Aggregation in water of nonionic amphiphilic cyclodextrins with short hydrophobic substituents

A range of chemically modified amphiphilic cyclodextrins has been synthesized with the aim of providing versatile carrier and delivery systems for drug molecules. Amphiphilic cyclodextrins combine the properties of macrocyclic hosts and self-organizing amphiphiles An adequate balance between hydrophobic tails and hydrophilic heads is required for the preparation of equilibrium systems of amphiphilic cyclodextrins in acqueous solutions. In our case the introduction of hydrophilic oligo(ethylene glycol) onto the secondary side of heptakis(6-deoxy-6-alkylthio)-beta -cyclodextrins results in the formation of amphiphilic macrocycles with dramatically increased water solubility. In this paper we describe the properties of aqueous solutions of heptakis[6-alkylthio-6-deoxy-2-oligo(ethylene glycol)]-beta-cyclodextrins where alkyl is ethyl or hexyl. Our study compares three compounds with a different balance of hydrophobic alkyl substituents at C6 and hydrophilic oligo(ethylene glycol) substituents at C2.