Nanotexturing creates bacteria-killing spikes on stainless steel surfaces
By using an electrochemical etching process on a common stainless steel alloy, researchers have created a nanotextured surface that kills bacteria while not harming mammalian cells. If additional research supports early test results, the process might be used to attack microbial contamination on implantable medical devices and on food processing equipment made with the metal
While the specific mechanism by which the nanotextured material kills bacteria requires further study, the researchers believe tiny spikes and other nano-protrusions created on the surface puncture bacterial membranes to kill the bugs. The surface structures don’t appear to have a similar effect on mammalian cells, which are an order of magnitude larger than the bacteria.
Beyond the anti-bacterial effects, the nano-texturing also appears to improve corrosion resistance. The research was reported December 12 in the journal ACS Biomaterials Science & Engineering by researchers at the Georgia Institute of Technology.
“This surface treatment has potentially broad-ranging implications because stainless steel is so widely used and so many of the applications could benefit,” said Julie Champion, an associate professor in Georgia Tech’s School of Chemical and Biomolecular Engineering. “A lot of the antimicrobial approaches currently being used add some sort of surface film, which can wear off. Because we are actually modifying the steel itself, that should be a permanent change to the material.”
Champion and her Georgia Tech collaborators found that the surface modification killed both Gram negative and Gram positive bacteria, testing it on Escherichia coli and Staphylococcus aureus. But the modification did not appear to be toxic to mouse cells — an important issue because cells must adhere to medical implants as part of their incorporation into the body.
The research began with a goal of creating a super-hydrophobic surface on the stainless steel in an effort to repel liquids — and with them, bacteria. But it soon became clear that creating such a surface would require the use of a chemical coating, which the researchers didn’t want to do. Postdoctoral Fellows Yeongseon Jang and Won Tae Choi then proposed an alternative idea of using a nanotextured surface on stainless steel to control bacterial adhesion, and they initiated a collaboration to demonstrate this effect.
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.