Antibacterial Nanoscale Etching of Stainless Steel Surfaces

At Georgia Tech, researchers have developed a way of etching stainless steel surfaces so finely that bacteria that come in contact with them end up being pierced and killed. Interestingly, because of the physiological differences between cell types, mammalian cells don’t seem to be significantly impacted by these surfaces.

This may point to interesting applications for the technology beyond just treating commonly used surfaces in hospitals and clinics, such as medical implants that resist the formation of bacterial biofilms.

Scanning electron microscope images showing the difference in adhesion of E. coli bacteria. The stainless steel sample on top had no treatment, while the sample on the bottom was treated to create a nanotextured surface. (Credit: Yeongseon Jang, Georgia Tech)

The electrochemical etching process creates a permanent texture on the metal surface, which means that the antimicrobial effects may last indefinitely. Helping it do so is the surprising benefit that this surface also seems to be particularly resistant to corrosion.

The etched surfaces work both against Gram positive and Gram negative bacteria, including E. coli and Staph. When tested on mouse cells, which are considerably larger, the surfaces didn’t have much of an effect.

Moe details about the etching process from Georgia Tech:

The research team experimented with varying levels of voltage and current flow in a standard electrochemical process. Typically, electrochemical processes are used to polish stainless steel, but Champion and collaborator Dennis Hess – a professor and Thomas C. DeLoach, Jr. Chair in the School of Chemical and Biomolecular Engineering – used the technique to roughen the surface at the nanometer scale.

“Under the right conditions, you can create a nanotexture on the grain surface structure,” Hess explained. “This texturing process increases the surface segregation of chromium and molybdenum and thus enhances corrosion resistance, which is what differentiates stainless steel from conventional steel.”

Microscopic examination showed protrusions 20 to 25 nanometers above the surface. “It’s like a mountain range with both sharp peaks and valleys,” said Champion. “We think the bacteria-killing effect is related to the size scale of these features, allowing them to interact with the membranes of the bacterial cells.”

Study in ACS Biomaterials Science & Engineering : Inhibition of Bacterial Adhesion on Nanotextured Stainless Steel 316L by Electrochemical Etching…

Via: Georgia Tech…