Bioactive chitosan scaffolds reinforced with Zn-Fe-containing biphasic calcium phosphate: Nanocomposite for potential bone repair and antibacterial applications.

Osteomyelitis is a severe orthopedic infection that demands advanced biomaterial-based strategies for local infection control and bone defect management. Calcium-phosphate-based hydroxyapatite (HAp) is widely used for bone regeneration due to its compositional similarity to natural bone; however, poor mechanical and antibacterial properties limit its performance. In the present study, Zn-Fe-containing biphasic calcium phosphate (ZFHAp) nanomaterials, composed of Calcium Iron Hydrogen Phosphate (CIHP) (69.86%) and Parascholzite (PS) (30.14%), were incorporated into 3D chitosan scaffolds to fabricate multifunctional porous constructs. Nanomaterials incorporation enhanced the elastic modulus (Emod) from 70 kPa to 996 kPa (6 wt%), within the lower range of cancellous bone stiffness. The scaffolds exhibited rapid swelling (up to 1.4 min-1) and first-order enzymatic degradation, with rates ranging from 0.0047 to 0.0148 day-1. Sustained Zn2+ and Fe3+ release over 7 days correlated with >80% growth inhibition of S. aureus and E. coli, while maintaining the acceptable cytocompatibility of MG-63 cells. Structure-property analysis indicated a nonlinear relationship between nanomaterial loading and mechanical performance, with parabolic fitting suggesting an optimal composition of 5-6 wt% for balanced modulus and cell surface coverage. Overall, these chitosan-ZFHAp composite scaffolds demonstrate tunable mechanical properties, controlled degradation, antibacterial activity, and cytocompatibility, supporting their potential as multifunctional scaffolds for bone-related defect management.