Lipid-cyclodextrin complexes

Lopez-Nicolas JM, Bru R, Sanchez-Ferrer A and Garcia-Carmona F. 1995. Use of soluble lipids for biochemical processes linoleic acid cyclodextrin inclusion complexes in aqueous solutions. Biochem J 308 151-154. 

Tian, YQ, N Yang, Y Li, XM Xu, JL Zhan and ZY lin (2010). Potential interaction between /3-cyclodextrin and amylose-lipid complex in retrograded rice starch. 

Gunaratne, A and H Corke (2007). Influence of unmodified and modified cycloheptaamylose (/8-cyclodextrin) on transition parameters of amylose-lipid complex and functional properties of starch. Carbohydrate Polymer, 68,226-234. 

Examples illustrate the rapidly-growing and promising uses of cydodextrins in various operations the intensification of the conversion of hydrocortisone to prednisolone, the improvement in the yield of fermentation of lankaci-dine and podophyllotoxin, the stereoselective reduction of benzaldehyde to L-phenylacetyl carbinol, and the reduction in toxicity of vanillin to yeast, or organic toxic substances to detoxificating microorganisms. In the presence of an appropriate cyclodextrin derivative (e.g., 2,6-dimethyl-(3-cyclodextrin), lipid-like inhibitor substances are complexed. The propagation of Bordatella pertussis and the production of pertussis toxin therefore increases up to hundred-fold. Cydodextrins and their fatty acid complexes can substitute for mammalian serum in tissue cultures. 

Key words Dimethyl-y5-cyclodextrin, inclusion complex, bile substituent, lipid absorption enhancement. 

Dihydroquercetin (taxifolin, DHQ) is a natural flavonoid, which possesses antioxidant activity and other pharmacological properties (anti-inflammatory, anti-atherosclerotic, etc.). Dihydroquercetin is hydrophobic compound, that s why it can t be administered intravenously, also its oral bioavailability is reduced. Recently, many new dihydroquercetin derivatives were synthesized, including water-soluble forms (cyclodextrin inclusion complexes with dihydroquercetin derivatives). In addition to the protective effect of antioxidants against lipid peroxidation, increasing attention is paid to the possibilities of antioxidants including dihydroquercetin to prevent an oxidation of proteins. Fibrinogen is more susceptible to oxidation than most other plasma proteins. 

Cavalli R. et ah. Solid lipid nanoparticles as carriers of hydrocortisone and progesterone complexes with b-cyclodextrins, Int. J. Pharm., 182, 59, 1999. 

Unlike lipid bilayer membranes and proteins in which the ESPT of aromatic hydroxy compounds have been extensively used for probe purposes, a diverse variety of ESPT molecules have been studied as inclusion complexes in cyclodextrin cavities. The well-defined CD cavities often accommodate molecules in distinctly different but well-defined orientations. This is reflected in their ESPT behavior. For the conventional range of ESPT molecules, the size of (3-CD seem to be more appropriate and a fairly large number of studies are reported on it a-CD appears too small and 7-CD too large for forming suitable inclusion complexes. The effects of local polarity and water accessibility in ESIPT have been topics of active interest recently. These aspects are discussed next. 

Lipids also can be beneficial for cells in culture, since some substances absorbed by the cells need to be solubilized in lipids, or in some cases the toxicity of compounds may be reduced by complexation with lipids. The absence of essential lipids such as linoleic acid, lecithin, cholesterol, ethanolamine, or phosphorylcholine can result in the decrease of cloning efficiency and in reduction in the size of colonies, as shown for insect cells by Echalier (1997). However, one of the difficulties in supplying lipids at reasonable concentrations is their low solubility. To circumvent this limitation, lipids can be emulsified with complexing agents such as Pluronic F68 or cyclodextrin (Maiorella et al., 1998). 

A recent study has explored the potential of the ternary complex formed between a poly(p-cyclodextrin) (formed by polycondensation of p-cyclodextrin), a cationic surfactant (dodecyltrimethylammonium chloride), and a polyanion in water, to act as a delivery system for gene therapy,using a combination of viscometric and SANS studies as well as visual observations to determine the macroscopic and microscopic properties of the complexes. In the study, sodium dextran sulfate was used as a substitute for DNA. The potential advantages of the use of such ternary complexes over the more commonly investigated DNA-lipid or polymer complexes (lipoplexes and poly-plexes, respectively) include a high water solubility of the resulting complex (lipoplexes and polyplexes often... 

Bilirubin is a lipid-soluble metabolite of hemoglobin that is transported through the bloodstream as an albumin complex to the liver where it is esterified for excretion in urine. It plays an important role in the pathology of many diseases. Its Raman spectrum has been difficult to observe because of its sensihvity to photoisomerization and decomposition. However, under condihons of SERS on Ag electrodes this is suppressed allowing potenhal-dependent spectra to be observed in its free form as well as complexed with cyclodextrins and albumin [327]. The band intensities are higher at more posihve potenhals implicahng adsorption of anionic species on the electrode. 

Also, liposomes (see later) are very similar but are formed by the self-assembly of phospholipid molecules in an aqueous environment. The amphiphilic phospholipid molecules form a closed spherical bilayer in an attempt to shield their hydrophobic groups from the aqueous environment, whilst still maintaining contact with the aqueous phase via the hydrophilic head group. The resulting closed sphere may encapsulate water-soluble drugs within the inner aqueous compartment or may encapsulate lipid soluble drugs within the bilayer membrane. Alternatively, lipid soluble drugs may be complexed with a hydrophilic cyclodextrin and then encapsulated within the liposome aqueous compartment. 

Multicomponent liposomes reveal optimal UV protection in combination with me y-cyclodextrin complex of me vitamin present in me aqueous phases and lipid-soluble protectors (UV absorbers and antioxidants) present in me lipid phases (Loukas et al., 1995). The experimental photochemical half-life of riboflavin can be increased up to 266-fold by these complex liposome formulations. The liposomal composition is also important for me stabilizing effect obtained as incorporation of riboflavin into neutral and negatively charged liposomes increases photochemical stability, while association with positively charged liposomes leads to a decreased photochemical stability (Habib and Asker, 1991). Incorporation of retinol into multilamellar liposomes is demonstrated to extend the shelf-life of retinol under various conditions of pH, temperature, and light exposure (Lee et al., 2002). 

Some encapsulation processes have limited variability with regards to payload. For example, the payload capacity of molecular encapsulation or complexation in cyclodextrins is limited by affinity equilibrium of the active molecule to the host molecule. Conversely, the payload for some of the common emulsion-based processes, such as interfacial polymerization, will remain high due to the inability to increase shell thickness set by the diffusion limits of the reactive monomers used to form the shell. While liposomes can also have a core-shell structure, their formation process and structure severely limit payload. Lipophilic active ingredients can be entrapped within the lipid bilayer of the liposome but are limited to low percentages to avoid disrupting the bilayer structure. Hydrophilic active ingredients can be entrapped in the core of the liposome, but payload is again limited by their solubility or concentration in the inner aqueous environment. 

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