Celecoxib-Loaded "Nano-in-Nano" Hierarchical Delivery System: Structure-Driven Synergistic Optimization of Diffusion Efficiency and Mechanical Stability for Osteoarthritis Therapy.

PURPOSE: Osteoarthritis (OA) joints present abnormal mechanical environments that limit drug retention and therapeutic efficacy. Current intra-articular systems cannot provide both sustained anti-inflammatory delivery and mechanical support. A celecoxib (CXB)-loaded "Nano-in-Nano" Hierarchical Delivery System (NiN-HDS) was developed to simultaneously optimize drug release and joint reinforcement.

METHODS

In this study, celecoxib-loaded PLGA nanoparticles (CXB-NPs) were prepared by emulsion solvent evaporation and incorporated into an electrospun nanofiber membrane combined with a genipin-crosslinked gelatin layer to form NiN-HDS. The system was characterized for particle size, zeta potential, porosity, hydrophilicity, swelling, degradation, mechanical properties, and in vitro CXB release. Therapeutic potential was evaluated in a rat OA model using histological and immunohistochemical analyses of cartilage and inflammatory markers.

RESULTS

NiN-HDS maintained nanoparticle stability, with CXB-NPs showing an average particle size of 138.4 ± 4.3 nm and a zeta potential of -58.74 ± 16.58 mV. The system exhibited high porosity (87.16 ± 0.75%) and hydrophilicity (contact angle < 90°), achieved swelling equilibrium at 150 ± 10 min with a swelling ratio of 163.97 ± 9.76%, and degraded over 10 days with 88.53 ± 2.03% mass loss. Mechanical testing demonstrated high strength (Young's modulus 17.24 ± 2.65 MPa, elongation at break 307.48 ± 32.01%. NiN-HDS provided sustained CXB release over 7 days, reaching 67.16% cumulative release. In vivo, it reduced cartilage damage and suppressed IL-1β and MMP-13 expression, while maintaining mechanical support and controlled drug delivery.

CONCLUSION

In conclusion, we successfully developed NiN-HDS. Our results show that NiN-HDS combines sustained drug delivery with mechanical support, improves cartilage preservation and reduces local inflammation in a rat OA model, indicating that it can serve as a promising strategy for intra-articular therapy of osteoarthritis.