Amphiphilic cyclodextrins: Dimerization and diazepam binding explored by molecular dynamics simulations

Amphiphilic cyclodextrins spontaneously aggregate to form different supramolecular assemblies with potential applications in drug release. Herein, we employ extended molecular dynamics simulations in order to characterize the structure and dynamics in explicit solvent of several amphiphilic derivatives of the β-cyclodextrin (β-CD) molecule, with aliphatic chains ester-bound to the wide rim of the hydrophobic cavity. We also study the binding properties considering a typical guest (diazepam) and the dimerization of these macrocyclic systems, assessing the relative stability of the complexes by means of end-point free energy methods. Different lengths (C4, C10, and C14 atoms) are considered for the alkyl side chains included in the amphiphilic β-CD-Cn molecules. According to the simulations, the length of these Cn moieties determines the complexing and aggregation capabilities of the β-CD-Cn systems. Compared to the native β-CD, the alkyl side chains in the β-CD-Cn molecules destabilize the inclusion complexes with diazepam and hinder the access of guest molecules to the hydrophobic cavity. In turn, dimerization is favored in the largest amphiphilic derivatives associated to the hydrophobic interaction between the Cn fragments.