Hyaluronic acid-based hydrogel microspheres with multi-responsive properties for antibacterial therapy and bone regeneration in Staphylococcus aureus-infected skull defects

This study introduces hyaluronic acid-based (HA) hydrogel microspheres loaded with zinc oxide nanoparticles (ZnO-NPs) for the treatment of infectious bone defects. The microspheres were fabricated using a 3D-printing process, with a formulation consisting of 6 wt% HAD (methacrylated HA), 3 wt% AOHA (AMP-conjugated oxidized HA), 1 % BOHA (phenylboric acid-conjugated HA), 0.5 % photoinitiator, and 0.05 % ZnO-NPs. <i>In vitro</i>, the hydrogel microspheres demonstrated significant antibacterial activity against <i>Staphylococcus aureus</i>, with colony counts and biofilm inhibition assays showing a marked reduction in bacterial growth after 12 and 24 h. The release of antimicrobial peptides (AMPs) was enhanced in acidic conditions and in the presence of hyaluronidase. The microspheres also promoted osteogenic differentiation of bone marrow stromal cells (BMSCs), as evidenced by increased expression of osteogenic markers (ALP, OCN, OPN, and COL-1). <i>In vivo</i>, the hydrogel microspheres were tested in a rat skull defect model, showing significant bone regeneration, improved angiogenesis, and an anti-inflammatory response. These results indicate that ABOHA@ZnO hydrogel microspheres provide a promising strategy for treating infectious bone defects by combining antimicrobial, osteogenic.