Design and in vitro evaluation of gradient Schwarz Primitive scaffolds with thin-board integration for bone implants

Bone scaffolds for the repair of large-segment bone defects require a balance between mechanical stability and nutrient transport. This study proposes gradient Schwarz Primitive minimal surface scaffolds (P-TPMS) integrated with thin-board (B) structures, fabricated via selective laser melting (SLM). Finite element analysis (FEA) revealed that the gradient design reduced stress concentrations, achieving a layer-by-layer collapse failure mode under compression. This progressive energy absorption is critical for implant stability. Computational fluid dynamics (CFD) demonstrated that the gradient integrated scaffold (GPB70) with 70 % porosity maintained moderate permeability (6.37 × 10^-9 m²) while enhancing fluid transport efficiency, mimicking the characteristics of natural trabecular bone. Surface modification with TiO₂ improved hydrophilicity, reducing the contact angle from 110.8° to 31.6° for Ti6Al4V, and mitigated fabrication-induced defects. Dynamic impregnation tests revealed that the GPB70 scaffolds exhibited enhanced capillary-driven fluid transport, which is essential for efficient nutrient delivery in the early stages of implantation. In vitro studies confirmed superior adhesion and proliferation of the mouse osteoblastic cell line MC3T3-E1 within the GPB70 scaffold, attributed to the increased specific surface area. These findings suggest that the GPB70 scaffold offers a promising solution for enhanced bone tissue ingrowth by effectively balancing mechanical integrity, fluid transport, and cell ingrowth, making it a strong candidate for clinical applications in load-bearing bone defect repair.