3D-printed diopside/PCL composite scaffolds with improved bioactivity and tunable mechanical properties for bone repair

Bone tissue engineering focuses on restoring bone defects by combining mechanical support with biological functionality. Polycaprolactone (PCL) has been widely used in 3D printing because of its good processability and biocompatibility, although its low bioactivity and slow degradation are still limiting factors. In this work, diopside (CaMgSi 2 O 6 ) nanoparticles were synthesized using a sol–gel route and incorporated into PCL scaffolds at different contents (0, 20, 40, and 60 wt.%) through robocasting. The results from FE-SEM, XRD, and FTIR analyses showed that the particles were well distributed within the polymer matrix. With increasing diopside content, the scaffolds became more porous (from ∼58.1% to ∼66.1%) and more hydrophilic, as reflected by the reduction in contact angle from 105.3° to 70.9°. Among the samples, the scaffold with 40 wt.% diopside showed the most suitable mechanical behavior, reaching a compressive strength of 27.73 ± 1.23 MPa and a Young’s modulus of 75.81 ± 3.37 MPa. A higher weight loss was also observed during the 28-day degradation test compared to pure PCL. In addition, apatite formation was detected after immersion in simulated body fluid, and this effect became more pronounced at higher diopside contents. A similar trend has also been reported in other calcium silicate-based composite scaffolds. Cell studies further confirmed that the scaffolds were non-cytotoxic, and the presence of Ca 2+ , Mg 2+ , and Si 4+ ions appeared to support MG63 cell proliferation. Overall, the PCL–40% diopside scaffold provides a more appropriate balance between mechanical properties, degradation, and bioactivity, and can be considered a promising option for bone tissue engineering.