Ceramic-based piezoelectric material reinforced 3D printed polycaprolactone bone tissue engineering scaffolds

Recent studies confirm the piezoelectricity of human bone, sparking interest in biocompatible and biodegradable piezoelectric scaffold development. These scaffolds mimic native bone by matching its mechanical properties and piezoelectric behaviour i.e., generating local electrical stimulation under mechanical stress, or generating mechanical response under external electrical stimulation, thereby modulating cellular activity, accelerating cell proliferation and differentiation, ultimately speeding up the regeneration process. Although polymer-based piezoelectric materials offer high reproducibility for 3D scaffolds, their piezoelectric performance falls short of ceramic alternatives. While lead zirconate titanate (PZT) exhibits excellent piezoelectric properties, the hazardous nature of lead limits biomedical applications. Consequently, this research proposes novel lead-free Bi1/2Na1/2TiO3-based (BNT) piezoelectric materials, namely, direct piezoelectric ceramics (DPC) (>50 % d33 enhancement compared to undoped BNT) and converse piezoelectric ceramics (CPC) (>200 % Smax enhancement compared to undoped BNT), with properties optimized for bone tissue engineering (BTE). 3D BTE scaffolds are designed and fabricated considering biocompatible and biodegradable polycaprolactone (PCL) incorporating DPC and CPC as functional fillers. Comparative evaluations against hydroxyapatite (HA), a well-accepted bioceramic for clinical applications, are conducted for surface, mechanical, and biological properties. Results proved the incorporation of both DPC and CPC promotes the mechanical properties (88.6 % enhancement compared to neat PCL) and cell proliferation rate (46.3 % improvement compared to HA). Notably, hybrid scaffolds combining both PCL/DPC and PCL/CPC in a cascade manner also outperformed PCL/HA (by 7.4 %) in osteogenic differentiation, indicating promising potential for future studies.