Phase-separated hierarchical porous PLLA/Gelatin scaffolds for stem cell-mediated bone regeneration

Large bone defects remain a major clinical challenge due to limited self-regeneration and the drawbacks of conventional grafting strategies. In this study, a gelatin-modified poly(L-lactic acid) (PLLA) scaffold with a hierarchical porous architecture was fabricated via a controlled two-step thermally induced phase separation (TIPS) process. The optimized scaffold exhibited interconnected macropores (150-400 μm), micropores, and nanofibrous features (200-600 nm), with a high porosity of approximately 90% and a specific surface area of 11.45 m²/g. Introduction of gelatin through phase separation significantly enhanced hydrophilicity and protein adsorption, increasing serum protein adsorption to 8.44 mg/g after 12 h. The compressive modulus was markedly improved to 7.22 ± 0.13 MPa, compared with 2.79 ± 0.20 MPa for pristine PLLA scaffolds. In vitro studies demonstrated that gelatin-modified scaffolds supported robust adhesion and proliferation of human adipose-derived stem cells (hADSCs), and exhibited enhanced mineralization-related behavior, evidenced by enhanced calcium deposition and a 3.20 ± 0.74-fold increase in extracellular matrix production. These findings suggest that the combination of bioactive macromolecule incorporation and hierarchical architecture contributes to improved scaffold bioactivity, providing a promising platform for further investigation in bone tissue engineering.