Additive manufacturing of hydroxyapatite/3Y-ZrO2 bioceramics by digital light processing: enhanced mechanical strength, cytocompatibility, and antibacterial performance for potential load-bearing bone repair

Abstract

This study aims to develop hydroxyapatite (HA)-based bioceramic scaffolds reinforced with 3 mol% yttria-stabilized zirconia (3Y-ZrO2) using digital light processing (DLP) additive manufacturing, and to evaluate their mechanical strength, cytocompatibility and antibacterial performance for potential load-bearing bone repair. HA/3Y-ZrO2 scaffolds were fabricated via DLP 3D printing and sintered at optimized temperatures. Phase composition and microstructure were analyzed by XRD and scanning electron microscopy. Mechanical properties were assessed through compressive, flexural and fracture toughness tests. In vitro cytocompatibility was evaluated using osteoblast viability assays, while antibacterial functionality was imparted by chitosan coating and tested against Staphylococcus aureus and Escherichia coli. The DLP process enabled scaffolds with interconnected pores (>500 µm), porosity above 90% and high dimensional accuracy. The optimized HZ-3 scaffold achieved compressive strength of 285.36 MPa, flexural strength of 26.02 MPa and fracture toughness of 1.18 MPa·m½, with a relative density of 93.9% after sintering at 1250 °C. In vitro assays confirmed excellent cytocompatibility (up to 98.67% cell viability after 14 days). Chitosan-functionalized surfaces reduced bacterial adhesion by 99.1% (S. aureus) and 90.7% (E. coli). This work demonstrates a multifunctional HA/3Y-ZrO2 scaffold fabricated by DLP that combines high mechanical strength, biocompatibility and antibacterial activity. The integration of zirconia reinforcement with chitosan coating may provide a promising strategy for developing advanced bioceramic scaffolds with improved mechanical and antibacterial functionality for bone repair applications.