3D-printed piezoelectric scaffolds composed of uniform core-shell structured BaTiO3@ bioactive glasses particles for bone regeneration

Abstract

The piezoelectric property and biocompatibility of barium titanate (BTO) is exceptional, whereas its biological activity is limited. Bioactive glasses (BG) are widely recognized for osteoinductive bioactivities. Hence, it is meaningful to explore the reasonable design of BTO and BG combinations to achieve bioactive piezoelectric tissue engineering scaffolds that mimic natural bone. In this study, homogeneous core-shell particles of BTO wrapped in BG layer were firstly fabricated via a sol-gel process. Various BG weight ratios (5 wt%, 10 wt%, and 15 wt%) in BTO@BG particles have been able to achieve the shell thickness in the range of 4 nm–16 nm. Furthermore, the composite particles were three-dimensionally printed into porous scaffolds through gas extrusion using polyvinyl pyrrolidone as binders. The composite scaffolds have been extensively characterized with respect to their physical and functional properties. Desirable piezoelectric scaffolds (BTO@15BG-S) with compressive strength at ∼66 MPa, and piezoelectric constant (d33) of ∼1.1 pC/N were obtained after sintering and polarization. Our findings indicated that higher sintering temperatures led to denser scaffolds with reduced porosity, increased compressive strength and higher d33 constant. Additionally, an increase in the amount of BG coating promoted scaffold calcination via melt filling in pores, while reduced the piezoelectric constant d33. Among all scaffolds, BTO@15BG-S exhibited superior ability to induce apatite formation when sintered at 1250 °C and soaked in simulated body fluid for 7 days. In vitro culture rat bone marrow mesenchymal stem cells (rBMSCs) and cellular assessments confirmed that polarized piezoelectric ceramic scaffolds could effectively enhance cell adhesion, proliferation, and osteogenic differentiation compared to unpolarized scaffolds. An increase in BG coating amount enhanced the capacity of piezoelectric ceramic scaffolds to upgrade osteogenesis activities of rBMSCs. These results rendered BTO@BG-S composite scaffolds promising candidate in the field of bone repair.