Cyclodextrins (CD) are natural occurring cyclic oligosaccharides consisting of at least 6 (1→4)-linked α-D-glucosyl residues (figure 1). Cyclodextrins are produced from starch by the action of extracellular enzymes, cyclodextrin glycosyltransferases (CGTase, E.C. 18.104.22.168). Cyclodextrins consisting of 6 to 8 (1→4)-linked α-D-glucosyl residues, denoted α-, β- and γ-cyclodextrin, respectively, are the major products of prolonged action of all known CGTase and only small amounts of larger cyclodextrins (e.g. δ-CD containing 9 D-glycosyl recidues) are usually produced. While the outer surfaces of the cyclodextrins are hydrophilic, the inner cavities are highly hydrophobic, making them capable of inclusion complex formation with a large variety of smaller hydrophobic molecules (e.g. drugs, aromas and agrochemicals).
Due to their high availability, they have been intensively studied and constitute the most successful group of macrocyclic compounds within the field of supramolecular chemistry. Inclusion complexes formations with various molecules or parts of molecules leads to complexes with considerable altered physiochemical properties compared to that of the guest molecule itself. This can lead to enhanced solubility of the guest molecules, e.g. active drug molecules, and increase their bioavailability. Cyclodextrins´s are also used in the pharmaceutical industry as a mean to control the release of active ingredients in drug formulations. Moreover, cyclodextrins can stabilise labile molecules and protect them from degradation by light, temperature, oxidation, reduction and hydrolysis or by reducing their volatility. In the food industry, cyclodextrins are used for stabilizing aromas and for masking of unpleasant odors. In analytical chemistry the cyclodextrins have gained a position as the most widely applied chiral selector for separation of enantiomeric molecules. Furthermore, cyclodextrins or cyclodextrin derivatives have been shown to catalyse certain chemical reactions and are currently studied as enzyme models.
Our research interests within the field of cyclodextrins focuses on formulation of drugs and development of drug delivery systems based on well-known commercially available cyclodextrins and cyclodextrin derivatives, as well as novel cyclodextrin polymers. This includes the characterization of the inclusion complex forming properties of small cyclodextrins and a range of larger rare types. By combination of detailed thermodynamics characterization of the complex formation and high resolution NMR structural data detailed insight into structure-selectivity-stability of various types of complexes can be obtained. Besides the basic aspects of increasing the understanding of cyclodextrins and how they form complexes, several applied projects are conducted, mainly in collaboration with Danish pharmaceutical and chemical industries. Our interest in cyclodextrin applications includes development of novel drug delivery systems and drug formulations, functionalization of surfaces with cyclodextrin (textiles, chromatography matrices and implants).