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

Osteoarthritis (OA) is characterized by progressive degeneration of articular cartilage, and current treatments often result in suboptimal fibrous cartilage repair. This study explored the effects of polydopamine-coated gold nanoparticles (PD-AuNPs) on cartilage repair and OA-related changes.

PD-AuNPs were synthesized using dopamine hydrochloride as a surface coating for AuNPs and characterized by scanning electron microscopy and Fourier-transform infrared spectroscopy. Their effects were evaluated in vitro using adipose-derived mesenchymal stem cells and in vivo using a cartilage defect rat model and a monosodium iodoacetate-induced OA model. In the defect model, a biocompatible hydrogel composed of polydimethylsiloxane and sodium hyaluronate was used as a carrier.

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.