A design approach to facilitate selective attachment of bacteria and mammalian cells to additively manufactured implants

Additive manufacture (AM) of patient specific implants is rapidly growing, however, customized devices typically exhibit higher infection rates. Herein the possibility to differentially control bacterial and mammalian cell attachment on bespoke AM implants by process optimization is demonstrated. Surface analysis of Powder Bed Fusion (PBF) Ti-6Al-4 V cuboidal coupons printed at different orientations revealed an increase in roughness driven by a greater number of partially melted particles on higher angled surfaces, enticing a transition from hydrophilic to hydrophobic contact angles. These changes resulted in a linear increase of adhered S. epidermidis biomass, while osteoblast coverage was maximum for surfaces manufactured at 20 or 30°. To exploit the relationship between low roughness and enhanced biological response, a computational roughness model considering melt pool radii and partially melted particles was developed. Through two implant case studies we demonstrate the ability to predictably minimize surface finish of AM parts in-situ, providing a novel toolset for AM process control. Overall, a method to simultaneously reduce device infection while enhancing native cell attachment has been established, critical to improve musculoskeletal implant performance.