Structure–Property Evolution of Cubic and Gyroid PLA Scaffolds During In Vitro Degradation Under Physiologically Relevant Conditions

The design of innovative biomaterials increasingly aims to reproduce the structure, properties, and behavior of natural tissues. Biomimetic materials are generally considered to promote biointegration. In bone tissue regeneration materials, biomimicry and mechanical competence represent complementary design objectives whose relative importance depends on the clinical requirements and the expected timeline of bone regeneration. In the present investigation, two types of 3D-printed PLA scaffolds for bone tissue regeneration, featuring conventional cubic and biomimetic gyroid-based triply periodic minimal surface (TPMS) architectures, respectively, were evaluated. Their degradation behavior was investigated during immersion in a protein-rich cell culture medium under dynamic conditions at 37 °C, followed by mechanical characterization and analytical modeling of the property evolution. The cubic scaffolds exhibited approximately 210% higher apparent compressive modulus and more than fourfold higher apparent compressive strength compared with the gyroid scaffolds in the initial state. During 21 days of immersion, gyroid scaffolds showed progressive mass loss reaching approximately 13%, whereas cubic scaffolds exhibited a slight mass increase associated with fluid uptake. Both architectures experienced a reduction in mechanical properties; however, the gyroid structures showed faster structural deterioration due to their higher porosity, increased fluid accessibility, and greater fluid uptake and degradation-induced structural deterioration. The Residual Property Model accurately predicted the mechanical degradation of cubic scaffolds but was unable to predict the gyroid response due to the dominant contribution of mass loss and structural degradation. The overall results indicate a trade-off between the two architectural approaches, whereby enhanced biomimetic features are associated with reduced mechanical performance.