Pullulan–cyclodextrin microspheres: A chromatographic approach for the evaluation of the drug–cyclodextrin interactions and the determination of the drug release profiles

Pullulan microspheres containing cyclodextrin (CyD) were obtained by chemical crosslinking with epichlorohydrin of an alkaline solution of pullulan (Pul) and α-, β- or γ-CyD. The amount of α-, β- and γ-CyD in microspheres was 120, 156, and 138 μmol/g, respectively, as determined from the percentage of iodine incorporated in the hydrophobic cavity of CyD’s. Microspheres were packed in a glass column and the liquid chromatographic behaviour by isocratic elution of different drugs or typical organic compounds (TOC), taken as model drugs, was investigated. The increase of the retention volume (VR) of each compound, depending on the interaction(s) between CyD’s cavity and the considered molecule, is characterized by a broadening of the peaks. The interaction coefficient K, corresponding to the ratio between the VR value of each tested molecule on Pul–α-, Pul–β- and Pul–γ-CyD active stationary phase and the VR value of benzoic acid on St/maltodextrin neutral stationary phase, was determined. According to K values, the accurate prediction can be done on the potential drugs to be conditioned in suitable CyD cavity. Values of K allow to anticipate the release profiles of drugs considered.