Novel derivatives of cyclodextrins, modified with poly(ethylene oxide) and their complexation properties

A new family of bouquet-like molecules based on cyclodextrins is described. These compounds were obtained by polymerization of ethylene oxide. This reaction was initiated by primary and secondary hydroxyl groups of cyclodextrins, which constitute an organizing core. Analysis of structure and composition of conjugates based on alpha-CD and beta-CD was performed using the data of MALDI-MS, GC-MS, and 13C-NMR spectra. Glass transition behavior of the conjugates shows that the above compounds are amorphous. Complexation properties of the conjugates are described with respect to sodium 4-nitrophenolate and calcium acetylhomotaurinate, which are used as guest molecules. Binding interaction between cyclodextrins or their conjugates and sodium 4-nitrophenolate was studied using differential absorption spectra. Association constants Ka between CD hosts and calcium acetylhomotaurinate composed of two equal anionic moieties were studied using 1H-NMR spectroscopy. The values of binding constant for beta-CD were found to increase by more than 2 orders of magnitude than that of the corresponding system based on alpha-CD. alpha-CD was shown to form the inclusion complex with one anionic moiety, whereas beta-CD produces a ternary complex with two anionic moieties of CAHT. For PEO derivatives of CDs, Ka decreases as compared with that of parent CD for both guests. These conjugates may be used as potent drug-delivery systems.