A laser-induced periodic surface structure (LIPSS) was shown to have antibacterial adhesion properties in previous research. In this study, the antibacterial performance of LIPSS on traditional biometals (stainless steel and titanium alloy) and a potential biometal (zirconium-based bulk metallic glass, Zr-BMG) was investigated. A femtosecond laser was used to fabricate LIPSS on the specimens. Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) were used to examine the antibacterial behavior of the LIPSS samples. The bacterial adhesion force on each specimen was evaluated by an atomic force microscopy (AFM) cell probe. The results showed that the LIPSS on all three metal surfaces significantly lowered antibacterial adhesion compared to polished metal specimens. E. coli demonstrated a higher adhesion force but a lower surface adhesion rate compared to S. aureus. The Zr-BMG specimen with LIPSS has multiple antimicrobial mechanisms (physical antiadhesion and chemical elimination), while the traditional biometals (316L and TC4) mainly offer physical antiadhesion. Finally, an in vitro/vivo study showed that specimens with LIPSS surfaces did not significantly affect the biocompatibility of the specimens. This study reveals that the Zr-BMG specimen with femtosecond laser-processed LIPSS is an ideal choice for achieving an antibacterial surface.

As high-performing materials, bulk metallic glasses have attracted widespread attention for biomedical applications. Herein, the bacterial adhesion properties of femtosecond laser-nanostructured surfaces of four types of zirconium-based bulk metallic glasses are assessed. Laser-induced periodical surface structures and nanoparticle structures were fabricated by femtosecond laser irradiation under different energy intensities (0.23 and 2.3 J/mm2). Surface topography, roughness, wettability, and surface energy were investigated after femtosecond laser irradiation and the surface bacterial adhesion properties were explored using Escherichia coli and Staphylococcus aureus as respective representatives of Gram-negative and Gram-positive bacteria. 4′,6-Diamidino-2-phenylindole fluorescence staining was used to characterize and assess the bacterial surface coverage rate. The in vitro cytotoxicity of polished and laser-nanostructured surfaces was investigated using MC3T3-E cells. The obtained results demonstrate that femtosecond laser surface nanostructuring retained the amorphous structure of zirconium-based bulk metallic glasses and led to an obvious decrease in bacterial adhesion compared with polished surfaces. The inhibition of bacterial adhesion on laser-induced periodical surface structures was greater than on nanostructured surfaces after 24 h of bacterial incubation. In addition, femtosecond laser nanostructuring did not have an apparent effect on the cytotoxicity of zirconium-based bulk metallic glasses.

Zirconium-based metallic glasses (Zr-BMGs) have attracted tremendous attention in healthcare fields, especially in the design of surgical tools and orthopedic implants, due to their unique amorphous structure; however, the application of Zr-BMG-based medical devices is hindered by bacterial contamination. Here, a structure-element strategy is proposed to improve the antibacterial performance of Zr-BMGs by surface laser nanostructuring and silver nanoparticle (AgNP) deposition. The laser nanostructuring process generates a disordered nanoparticle structure (NP) and laser-induced periodic surface structure (LIPSS) to decrease the surface bacterial adhesion and increase the internal antimicrobial ion release. Moreover, after Ag deposition and hydrogen peroxide (H2O2) treatment, the antibacterial adhesion ability of the Zr-BMG surface can be further improved without any influence on the crystallization of Zr-BMGs and the release of antibacterial copper/nickel (Cu/Ni). The antibacterial effect of the LIPSS and the NP surfaces presents over 90% bacterial killing ratio, which is superior to that of the naked Zr-BMGs with less than 60% bacterial killing ratio. In vitro and in vivo tests show that the Ag-deposited and H2O2-treated LIPSS surfaces exhibit an optimal balance between the antibacterial property and the biocompatibility compared with the polished, NP structured or LIPSS structured surfaces. It is assumed that such structure-element surface modification strategy can improve the antibacterial activity of metal-containing surgical tools and orthopedic implants, improving the success rate of medical treatment.

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