Electrically active KNN bioceramics: Synthesis-driven modifications and their influence on stability and osteoblast response

(KNN), can be designed as electrically active biomaterials for the repair and regeneration of damaged tissue, particularly bone. Applied as functional components in tissue scaffolds or implanted devices, the electromechanical properties of piezoelectric bioceramics could be utilized for cellular stimulation to improve the healing of bone defects and implant sites. The microstructural and functional properties of KNN-based ceramic systems can be extensively modified by adjusting the precursor chemistry and synthesis. The effect of these modified systems on in vitro cytocompatibility and cell behavior is investigated in this study. Stoichiometric, 0.2 mol% alkali-excess, 0.2 mol% Nb-excess, and hybrid synthesis KNN ceramics were evaluated in unpolarized and polarized states. Bulk piezoelectric response was maintained up to 14 days in media. Cell spreading, morphology, metabolic activity, and reactive oxygen species (ROS) generation of MG-63 human osteoblast cells were assessed on each KNN system. All KNN compositions investigated displayed no cytotoxic effects, with comparable performance to titanium implant alloy (Ti4Al6V) controls. Alkali-excess and hybrid synthesis KNN systems exhibited increased stability over stoichiometric and Nb-excess KNN, largely due to the suppression of hygroscopic secondary phases in synthesis. This work concludes that these modified KNN systems present excellent candidate materials for active bioceramics with piezoelectric functionality.