Thiolated Cyclodextrin: The invisible drug delivery systems

Within this book, an effort to improve local drug delivery at the various mucosal tissues via encapsulation in CDs was undertaken by pursuing thiolation and pre-activation strategies to overcome low residence time, foreign body sensation, irritation and other biochemical barriers. The investigated CDs, α-CD and β-CD were successfully modified to obtain more mucoadhesion, prolong drug residence time, improved water solubility and improved drug tolerance by reducing its irritation effects. Thiolation of CDs was carried out via inducing aldehyde groups and subsequent conjugation of cysteamine. Non-ionic thiolated CDs were synthesized by substitution of hydroxyl groups with bromine and subsequent thiolation with thiourea. Thiolated CDs were further improved by making them resistant against oxidation at higher pH in solutions via pre-activating the free thiol groups. Thiomers, multifunctional polymers, exhibited advantages in prolonged drug residence time by mucoadhesive properties. The presence of thiol groups leads to disulfide bonds formation between the polymer and cysteine subunit of mucus glycoprotein, and thus prolong the residence time of the delivery system.