Metal-Organic Frameworks (MOFs) and Their Composites as Emerging Biomaterials for Osteoarthritis Treatment.

Metal-Organic Frameworks (MOFs) have emerged as a novel component in biomaterial formulations over the past 5 years. The bioactivity of MOFs in bone or cartilage tissue is mediated through the sustained delivery of metal ions, bioactive ligands, or drug molecules that are loaded into the porous MOF structures. Alternatively, bioactivity may also originate from structure-specific properties. The latter includes the availability and accessibility of open metal coordination sites for the catalytic conversion of biomolecules into active agents. This narrative highlight aims to inspire strategies to utilize MOFs for treating osteoarthritis (OA), with a special focus on augmenting hydrogel-based biomaterials with MOFs. The added value of MOFs in these hydrogel formulations is discussed, and the biological efficacy is compared to approaches applying classical injectable biomaterials for OA treatment. Possible future directions and pitfalls of these novel MOF-hydrogel composites are emphasized to assist future transition of MOFs into clinical applications.