Enhancing bioactivity of calcium-phosphate cement-based 3D printed scaffolds with human platelet lysates: in vitro and in vivo validation

The reconstruction of large bone defects remains a significant challenge due to the limited regenerative efficacy of engineered biomaterials compared to autologous grafts. Although ceramic substitutes based on calcium phosphates (CaP) have shown promising results for small bone defects, achieving an optimal balance between biological activity and mechanical performance is crucial for the successful repair of larger defects. Enhancing the bioactivity of CaP-based materials through the incorporation of growth factors could be a potential solution. However, the heat treatment required to ensure mechanical performance in ceramic-based products inhibits the incorporation of thermosensitive biomolecules into CaP-based printable formulations, limiting their bioactivity. This study developed apatite cement-based 3D-printed scaffolds with improved bioactivity through the integration of different amounts of human platelet lysates (PL), rich in growth factors, cytokines, and chemokines into the ink formulation. The ink formulations exhibited suitable rheological behaviour for extrusion-based 3D printing, and the scaffolds from all compositions demonstrated good shape fidelity. Remarkably, the delivery of PL from the optimized scaffolds significantly enhanced cell adhesion, proliferation, and function of cells seeded onto the scaffold surfaces compared to the non-loaded scaffolds, as shown in in vitro studies. In vivo studies further revealed that the apatite cement-based scaffolds loaded with 2 wt % of PL are biocompatible and exhibited a good integration into bone, significantly promoting new bone formation within the scaffold pores. This approach presents a promising solution for the repair of large bone defects and establishes these scaffolds as valuable biomaterials in regenerative medicine. STATEMENT OF SIGNIFICANCE: This study presents a promising strategy for advancing bone tissue engineering and regenerating large bone defects. Through synergistic integration of bioactive components and structural optimization, 3D-printable cement-based composite scaffolds combine biological cues with engineered architecture to enhance mechanical and cellular performance. Human platelet lysates improve bioactivity and regenerative potential, while the scaffold's macroporous design supports bone ingrowth and integration. The material allows for personalization using autologous components, reducing immunogenic risk and improving outcomes. Its architecture, including controlled macroporosity, supports bone integration, as shown by robust in vivo performance with effective tissue incorporation and minimal immune response. This work offers a customizable, biologically potent, and clinically adaptable solution with strong potential for large-scale bone repair and personalized regenerative therapies.