Dextran-based cyclodextrin polymers: Their solubilizing effect and self-association

Cyclodextrins and their water-soluble derivatives are excellent solubilizers and stabilizers and widely used as enabling pharmaceutical excipients. However, still new cyclodextrin derivatives are being designed and synthesized in an effort to improve their physicochemical properties. In this study physicochemical and self-associating characteristics of dextran-based cyclodextrin polymers, with ether or ester linkage between the β-cyclodextrin and the dextran backbone, were investigated. Methods applied include phase-solubility studies, permeation studies and dynamic light scattering. Results with a model drug, hydrocortisone, showed that the solubilization and binding efficiency slowly declined with increasing molecular weight. The degree of substitution had significant effect on the properties, making the polymers with ether linkage more favorable. Self-association of the drug–polymer complexes was observed, although the instability can hamper their utilization