Design and characterisation of ZIF-8/alginate composites as drug carrier systems

Metal-organic frameworks (MOFs) are promising candidates for drug carrier systems due to their high porosity and tuneable structures, however, their clinical translation is restrained. Integrating MOFs into processable matrices improves mechanical properties, processability, and often drug delivery performance. Hydrogels, as soft, three-dimensional polymer networks with high flexibility and biocompatibility, are particularly favourable candidates for advanced MOF-based drug carriers. However, a lack of fundamental material studies limits full exploitation of the potential and hinders further development of such composites. To address this, this study provides a physicochemical investigation of MOF/alginate hydrogels using ZIF-8 as a benchmark MOF and thioflavin T (ThT) as a model drug. A rapid, in situ encapsulation approach enabled the fabrication of ThT@ZIF-8 (14.2 wt% loading), which was incorporated into an alginate matrix (ThT@ZIF-8@Alg) at 95 wt%, putting MOF carrier functionality in a processable form. Characterisation including X-ray diffraction, infrared and diffuse-reflectance UV/Vis spectroscopy, and electron microscopy enabled a detailed investigation of MOF properties in the composite and confirmed its retained structural integrity. Drug release studies of ThT@ZIF-8@Alg closely mirrored the pure MOF's pH-triggered behaviour. Furthermore, by comparing different methods of incorporating ThT in (ZIF-8@)Alg matrices, we demonstrate the versatility of such composites in achieving customisable release profiles. In vitro preliminary studies of the antiproliferative activity of ThT@ZIF-8@Alg in cancerous and non-tumorigenic cells support the idea of sustained controlled release of ThT over 72 h at pH 7.4. This strategy advances MOF-hydrogel-based drug delivery systems, with potential applications in topical treatments and implant coatings.