Geometry driven fluid dynamics and cytocompatibility of 3D printed TPMS bone scaffolds

Triply Periodic Minimal Surfaces (TPMS) can mimic the complex architecture of trabecular bone while facilitating controlled fluid transport and cellular colonisation. This study integrates computational fluid dynamics (CFD), laser powder bed fusion (L-PBF), and in vitro cell assays to evaluate the structure-function relationship of four Ti6Al4V TPMS scaffolds informed by Schwartz Primitive (SSC), Lidinoid (LSC), Gyroid (GSC), and Diamond (DSC) featuring 60% porosity. CFD simulations at inlet velocities ranging from 0.001 to 0.01 m/s revealed architecture-specific permeability ranging from 1.89 × 10 ⁻⁹ m ² (DSC) to 4.29 × 10 ⁻⁹ m ² (SSC) at low flow rates, with a consistent inverse relationship between flow velocity and permeability (R ² > 0.99). Mid-plane velocity fields highlighted scaffold-specific vortex formations and nutrient mixing dynamics, with SSC exhibiting pronounced swirling zones, promoting fluid homogenisation. In vitro cytocompatibility assessed via MTT assay on U-2OS osteosarcoma cells showed >85% viability across all geometries after 24 h and >88% after 7 days, with the LSC scaffold exhibiting the most consistent viability (101.8 ± 7.7%) and SSC showing significant improvement over time (87.2 ± 3.3% to 121.4 ± 6.2%, p < 0.015). Immunofluorescence imaging confirmed cell attachment across all architectures, with GSC and DSC supporting uniform cytoskeletal spreading and enhanced cell-pore integration. Degradation studies in PBS at 37 °C showed that DSC scaffolds underwent the highest mass loss (4.42% at day 7), correlating with their larger surface area, while pH monitoring suggested early ion release followed by buffering over time. These results demonstrate that scaffold topology significantly impacts permeability, degradation, and biological performance with SSC and GSC emerging as promising 3D printed microenvironments.