Preparation and osteogenic properties of nano-hydroxyapatite/ polyvinylidene fluoride/polyacrylamide/carboxymethyl cellulose piezoelectric double-network hydrogel soaked with metal ions

Bones are naturally occurring piezoelectric materials that generate electrical signals to stimulate bone cells, thereby regulating bone growth. When a piezoelectric material is implanted into a bone defect, the generated electric field can restore the local potential environment on the bone surface, promoting bone regeneration. In this study, piezoelectric hydrogels with piezoelectric properties and high conductivity were developed for bone repair. A piezoelectric double-network (DN) hydrogel (PAC@HA) was synthesized using a one-pot method and immersed in CaCl2, MgCl2, and FeCl3 solutions, resulting in PAC@HA/Ca2 +, PAC@HA/Mg2 +, and PAC@HA/ Fe3 + piezoelectric DN hydrogels, respectively. The mechanical properties, microstructure, chemical composition, electrical properties, rheological properties, in vitro mineralization ability, and cell behavior were also evaluated. The results indicated that the PAC@HA/Fe3 + hydrogel (obtained by FeCl3 immersion) exhibited a more compact network structure, improved mechanical properties, higher swelling capacity, better electrical conductivity, and enhanced piezoelectric properties compared to the other composite hydrogels. The hydrogel also showed superior in vitro mineralization ability after ion immersion in simulated body fluid. Co-culturing with bone marrow mesenchymal stem cells (BMSCs) revealed that the PAC@HA/Fe3 + DN hydrogel exhibited the best cell compatibility, along with strong osteogenic and mineralization-promoting capabilities. These results suggest that the prepared hydrogel has significant potential for bone repair applications.