Laser powder bed fusion of copper-bearing AISI 316 L: Microstructure, biofunctional and corrosion performance

Abstract

Developing strategies to impart antibacterial properties to biomaterials while preserving cytocompatibility is essential for addressing implant-associated infections. In this study, copper-alloyed AISI 316 L stainless steel produced by laser powder bed fusion (L-PBF) was investigated as a dual-functional biomaterial with both antibacterial and cytocompatible characteristics. Unlike previous studies that mainly focus on bulk composition, this study emphasizes the role of microstructural features unique to L-PBF processing, specifically copper micro-segregation at cellular boundaries and nanoscale oxides and examines how these influence electrochemical behavior and biological responses. Electrochemical tests suggest that the AISI 316 L-Cu samples exhibit corrosion behavior comparable to that of conventional AISI 316 L. Nevertheless, the addition of Cu resulted in diminished pitting resistance, which subsequently affected the characteristics of the passive film. Importantly, AISI 316 L-Cu demonstrate significant antibacterial activity against both Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli). Moreover, AISI 316 L-Cu reveals in vitro bioactivity and cytocompatibility in contact with osteoblast-like MG63 cells, supporting cell proliferation and spreading. The daily release of copper ions in physiological saline solution is measured at a trace level of parts per billion (2.5 ppb/cm2), which is considered to pose minimal risk to human health. In summary, AISI 316 L-Cu exhibited a strong capacity to enhance both antibacterial properties and cytocompatibility, suggesting a distinct advantage for its application in orthopedic settings.