Antibacterial surface functionalization by silver nano-powder mixed electrical discharge machining of biomaterials

Abstract text (incl. figure legends and references)
Introduction

Electrical Discharge Machining (EDM) is widely used for machining biomaterials such as stainless steel, titanium and its alloys. In order to reduce biomaterial-associated infections (BAIs), antibacterial coatings are applied. However, coating usually requires additional, time-consuming and cost-intensive processes. As an alternative, powder mixed EDM is investigated, by adding silver nano-powder to the dielectric for process-integrated antibacterial functionalization while shaping biomaterial surfaces.

Objectives

Shaping biomaterial components and simultaneously alloying a layer on the surface that has a long-term antibacterial effect.

Materials & methods

During the EDM process, silver nano-powder with a particle size of (50…60) µm is suspended in the dielectric with different concentrations up to 25 g/L to modify Ti6Al4V surfaces by forming alloyed layers containing silver. Staphylococcus aureus and Staphylococcus capitis bacteria, as well as the osteoblasts cell line are used for in vitro antibacterial and biocompatibility investigations, respectively. For in vivo evaluations, a Galleria mellonella infection model is utilized.

Results

Current in vitro evaluations show promising results in terms of antibacterial effect combined with good biocompatibility. EDM modified surfaces alloyed with silver show significant reduction of the bacterial number and the amount of bacterial clusters compared to EDM modified surfaces without silver and polished surfaces. No negative influence on the osteoblast function was observed. Furthermore, a long-term effect of antibacterial capacity has been demonstrated both in vitro and in vivo.

Conclusion

Silver nano-powder mixed EDM represents a promising technology to shape biomaterial parts and concurrently modify the surfaces to reduce BAIs with a long-term antibacterial effect.