New insights into the mechanisms of the interactions between doxorubicin and the ion-exchange hydrogel DC Bead™ for use in transarterial chemoembolization (TACE)

Ion-exchange microspheres (IEMs) are widely employed in controlled drug delivery of ionic drugs due to their high loading capacity and the possibility to obtain the controlled release of the loaded drug(s) at a specific site. Among IEMs, DC Bead(™) are embolic microdevices (100-300 μm diameter) designed for transarterial chemoembolization (TACE) and composed of cross-linked poly(vinyl alcohol) (PVA) hydrogel, bearing anionic sulfonate moieties on the cross-links, and able to bind cationic drugs such as doxorubicin hydrochloride (Dox). Even if DC Bead(™) were studied for their release and bulk characteristics, a thorough characterization of these devices is still lacking. In particular, the aim of this work was the determination of bound and free water, Dox distribution within the microdevices and drug-DC Bead(™) interactions, in terms of transport features within the device. Compared with previous results, different Dox radial distributions in DC Bead(™) were found, and related to bead microsctructure and ion exchange mechanism. Artifacts due to the self-quenching of Dox at high concentration were prevented and the diffusion coefficients of drug-polymer (Dox-ionic sites) evaluated in different sections of the microspheres. Furthermore, DSC results indicated that in the hydrogel either free (bulk) or bound (non-freezable) water could be found, and that no freezing-bound water was present.