In order to design a drug delivery system (DDS), various kinds of high-performance carrier materials are being developed to deliver the necessary amount of drug to the targeted site for the required period of time, both efficiently and precisely. Cyclodextrins (CyDs) are potential candidates for such a role, because of their ability to alter physical, chemical, and biological properties of guest molecules through the formation of inclusion complexes. For the last 25 years, all our laboratory members have been absorbed in the supra-molecular properties of CyDs, focusing on the potential use of molecular-encapsulation in pharmaceutical formulations, and we have published over 400 papers including review articles so far.
More recently, we are developing various kinds of new CyD derivatives such as hydrophilic, hydrophobic, and ionic derivatives so as to extend the physicochemical properties and inclusion capacity of natural CyDs as novel drug carriers in DDS. To realize the potential of these CyDs in pharmaceutical formulations, their relevant physicochemical and biological profiles including in-vivo fate and toxic effects have to be thoroughly characterized before practical use. Therefore, one of the objectives of our research is to determine how well the CyD derivatives can satisfy the requirements for drug carriers of advanced dosage forms, comparing them with those of natural CyDs. Among the desirable properties of drug carriers is that they should be high quality and safe particularly in parenteral applications. Desirable attributes of the drug carriers are firstly the ability to control the rate and time profile of drug release; hydrophobic CyDs may serve as multifunctional carriers to control the release of water-soluble drugs including peptide and protein drugs via various routes of administration. In contrast, amphiphilic or ionizable CyDs can modify the rate or time of drug release, and bind to the surface membrane of cells, which may be used for the enhancement of drug absorption across biological barriers. In addition, a combination of molecular encapsulation with other pharmaceutical excipients is effective and a valuable tool in the improvement of carrier properties of CyDs. Another important requirement of a drug carrier is its ability to deliver a drug to a targeted site, including gene delivery. Conjugates of a drug with CyDs partially fulfil this requirement.
For these goals, we are currently engaging in a number of research projects collectively entitled "Design and Evaluation of CyD-based Drug Delivery Systems" as follows:

• Development of Novel Colonic Targeting Systems using Drug/CyclodextrinConjugates
• Control of Solid-state Properties of Drug Molecules by Amorphous CyclodextrinDerivatives
• Development of Novel DNA Delivery Systems using Cationic Cyclodextrin Derivatives
• Regulation of Lipopolysaccharide Induced Immune-activation by CyclodextrinInclusion Complexation
• Elucidation of Absorption Mechanism of Drug/Cyclodextrin Complexes fromGastrointestinal Tracts
• Improvement of Pharmaceutical Properties of Peptide and Protein Drugs byCyclodextrin Inclusion Complexation
• Application of Adhesive Film-forming Acylated Cyclodextrins to ParenteralPreparations
• Control of Pharmacokinetic Properties of Drugs by Cyclodextrin-containingLoposomes
• Design and Evaluation of Rapidly Dissolving and Disintegrating Oral DosageForms for Elderly Patients using Cyclodextrin Complexes