Aggregate Determination by Permeation Technique.

Permeation technique is used to study molecular aggregation in aqueous solutions including formation of cyclodextrin guest/host aggregates. Since only guest molecules, host molecules and guest/host aggregates that are smaller than the pore size of a given semipermeable membrane are able to permeate through the membrane, negative deviation of permeation profiles indicates formation of guest/host aggregates or self-aggregates. This chapter describes how the method is used to detect formation of nano-sized aggregates and to determine the critical aggregation concentration (cac) from permeation profiles of a guest molecule.

Self-assembly of cyclodextrin complexes: detection, obstacles and benefits.

Cyclodextrins (CDs) are cyclic oligosaccharides that form water-soluble inclusion complexes of lipophilic molecules. They are commonly used as pharmaceutical excipients. Recently it has been observed that CDs and CD complexes self-assemble in aqueous solutions to form transient clusters, nanoparticles and small microparticles.

Characterization and Evaluation of Ternary Complexes of Ascorbic Acid with γ-Cyclodextrin and Poly(vinyl Alcohol).

Ascorbic acid (AA) is a general antioxidant used in aqueous pharmaceutical formulations. However, in aqueous solutions, AA is unstable and easily oxidized when exposed to air, light and/or heat. Cyclodextrins are well known for their ability to form inclusion complexes with various compounds to improve their solubility and stability.

Self-association of cyclodextrins and cyclodextrin complexes in aqueous solutions.

Cyclodextrins (CDs) are oligosaccharides that self-assemble in aqueous solutions to form transient clusters, nanoparticles and small microparticles. The critical aggregation concentration (cac) of the natural αCD, βCD and γCD in pure aqueous solutions was estimated to be 25, 8 and 9 mg/ml, respectively. The cac of 2-hydroxypropyl-β-cyclodextrin (HPβCD), that consists of mixture of isomers, was estimated to be significantly higher or 118 mg/ml.

Solubility of Cyclodextrins and Drug/Cyclodextrin Complexes.

Cyclodextrins (CDs), a group of oligosaccharides formed by glucose units bound together in a ring, show a promising ability to form complexes with drug molecules and improve their physicochemical properties without molecular modifications. The stoichiometry of drug/CD complexes is most frequently 1:1. However, natural CDs have a tendency to self-assemble and form aggregates in aqueous media.