Design of bismuth polydopamine particle embedded, 3D-printed polycaprolactone scaffolds for antibacterial and...

Implant associated infection disrupts the local immune balance and compromises scaffold integration, motivating the development of biodegradable materials that can both limit bacterial burden and modulate inflammatory responses. Here, 3D-printed polycaprolactone (PCL) scaffolds incorporating polydopamine coated bismuth particles (Bi/PDA) were developed as a bioactive platform for peri-implant microenvironment modulation. The PDA coating modulated the release behavior of Bi³⁺ and contributed to the immunomodulatory properties of the scaffold without compromising printing fidelity or mechanical strength. As a result, the 10% Bi/PDA-PCL scaffolds exhibited effective 77.27 ± 7.87% antibacterial activity against S. aureus and attenuated infection associated inflammation. Mechanistically, 10% Bi/PDA-PCL reduced intracellular ROS by 9.22 ± 4.31% and suppressed NF-κB activation, thereby promoting macrophage polarization from M1 toward M2, reducing TNF-α, IL-6 secretion by 39.38 ± 2.54% and 51.43 ± 13.16%, respectively. In an initial in vivo proof of concept evaluation, the scaffolds reduced peri-implant bacterial burden and alleviated inflammatory tissue responses, while maintaining favorable biocompatibility. Collectively, these findings suggest that integrating Bi/PDA into a 3D-printed PCL scaffold enables coordinated antibacterial and NF-κB mediated immunomodulatory effects, thereby alleviating infection-associated inflammatory imbalance and creating a more favorable peri-implant environment for scaffold integration.