Guest Molecules Release from MOF-808 and MOF-Based Hydrogel: An EPR Study

Precise, long-term control of drug concentration in organs and tissues of patients remains a significant challenge in modern pharmaceutics. In this work we investigate the metal–organic framework MOF-808, both in its pristine form and incorporated into a carboxymethylcellulose/chitosan (CMC-chitosan) hydrogel polyelectrolyte dressing, as a prospective platform for controlled drug release. Using electron paramagnetic resonance (EPR) spectroscopy and spin probes (radicals) that model drug molecules, we demonstrate that the controllable release kinetics from MOF-808 into water strongly depends on the functional groups of the released guests. The MOF-808 effectively functions as a reservoir, maintaining a stable target concentration of guest molecules in practical water volumes. Furthermore, embedding the MOF particles into CMC-chitosan hydrogel creates convenient platform for practical applications. Although conjugation of MOF-808 and hydrogel leads to an extra release of the cargo radicals, upon their elimination the release profile approaches that of the pristine MOF-808. This study underscores the potential of MOF-808 for sustained drug release applications and highlights critical considerations for its integration into composite hydrogel materials using EPR spectroscopy as the primary investigative tool.