Polydopamine-coated gold nanoparticles promote cartilage regeneration and alleviate osteoarthritis in rats

In vitro, PD-AuNPs was associated with upregulated expression of the chondrogenic markers aggrecan (ACAN) (∼ 1.6-fold) and SRY-box transcription factor 9 (SOX9) (∼ 1.2-fold) compared with AuNPs alone. In vivo, PD-AuNPs improved repair outcomes in the defect model, showing higher scores for defect filling (3.7 vs. 2.3), osteochondral reconstitution (1.7 vs. 0.6), cell morphology (2.3 vs. 1.2), and matrix staining (3.3 vs. 1.3), along with enhanced ACAN and SOX9 expression. In the OA model, PD-AuNP was associated with reduced OA-related changes, including improved weight-bearing (49.5 % vs. 47.0 %), reduced joint swelling, and a markedly lower final OARSI score (2.7 vs. 12.8). They also increased ACAN and SOX9 while decreasing IL-6 and MMP-9 compared with AuNPs. Collectively, these results suggest that PD-AuNPs contribute to cartilage preservation and repair, offering a potential approach for improving cartilage regeneration strategies.