Magnetic hyaluronate hydrogels: preparation and characterization

•Novel hyaluronate(HyA)-based biocompatible magnetic hydrogels were prepared.•Chondroitin-sulfate-A coating is needed to disperse magnetite particles in HyA-gel.•Rheological behavior of hydrogels was independent of the magnetite content (<2 g/L).•Gels remained in stable and homogeneously dispersed state even after 90 days storage.•Magnetic HyA-gels are promising candidates for use as intra-articular injection.

A novel soft way of hyaluronate (HyA) based magnetic hydrogel preparation was revealed. Magnetite nanoparticles (MNPs) were prepared by co-precipitation. Since the naked MNPs cannot be dispersed homogenously in HyA-gel, their surface was modified with natural and biocompatible chondroitin-sulfate-A (CSA) to obtain CSA-coated MNPs (CSA@MNPs). The aggregation state of MNPs and that loaded with increasing amount of CSA up to 1 mmol/g was measured by dynamic light scattering at pH~6. Only CSA@MNP with ≥0.2 mmol/g CSA content was suitable for magnetic HyA-gel preparation. Rheological studies showed that the presence of CSA@MNP with up to 2 g/L did not affect the hydrogel's rheological behavior significantly. The results suggest that the HyA-based magnetic hydrogels may be promising formulations for future biomedical applications, e.g. as intra-articular injections in the treatment of osteoarthritis.