Enhancing antibacterial activity of surface-grafted chitosan with immobilized lysozyme on bioinspired stainless steel substrates

[Display omitted] ► Stainless steel substrates were activated via a catecholic dopamine anchor. ► A natural defensive lysozyme enzyme was conjugated to the surface-grafted chitosan via a bifunctional carbonyldiimidazole linker. ► The substantially-enhanced antibacterial activity was achieved on the lysozyme-immobilized stainless steel substrates. ► High stability and persistence of antibacterial activity of the lysozyme–chitosan conjugate layers were ascertained. Bacterial infections have been widely recognized as a major cause of the failure of medical implants and devices. One promising strategy to reduce the incidence of infections is to impart the material surfaces with bactericidal function for inhibiting bacterial adhesion and biofilm formation. In this study, stainless steel (SS) surface was first activated by a biomimetic dopamine anchor to provide active amino groups, followed by covalently immobilizing chitosan (CS) with glutaraldehyde (GA) as a bifunctional linker. Hen egg white lysozyme, a natural defensive enzyme, was finally conjugated to the grafted chitosan to enhance biocidal functionality. The antibacterial assay results demonstrated substantial enhancement in bactericidal efficiency against Staphylococcus aureus (S. aureus) on the lysozyme-immobilized SS substrates under the neutral pH conditions as compared to the chitosan-grafted SS substrates. With the inherent advantages of robust anchoring ability of dopamine and specific functionality of lysozyme, the metallic substrates can be readily tailored with antibacterial property to combat biomaterial-centered infection for potential biomedical applications.