Piezoelectric-bioactive coupling of PVDF and hydroxyapatite for enhancing the interfacial bioactivity and osteogenic potential of the 3D-printed polyurethane scaffolds

The shortage and high cost of autologous bone grafts have created an urgent need to the development of biocompatible materials for bone defect repair. Bone is a natural piezoelectric tissue that generates electrical stimulation to induce osteogenic differentiation. However, most biodegradable polymers lack inherent piezoelectric properties, making the design of controllably degradable piezoelectric biomaterials particularly significant. In this work, poly(ε-caprolactone) (PCL) was used as a raw material to synthesize a polyurethane (PU)-based bio-ink consisting of polyvinylidene fluoride (PVDF) and hydroxyapatite (HA) via a one-step method. Personalized composite scaffolds (PU/PVDF/HA) were then fabricated by extrusion-based 3D printing. Characterization results from FTIR, XRD, water contact angle, and degradation tests confirmed the successful formation of PU/PVDF/HA composite scaffolds and demonstrated that the incorporation of HA effectively enhanced the bioactivity of the composite material with pronounced piezoelectric properties, suggesting potential relevance for osteogenic applications. Further, the PU/PVDF/HA15 group (containing 15 wt% HA and 5 wt% PVDF) had a good biocompatibility, which was clearly reflected by CCK-8 detection and live/death fluorescence imaging compared with the other groups. Overall, the synergistic action of piezoelectricity and bioactivity in PU/PVDF/HA scaffolds improved the physicochemical characteristics of the material-tissue interface, and then promoted the osteogenic activity. This study provides experimental evidence supporting the feasibility of integrating piezoelectric functionality and bioactivity into polymer-based scaffolds for bone tissue engineering.