Computational study on the nanotubes formation between olsalazine and β-cyclodextrin

Abstract

Interests in cyclodextrin-derived nano-assembled supramolecular systems have recently grown notably [1,2]. Cyclodextrins are a family of oligosaccharides that possess very characteristic features of conical shape with hydrophobic and hydrophilic interiors and exteriors, respectively. As a host molecule, cyclodextrin (CD) can encapsulate various types of molecules inside its cavity as host-guest supramolecular interaction that is in turn stabilized by non-covalent interactions [3-5]. Under specific conditions, cyclodextrins can self-aggregate to form nanoarchitectures, such as nanotubes and nanorods. However, guest-induced nanotubular architecture can be assembled with gust molecules of suitable size, such as olsalazine drug. The objective of this work is to computationally investigate the formation and the corresponding molecular properties of olsalazine--CD nanotubes using the semi-empirical method (SQM) PM7. Different guest:host ratios of inclusion complexes that can lead to the formation of the olsalazine--CD nanotubes were examined, namely 1:2 and 2:2. Furthermore, the side of penetration of the guest molecule is another factor that is considered herein, where head and tail inclusions correspond to the penetration inside the cavity of -CD through the wide and narrow rims of -CD, respectively. On the other hand, the head-to-head, tail-to-tail, head-to-tail aggregations of -CD nanotubes are considered.