Microporous polylactic acid/chitin nanocrystals composite scaffolds using in-situ foaming 3D printing for bone tissue engineering.

Bone injury represents an urgent clinical problem, and implantable bioscaffolds offer suitable means for replacing and regenerating damaged tissues. This paper proposes an in-situ foaming printing method employing material extrusion additive manufacturing technology and physical foaming to prepared poly(lactic acid)/chitin nanocrystals (CHNCs) microporous composite scaffolds, featuring pore sizes ranging from 9 ± 5 μm. This method offers a novel strategy for the preparation of poly(lactic acid)-based scaffolds with good biocompatibility. Material characterization and mechanical property testing demonstrated that the in-situ foaming printed PLA scaffolds exhibited excellent foam printability, and the expansion ratio and compression properties of the scaffolds could be adjusted by modifying the CHNCs concentration and the printing speed, achieving a compression modulus between 39.2 MPa and 54.3 MPa. Furthermore, at equivalent foaming multiplicity (1.5-2.6 times), the compression modulus increased by nearly 100 % compared to previously reported PLA-based foam scaffolds. Importantly, the PLA/CHNCs scaffolds produced via in-situ foaming exhibited superior biocompatibility compared to directly printed PLA scaffolds. This PLA/CHNCs composite scaffold provides a promising approach to addressing and repairing bone defects.