Antibacterial properties, biocompatibility and superelastic behavior of Au-cysteine-gentamicin-functionalized Ti–Zr–Nb alloy

Abstract

Superelastic Ti–18Zr–15Nb alloy capable of mimicking the mechanical behavior of a bone tissue is a promising biomaterial but suffers from the lack of antibacterial properties. To address this problem, we developed a combined surface treatment method: formation of a porous sub-surface layer, deposition/precipitation of Au nanoparticles (AuNPs), surface functionalization with cysteine amino acid and grafting of gentamicin. The sizes distribution and AuNPs content were greatly effected by the synthesis methods. The AuNPs with an average size of 3 nm were obtained by precipitation from a AuNP colloidal solution. Larger AuNPs were formed by preliminary alloy functionalization in a NaBH4 solution followed by treatment in a HAuCl4 solution. Successful surface functionalization with L-cysteine and attachment of gentamicin were confirmed by XPS analysis. Due to the formation of stable cysteine-gentamicin complexes attached to AuNPs, the materials showed high antibacterial activity against Escherichia coli and Staphylococcus aureus strains. Better antibacterial properties are ascribed to fine isolated AuNPs as compared to larger ones. Cytocompatibility was assessed for osteoblast cells. In the case of smaller AuNPs, an accelerated restoration of osteoblastic cell proliferation and a more organized actin cytoskeleton were observed. Hemolytic activity of the developed materials was investigated. Functional mechanical properties were not affected by the surface treatment.