Interaction of Heptakis (2,3,6-Tri-<i>O</i>-methyl)-&beta;-cyclodextrin with Cholesterol in Aqueous Solution

Abstract

Heptakis (2,3,6-tri-O-methyl)-b-cyclodextrin (TOM-b-CyD) has recently been used to alter the membrane cholesterol content. For example, using TOM-b-CyD, cholesterol of the myometrial plasma was selectively depleted from the myometrial plasma membrane.1) TOM-b-CyD has also been used to clarify whether membrane proteins exist at an association with specialized microdomains called lipid rafts by depleting cholesterol contained in them.2) It is clear that cholesterol forms a soluble complex with TOM-b-CyD in aqueous solution. Although the interactions of cholesterol with TOM-b-CyD are particularly important, to the best of our knowledge, no studies on the thermodynamic parameters of the interaction in aqueous solution have been reported.We therefore investigated the interactions of cholesterol with TOM-b-CyD in aqueous solution quantitatively using the solubility measurement method now common in the pharmaceutical field, measurement of proton nuclear magnetic resonance ( 1 H-NMR), and Corey-Pauling-Koltum (CPK) atomic models. As cholesterol exists in a buried form in the phospholipid bilayer in biomembranes 3,4) the interactions of cholesterol with phospholipids are suggested to be based on the hydrophobic interaction. On the other hand, TOM-b-CyD has a deeper and more hydrophobic cavity than the parent cyclodextrin.5) Therefore, it is suggested that the interaction of cholesterol with TOM-b-CyD is based on the hydrophobic interaction in aqueous solution. In a previous paper, 6) we reported that heptakis (2,6-di-O-methyl)-b-cyclodextrin (DOM-b-CyD), which like TOM-b-CyD has a deeper and more hydrophobic cavity than the parent cyclodextrin, forms soluble complexes with cholesterol in aqueous solution.However, the inclusion behaviors of these hydrophobic cyclodextrins differ in general. For example, DOM-b-CyD penetrates the matrix of liposomes and extracts phospholipid from liposomes to form a soluble complex, whereas only a small amount of TOM-b-CyD penetrates the matrix of liposomes to remain there and therefore, TOM-b-CyD has very week ability to form a soluble complex with phospholipids. 7,8) For these reasons, TOM-b-CyD is used to alter membrane cholesterol content as mentioned above, although DOM-b-CyD is not used for this purpose. As another example, the formation constant of the complex between TOMb-CyD 9) and 8-anilino-1-naphthalenesulfonate (ANS) is smaller than that between DOM-b-CyD 10) and ANS. Furthermore, each incluson mode is different in the TOM-b-CyD-ANS complex and DOM-b-CyD-ANS complex. Therefore the comparison of the interaction between TOM-b-CyD and cholesterol with that between DOM-b-CyD and cholesterol in present paper would be informative and pertinent. ExperimentalMaterials TOM-b-CyD purchased from Nacalai Tesque Co. (Kyoto, Japan) was used after recrystallization from water and dried for 12 h at 110°C in a vacuum before use. Cholesterol purchased from Sigma (St. Louis, MO, U.S.A.) was used without further purification. Water purified with Milli-Q Labo (Ͼ18 MW · cm) was used throughout the ex...

Spectroscopic studies and molecular modeling for understanding the interactions between cholesterol and cyclodextrins

“…Among these, the interaction of cholesterol with CDs in aqueous solution was investigated quantitatively (phase solubility diagrams) and correlated with liposome loss of integrity (19,21). Another method such as NMR spectroscopy (22) could be used to determine the interaction between CDs and cholesterolDifferent authors already studied the interactions of cholesterol with -CD and its dimethylated (Dimeb) and trimethylated (Trimeb) derivatives (23)(24)(25). In the present work, 1 H NMR and ROESY spectra were taken in the same conditions in order to compare complexes with Dimeb and Trimeb with the one obtained with the randomly methylated derivative (Rameb) and a low substituted derivative (Crysmeb  ).…”

“…The protons of Trimeb alone were assigned by comparison to the spectrum obtained by Nishijo et al (25) (Fig.4B). As shown in the figure, the 1 H NMR spectrum of Trimeb in presence of cholesterol is deformed when compared to the one of Trimeb alone.…”

Polymer-associated liposomes as a novel delivery system for cyclodextrin-bound drugs

“…As noted above, the liposomes lose vesicle stability with time because CDs extract, or interact with, the lipid components hence the vesicle structure of liposomes is destabilized [14][15][16][17][18][19][22][23][24]. In contrast, the extraction of lipid components by CDs in polymer-associated liposomes might be restricted by the outer covering of polyelectrolytes on the bilayer, which is evidenced by as evidenced by a zetapotential of −50 to −42 mV for the polymer-associated liposomes, which contrasts with other liposomes where the zetapotential is −3 to +2 mV.…”

“…It has been reported that the degree of lipid extraction is highly dependent on the CD concentration [17][18][19][20]. In several studies calorimetric methods have been used to monitor carboxyfluorescein leakage from vesicles in order to clarify the extraction/reorganization of vesicle phospholipids by CDs [11,[21][22][23][24]. Destabilization of vesicles by CDs can reduce liposome carrier function, that is, increasing the amount of drug released into cells or the permeability of drugs into skin.…”

Inclusion complex of cantharidin with β‐cyclodextrin: Preparation, characterization, in vitro and in vivo evaluation

“…18,19 In the case of b-CD, it is important to demonstrate whether the drug is included in the cavity or entrapped within the chains of the molecule. During complexation, the chemical environment of some protons changes, and this results in changes in chemical shifts of 1 H-NMR lines of the protons that are due to shielding or deshielding effects.…”