Abstract: BACKGROUND: The biomimetic design and functional gradient regulation of bone scaffolds are key to improving the efficacy of bone defect repair. Currently, homogeneous scaffolds struggle to balance mechanical load-bearing and material transport, often leading to stress concentration or inadequate nutrient supply after implantation, thus limiting bone regeneration outcomes.
OBJECTIVE: To investigate the differences in mechanical performance, mass transport capacity, and cellular microenvironment construction among Primitive (P-type), Gyroid (G-type), and GP composite scaffold structures.
METHODS: Based on digital light processing and triply periodic minimal surface theory, a Sigmoid function-driven topological gradient algorithm was proposed to fabricate β-calcium silicate/bioglass radially graded scaffolds with single G-type structure, single P-type structure, and GP type composite structure. The performance of the three types of scaffolds was systematically compared through mechanical simulation, fluid dynamics simulation, and wall shear stress analysis.
RESULTS AND CONCLUSION: (1) Finite element analysis showed that the G-type structure scaffold had a uniform stress distribution and the highest maximum Mises stress, while the GP-type composite structure scaffold had the lowest maximum Mises stress and a more uniform stress distribution than the single-structure scaffolds. The P-type structure scaffold had the largest maximum displacement, while the GP-type composite structure scaffold had the smallest maximum displacement. Static compression test results showed that the elastic moduli of the G-type, P-type, and GP-type composite structure scaffolds were 2.90, 3.39, and 3.38 GPa, respectively. Fluid dynamics simulation and permeability tests showed that the permeability of the GP-type composite structure scaffold was 3.4 × 10⁻⁹ m², significantly higher than that of the single-structure scaffolds, and within the optimal range of cancellous bone permeability. The average wall shear stress of the G-type structure scaffold was 0.86 Pa, with a maximum of 1.13 Pa; the average wall shear stress of the P-type structure scaffold was 1.40 Pa, with a maximum of 2.65 Pa; and the average wall shear stress of the GP-type composite structure scaffold was 1.01 Pa, with a maximum of 1.68 Pa, which is within the optimal range for bone regeneration stimulation. (2) The results indicate that the GP-type composite structure scaffold, designed with a biomimetic Haversian system gradient, can effectively balance mechanical support and biological function.

Key words: β-calcium silicate, bioactive glass, bone scaffold, functionally graded scaffold, triply periodic minimal surface, wall shear stress