Biphasic Bone Implants through Hybrid Extrusion Printing of Thermoplastic Poly(lactic-co-glycolic) acid and...

Biphasic scaffolds that integrate bioactive ceramics with biodegradable polymers hold considerable potential for bone regeneration, but they present challenges in terms of interfacial integration and processability. In this study, biphasic scaffolds consisting of alternating strands of strontium-modified calcium phosphate cement (SrCPC) and poly-(l-lactide-co-glycolide) (PLLA-PGA) were successfully fabricated using an optimized extrusion-based 3D printing and postprocessing protocol. Degradation studies in water showed that the presence of the SrCPC phase in the biphasic scaffolds buffered the acidic degradation products of PLLA-PGA, delaying and attenuating the pH drop over time and influencing the degradation of the polymer phase. Uniaxial compression tests revealed intermediate mechanical properties of the biphasic compared to monophasic PLLA-PGA and SrCPC scaffolds, which declined over the 24-week observation period. Aging experiments in cell culture medium under near-physiological conditions indicated a significant mutual influence of the two materials, as evidenced by an altered strontium and phosphate ion release profile from the SrCPC phase and the formation of a different surface structure on the materials in the biphasic system compared to the monophasic system. This was also reflected by the cellular response of osteoblast-like SaOS-2 cells, showing a local heterogeneity in cell-material interactions. Nevertheless, the cell experiments demonstrated the strong positive effect of the bioactive SrCPC component in the biphasic scaffolds on cell proliferation and alkaline phosphatase activity, which were significantly higher than those in the monophasic PLLA-PGA scaffolds.