Additively-manufactured gradient porous bio-scaffolds: Permeability, cytocompatibility and mechanical properties

The additive manufacturing technology enables the customization of artificial bone scaffolds, especially those with internal gradient porous structures (GS). It is of great significance to study the correlation between parametric design of GS and its properties. In this study, GS scaffolds were obtained by triply periodic minimal surfaces (TPMS) parametric design and fabricated by selective laser sintering. The stress distribution and permeability of GS scaffolds were elucidated by a combination of numerical simulation and experimental testing. Experimental tests indicated that the pore size of GS scaffold is in the range of 570 - 1440 mu m, corresponding to the average compressive strength of 3.0 - 9.3 MPa, respectively. The test permeability of GS scaffolds ranged from 1.241 x 10-9 to 2.231 x 10-9 m2, all within the range of human bones (2.56 x 10-11 to 7.43 x 10-8 m2). Moreover, in vitro biomineralization and biological testing of GS scaffolds showed excellent calcium-phosphorus formation induction and biocompatibility. In summary, GS scaffold successfully realizes flexible control of structural parameters, especially GP-type scaffolds with radial gradient porous structures exhibit mechanical properties and permeability comparable to natural bone tissue, and even effectively regulate cell behavior. Therefore, the GS scaffolds proposed in this work is expected to exhibit great application potential in orthopedic implants.