3D-printed polycaprolactone/nano-hydroxyapatite scaffold coated by zein for controlled release of tetracycline hydrochloride in bone tissue engineering

The development of multifunctional scaffolds capable of promoting bone regeneration while preventing infection remains a major challenge in bone tissue engineering. Herein, we report a 3D-printed polycaprolactone/nano-hydroxyapatite (PCL/HA) scaffold coated with zein for the sustained release of tetracycline hydrochloride (TCH). The optimized scaffold containing 20 wt% HA exhibited enhanced apparent mechanical performance while maintaining an interconnected porosity of approximately 51%, providing a physiologically relevant mechanical and structural context for trabecular bone tissue engineering applications. Zein coating at 7 wt/v% produced a uniform, crack-free surface without pore obstruction, significantly reducing the initial burst release of TCH and enabling controlled drug release for up to 14 days. The scaffold demonstrated antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), and supported adhesion, spreading, and viability of MG-63 osteoblast-like cells, particularly at 10 wt% TCH loading. These findings highlight the synergistic effects of the PCL/HA framework, zein coating, and localized antibiotic delivery, providing a cost-effective and clinically translatable platform for bone regeneration in infection-prone environments.