Lipid dispersal systems

T. Ogiso, N. Niinaka, and M. Iwaki. Mechanism for enhancement effect of lipid disperse system on percutaneous absorption, J. Pharm. Sci. 6 5 57-64 (1996). 

Some fatty acids, especially unsaturated fatty acids, are well-known skin penetration enhancers. The addition of PC to dermal dosage forms has been reported to increase percutaneous absorption. Lipid disperse systems (LDSs) containing polar lipids, such as PC and glycosylceramide, are also useful for increasing the percutaneous permeation of drug through rat abdominal skin in both in vitro and in vivo systems. 

Y. Kurosaki, N. Nagahara, T. Tanizawa, H. Nishimura, T. Nakayama, T. Kimura, Use of lipid disperse systems in transdermal drug delivery comparative-study of flufenamic acid permeation among rat abdominal skin, silicon rubber membrane and stratum-comeum sheet isolated from hamster-cheek pouch. Int. J. Pharm. 114, 151-157 (1991)... 

Modulation of epidermal lipid biosynthesis has been reported to boost drag delivery. It has also been suggested that it is both the hydrophobic nature of the lipids as well as their tortuous, extracellular localization that are responsible for the restriction in the transport of most molecules across the stratum comeum. The function of this barrier depends on three key lipids cholesterol, fatty acid, or ceramides. Delays of synthesis ceramides in the epidermis have been reported as means of barrier perturbation. Inhibitors of lipid synthesis were used to enhance the trans-A cmaV dehvery of hdocaine or caffeine. Alteration of barrier function was produced by the fatty acid synthesis inhibitor S-(tetradecyloxy)-2-furancarboxylic acid, the cholesterol synthesis inhibitor fluvastatin, or the cholesterol sulfate, which resulted in a further increase in lidocaine absorption (38). The major components of sebaceous lipids in the skin are 45-60% TAGs, 25% wax and sterol esters, 12-15% squalene and 10% free fatty acids (39). Some fatty acids, especially unsaturated fatty acids, are well-known skin penetration enhancers. The addition of PC to dermal dosage forms has been reported to increase percutaneous absorption. Lipid disperse systems (LDSs) containing polar lipids, such as PC and glycosylceramide, are also useful for... 

The mechanism of prooxidant effect of a-tocopherol in aqueous lipid dispersions such as LDLs has been studied [22], This so-called tocopherol-mediated peroxidation is considered in detail in Chapter 25, however, in this chapter we should like to return once more to the question of possible prooxidant activity of vitamin E. The antioxidant effect of a-tocopherol on lipid peroxidation including LDL oxidation is well established in both in vitro and in vivo systems (see, for example, Refs. [3,4] and many other references throughout this book). However, Ingold et al. [22] suggested that despite its undoubted high antioxidant efficiency in homogenous solution a-tocopherol can become a chain transfer agent in aqueous LDL... 

Protein and Lipid-Protein Systems. The high surface viscosity of BSA and the low surface viscosity of RNase had been observed by a torsion rotational method that used an extremely large torque (2, 6). In the present experiments, the protein is dispersed in the aqueous subphase to a final concentration of 10 /xg/ml. Both film pressure and surface viscosity are measured as a function of time (to 40 min). The film pressure of BSA was 21 dynes/cm at mixing and remained constant for 40 min. Also, surface viscosity reached a high value instantaneously (although the first measurement was made at 5 min) and remained constant for 40 min. In contrast, RNase built up pressure slowly, from 3 dynes/cm... 

The enterocytes of the small intestine can be isolated and used for study of intracellular aspects of intestinal lipid transport like triglyceride synthesis [52]. The disappearance of the mucus barrier during isolation of the epithelial cells results in plasma membrane disintegration and loss of cellular integrity when the cells are exposed to bile salts. As is the case for brush border vesicles, the system of isolated cells does not allow study of interaction between enterocytes and lipids dispersed in a form that resembles physiological conditions, i.e. solubilized in mixed bile salt micelles. 

Interactions of apolipoproteins with PL are essential for the assembly of lipoproteins, stabilization of lipoprotein structures, and expression and modulation of apolipoprotein functions. The main experimental approaches for the study of apolipoprotein interactions with PL have used isolated, exchangeable apolipoproteins in conjunction with aggregated lipids dispersed in water or spread at the air-water interface. The aggregated lipid states include lipid monolayers, various types of liposomes (small unilamellar vesicles, large unilamellar vesicles, multilamellar vesicles), and emulsions. All these lipid systems consist of or include PL, especially PC. 

This principle of anhydrous concentrates was named SMEDDS , self micro-emulsifying dmg delivery systems. Such formulations lack the aqueous phase. On dilution, a SMEDDS spontaneously converts to an optically clear, thermodynamically stable microemulsion, which contains the dmg in molecular dispersion. The same principle of a water-free concentrate which leads to a macro -emulsion is called SEDDS, a self-emulsifying dmg delivery system. A recent review on self-dispersing lipid based systems was... 

In many lipid-based food systems, in addition to performing rheological experiments to determine global structure, the measurement of surface rheological properties can play a crucial role in determining the quality of the final product. Therefore, the measurement of interfacial tension is sometimes a matter of utmost importance. It is particularly valuable for dispersed lipid food systems, primarily for W/O or... 

One of the major problems encountered with dispersed systems appears during their preparation, and often results from poor water solubility of drugs leading to either a low yield in drug loading or a slow or incomplete release of the drug. In order to overcome these drawbacks, several authors have proposed the use of cyclodextrins (CyDs) in the formulation of these systems. Alternatively, CyDs themselves can be employed as raw materials for particle preparation, instead of polymers and lipids. 

This section reviews the advantages and potentialities of CyD associated with dispersed systems, focusing on the different roles of CyDs in such systems. CyDs can enhance drug solubility, drug stability, and drug loading. In addition, CyDs themselves can be employed as a raw material for particle preparation, instead of polymers and lipids. Associated to dispersed systems, they can also influence the drug... 

Asumadu-Mensah A, Smith KW, Ribeiro HS. Solid lipid dispersions Potential delivery system for functional ingredients in foods. J Food Sci. 78(7) (2013) E1000-E1008. 

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