. The effect of ultrasound on electrochemical reactions in emulsions may vary depending on the reaction in some cases solubilization of an insoluble reaction product is furthered, whereas in other cases the heterogeneous rate constant is influenced [284]. 

Salt is needed in the aqueous phase to prevent the formation of emulsions at the interface." The best solvents for solubilization of ELAs in Method 3 are reported to be hydrophobic (isooctane, decalin, tert-amyl alcohol), while polar solvents (chloroform, methylene chloride, tetrahydrofuran, and tert-amyl alcohol) promote loss of catalytic activity due to denaturation. "-... 

Although PL liposomes are favored systems for the study of apolipoprotein binding to PL surfaces, vesicle-apolipoprotein complexes are not the ideal models for lipoproteins. Vesicles have an interior water compartment not present in lipoproteins, are incapable of solubilizing large amounts of neutral lipids within the PL bilayer, and are too large to mimic the surface curvature of HDL. Thus, methods have been developed to prepare small, micellar complexes of exchangeable apolipoproteins (in particular apo Al) with lipids that mimic discoidal and spherical HDL in shape, composition, and functional properties. For LDL and VLDL, microemulsions and emulsions of lipids of selected diameter and composition, with added apo B 100, make good models of the native lipoproteins. 

It is, of course, not necessary to form an emulsion by mechanical dispersion of oil and water phases. One method that has been nsed to form oil-in-water emnlsions with small and uniform drops in a nonionic snrfactant system is to start with the surfactant phase near the PIT and cool it rapidly by perhaps 20°C to 30°C (Friberg and Solans, 1968 Forster et al., 1995 Sagitani, 1992). The capacity for solubilization of oil decreases dramatically npon cooling, and the excess oil nucleates as small drops from the supersaturated microemulsion. Provided that it solubihzes substantial oil, the lamellar liqnid crystalline can also be cooled in this manner to form oil-in-water emulsions (Forster et al., 1995). Spontaneous emulsification can also be prodnced by diffusion, as discussed in Chapter 6. 

The method for preparing biodegradable poly(alkylcyanoacr 4ate) nanospheres has provided the basis for the development of polycyanoacrylate nanocapsules. Al Khouri-Fallouh et al (1986) proposed an original method in which the monomer is solubilized in an alcohol phase containing an oil and is then dispersed in an aqueous phase containing surfactants. In contact with water, the alcohol phase diffuses and favours the formation of aver fine oil-in-water emulsion. The monomer, insoluble in water, polymerizes at the interface of the phases to form the wall of the nanocapsules. 

---