Biocompatibility of silver and copper plasma doped polyethylene

Plasma immersion ion implantation (PIII) is a viable technique to implant antibacterial metals into polymers to enhance the antibacterial properties. It has been shown that Ag and Cu PIII can produce excellent antibacterial results on polyethylene (PE). In the work described here, their biocompatibility is investigated and the effectiveness of Ag PIII and Cu PIII PE is experimentally compared. Our data reveal that the Ag elemental depth profiles are similar to those of Cu but there is a larger amount of surface Ag compared to Cu possibly due to the different charge states in the plasma. Moreover, Cu PIII induces more polar oxygen containing groups on the PE surface than Ag PIII, and more CC bonds are observed on the Ag PIII PE surface. The different chemical states lead to better hydrophilicity on the Cu PIII PE. Based on cell assays, the Ag PIII PE and Cu PIII PE samples exhibit excellent biocompatibility for bone cells, demonstrating that Ag and Cu PIII not only enhances antibacterial properties but improves cell biocompatibility of PE as well. The biocompatibility is found to not greatly relate to the metal species but rather the chemical functional groups formed during the interactions between the plasma-implanted metals and molecules in the polymer.