Supercritical CO₂-foamed hierarchically porous PLA/PBS-based scaffold for advanced bone regeneration

This study presents a novel porous bone scaffold system (PBCMH) fabricated by melt blending and supercritical CO₂ (scCO₂) foaming, incorporating nano-hydroxyapatite (nHA), chitosan, polylactic acid (PLA), and polybutylene succinate (PBS). Four formulations with varying nHA content (0 %, 10 %, 20 %, 30 %) were evaluated to optimize the balance of structure, mechanical properties, and osteogenic bioactivity for bone regeneration. The scaffolds demonstrated interconnected porous networks with tunable pore sizes and mechanical strengths (57.2-184.3 μm). The PBCMH3 group (30 % nHA) exhibited the smallest average pore size, highest surface hydrophilicity (61.1°), and the best mechanical properties (elastic modulus ~4.26 MPa), resembling cancellous bone. Physicochemical analysis confirmed uniform dispersion of components and strong interfacial interactions. In vitro studies demonstrated that PBCMH3 significantly promoted rBMSC proliferation and osteogenic differentiation, as indicated by enhanced cytoskeletal organization, elevated alkaline phosphatase (ALP) activity, and increased mineral deposition. These in vitro findings were further supported by in vivo results: in a rat calvarial defect model, micro-CT and histological analyses confirmed superior bone regeneration in the PBCMH3 group, characterized by extensive new bone formation and the presence of mature lamellar bone. Importantly, no signs of systemic toxicity or pathological changes were observed in major organs, validating the biosafety of the scaffold. Together, these results underscore the potential of PBCMH3 as a promising scaffold for clinical bone tissue engineering, offering a comprehensive solution to the challenges of bone regeneration.