Abstract:
Introduction: Osteoarthritis and focal osteochondral defects represent a major clinical challenge due
to the avascular nature and limited regenerative capacity of articular cartilage. While mesenchymal
stem cell (MSC)-based therapies offer immense potential, directing their specific chondrogenic lineage
remains a bottleneck. Zinc oxide nanoparticles (ZnO-NPs) have emerged as promising bioactive agents
providing structural reinforcement and osteochondrogenic signaling cues.
Material and Methods: A comprehensive mapping of the literature was conducted, analyzing
extensive pre-clinical data (~300 citations) to evaluate the therapeutic efficacy, physicochemical
properties, and cytotoxicity profiles of ZnO-NPs in cartilage tissue engineering. Data were
systematically clustered based on nanoparticle morphology, concentration, signaling pathways, and
scaffold integration.
Results: The therapeutic window of ZnO-NPs is strictly dose- and morphology-dependent.
Concentrations below 10–15 µg/mL demonstrate excellent biocompatibility and promote MSC
chondrogenesis without inducing apoptosis. However, smaller (<30 nm) and spherical NPs accelerate
Zn²⁺ burst release, increasing the risk of acute reactive oxygen species (ROS) generation and
cytotoxicity. Conversely, anisotropic and streamlined ZnO-NPs exhibit a gradual ion release, offering
sustained biological effects and enhanced rheological properties in hydrogels. Molecularly, ZnO-NPs
effectively upregulate key chondrogenic markers (SOX9, COL2A1) and modulate critical pathways
(TGF-β, Wnt/β-catenin). Furthermore, integrating ZnO-NPs into synthetic, natural, or 3D-printed
scaffolds significantly improves biomechanical stability and cellular integration in various in vivo
models.
Conclusions: ZnO-NPs represent a highly versatile platform for cartilage regeneration, actively
driving chondrogenic differentiation while suppressing hypertrophic degeneration. Standardizing their
physicochemical parameters (size, shape, dose) is essential to maximize therapeutic efficacy, avoid
nanotoxicity, and accelerate successful clinical translation.
