Application of cyclodextrins

Cyclodextrin-modified solvent extraction has been used to extract several PAHs from ether to an aqueous phase. Data evaluation shows that the degree of extraction is related to the size of the potential guest molecule and that the method successfully separates simple binary mixtures in which one component does not complex strongly with CDx. The most useful application of cyclodextrin-modified solvent extraction is for the simplification of complex mixtures. The combined use of CDx modifier and data-analysis techniques may simplify the qualitative analysis of PAH mixtures. 

Of particular interest in the application of cyclodextrins is the enhancement of luminescence from molecules when they are present in a cyclodextrin cavity. Polynuclear aromatic hydrocarbons show virtually no phosphorescence in solution. If, however, these compounds in solution are encapsulated with 1,2-dibromoethane (enhances intersystem crossing by increasing spin-orbit coupling external heavy atom effect) in the cavities of P-cyclodextrin and nitrogen gas passed, intense phosphorescence emission occurs at room temperature. Cyclodextrins form complexes with guest molecules, which fit into the cavity so that the microenvironment around the guest molecule is different from that in... 

In 1990, the applicability of cyclodextrin-modified MEKC (CD-MEKC) was successfully explored for the first time by adding a neutral CD to the micellar solution for the separation of highly hydrophobic and closely related compounds such as chlorinated benzene congeners, polychlorinated biphenyl (PCB) congeners, and tetrachlorodibenzo-p-dioxin (TCDD)... 

Application of cyclodextrins and other host molecules in aqueous organometallic catalysis... 

Loftsson T, Brewster ME. Pharmaceutical applications of cyclodextrins. I. Drug solubilization and stabilization. J Pharm Sci 1996 85(10) 1017. 

The limits of the application of cyclodextrin complexation in the formulation of flavors can be listed as follows ... 

Irie, T. and K. Uekama (1997). Pharmaceutical applications of cyclodextrins. 3. Toxicological issues and safety evaluationJ. Pharm. Sci., 86 147-162. 

Hinze WL, Applications of cyclodextrins in chromatographic separations and purification methods, in Separations and Purification Methods (Van Oss C, Ed.), Vol. 10, p. 159, Marcel Dekker, New York (1981). 

Frijlink, H.W., et al. 1992. The effects of cyclodextrins on drug release from fatty suppository bases. III. Application of cyclodextrin derivatives. Eur J Pharm Biopharm 38 174. 

Due also to their controllable size, low cytotoxicity, and unique architecture, cyclodextrin-based polyrotaxanes and pseudopolyrotaxanes have been developed to encompass a broad range of diverse medical applications from erodable hydrogels to drug and gene delivery. A recent review about biomedical applications of cyclodextrin based polyrotaxanes have been reported by Loethen et al. [64],... 

Cvclodextrin-Silica stationary Tfriaaag. since excellent reviews deal with the preparation, properties, and analytical applications of cyclodextrin-silica stationary phases (11,12.14-16), the following paragraphs will discuss these topics very briefly, only to the extent that the information will be used in the rest of this chapter. 

The chromatographic separation of positional isomers (26-31), geometrical isomers (27,32-36) and enantiomers (37-49) has been achieved by utilizing the concerted action of inclusion complex formation, additional primary and secondary hydrogen-bond formation and steric hindrance effects between the solutes and the cyclodextrins (11,12,14-23,50). There is an abundant literature on the analytical applications of cyclodextrin-silicas (13-50), but not on their preparative chromatographic use. 

In this review, recent progress on integrated bioprocessing, including in situ adsorption using polymeric resins, in situ extraction with adequate solvents, application of cyclodextrins, and the use of aqueous two-phase systems, are summarized and their advantages and disadvantages are described in detail. 

Pharmaceutical applications of cyclodextrins have been studied the most extensively. The identified roles of cyclodextrins are primarily to increase solubility, stability, and the bio availability of drugs with limited water solubility, to reduce the side effects and toxicity of drugs, and to alter their physical properties such as smell and taste. There have been many excellent reviews on the pharmaceutical utilization of cyclo dextrin and its derivatives by Loftsson and Brewster [45],Rajewski and Stella [46], and Irie et al. [47]. 

Application of cyclodextrins can be also found in cell cultures. Cyclodextrin was used to remove unwanted cholesterol from cultures of L-cell mouse fibroblasts [48]. 

Proper modification of the chemical moiety of cyclodextrin will be required to broaden the spectrum of application of cyclodextrins. However, achieving industrial significance using cyclodextrins in the plant cell system is dependent on cost, aqueous solubility, and safety. 

The ability of some components of nucleic acids, especially those with an adenine base, to form complex with 8-cyclodextrin, can also be readily used for chromatographic separations of various nucleotides and nucleosides (59). A substantial problem associated with application of cyclodextrin polymer gels, is that the accessibility of the cyclodextrin cavities on the surface and within the interior of the polymer particle is rather different. The rate of entrapment and release of solutes from the streaming liquid is obviously a diffusion controlled process. Consequently, a longer time is needed to reach an equilibrium within the particle than on its surface. The accessibility of the cyclodextrin rings will be more uniform, if the cyclodextrin is immobilized on the surface of non-complexing polymer particles (polyacrylamide, agarose (60,61) cellulose (62), and silica (63)). Therefore, a better separation (however lower capacity) is expected. 

Potentially, one of the most valuable applications of cyclodextrin as an analytical tool is its use in resolving enantiomeric compounds, those compounds which are mirror images of each other. This is an important concern with synthetic pharmaceuticals, which are often produced as enantiomers. In most cases, both isomers can have physiological activity, although only one actually has capacity to produce the desired therapeutic action. The inactive isomer will often contribute to host toxicity or other undesired actions which can limit the effectiveness of the active isomer. The ability of cyclodextrin to resolve many types of enantiomers is of obvious benefit, and has been demonstrated for a number of relevant pharmaceuticals (6). 

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