Alginate-PVDF piezoelectric hydrogel containing calcium copper titanate- hydroxyapatite as a self-powered scaffold for bone tissue engineering and energy harvesting

We have developed a piezoelectric hydrogel composite comprising cross-linked polyvinylidene fluoride-sodium alginate (PVDF-SA) and calcium copper titanate nanowires (CCTO) as the piezoelectric filler, and hydroxyapatite nanoparticles (HA) as the mineral filler. A freeze-drying method was used to prepare piezoelectric hydrogel scaffold. The PVDF/SA-CCTOs-HA hydrogel composite with 0.5% CCTO and 0.4% HA content demonstrated significantly improved piezoelectric performance. Specifically, it exhibited the highest piezoelectric performance among all samples, with VOC of 7 V and ISC of 3.5 μA. These values were 5.5 and 4.9 times higher, than those of the pure PVDF-SA hydrogel scaffold. The rheology studies explored the viscoelastic properties of hydrogel and found that the hydrogel's solid characteristics led to a higher elastic modulus in comparison to the viscous modulus. The composite exhibited higher compressive and tensile strengths at 8.2 and 0.8 MPa, respectively, compared to the pure hydrogel, which has strengths of 6.3 and 0.4 MPa. In vitro studies revealed the good cytocompatibility, cell proliferation of MC3T3-E1 cells on piezoelectric composite. The PVDF-SA/CCTO-HA demonstrated significant antibacterial properties, offering further advantages for its practical applications. The hydrogel composite can identify various human activities, such as wrist and elbow movements, finger pressing and releasing, and heel pressure. Furthermore, it demonstrated its energy storage capability by charging a 1 μF capacitor. This work offers a practical approach to fabricate hydrogel scaffolds possessing favorable piezoelectric characteristics, biocompatibility, robust mechanical properties, and enhanced proliferation, thereby enabling their extensive utilization in bone tissue engineering applications, human movement detection, and energy harvesting.