A Biomimetic Layered Silk Fibroin Microsphere Modulating Redox Homeostasis and Enhancing Osteogenic Differentiation for Synergistic Periodontal Regeneration

Periodontitis-associated alveolar bone loss results from a persistent inflammatory and oxidative microenvironment that impairs regenerative healing. To address this challenge, we developed a biomimetic, spatially stratified silk fibroin (SF)-based microsphere system (Cu/Ce-TA@HA-SF) that restores redox homeostasis and serves as a bone filling material to support periodontal bone regeneration. The microsphere features a three-layered architecture: a SF core produced via microfluidic technology ensures uniformity and adjustable mechanical properties, facilitating dynamic structural support during regeneration and adaptation to irregular defect sites. Surrounding the core, a hydroxyapatite (HA) layer enhances osteoconductivity, while the outer Cu²⁺/Ce⁴⁺-tannic acid (TA) nanozyme shell imparts antibacterial and reactive oxygen species (ROS)-scavenging functionality. The nanozyme exhibits catalase CAT- and SOD-like activities, effectively scavenging ROS, restoring mitochondrial function, and preserving human periodontal ligament stem cell (hPDLSC) viability. Notably, the microspheres inhibit ROS-induced pyroptosis via suppression of the NLRP3/Caspase-1/GSDMD signaling pathway. Concurrently, redox modulation regulates immune responses by activating Nrf2 and inhibiting NF-κB signaling, thereby suppressing M1 macrophage polarization and enhancing M2 phenotypes. In vivo, Cu/Ce-TA@HA-SF microspheres achieved coordinated inflammation resolution, angiogenesis, and alveolar bone regeneration in a rat periodontitis model. This multifunctional, hierarchically engineered microsphere offers a promising strategy for redox-driven immunomodulation and functional periodontal regeneration.