• bone
• ceramic
• piezoelectricity
• Polyhydroxyalkanoates
• polymers
• scaffold
• Tissue engineering

Bone defects resulting from trauma, disease or surgery are a significant health problem worldwide. The significant healthcare costs required to manage this problem are further aggravated by the long healing times experienced with current treatment practices. Novel treatment approaches in the tissue engineering field, is using biomaterial scaffolds to stimulate and guide the regeneration of damaged tissue that cannot heal spontaneously. Therefore, bone tissue engineering aims to induce new functional bone regeneration through the synergistic combination of biomaterials and cells. Scaffolds provide a three-dimensional network that mimics the extra cellular micro-environment supporting the viability, attachment, and growth of cells. In particular, the porosity of biomaterials plays an essential role in the context of osteointegration and osteoconduction. The purpose of this work is to prepare and characterize new stimuli-responsive porous scaffolds to provide electric bio-signals naturally present in bone and vascular tissues. Processing techniques, such as mixing and extrusion, were used to create nanocomposites made by polyhydroxybutyrate (PHB) as matrix, a green polymer, biobased, biodegradable, and biocompatible, and the barium titanate (BaTiO3) nanoparticles as fillers, a piezoelectric and biocompatible nanoceramic with antibacterial properties. Nanocomposites, containing different percentages of BaTiO3 (5, 10, 15, 20 wt%), were created to prove the change of the polymer properties once the filler has been added. Processed materials were characterized in terms of morphological, thermal, and mechanical properties. Scanning electron microscopy results showed that the increase in the extrusion number can enhance the nanoparticles dispersion within the polymer matrix. In terms of mechanical properties considerable increases in the Young’s modulus and compressive strength were observed with the increase of the BaTiO3 content. Once nanocomposites were characterized, 3D printing was used to create 3D porous cubic scaffolds. The application of piezoelectric ceramics as a biomaterial processed via additive manufacturing represents a promising and novel approach in biomaterial manufacturing. The processing of the PHB/BaTiO3 nanocomposites was possible and resulted in the fabrication of interconnected, porous scaffolds with an average pore size of about 1 mm. The scaffolds were successfully fabricated using 90° lay down pattern with a continuous contour filament to achieve interconnected porous reticular structure. Temperature and injection speed were changed during the printing process to obtain good mechanical stability. Results from compression tests showed that the porous structure decreased their compressive strength compared to a filled cube of the same material, but, thanks to porosity, scaffolds seem to be good candidates for stem cells loading. Besides the promising results, the study also demonstrates that the fabricated scaffolds exhibit high microporosity through weak mechanical properties. Future investigations will focus on eliminating these disadvantages by a deeper investigation of the microstructure and alteration of the material composition. In conclusion, the additive manufacturing of piezoelectric PHB/BaTiO3-based nanocomposites represents a promising approach to yield scaffolds of designed porosity, equipped with piezoelectric properties for enhanced bone regeneration. The scaffold purpose is not to achieve the same mechanical properties of the natural bone, but to ensure the piezoelectric properties, due to nanoceramic presence, needed for cells stimulation until complete bone regeneration once the polymer matrix is degraded.